Absorb existing domain data.

21 files changed, 1948 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..55cf0fd
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,6 @@
+# Compilation artifacts
+compiled/
+# Backup files
+*~
+# SQLite3 database
+*.sqlite
\ No newline at end of file
diff --git a/db/conn.rkt b/db/conn.rkt
new file mode 100644
index 0000000..e083d94
--- /dev/null
+++ b/db/conn.rkt
@@ -0,0 +1,41 @@
+#lang racket
+
+(require db)
+
+(provide current-conn
+         connect!
+         disconnect!
+         with-db
+         with-tx)
+
+(define current-conn (make-parameter #f))
+
+(define (connect! #:path [path 'memory])
+  (cond
+    [(connection? (current-conn))
+     (printf "Database connection already exists: ~e\n" (current-conn))]
+    [else
+     (current-conn (sqlite3-connect #:database path
+                                    #:mode 'create))
+     (printf "Created database connection at path: ~a\n" path)]))
+
+(define (disconnect!)
+  (disconnect (current-conn))
+  (printf "Closing database connection: ~e\n" (current-conn))
+  (current-conn #f))
+
+(define-syntax-rule (with-db body ...)
+  (begin (connect!) body ...))
+
+(define-syntax-rule (with-tx body ...)
+  (call-with-transaction (current-conn) (λ () body ...)))
+
+(module+ test
+  (require rackunit)
+  (check-equal? (current-conn) #f)
+  (connect!)
+  (check-true (connection? (current-conn)))
+  (disconnect!)
+  (check-equal? (current-conn) #f)
+  (with-db
+    (check-true (connection? (current-conn)))))
diff --git a/db/data/dolibarr_crop_requirements_ppm.csv b/db/data/dolibarr_crop_requirements_ppm.csv
new file mode 100644
index 0000000..e9bf8fd
--- /dev/null
+++ b/db/data/dolibarr_crop_requirements_ppm.csv
@@ -0,0 +1,9 @@
+Plante,Profil,NNO3,P,K,Ca,Mg,S,Na,Cl,Si,Fe,Zn,B,Mn,Cu,Mo,NNH4
+,générique croissance,160,30,230,100,30,60,0,0,0,5,0.15,0.3,0.5,0.15,0.05,0
+,générique floraison,130,60,300,100,30,60,0,0,0,2,0.1,0.5,0.5,0.05,0.05,0
+Laitue,générique,190,50,210,200,50,66,0,0,0,5,0.15,0.3,0.5,0.15,0.05,0
+Tomate,cycle entier,140,50,352,180,50,168,0,0,0,5,0.1,0.3,0.8,0.07,0.03,0
+Tomate,10-14 jours,100,40,200,100,20,53,0,0,0,3,0.1,0.3,0.8,0.07,0.03,0
+Tomate,1ère grappe,130,55,300,150,33,109,0,0,0,3,0.1,0.3,0.8,0.07,0.03,0
+Tomate,à maturité,180,65,400,400,45,144,0,0,0,3,0.1,0.3,0.8,0.07,0.03,0
+Framboise,tous stades,70,12,88,90,24,48,0,0,50,0.56,0.325,0.11,0.11,0.032,0.01,0
diff --git a/db/data/dolibarr_fertilizer_compositions_percentage.csv b/db/data/dolibarr_fertilizer_compositions_percentage.csv
new file mode 100644
index 0000000..f58042c
--- /dev/null
+++ b/db/data/dolibarr_fertilizer_compositions_percentage.csv
@@ -0,0 +1,18 @@
+Ref,Libellé,Nom commercial,NNO3,P,K,Ca,Mg,S,Na,Cl,Fe,Zn,B,Mn,Cu,Mo,NNH4
+Nitrate_de_Potassium,Nitrate de potassium,Multi K Reci,13.50,0,38.60,0,0,0,0.015,0,0,0,0,0,0,0,0
+Acide_nitrique_53%,Acide nitrique 53%,,11.70,0,0,0,0,0,0,0,0,0,0,0,0,0,0
+Bicarbonate_de_potassium,Bicarbonate de potassium,,0,0,0,39.05,0,0,0,0,0,0,0,0,0,0,0
+Boronia_LS,Bore-Molybdène,,0,0,0,0,0,0,0,0,0,13.50,0,0,0,0.028,0
+Phosphate_de_diammonium,Phosphate de diammonium,DAP 18/46/00,21.00,53.00,0,0,0,0,0,0,0,0,0,0,0,0,0
+Ferexel_D12,Fer chélaté DTPA,,0,0,0,0,0,0,0,0,0,11.80,0,0,0,0,0
+Nitrate_de_calcium,Nitrate de calcium,Multi-Cal Haïfa,15.50,0,0,18.94,0,0,0,0,0,0,0,0,0,0,0
+Sulfate_de_Potassium,Sulfate de potassium,Patenkali,0,22.66,0,0.44,6.16,17.77,2.16,3.34,0,0,0,0,0,0,0
+Sulfate_de_Manganese,Sulfate de Manganèse,Fixa Mn,0,0,0,0,0,7.17,0,0,0,0,12.00,0,0,0,0
+Sulfate_de_Magnesium,Sulfate de Magnésium,Eso Top,0,0,0,9.648,13.016,0,0,0,0,0,0,0,0,0,0
+Nitrate_d_ammonium,Nitrate d’ammonium,,27.00,0,0,0,0,0,0,0,0,0,0,0,0,0,0
+Carbonate_de_Calcium,Carbonate de Calcium,,0,0,0,38.00,0,0,0,0,0,0,0,0,0,0,0
+Nitrate_d_ammonium_27kg,Nitrate d’ammonium 27 en 25 kg,Ammonitrate 27,13.50,0,0,0,0,0,0,0,0,0,0,0,0,0,13.5
+Fixa_Zinc,Fixa Zinc,,0,0,0,0,0,0,0,0,0,0,5.00,0,12.00,0,0
+HelioCuivre,HelioCuivre,,0,0,0,0,0,0,0,0,0,0,0,40.00,0,0,0
+Boronia_Molybdène_-_Boronia,Boronia MO12 10L,,0,0,0,0,0,0,0,0,0,0,8.90,0.089,0,0.89,0
+Molybdate_de_sodium,Molybdate de sodium,,0,0,0,0,0,0,39.50,0,0,0,0,0,0,0,0
diff --git a/db/data/dolibarr_nutrient_measurements_ppm.csv b/db/data/dolibarr_nutrient_measurements_ppm.csv
new file mode 100644
index 0000000..c5d12e6
--- /dev/null
+++ b/db/data/dolibarr_nutrient_measurements_ppm.csv
@@ -0,0 +1,44 @@
+date,NNO3,P,K,Ca,Mg,S,Na,Cl,Si,Fe,Zn,B,Mn,Cu,Mo,NNH4
+08/05/2021,1.87,0.0031936,0.91,100.79,8.37,1.08666558,6.73,12.28,5.42,0.01,0.01,0.01,0.01,0.01,0.01,0.02
+02/07/2021,66.3,0.0095808,110.91,93.09,17.95,32.84663382,10.27,18.53,5.02,4.37,0.03,0.18,0.15,0,0,0.63
+12/07/2021,61.66,2.011968,122.53,73.5,17.44,47.64328569,0.45,0.82,0.36,1.76,0.05,0.13,0.32,0,0,0
+12/08/2021,67.27,0.351296,94.45,89.48,16.25,9.11665755,10.76,16.51,4.95,3.2,0.03,0.14,0.07,0,0,0.06
+06/09/2021,77.8,7.1153408,96.29,86.31,14.21,23.90664276,9.32,14.92,4.61,2.45,0.08,0.12,0.05,0.03,0,0.02
+21/09/2021,87.88,11.33728,117.24,90.64,17.25,29.90663676,9.92,15.96,4.68,2.4,0.08,0.27,0.12,0.04,0.01,0.02
+19/10/2021,77.84,13.4195072,121.91,94.71,18.3,33.19663347,12.36,15.28,4.47,2.72,0.11,0.74,0.04,0.04,0.02,0.03
+01/12/2021,57.09,6.6842048,81.46,61.45,10.52,17.72331561,17.36,23.05,2.11,1.27,0.17,0.32,0.01,0.03,0.02,0.07
+04/02/2022,43.56,6.5979776,63.1,63.72,9.92,17.3999826,17.08,21.15,1.44,1.6,0.22,0.34,0.01,0.04,0.01,0.03
+12/04/2022,38.36,6.5021696,83.48,49.75,6.42,14.14331919,29.8,38.85,0.23,0.3,0.2,0,0.02,0.01,0.4,0.07
+16/05/2022,24.63,0.542912,30.22,39.79,6.75,0.0666666,25.98,25.89,0.14,1.13,0.3,0.23,0.01,0.02,0.005,0.12
+15/06/2022,2.45,0.0606784,0.69,24.58,4.14,1.24999875,19.59,11.33,0.32,0.79,0.25,0.13,0.01,0.02,0.01,0.1
+04/07/2022,24.3,3.081824,42.34,39.79,8.09,0.41333292,19.79,11.32,1.24,0.7,0.18,0.07,0.02,0.01,0.005,0.68
+01/08/2022,4.88,0.2299392,27.77,22.48,6.71,18.68331465,23,5,0.64,0.97,0.17,0.04,0.005,0.005,0.005,0.07
+07/09/2022,29.28,2.07584,79.65,36.05,13.82,31.17663549,33.41,12.32,0.83,0.84,0.13,0.07,0.01,0.005,0.005,0.8
+24/10/2022,41.61,1.2646656,68.38,47.44,11.54,21.55664511,28.22,18.73,0.81,0.41,0.1,0.05,0.005,0.005,0.005,0.09
+21/11/2022,40.34,3.1105664,53.6,51.09,9.69,17.97331536,25.5,18.85,0.97,0.58,0.11,0.07,0.005,0.005,0.005,0.04
+09/01/2023,48.71,6.6171392,63.08,71.45,11.58,6.55666011,23.81,21.32,1.46,1.04,0.13,0.13,0.01,0.01,0.01,0.03
+21/02/2023,56.03,7.5273152,53.3,81.75,12.11,19.31998068,23.16,27.27,1.86,0.95,0.18,0.19,0.01,0.005,0.02,0.13
+20/04/2023,50.67,7.0546624,76.45,76.63,10.57,15.54331779,22.25,26.97,0.95,0.96,0.19,0.12,0.005,0.005,0.005,0.21
+07/06/2023,48.82,7.3005696,90.04,64.58,9.96,16.92664974,22.39,25.93,0.78,0.42,0.2,0.11,0.005,0.005,0.005,0.16
+13/07/2023,21.79,1.5712512,77.61,40.41,9.74,20.82331251,26.23,22.49,0.6,1.16,0.22,0.31,0,0,0.02,0.14
+17/07/2023,21.79,4.9213376,77.61,40.41,9.74,20.82331251,26.23,22.49,0.6,1.16,0.22,0.31,0.01,0.01,0.02,0.14
+23/08/2023,23.88,2.778432,97.75,49.74,26.25,31.24996875,31.11,16.43,1.33,0.8,0.18,0.14,0,0,0.01,1.01
+02/09/2023,23.88,2.778432,97.75,49.74,16.15,31.24996875,31.11,16.43,1.33,0.8,0.18,0.14,0,0,0.01,1.01
+13/10/2023,71.9,5.0905984,106.35,91.03,18.11,34.90663176,32.36,14.59,1.43,0.97,0.17,0.05,0,0,0,0.24
+28/12/2023,70.58,9.1368896,141.05,68.18,11.96,24.18664248,27.95,21.57,1.31,0.88,0.16,0.15,0,0,0.02,0.06
+16/01/2024,77.26,11.433088,149.17,68.71,12.14,23.24331009,29.88,27.04,1.15,1.14,0.26,0.14,0,0,0,0.09
+04/03/2024,84.65,13.4418624,185.21,66.05,15.61,30.69330264,40.12,36.82,0.66,0.93,0.39,0.35,0,0,0.03,0.16
+23/04/2024,69.17,11.2350848,116.41,52.96,14.07,28.95330438,80.73,37.54,0.57,0.79,0.42,0.38,0.01,0,0.03,0.16
+30/05/2024,46.74,7.520928,81.84,38.61,10.48,26.52997347,79.96,40.47,0.34,0.87,0.45,0.37,0,0.03,0.03,0.12
+05/07/2024,27.51,3.960064,75.58,27.78,8.29,25.99330734,92.2,44.74,0.32,0.59,0.45,0.37,0,0.03,0.03,0.15
+23/07/2024,16.55,2.4143616,83.62,16.52,4.9,20.45997954,79.04,40.51,0.32,0.77,0.43,0.26,0,0.03,0.02,0.43
+06/08/2024,0,0.3001984,74.41,6.82,2.56,17.28664938,78.79,35.04,0.42,0.9,0.37,0.29,0,0.03,0.02,0.13
+09/09/2024,18.3,2.87424,85.3,8.7,1.7,10.5666561,53.7,22.7,2.5,0.7,0.2,0.1,0,0,0,0
+01/10/2024,22.94,4.1740352,112.46,9.44,2,13.51998648,58.57,28.76,0.27,0.6,0.26,0.17,0,0.02,0,0.2
+22/11/2024,66,2.87424,127,33,9,7.333326,63,40,2.8,0.73,0.37,0.16,0.01,0.01,0.01,0
+20/01/2025,94.26,15.664608,146.27,76.06,14.24,32.05663461,64.29,46.99,0.45,0.37,0.48,0.16,0.08,0.03,0.01,0.11
+06/03/2025,95.82,20.007904,171.83,92.24,15.75,35.2332981,82.27,54.5,0.45,0.17,0.49,0.16,0.03,0.02,0,0.06
+04/04/2025,85.49,17.2646016,109.91,88.54,13.47,31.08663558,65.02,53.96,0.28,0.65,0.51,0.13,0.01,0.01,0,0
+22/05/2025,49.8,9.9927744,92.41,61.42,8.47,22.42331091,52.95,38.25,0.32,0.86,0.48,0.23,0.03,0,0.02,0.13
+11/06/2025,30.28,5.700576,50.2,48.96,5.73,22.10664456,51.34,33.41,0,0.96,0.51,0.26,0,0,0,0
+01/08/2025,1.34,0.4854272,77.64,16.45,5.52,22.93997706,58.45,25.83,0.5,0.48,0.44,0.17,0,0,0,0
diff --git a/db/migrations.rkt b/db/migrations.rkt
new file mode 100644
index 0000000..95164e4
--- /dev/null
+++ b/db/migrations.rkt
@@ -0,0 +1,167 @@
+#lang racket
+
+(provide migrate-all!)
+
+(require db
+         sql
+         "conn.rkt")
+
+(define migrations-box (box '()))
+
+(define (migrate-all!)
+  (printf "Applying migrations on connection ~a...\n"
+          (dbsystem-name (connection-dbsystem (current-conn))))
+  (for ([pair (in-list (unbox migrations-box))])
+    (match pair
+      [(cons migration-name stmts)
+       (with-tx
+         (for ([stmt (in-list stmts)])
+           (query-exec (current-conn) stmt)))
+       (printf "Applied migration: ~a\n" migration-name)])))
+
+(define-syntax-rule (define-migration migration-name sql)
+  (let ((migrations (unbox migrations-box))
+        (name-symbol (string->symbol migration-name)))
+    (if (assoc name-symbol migrations)
+        (error 'define-migration "migration '~a' declared more than once" migration-name)
+        (set-box! migrations-box (append migrations (list (cons name-symbol sql)))))))
+
+
+;;;;;;;;;;;;
+;; NUTRIENTS
+;;;;;;;;;;;;
+
+(define-migration "create table nutrients"
+  (list
+   (create-table #:if-not-exists
+                 nutrients
+                 #:columns
+                 [id integer #:not-null]
+                 [canonical_name text #:not-null]
+                 [formula text #:not-null]
+                 #:constraints
+                 (primary-key id)
+                 (unique canonical_name)
+                 (unique formula))))
+
+(define-migration "create table nutrient_value_sets"
+  (list
+   (create-table #:if-not-exists
+                 nutrient_value_sets
+                 #:columns
+                 [id integer #:not-null]
+                 [nutrient_measurement_id integer]
+                 [nutrient_target_id integer]
+                 [crop_requirement_id integer]
+                 [fertilizer_product_id integer]
+                 #:constraints
+                 (primary-key id)
+                 (foreign-key nutrient_measurement_id
+                              #:references (nutrient_measurement id)
+                              #:on-delete #:cascade)
+                 (foreign-key nutrient_target_id
+                              #:references (nutrient_target id)
+                              #:on-delete #:cascade)
+                 (foreign-key crop_requirement_id
+                              #:references (crop_requirements id)
+                              #:on-delete #:cascade)
+                 (foreign-key fertilizer_product_id
+                              #:references (fertilizer_products id)
+                              #:on-delete #:cascade))
+   "CREATE INDEX IF NOT EXISTS idx_nvs_meas ON nutrient_value_sets(nutrient_measurement_id)"
+   "CREATE INDEX IF NOT EXISTS idx_nvs_targ ON nutrient_value_sets(nutrient_target_id)"
+   "CREATE INDEX IF NOT EXISTS idx_nvs_crop ON nutrient_value_sets(crop_requirement_id)"
+   "CREATE INDEX IF NOT EXISTS idx_nvs_prod ON nutrient_value_sets(fertilizer_product_id)"))
+
+(define-migration "create table nutrient_values"
+  (list
+   (create-table #:if-not-exists
+                 nutrient_values
+                 #:columns
+                 [value_set_id integer #:not-null]
+                 [nutrient_id integer #:not-null]
+                 [value_ppm real #:not-null]
+                 #:constraints
+                 (primary-key value_set_id nutrient_id)
+                 (foreign-key value_set_id
+                              #:references (nutrient_value_sets id)
+                              #:on-delete #:cascade)
+                 (foreign-key nutrient_id
+                              #:references (nutrients id)
+                              #:on-delete #:cascade))
+   "CREATE INDEX IF NOT EXISTS idx_nv_set_nutrient ON nutrient_values(value_set_id, nutrient_id)"))
+
+(define-migration "create table nutrient_measurements"
+  (list
+   (create-table #:if-not-exists
+                 nutrient_measurements
+                 #:columns
+                 [id integer #:not-null]
+                 ;; ISO8601 date
+                 [measured_on text #:not-null]
+                 #:constraints
+                 (primary-key id)
+                 (unique measured_on))))
+
+(define-migration "create table nutrient_targets"
+  (list
+   (create-table #:if-not-exists
+                 nutrient_targets
+                 #:columns
+                 [id integer #:not-null]
+                 ;; ISO8601 date
+                 [effective_on text #:not-null]
+                 #:constraints
+                 (primary-key id)
+                 (unique effective_on))))
+
+
+;;;;;;;;
+;; CROPS
+;;;;;;;;
+
+(define-migration "create table crops"
+  (list
+   (create-table #:if-not-exists
+                 crops
+                 #:columns
+                 [id integer #:not-null]
+                 [canonical_name integer #:not-null]
+                 #:constraints
+                 (primary-key id)
+                 (unique canonical_name))))
+
+(define-migration "create table crop_requirements"
+  (list
+   (create-table #:if-not-exists
+                 crop_requirements
+                 #:columns
+                 [id integer #:not-null]
+                 [crop_id integer]
+                 [profile text #:not-null]
+                 #:constraints
+                 (primary-key id)
+                 (foreign-key crop_id
+                              #:references (crops id)
+                              #:on-delete #:cascade))))
+
+
+;;;;;;;;;;;;;;
+;; FERTILIZERS
+;;;;;;;;;;;;;;
+
+(define-migration "create table fertilizer_products"
+  (list
+   (create-table #:if-not-exists
+                 fertilizer_products
+                 #:columns
+                 [id integer #:not-null]
+                 [canonical_name text #:not-null]
+                 [brand_name text]
+                 #:constraints
+                 (primary-key id)
+                 (unique canonical_name))))
+
+(module+ test
+  (connect!)
+  (migrate-all!))
diff --git a/db/seed.rkt b/db/seed.rkt
new file mode 100644
index 0000000..6b253a6
--- /dev/null
+++ b/db/seed.rkt
@@ -0,0 +1,137 @@
+#lang racket
+
+;; Seed the database with default values.
+
+(provide seed-database!)
+
+(require csv-reading
+         "conn.rkt"
+         "../models/nutrient.rkt"
+         "../models/nutrient-measurement.rkt"
+         "../models/crop.rkt"
+         "../models/crop-requirement.rkt"
+         "../models/fertilizer-product.rkt")
+
+(define (seed-database!)
+  (seed-nutrients!)
+  (seeded "nutrients")
+  (seed-historical-nutrient-measurements!)
+  (seeded "historical nutrient measurements")
+  (seed-crops!)
+  (seeded "crops")
+  (seed-crop-requirements!)
+  (seeded "crop requirements")
+  (seed-existing-fertilizer-products!)
+  (seeded "existing fertilizer products"))
+
+(define (seeded entity)
+  (displayln (format "Seeded entity: ~a" entity)))
+
+(define (seed-nutrients!)
+  (define nutrient-names (map nutrient-name (get-nutrients)))
+  (define default-nutrients
+    '(("Nitrate Nitrogen"  "NNO3")
+      ("Phosphorus"        "P")
+      ("Potassium"         "K")
+      ("Calcium"           "Ca")
+      ("Magnesium"         "Mg")
+      ("Sulfur"            "S")
+      ("Sodium"            "Na")
+      ("Chloride"          "Cl")
+      ("Silicon"           "Si")
+      ("Iron"              "Fe")
+      ("Zinc"              "Zn")
+      ("Boron"             "B")
+      ("Manganese"         "Mn")
+      ("Copper"            "Cu")
+      ("Molybdenum"        "Mo")
+      ("Ammonium Nitrogen" "NNH4")))
+  (with-tx
+    (for ([pair (in-list default-nutrients)])
+      (define name (first pair))
+      (define formula (second pair))
+      ;; Ensure idempotence
+      (unless (member name nutrient-names)
+        (create-nutrient! name formula)))))
+
+(define (seed-historical-nutrient-measurements!)
+  (define input-csv "/home/blendux/git/ferti-v2/db/data/dolibarr_nutrient_measurements_ppm.csv")
+  (define next-row (make-csv-reader (open-input-file input-csv)))
+  (define header (next-row))
+  (define (row->seed! row)
+    (define row-alist (map cons header row))
+    (define measured-on (cdar row-alist))
+    (define nutrient-values
+      (for/list ([nm (in-list (cdr row-alist))])
+        (define formula (car nm))
+        (define n (get-nutrient #:formula formula))
+        (define v (string->number (cdr nm)))
+        (cons n v)))
+    (create-nutrient-measurement! measured-on nutrient-values))
+  (with-tx
+    (csv-for-each row->seed! next-row)))
+
+(define (seed-crops!)
+  (define crop-names (map crop-name (get-crops)))
+  (define default-crops
+    '("salade"
+      "laitue"
+      "tomate"
+      "framboise"))
+  (with-tx
+    (for ([name (in-list default-crops)])
+      ;; Ensure idempotence
+      (unless (member name crop-names)
+        (create-crop! name)))))
+
+(define (seed-crop-requirements!)
+  (define input-csv "/home/blendux/git/ferti-v2/db/data/dolibarr_crop_requirements_ppm.csv")
+  (define next-row (make-csv-reader (open-input-file input-csv)))
+  (define header (next-row))
+  (define (row->seed! row)
+    (define row-alist (map cons header row))
+    (define crop-name (string-downcase (cdr (assoc "Plante" row-alist))))
+    (define profile (cdr (assoc "Profil" row-alist)))
+    (define nutrient-values
+      (for/list ([crop-requirement (in-list (list-tail row-alist 2))])
+        (define formula (car crop-requirement))
+        (define n (get-nutrient #:formula formula))
+        (define v (string->number (cdr crop-requirement)))
+        (cons n v)))
+    (cond
+      [(non-empty-string? crop-name)
+       (define crop (get-crop #:name crop-name))
+       (create-crop-requirement! profile nutrient-values crop)]
+      [else
+       (create-crop-requirement! profile nutrient-values)]))
+  (with-tx
+    (csv-for-each row->seed! next-row)))
+
+(define (seed-existing-fertilizer-products!)
+  (define input-csv "/home/blendux/git/ferti-v2/db/data/dolibarr_fertilizer_compositions_percentage.csv")
+  (define next-row (make-csv-reader (open-input-file input-csv)))
+  (define header (next-row))
+  (define (row->seed! row)
+    (define row-alist (map cons header row))
+    (define canonical-name (cdr (assoc "Libellé" row-alist)))
+    (define brand-name (cdr (assoc "Nom commercial" row-alist)))
+    (define nutrient-values
+      (for/list ([fertilizer-component (in-list (list-tail row-alist 3))])
+        (define formula (car fertilizer-component))
+        (define n (get-nutrient #:formula formula))
+        (define v (string->number (cdr fertilizer-component)))
+        (cons n v)))
+    (cond
+      [(non-empty-string? brand-name)
+       (create-fertilizer-product! canonical-name nutrient-values brand-name)]
+      [else
+       (create-fertilizer-product! canonical-name nutrient-values)]))
+  (with-tx
+    (csv-for-each row->seed! next-row)))
+
+(module+ test
+  (require "migrations.rkt")
+  (connect! #:path "test.sqlite3"
+            )
+  (migrate-all!)
+  (seed-database!))
diff --git a/formlets.rkt b/formlets.rkt
new file mode 100644
index 0000000..406a54a
--- /dev/null
+++ b/formlets.rkt
@@ -0,0 +1,53 @@
+#lang racket
+
+(provide measurements-formlet)
+
+(require gregor
+         web-server/http
+         web-server/formlets
+         "models/nutrient.rkt")
+
+
+(define date-formlet
+  (formlet
+   ,{=> (to-string
+         (required
+          (input #:type "date"
+                 #:value (date->iso8601 (today))
+                 #:attributes '([class "form-control"] [required "required"]))))
+        date-b}
+   date-b))
+
+(define (measurement-formlet nutrient)
+  (define id (nutrient-id nutrient))
+  (define number-input
+    (input #:type "number"
+           #:attributes `([class "form-control"]
+                          [id ,(number->string id)]
+                          [step "0.1"]
+                          [placeholder ,(nutrient-name nutrient)])))
+  (define input-label `(label ((for ,(number->string id))) ,(nutrient-name nutrient)))
+  (formlet
+   (#%#
+    (div ([class "form-floating mb-3"])
+         ,{=> number-input nutrient-value-b}
+         ,input-label))
+   (let ([nutrient-value (string->number
+                          (bytes->string/utf-8
+                           (binding:form-value nutrient-value-b)))])
+     (and nutrient-value (cons id nutrient-value)))))
+
+(define (measurements-formlet)
+  (formlet*
+   (#%#
+    `(div ([class "mb-3"])
+          (h5 "Date du relevé")
+          ,{=>* date-formlet measured-on*})
+    `(div ([class "mb-3"])
+          (h5 "Valeurs du relevé")
+          ,@(for/list ([nutrient (get-nutrients)])
+              {=>* (measurement-formlet nutrient) measurements*}))
+    {=>* (submit "Enregistrer le relevé" #:attributes '([class "btn btn-primary"])) _})
+   (let ([measured-on (first measured-on*)]
+         [measurements (filter pair? measurements*)]) ; drop #f’s from empty values
+     (values measured-on measurements))))
diff --git a/handlers.rkt b/handlers.rkt
new file mode 100644
index 0000000..42e4a76
--- /dev/null
+++ b/handlers.rkt
@@ -0,0 +1,48 @@
+#lang racket
+
+(provide app-dispatch)
+
+(require web-server/dispatch
+         web-server/http
+         web-server/formlets
+         "views.rkt"
+         "formlets.rkt"
+         "models/nutrient.rkt"
+         "models/nutrient-measurement.rkt")
+
+
+(define (index _)
+  (define measurements (get-nutrient-measurements))
+  (response/xexpr
+   #:preamble #"<!DOCTYPE html>"
+   (index-page measurements)))
+
+(define (new-measurement _)
+  (response/xexpr
+   #:preamble #"<!DOCTYPE html>"
+   (new-measurement-page)))
+
+(define (create-measurement req)
+  (define-values (measured-on measurements)
+    (formlet-process (measurements-formlet) req))
+  (create-nutrient-measurement! measured-on measurements)
+  (redirect-to "/"))
+
+(define (destroy-measurement req)
+  (define-values (measured-on measurements)
+    (formlet-process (measurements-formlet) req))
+  (create-nutrient-measurement! measured-on measurements)
+  (redirect-to "/"))
+
+(define (fallback req)
+  (response/xexpr
+   #:preamble #"<!DOCTYPE html>"
+   (fallback-page 404)))
+
+(define-values (app-dispatch app-url)
+  (dispatch-rules
+   [("measurement" "new")     #:method "get"  new-measurement]
+   [("measurement" "create")  #:method "post" create-measurement]
+   [("measurement" "destroy") #:method "post" destroy-measurement]
+   [("")                      #:method "get"  index]
+   [else fallback]))
diff --git a/main.rkt b/main.rkt
new file mode 100644
index 0000000..7b6c25e
--- /dev/null
+++ b/main.rkt
@@ -0,0 +1,14 @@
+#lang racket
+
+(require web-server/dispatch
+         "handlers.rkt"
+         "db/conn.rkt"
+         "db/migrations.rkt"
+         "db/seed.rkt")
+
+(module+ main
+  (connect! #:path "storage/development.sqlite3")
+  (migrate-all!)
+  (seed-database!)
+  (serve/dispatch
+   app-dispatch))
diff --git a/models/crop-requirement.rkt b/models/crop-requirement.rkt
new file mode 100644
index 0000000..f213441
--- /dev/null
+++ b/models/crop-requirement.rkt
@@ -0,0 +1,180 @@
+#lang racket
+
+(provide
+ ;; Struct definitions
+ crop-requirement
+ crop-requirement?
+ crop-requirement-id crop-requirement-profile
+ ;; SQL CRUD
+ (contract-out
+  [create-crop-requirement! (->* (string?
+                                  (listof (cons/c
+                                           nutrient?
+                                           number?)))
+                                 ((or/c #f crop?))
+                                 crop-requirement?)]
+  [get-crop-requirements (->* ()
+                              (#:id
+                               (or/c #f exact-nonnegative-integer?)
+                               #:profile
+                               (or/c #f string?))
+                              (listof crop-requirement?))]
+  [get-crop-requirement (->* ()
+                             (#:id
+                              (or/c #f exact-nonnegative-integer?)
+                              #:profile
+                              (or/c #f string?))
+                             (or/c crop-requirement? #f))]
+  [get-crop-requirement-values (-> crop-requirement?
+                                   (listof (cons/c
+                                            nutrient?
+                                            number?)))]
+  [get-crop-requirement-value (-> crop-requirement?
+                                  nutrient?
+                                  number?)]
+  [get-latest-crop-requirement-value (-> nutrient? number?)]
+  #; [update-crop-requirement! (->* (crop-requirement?)
+                                    (#:profile     (or/c #f string?)
+                                     #:nutrient-values (or/c #f (listof (cons/c
+                                                                         nutrient?
+                                                                         number?))))
+                                    (or/c crop-requirement? #f))]
+  [delete-crop-requirement! (-> crop-requirement?
+                                void?)]))
+
+(require racket/contract
+         db
+         sql
+         "../db/conn.rkt"
+         "nutrient.rkt"
+         "crop.rkt")
+
+;; Instances of this struct are persisted in the crop_requirements table.
+(struct crop-requirement (id profile) #:transparent)
+
+
+;; CREATE
+
+
+(define (create-crop-requirement! profile nutrient-values [crop #f])
+  (define existing-crop-requirement (get-crop-requirement #:profile profile))
+  (define (new-crop-requirement)
+    (with-tx
+      (query-exec (current-conn)
+                  (if crop
+                      (insert #:into crop_requirements
+                              #:set [crop_id ,(crop-id crop)] [profile ,profile])
+                      (insert #:into crop_requirements
+                              #:set [profile ,profile])))
+      (define cr-id (crop-requirement-id (get-crop-requirement #:profile profile)))
+      (query-exec (current-conn)
+                  (insert #:into nutrient_value_sets
+                          #:set [crop_requirement_id ,cr-id]))
+      (define nvs-id (query-value (current-conn)
+                                  (select id
+                                          #:from nutrient_value_sets
+                                          #:where (= crop_requirement_id ,cr-id))))
+      (for ([nv nutrient-values])
+        (match nv
+          [(cons n v)
+           (query-exec (current-conn)
+                       (insert #:into nutrient_values
+                               #:set
+                               [value_set_id ,nvs-id]
+                               [nutrient_id  ,(nutrient-id n)]
+                               [value_ppm    ,v]))])))
+    (get-crop-requirement #:profile profile))
+  (or existing-crop-requirement
+      (new-crop-requirement)))
+
+
+;; READ
+
+(define (get-crop-requirements #:id [id #f]
+                                   #:profile [profile #f])
+  (define (where-expr)
+    (define clauses
+      (filter values
+              (list (and id (format "id = ~e" id))
+                    (and profile (format "profile = ~e" profile)))))
+    (cond
+      [(null? clauses) ""]
+      [else (format "WHERE ~a" (string-join clauses " AND "))]))
+  (define query (string-join
+                 `("SELECT id, profile"
+                   "FROM crop_requirements"
+                   ,(where-expr)
+                   "ORDER BY id ASC")))
+  (for/list ([(id* profile*)
+              (in-query (current-conn) query)])
+    (crop-requirement id* profile*)))
+
+(define (get-crop-requirement #:id [id #f]
+                                  #:profile [profile #f])
+  (define (where-expr)
+    (define clauses
+      (filter values
+              (list
+               (and id (format "id = ~e" id))
+               (and profile (format "profile = ~e" profile)))))
+    (cond
+      [(null? clauses) ""]
+      [else (format "WHERE ~a" (string-join clauses " AND "))]))
+  (define query (string-join
+                 `("SELECT id, profile"
+                   "FROM crop_requirements"
+                   ,(where-expr)
+                   "ORDER BY id ASC"
+                   "LIMIT 1")))
+  (match (query-maybe-row (current-conn) query)
+    [(vector id* profile*)
+     (crop-requirement id* profile*)]
+    [#f #f]))
+
+(define (get-crop-requirement-values crop-requirement)
+  (for/list ([(nutrient-id name formula value_ppm)
+              (in-query (current-conn)
+                        (string-join
+                         '("SELECT n.id, n.canonical_name, n.formula, nv.value_ppm"
+                           "FROM nutrient_values nv"
+                           "JOIN nutrient_value_sets nvs ON nvs.id = nv.value_set_id"
+                           "JOIN crop_requirements cr ON cr.id = nvs.crop_requirement_id"
+                           "JOIN nutrients n ON n.id = nv.nutrient_id"
+                           "WHERE cr.id = $1"))
+                        (crop-requirement-id crop-requirement))])
+    (cons (nutrient nutrient-id name formula) value_ppm)))
+
+(define (get-crop-requirement-value crop-requirement nutrient)
+  (query-maybe-value (current-conn)
+                     (string-join
+                      '("SELECT value_ppm"
+                        "FROM nutrient_values nv"
+                        "JOIN nutrient_value_sets nvs ON nvs.id = nv.value_set_id"
+                        "JOIN crop_requirements cr ON cr.id = nvs.crop_requirement_id"
+                        "WHERE cr.id = $1 AND nv.nutrient_id = $2"))
+                     (crop-requirement-id crop-requirement)
+                     (nutrient-id nutrient)))
+
+(define (get-latest-crop-requirement-value nutrient)
+  (query-maybe-value (current-conn)
+                     (string-join
+                      '("SELECT value_ppm"
+                        "FROM nutrient_values nv"
+                        "JOIN nutrient_value_sets nvs ON nvs.id = nv.value_set_id"
+                        "JOIN crop_requirements cr ON cr.id = nvs.crop_requirement_id"
+                        "WHERE nv.nutrient_id = $1"
+                        "ORDER BY cr.profile DESC"
+                        "LIMIT 1"))
+                     (nutrient-id nutrient)))
+
+
+;; UPDATE
+
+
+;; DELETE
+
+(define (delete-crop-requirement! crop-requirement)
+  (define id (crop-requirement-id crop-requirement))
+  (query-exec (current-conn)
+              (delete #:from crop_requirements
+                      #:where (= id ,id))))
diff --git a/models/crop.rkt b/models/crop.rkt
new file mode 100644
index 0000000..7163cbd
--- /dev/null
+++ b/models/crop.rkt
@@ -0,0 +1,103 @@
+#lang racket
+
+(provide
+ ;; Struct definitions
+ crop
+ crop?
+ crop-id crop-name
+ ;; SQL CRUD
+ (contract-out
+  [create-crop! (-> string? void?)]
+  [get-crops (->* ()
+                  (#:id      (or/c #f exact-nonnegative-integer?)
+                   #:name    (or/c #f string?))
+                  (listof crop?))]
+  [get-crop (->* ()
+                 (#:id      (or/c #f exact-nonnegative-integer?)
+                  #:name    (or/c #f string?))
+                 (or/c crop? #f))]
+  [update-crop! (->* (exact-nonnegative-integer?)
+                     (#:name    (or/c #f string?))
+                     (or/c crop? #f))]
+  [delete-crop! (-> exact-nonnegative-integer? void?)]))
+
+(require racket/contract
+         db
+         sql
+         "../db/conn.rkt")
+
+(struct crop (id name) #:transparent)
+
+
+;; CREATE
+
+(define (create-crop! name)
+  (query-exec (current-conn)
+              (insert #:into crops
+                      #:set [canonical_name ,name])))
+
+
+;; READ
+
+(define (get-crops #:id [id #f]
+                   #:name [name #f])
+  (define (where-expr)
+    (define clauses
+      (filter values
+              (list
+               (and id (format "id = ~e" id))
+               (and name (format "canonical_name = ~e" name)))))
+    (cond
+      [(null? clauses) ""]
+      [else (format "WHERE ~a" (string-join clauses " AND "))]))
+  (define query (string-join
+                 `("SELECT id, canonical_name"
+                   "FROM crops"
+                   ,(where-expr)
+                   "ORDER BY id ASC")))
+  (for/list ([(id* name*)
+              (in-query (current-conn) query)])
+    (crop id* name*)))
+
+(define (get-crop #:id [id #f]
+                  #:name [name #f])
+  (define (where-expr)
+    (define clauses
+      (filter values
+              (list (and id (format "id = ~e" id))
+                    (and name (format "canonical_name = ~e" name)))))
+    (cond
+      [(null? clauses) ""]
+      [else (format "WHERE ~a" (string-join clauses " AND "))]))
+  (define query (string-join
+                 `("SELECT id, canonical_name"
+                   "FROM crops"
+                   ,(where-expr)
+                   "ORDER BY id ASC"
+                   "LIMIT 1")))
+  (match (query-maybe-row (current-conn) query)
+    [(vector id* name*)
+     (crop id* name*)]
+    [#f #f]))
+
+
+;; UPDATE
+
+(define (update-crop! id
+                      #:name [name #f])
+  (cond
+    [name
+     (query-exec (current-conn)
+                 (update crops
+                         #:set [canonical_name ,name]
+                         #:where (= id ,id)))]
+    [else (void)])
+  (or (get-crop #:id id)
+      (error 'update-crop! "No crop with id ~a" id)))
+
+
+;; DELETE
+
+(define (delete-crop! id)
+  (query-exec (current-conn)
+              (delete #:from crops #:where (= id ,id))))
diff --git a/models/fertilizer-product.rkt b/models/fertilizer-product.rkt
new file mode 100644
index 0000000..254ce35
--- /dev/null
+++ b/models/fertilizer-product.rkt
@@ -0,0 +1,177 @@
+#lang racket
+
+(provide
+ ;; Struct definitions
+ fertilizer-product
+ fertilizer-product?
+ fertilizer-product-id fertilizer-product-brand-name
+ ;; SQL CRUD
+ (contract-out
+  [create-fertilizer-product! (->* (string?
+                                    (listof (cons/c
+                                             nutrient?
+                                             number?)))
+                                   (string?)
+                                   fertilizer-product?)]
+  [get-fertilizer-products (->* ()
+                                (#:id
+                                 (or/c #f exact-nonnegative-integer?)
+                                 #:brand-name
+                                 (or/c #f string?))
+                                (listof fertilizer-product?))]
+  [get-fertilizer-product (->* ()
+                               (#:id
+                                (or/c #f exact-nonnegative-integer?)
+                                #:brand-name
+                                (or/c #f string?))
+                               (or/c fertilizer-product? #f))]
+  [get-fertilizer-product-values (-> fertilizer-product?
+                                     (listof (cons/c
+                                              nutrient?
+                                              number?)))]
+  [get-fertilizer-product-value (-> fertilizer-product?
+                                    nutrient?
+                                    number?)]
+  [get-latest-fertilizer-product-value (-> nutrient? number?)]
+  [delete-fertilizer-product! (-> fertilizer-product?
+                                  void?)]))
+
+(require racket/contract
+         db
+         sql
+         "../db/conn.rkt"
+         "nutrient.rkt")
+
+;; Instances of this struct are persisted in the fertilizer_products table.
+(struct fertilizer-product (id canonical-name brand-name) #:transparent)
+
+
+;; CREATE
+
+
+(define (create-fertilizer-product! canonical-name nutrient-values [brand-name #f])
+  (define existing-fertilizer-product (get-fertilizer-product #:canonical-name canonical-name))
+  (define (new-fertilizer-product)
+    (with-tx
+      (query-exec (current-conn)
+                  (cond
+                    [brand-name
+                     (insert #:into fertilizer_products
+                             #:set [canonical_name ,canonical-name] [brand_name ,brand-name])]
+                    [else
+                     (insert #:into fertilizer_products
+                             #:set [canonical_name ,canonical-name])]))
+      (define nm-id (fertilizer-product-id (get-fertilizer-product #:canonical-name canonical-name)))
+      (query-exec (current-conn)
+                  (insert #:into nutrient_value_sets
+                          #:set [fertilizer_product_id ,nm-id]))
+      (define nvs-id (query-value (current-conn)
+                                  (select id
+                                          #:from nutrient_value_sets
+                                          #:where (= fertilizer_product_id ,nm-id))))
+      (for ([nv nutrient-values])
+        (match nv
+          [(cons n v)
+           (query-exec (current-conn)
+                       (insert #:into nutrient_values
+                               #:set
+                               [value_set_id ,nvs-id]
+                               [nutrient_id  ,(nutrient-id n)]
+                               [value_ppm    ,v]))])))
+    (get-fertilizer-product #:canonical-name canonical-name))
+  (or existing-fertilizer-product
+      (new-fertilizer-product)))
+
+
+;; READ
+
+(define (get-fertilizer-products #:id [id #f]
+                                   #:brand-name [brand-name #f])
+  (define (where-expr)
+    (define clauses
+      (filter values
+              (list (and id (format "id = ~e" id))
+                    (and brand-name (format "brand_name = ~e" brand-name)))))
+    (cond
+      [(null? clauses) ""]
+      [else (format "WHERE ~a" (string-join clauses " AND "))]))
+  (define query (string-join
+                 `("SELECT id, brand_name"
+                   "FROM fertilizer_products"
+                   ,(where-expr)
+                   "ORDER BY id ASC")))
+  (for/list ([(id* brand-name*)
+              (in-query (current-conn) query)])
+    (fertilizer-product id* brand-name*)))
+
+(define (get-fertilizer-product #:id [id #f]
+                                #:canonical-name [canonical-name #f]
+                                #:brand-name [brand-name #f])
+  (define (where-expr)
+    (define clauses
+      (filter values
+              (list
+               (and id (format "id = ~e" id))
+               (and canonical-name (format "canonical_name = ~e" canonical-name))
+               (and brand-name (format "brand_name = ~e" brand-name)))))
+    (cond
+      [(null? clauses) ""]
+      [else (format "WHERE ~a" (string-join clauses " AND "))]))
+  (match (query-maybe-row (current-conn)
+                          (string-join
+                           `("SELECT id, canonical_name, brand_name"
+                             "FROM fertilizer_products"
+                             ,(where-expr)
+                             "ORDER BY id ASC"
+                             "LIMIT 1")))
+    [(vector id* canonical-name* brand-name*)
+     (fertilizer-product id* canonical-name* brand-name*)]
+    [#f #f]))
+
+(define (get-fertilizer-product-values fertilizer-product)
+  (for/list ([(nutrient-id name formula value_ppm)
+              (in-query (current-conn)
+                        (string-join
+                         '("SELECT n.id, n.canonical_name, n.formula, nv.value_ppm"
+                           "FROM nutrient_values nv"
+                           "JOIN nutrient_value_sets nvs ON nvs.id = nv.value_set_id"
+                           "JOIN fertilizer_products nm ON nm.id = nvs.fertilizer_product_id"
+                           "JOIN nutrients n ON n.id = nv.nutrient_id"
+                           "WHERE nm.id = $1"))
+                        (fertilizer-product-id fertilizer-product))])
+    (cons (nutrient nutrient-id name formula) value_ppm)))
+
+(define (get-fertilizer-product-value fertilizer-product nutrient)
+  (query-maybe-value (current-conn)
+                     (string-join
+                      '("SELECT value_ppm"
+                        "FROM nutrient_values nv"
+                        "JOIN nutrient_value_sets nvs ON nvs.id = nv.value_set_id"
+                        "JOIN fertilizer_products nm ON nm.id = nvs.fertilizer_product_id"
+                        "WHERE nm.id = $1 AND nv.nutrient_id = $2"))
+                     (fertilizer-product-id fertilizer-product)
+                     (nutrient-id nutrient)))
+
+(define (get-latest-fertilizer-product-value nutrient)
+  (query-maybe-value (current-conn)
+                     (string-join
+                      '("SELECT value_ppm"
+                        "FROM nutrient_values nv"
+                        "JOIN nutrient_value_sets nvs ON nvs.id = nv.value_set_id"
+                        "JOIN fertilizer_products nm ON nm.id = nvs.fertilizer_product_id"
+                        "WHERE nv.nutrient_id = $1"
+                        "ORDER BY nm.brand_name DESC"
+                        "LIMIT 1"))
+                     (nutrient-id nutrient)))
+
+
+;; UPDATE
+
+
+;; DELETE
+
+(define (delete-fertilizer-product! fertilizer-product)
+  (define id (fertilizer-product-id fertilizer-product))
+  (query-exec (current-conn)
+              (delete #:from fertilizer_products
+                      #:where (= id ,id))))
diff --git a/models/nutrient-measurement.rkt b/models/nutrient-measurement.rkt
new file mode 100644
index 0000000..8364aa7
--- /dev/null
+++ b/models/nutrient-measurement.rkt
@@ -0,0 +1,212 @@
+#lang racket
+
+(provide
+ ;; Struct definitions
+ nutrient-measurement
+ nutrient-measurement?
+ nutrient-measurement-id nutrient-measurement-measured-on
+ ;; SQL CRUD
+ (contract-out
+  [create-nutrient-measurement! (-> string?
+                                    (listof (cons/c
+                                             nutrient?
+                                             number?))
+                                    nutrient-measurement?)]
+  [get-nutrient-measurements (->* ()
+                                  (#:id          (or/c #f exact-nonnegative-integer?)
+                                   #:measured-on (or/c #f string?))
+                                  (listof nutrient-measurement?))]
+  [get-nutrient-measurement (->* ()
+                                 (#:id          (or/c #f exact-nonnegative-integer?)
+                                  #:measured-on (or/c #f string?))
+                                 (or/c nutrient-measurement? #f))]
+  [get-nutrient-measurement-values (-> nutrient-measurement?
+                                       (listof (cons/c
+                                                nutrient?
+                                                number?)))]
+  [get-nutrient-measurement-value (-> nutrient-measurement?
+                                      nutrient?
+                                      number?)]
+  [get-latest-nutrient-measurement-value (-> nutrient? number?)]
+  #; [update-nutrient-measurement! (->* (nutrient-measurement?)
+                                        (#:measured-on     (or/c #f string?)
+                                         #:nutrient-values (or/c #f (listof (cons/c
+                                                                             nutrient?
+                                                                             number?))))
+                                        (or/c nutrient-measurement? #f))]
+  [delete-nutrient-measurement! (-> nutrient-measurement?
+                                    void?)]))
+
+(require racket/contract
+         db
+         sql
+         "../db/conn.rkt"
+         "nutrient.rkt")
+
+;; Instances of this struct are persisted in the nutrient_measurements table.
+(struct nutrient-measurement (id measured-on) #:transparent)
+
+
+;; CREATE
+
+(define (create-nutrient-measurement! measured-on nutrient-values)
+  (define existing-nutrient-measurement (get-nutrient-measurement #:measured-on measured-on))
+  (define (new-nutrient-measurement)
+    (with-tx
+      (query-exec (current-conn)
+                  (insert #:into nutrient_measurements
+                          #:set [measured_on ,measured-on]))
+      (define nm-id (nutrient-measurement-id (get-nutrient-measurement #:measured-on measured-on)))
+      (query-exec (current-conn)
+                  (insert #:into nutrient_value_sets
+                          #:set [nutrient_measurement_id ,nm-id]))
+      (define nvs-id (query-value (current-conn)
+                                  (select id
+                                          #:from nutrient_value_sets
+                                          #:where (= nutrient_measurement_id ,nm-id))))
+      (for ([nv nutrient-values])
+        (match nv
+          [(cons n v)
+           (query-exec (current-conn)
+                       (insert #:into nutrient_values
+                               #:set
+                               [value_set_id ,nvs-id]
+                               [nutrient_id  ,(nutrient-id n)]
+                               [value_ppm    ,v]))])))
+    (get-nutrient-measurement #:measured-on measured-on))
+  (or existing-nutrient-measurement
+      (new-nutrient-measurement)))
+
+
+;; READ
+
+(define (get-nutrient-measurements #:id [id #f]
+                                   #:measured-on [measured-on #f])
+  (define (where-expr)
+    (define clauses
+      (filter values
+              (list (and id (format "id = ~e" id))
+                    (and measured-on (format "measured_on = ~e" measured-on)))))
+    (cond
+      [(null? clauses) ""]
+      [else (format "WHERE ~a" (string-join clauses " AND "))]))
+  (define query (string-join
+                 `("SELECT id, measured_on"
+                   "FROM nutrient_measurements"
+                   ,(where-expr)
+                   "ORDER BY id ASC")))
+  (for/list ([(id* measured-on*)
+              (in-query (current-conn) query)])
+    (nutrient-measurement id* measured-on*)))
+
+(define (get-nutrient-measurement #:id [id #f]
+                                  #:measured-on [measured-on #f])
+  (define (where-expr)
+    (define clauses
+      (filter values
+              (list
+               (and id (format "id = ~e" id))
+               (and measured-on (format "measured_on = ~e" measured-on)))))
+    (cond
+      [(null? clauses) ""]
+      [else (format "WHERE ~a" (string-join clauses " AND "))]))
+  (define query (string-join
+                 `("SELECT id, measured_on"
+                   "FROM nutrient_measurements"
+                   ,(where-expr)
+                   "ORDER BY id ASC"
+                   "LIMIT 1")))
+  (match (query-maybe-row (current-conn) query)
+    [(vector id* measured-on*)
+     (nutrient-measurement id* measured-on*)]
+    [#f #f]))
+
+(define (get-nutrient-measurement-values nutrient-measurement)
+  (for/list ([(nutrient-id name formula value_ppm)
+              (in-query (current-conn)
+                        (string-join
+                         '("SELECT n.id, n.canonical_name, n.formula, nv.value_ppm"
+                           "FROM nutrient_values nv"
+                           "JOIN nutrient_value_sets nvs ON nvs.id = nv.value_set_id"
+                           "JOIN nutrient_measurements nm ON nm.id = nvs.nutrient_measurement_id"
+                           "JOIN nutrients n ON n.id = nv.nutrient_id"
+                           "WHERE nm.id = $1"))
+                        (nutrient-measurement-id nutrient-measurement))])
+    (cons (nutrient nutrient-id name formula) value_ppm)))
+
+(define (get-nutrient-measurement-value nutrient-measurement nutrient)
+  (query-maybe-value (current-conn)
+                     (string-join
+                      '("SELECT value_ppm"
+                        "FROM nutrient_values nv"
+                        "JOIN nutrient_value_sets nvs ON nvs.id = nv.value_set_id"
+                        "JOIN nutrient_measurements nm ON nm.id = nvs.nutrient_measurement_id"
+                        "WHERE nm.id = $1 AND nv.nutrient_id = $2"))
+                     (nutrient-measurement-id nutrient-measurement)
+                     (nutrient-id nutrient)))
+
+(define (get-latest-nutrient-measurement-value nutrient)
+  (query-maybe-value (current-conn)
+                     (string-join
+                      '("SELECT value_ppm"
+                        "FROM nutrient_values nv"
+                        "JOIN nutrient_value_sets nvs ON nvs.id = nv.value_set_id"
+                        "JOIN nutrient_measurements nm ON nm.id = nvs.nutrient_measurement_id"
+                        "WHERE nv.nutrient_id = $1"
+                        "ORDER BY nm.measured_on DESC"
+                        "LIMIT 1"))
+                     (nutrient-id nutrient)))
+
+
+;; UPDATE
+
+#; (define (update-nutrient-measurement! nutrient-measurement
+                                         #:measured-on [measured-on #f]
+                                         #:nutrient-values [nutrient-values '()])
+     (define nm-id (nutrient-measurement-id nutrient-measurement))
+     (define (nvs-id nm-id)
+       (query-maybe-row (current-conn)
+                        (select id
+                                #:from nutrient_value_sets
+                                #:where (= nutrient_measurement_id ,nm-id))))
+     (with-tx
+       (when measured-on
+         (query-exec (current-conn)
+                     (update nutrient_measurements
+                             #:set [measured_on ,measured-on]
+                             #:where (= id ,id))))
+       (unless (null? nutrient-values)
+         (upsert-nutrient-values nm-id))
+       (get-nutrient-measurement #:id id)))
+
+#; (define (upsert-nutrient-values nutrient-measurement-id)
+  (define maybe-nvs-id (nvs-id nm-id))
+  (case maybe-nvs-id
+    [(#f)
+     (query-exec (current-conn)
+                 (insert #:into nutrient_values_sets
+                         #:set
+                         [nutrient_measurement_id ,id]))
+     (define new-nvs-id (nvs-id nm-id))
+     (query-exec (current-conn)
+                 (string-join
+                  '("INSERT INTO nutrient_values"
+                    "VALUES $1 $2 $3"
+                    ""))
+                 new-nvs-id
+                 )]
+    [else
+     (query-exec (current-conn)
+                 (update nutrient_measurement_values
+                         #:set   [value ,value]
+                         #:where (and (= measurement_id ,measurement-id)
+                                      (= nutrient_id    ,nutrient-id))))]))
+
+
+;; DELETE
+
+(define (delete-nutrient-measurement! nutrient-measurement)
+  (define id (nutrient-measurement-id nutrient-measurement))
+  (query-exec (current-conn)
+              (delete #:from nutrient_measurements
+                      #:where (= id ,id))))
diff --git a/models/nutrient-target.rkt b/models/nutrient-target.rkt
new file mode 100644
index 0000000..6483997
--- /dev/null
+++ b/models/nutrient-target.rkt
@@ -0,0 +1,217 @@
+#lang racket
+
+(provide
+ ;; Struct definitions
+ nutrient-target
+ nutrient-target?
+ nutrient-target-id nutrient-target-effective-on
+ ;; SQL CRUD
+ (contract-out
+  [create-nutrient-target! (-> string?
+                               (listof (cons/c
+                                        nutrient?
+                                        number?))
+                               nutrient-target?)]
+  [get-nutrient-targets (->* ()
+                             (#:id
+                              (or/c #f exact-nonnegative-integer?)
+                              #:effective-on
+                              (or/c #f string?))
+                             (listof nutrient-target?))]
+  [get-nutrient-target (->* ()
+                            (#:id
+                             (or/c #f exact-nonnegative-integer?)
+                             #:effective-on
+                             (or/c #f string?))
+                            (or/c nutrient-target? #f))]
+  [get-nutrient-target-values (-> nutrient-target?
+                                  (listof (cons/c
+                                           nutrient?
+                                           number?)))]
+  [get-nutrient-target-value (-> nutrient-target?
+                                 nutrient?
+                                 number?)]
+  [get-latest-nutrient-target-value (-> nutrient? number?)]
+  #; [update-nutrient-target! (->* (nutrient-target?)
+                                   (#:effective-on     (or/c #f string?)
+                                    #:nutrient-values (or/c #f (listof (cons/c
+                                                                        nutrient?
+                                                                        number?))))
+                                   (or/c nutrient-target? #f))]
+  [delete-nutrient-target! (-> nutrient-target?
+                               void?)]))
+
+(require racket/contract
+         db
+         sql
+         "../db/conn.rkt"
+         "nutrient.rkt")
+
+;; Instances of this struct are persisted in the nutrient_targets table.
+(struct nutrient-target (id effective-on) #:transparent)
+
+
+;; CREATE
+
+
+(define (create-nutrient-target! effective-on nutrient-values)
+  (define existing-nutrient-target (get-nutrient-target #:effective-on effective-on))
+  (define (new-nutrient-target)
+    (with-tx
+      (query-exec (current-conn)
+                  (insert #:into nutrient_targets
+                          #:set [effective_on ,effective-on]))
+      (define nm-id (nutrient-target-id (get-nutrient-target #:effective-on effective-on)))
+      (query-exec (current-conn)
+                  (insert #:into nutrient_value_sets
+                          #:set [nutrient_target_id ,nm-id]))
+      (define nvs-id (query-value (current-conn)
+                                  (select id
+                                          #:from nutrient_value_sets
+                                          #:where (= nutrient_target_id ,nm-id))))
+      (for ([nv nutrient-values])
+        (match nv
+          [(cons n v)
+           (query-exec (current-conn)
+                       (insert #:into nutrient_values
+                               #:set
+                               [value_set_id ,nvs-id]
+                               [nutrient_id  ,(nutrient-id n)]
+                               [value_ppm    ,v]))])))
+    (get-nutrient-target #:effective-on effective-on))
+  (or existing-nutrient-target
+      (new-nutrient-target)))
+
+
+;; READ
+
+(define (get-nutrient-targets #:id [id #f]
+                                   #:effective-on [effective-on #f])
+  (define (where-expr)
+    (define clauses
+      (filter values
+              (list (and id (format "id = ~e" id))
+                    (and effective-on (format "effective_on = ~e" effective-on)))))
+    (cond
+      [(null? clauses) ""]
+      [else (format "WHERE ~a" (string-join clauses " AND "))]))
+  (define query (string-join
+                 `("SELECT id, effective_on"
+                   "FROM nutrient_targets"
+                   ,(where-expr)
+                   "ORDER BY id ASC")))
+  (for/list ([(id* effective-on*)
+              (in-query (current-conn) query)])
+    (nutrient-target id* effective-on*)))
+
+(define (get-nutrient-target #:id [id #f]
+                                  #:effective-on [effective-on #f])
+  (define (where-expr)
+    (define clauses
+      (filter values
+              (list
+               (and id (format "id = ~e" id))
+               (and effective-on (format "effective_on = ~e" effective-on)))))
+    (cond
+      [(null? clauses) ""]
+      [else (format "WHERE ~a" (string-join clauses " AND "))]))
+  (define query (string-join
+                 `("SELECT id, effective_on"
+                   "FROM nutrient_targets"
+                   ,(where-expr)
+                   "ORDER BY id ASC"
+                   "LIMIT 1")))
+  (match (query-maybe-row (current-conn) query)
+    [(vector id* effective-on*)
+     (nutrient-target id* effective-on*)]
+    [#f #f]))
+
+(define (get-nutrient-target-values nutrient-target)
+  (for/list ([(nutrient-id name formula value_ppm)
+              (in-query (current-conn)
+                        (string-join
+                         '("SELECT n.id, n.canonical_name, n.formula, nv.value_ppm"
+                           "FROM nutrient_values nv"
+                           "JOIN nutrient_value_sets nvs ON nvs.id = nv.value_set_id"
+                           "JOIN nutrient_targets nm ON nm.id = nvs.nutrient_target_id"
+                           "JOIN nutrients n ON n.id = nv.nutrient_id"
+                           "WHERE nm.id = $1"))
+                        (nutrient-target-id nutrient-target))])
+    (cons (nutrient nutrient-id name formula) value_ppm)))
+
+(define (get-nutrient-target-value nutrient-target nutrient)
+  (query-maybe-value (current-conn)
+                     (string-join
+                      '("SELECT value_ppm"
+                        "FROM nutrient_values nv"
+                        "JOIN nutrient_value_sets nvs ON nvs.id = nv.value_set_id"
+                        "JOIN nutrient_targets nm ON nm.id = nvs.nutrient_target_id"
+                        "WHERE nm.id = $1 AND nv.nutrient_id = $2"))
+                     (nutrient-target-id nutrient-target)
+                     (nutrient-id nutrient)))
+
+(define (get-latest-nutrient-target-value nutrient)
+  (query-maybe-value (current-conn)
+                     (string-join
+                      '("SELECT value_ppm"
+                        "FROM nutrient_values nv"
+                        "JOIN nutrient_value_sets nvs ON nvs.id = nv.value_set_id"
+                        "JOIN nutrient_targets nm ON nm.id = nvs.nutrient_target_id"
+                        "WHERE nv.nutrient_id = $1"
+                        "ORDER BY nm.effective_on DESC"
+                        "LIMIT 1"))
+                     (nutrient-id nutrient)))
+
+
+;; UPDATE
+
+#; (define (update-nutrient-target! nutrient-target
+                                         #:effective-on [effective-on #f]
+                                         #:nutrient-values [nutrient-values '()])
+     (define nm-id (nutrient-target-id nutrient-target))
+     (define (nvs-id nm-id)
+       (query-maybe-row (current-conn)
+                        (select id
+                                #:from nutrient_value_sets
+                                #:where (= nutrient_target_id ,nm-id))))
+     (with-tx
+       (when effective-on
+         (query-exec (current-conn)
+                     (update nutrient_targets
+                             #:set [effective_on ,effective-on]
+                             #:where (= id ,id))))
+       (unless (null? nutrient-values)
+         (upsert-nutrient-values nm-id))
+       (get-nutrient-target #:id id)))
+
+#; (define (upsert-nutrient-values nutrient-target-id)
+  (define maybe-nvs-id (nvs-id nm-id))
+  (case maybe-nvs-id
+    [(#f)
+     (query-exec (current-conn)
+                 (insert #:into nutrient_values_sets
+                         #:set
+                         [nutrient_target_id ,id]))
+     (define new-nvs-id (nvs-id nm-id))
+     (query-exec (current-conn)
+                 (string-join
+                  '("INSERT INTO nutrient_values"
+                    "VALUES $1 $2 $3"
+                    ""))
+                 new-nvs-id
+                 )]
+    [else
+     (query-exec (current-conn)
+                 (update nutrient_target_values
+                         #:set   [value ,value]
+                         #:where (and (= target_id ,target-id)
+                                      (= nutrient_id    ,nutrient-id))))]))
+
+
+;; DELETE
+
+(define (delete-nutrient-target! nutrient-target)
+  (define id (nutrient-target-id nutrient-target))
+  (query-exec (current-conn)
+              (delete #:from nutrient_targets
+                      #:where (= id ,id))))
diff --git a/models/nutrient-value-set.rkt b/models/nutrient-value-set.rkt
new file mode 100644
index 0000000..5f3759a
--- /dev/null
+++ b/models/nutrient-value-set.rkt
@@ -0,0 +1,98 @@
+#lang racket
+
+(provide nutrient-value-set
+         nutrient-value-set?
+         nutrient-value-set-id
+         ;; nutrient-value-set-nm-id
+         ;; nutrient-value-set-nt-id
+         ;; nutrient-value-set-cr-id
+         ;; nutrient-value-set-fp-id
+         ;; SQL CRUD
+         (contract-out
+          [create-nutrient-value-set! (-> symbol?
+                                          exact-nonnegative-integer?
+                                          (listof (cons/c
+                                                   nutrient?
+                                                   number?))
+                                          void?)]
+          [get-nutrient-value-set (->* ()
+                                       (#:id exact-nonnegative-integer?
+                                        #:nutrient-measurement-id exact-nonnegative-integer?
+                                        #:nutrient-target-id exact-nonnegative-integer?
+                                        #:crop-requirement-id exact-nonnegative-integer?
+                                        #:fertilizer-product-id exact-nonnegative-integer?)
+                                       (or/c nutrient-value-set? #f))]))
+
+(require racket/contract
+         db
+         sql
+         "../db/conn.rkt"
+         "nutrient.rkt")
+
+(struct nutrient-value-set (id nm-id nt-id cr-id fp-id) #:transparent)
+
+
+;; CREATE
+
+(define (create-nutrient-value-set! type id nutrient-values)
+  (define nvs (case type
+                [(nutrient-measurement)
+                 (query-exec (current-conn)
+                             (insert #:into nutrient_value_sets
+                                     #:set [nutrient_measurement_id ,id]))
+                 (get-nutrient-value-set #:nutrient-measurement-id id)]
+                [(nutrient-target)
+                 (query-exec (current-conn)
+                             (insert #:into nutrient_value_sets
+                                     #:set [nutrient_target_id ,id]))
+                 (get-nutrient-value-set #:nutrient-target-id id)]
+                [(crop-requirement)
+                 (query-exec (current-conn)
+                             (insert #:into nutrient_value_sets
+                                     #:set [crop_requirement_id ,id]))
+                 (get-nutrient-value-set #:crop-requirement-id id)]
+                [(fertilizer-product)
+                 (query-exec (current-conn)
+                             (insert #:into nutrient_value_sets
+                                     #:set [fertilizer_product_id ,id]))
+                 (get-nutrient-value-set #:fertilizer-product-id id)]))
+  (for ([nv nutrient-values])
+    (match nv
+      [(cons n v)
+       (query-exec (current-conn)
+                   (insert #:into nutrient_values
+                           #:set
+                           [value_set_id ,(nutrient-value-set-id nvs)]
+                           [nutrient_id  ,(nutrient-id n)]
+                           [value_ppm    ,v]))])))
+
+
+;; READ
+
+(define (get-nutrient-value-set #:id [id #f]
+                                #:nutrient-measurement-id [nm #f]
+                                #:nutrient-target-id [nt #f]
+                                #:crop-requirement-id [cr #f]
+                                #:fertilizer-product-id [fp #f])
+  (define (where-expr)
+    (define clauses
+      (filter values
+              (list
+               (and id (format "id = ~e" id))
+               (and nm (format "nutrient_measurement_id = ~e" nm))
+               (and nt (format "nutrient_target_id = ~e" nt))
+               (and cr (format "crop_requirement = ~e" cr))
+               (and fp (format "fertilizer_product = ~e" fp)))))
+    (cond
+      [(null? clauses) ""]
+      [else (format "WHERE ~a" (string-join clauses " AND "))]))
+  (define query (string-join
+                 `("SELECT *"
+                   "FROM nutrient_value_sets"
+                   ,(where-expr)
+                   "ORDER BY id ASC"
+                   "LIMIT 1")))
+  (match (query-maybe-row (current-conn) query)
+    [(vector id* nm-id* nt-id* cr-id* fp-id*)
+     (nutrient-value-set id* nm-id* nt-id* cr-id* fp-id*)]
+    [#f #f]))
diff --git a/models/nutrient.rkt b/models/nutrient.rkt
new file mode 100644
index 0000000..5a32e70
--- /dev/null
+++ b/models/nutrient.rkt
@@ -0,0 +1,123 @@
+#lang racket
+
+(provide
+ ;; Struct definitions
+ nutrient
+ nutrient?
+ nutrient-id nutrient-name nutrient-formula
+ ;; SQL CRUD
+ (contract-out
+  [create-nutrient! (-> string? string? void?)]
+  [get-nutrients (->* ()
+                      (#:id      (or/c #f exact-nonnegative-integer?)
+                       #:name    (or/c #f string?)
+                       #:formula (or/c #f string?))
+                      (listof nutrient?))]
+  [get-nutrient (->* ()
+                     (#:id      (or/c #f exact-nonnegative-integer?)
+                      #:name    (or/c #f string?)
+                      #:formula (or/c #f string?))
+                     (or/c nutrient? #f))]
+  [update-nutrient! (->* (nutrient?)
+                         (#:name    (or/c #f string?)
+                          #:formula (or/c #f string?))
+                         (or/c nutrient? #f))]
+  [delete-nutrient! (-> nutrient? void?)]))
+
+(require racket/contract
+         db
+         sql
+         "../db/conn.rkt")
+
+(struct nutrient (id name formula) #:transparent)
+
+
+;; CREATE
+
+(define (create-nutrient! name formula)
+  (query-exec (current-conn)
+              (insert #:into nutrients
+                      #:set [canonical_name ,name] [formula ,formula])))
+
+
+;; READ
+
+(define (get-nutrients #:id [id #f]
+                       #:name [name #f]
+                       #:formula [formula #f])
+  (define (where-expr)
+    (define clauses
+      (filter values
+              (list
+               (and id (format "id = ~e" id))
+               (and name (format "canonical_name = ~e" name))
+               (and formula (format "formula = ~e" formula)))))
+    (cond
+      [(null? clauses) ""]
+      [else (format "WHERE ~a" (string-join clauses " AND "))]))
+  (for/list ([(id* name* formula*)
+              (in-query (current-conn)
+                        (string-join
+                         `("SELECT id, canonical_name, formula"
+                           "FROM nutrients"
+                           ,(where-expr)
+                           "ORDER BY id ASC")))])
+    (nutrient id* name* formula*)))
+
+(define (get-nutrient #:id [id #f]
+                      #:name [name #f]
+                      #:formula [formula #f])
+  (define (where-expr)
+    (define clauses
+      (filter values
+              (list (and id (format "id = ~e" id))
+                    (and name (format "canonical_name = ~e" name))
+                    (and formula (format "formula = ~e" formula)))))
+    (cond
+      [(null? clauses) ""]
+      [else (format "WHERE ~a" (string-join clauses " AND "))]))
+  (match (query-maybe-row (current-conn)
+                          (string-join
+                           `("SELECT id, canonical_name, formula"
+                             "FROM nutrients"
+                             ,(where-expr)
+                             "ORDER BY id ASC"
+                             "LIMIT 1")))
+    [(vector id* name* formula*)
+     (nutrient id* name* formula*)]
+    [#f #f]))
+
+
+;; UPDATE
+
+(define (update-nutrient! nutrient
+                          #:name [name #f]
+                          #:formula [formula #f])
+  (define id(nutrient-id nutrient))
+  (cond
+    [(and name formula)
+     (query-exec (current-conn)
+                 (update nutrients
+                         #:set [canonical_name ,name] [formula ,formula]
+                         #:where (= id ,id)))]
+    [name
+     (query-exec (current-conn)
+                 (update nutrients
+                         #:set [canonical_name ,name]
+                         #:where (= id ,id)))]
+    [formula
+     (query-exec (current-conn)
+                 (update nutrients
+                         #:set [formula ,formula]
+                         #:where (= id ,id)))]
+    [else (void)])
+  (or (get-nutrient #:id id)
+      (error 'update-nutrient! "No nutrient with id ~a" id)))
+
+
+;; DELETE
+
+(define (delete-nutrient! nutrient)
+  (query-exec (current-conn)
+              (delete #:from nutrients
+                      #:where (= id ,(nutrient-id nutrient)))))
diff --git a/storage/.gitignore b/storage/.gitignore
new file mode 100644
index 0000000..6e9bc0c
--- /dev/null
+++ b/storage/.gitignore
@@ -0,0 +1 @@
+*.sqlite3
\ No newline at end of file
diff --git a/tests/nutrient-measurement-model.rkt b/tests/nutrient-measurement-model.rkt
new file mode 100644
index 0000000..b0b053d
--- /dev/null
+++ b/tests/nutrient-measurement-model.rkt
@@ -0,0 +1,72 @@
+#lang racket
+
+(module+ test
+  (require rackunit
+           rackunit/text-ui
+           "../db/conn.rkt"
+           "../db/migrations.rkt"
+           "../models/nutrient.rkt"
+           "../models/nutrient-measurement.rkt")
+
+  (define measured-on "2025-09-01")
+
+  (run-tests
+   (test-suite
+    "Nutrient measurement model"
+    #:before (λ ()
+               (connect! #:path 'memory)
+               ;; (connect! #:path "test.sqlite3")
+               (migrate-all!)
+               (create-nutrient! "Nitrogen" "N")
+               (create-nutrient! "Phosphorus" "P")
+               (create-nutrient! "Potassium" "K"))
+    #:after (λ ()
+              (disconnect!))
+
+    (test-case "Create measurement with values"
+      (define nitrogen (get-nutrient #:name "Nitrogen"))
+      (define phosphorus (get-nutrient #:name "Phosphorus"))
+      (create-nutrient-measurement! measured-on (list
+                                                 (cons nitrogen 12.3)
+                                                 (cons phosphorus 4.5)))
+      (check-equal? (length (get-nutrient-measurements)) 1)
+      (define nm (get-nutrient-measurement #:measured-on measured-on))
+      (check-true (nutrient-measurement? nm))
+      (check-equal? (nutrient-measurement-measured-on nm) measured-on)
+      (define mvs (get-nutrient-measurement-values nm))
+      (check-equal? (length mvs) 2)
+      (check-equal? (cdr (assoc nitrogen mvs)) 12.3)
+      (check-equal? (cdr (assoc phosphorus mvs)) 4.5)
+      )
+
+    #;(test-case "Update a single measurement value"
+        (define nitrogen (get-nutrient #:name "Nitrogen"))
+        (define nm (get-nutrient-measurement #:measured-on measured-on))
+        (update-nutrient-measurement! nm #:nutrient-values (list (cons nitrogen 1.1)))
+        (define mvs (get-nutrient-measurement-values nm))
+        (check-equal? (length mvs) 2)
+        (check-equal? (cdr (assoc nitrogen mvs)) 1.1))
+
+    #;(test-case "Upsert measurement values"
+        (define nitrogen (get-nutrient #:name "Nitrogen"))
+        (define phosphorus (get-nutrient #:name "Phosphorus"))
+        (define potassium (get-nutrient #:name "Potassium"))
+        (define nm (get-nutrient-measurement #:measured-on measured-on))
+        ;; Upsert: set K=8.8 and change N to 10.0, keep P as-is
+        (update-nutrient-measurement! nm
+                                      #:nutrient-values (list
+                                                         (cons nitrogen 10.0)
+                                                         (cons potassium 8.8)))
+        (define mvs (get-nutrient-measurement-values nm))
+        (check-equal? (length mvs) 3)
+        (check-equal? (cdr (assoc nitrogen mvs)) 10.0)
+        (check-equal? (cdr (assoc potassium mvs)) 8.8)
+        ;; P should still be present at 4.5
+        (check-equal? (cdr (assoc phosphorus mvs)) 4.5))
+
+    (test-case "Delete measurement cascades its values"
+      (define nm (get-nutrient-measurement #:measured-on measured-on))
+      (delete-nutrient-measurement! nm)
+      (check-false (get-nutrient-measurement #:id (nutrient-measurement-id nm)))
+      (check-equal? (length (get-nutrient-measurements)) 0)
+      (check-true (null? (get-nutrient-measurement-values nm)))))))
diff --git a/tests/nutrient-model.rkt b/tests/nutrient-model.rkt
new file mode 100644
index 0000000..39a574c
--- /dev/null
+++ b/tests/nutrient-model.rkt
@@ -0,0 +1,76 @@
+#lang racket
+
+(module+ test
+  (require rackunit
+           rackunit/text-ui
+           "../db/conn.rkt"
+           "../db/migrations.rkt"
+           "../models/nutrient.rkt")
+
+  (run-tests
+   (test-suite
+    "Nutrient model"
+    #:before (λ ()
+               (connect! #:path 'memory)
+               (migrate-all!))
+    #:after (λ ()
+              (disconnect!))
+
+    (test-case "Create nutrients"
+      (create-nutrient! "Examplium" "Ex")
+      (check-equal? (length (get-nutrients)) 1)
+      (create-nutrient! "Ignorium" "Ig")
+      (check-equal? (length (get-nutrients)) 2))
+
+    (test-case "Read nutrient"
+      (define examplium (get-nutrient #:id 1))
+      (check-true (nutrient? examplium))
+      (check-equal? (nutrient-id examplium) 1))
+    
+    (test-case "Read nutrient by name"
+      (define examplium (get-nutrient #:name "Examplium"))
+      (check-true (nutrient? examplium))
+      (check-equal? (nutrient-name examplium) "Examplium"))
+
+    (test-case "Read nutrient by formula"
+      (define examplium (get-nutrient #:formula "Ex"))
+      (check-true (nutrient? examplium))
+      (check-equal? (nutrient-formula examplium) "Ex"))
+    
+    (test-case "Read inexisting nutrient"
+      (check-false (get-nutrient #:name "Inexistium")))
+
+    (test-case "Update nutrient name"
+      (define examplium (get-nutrient #:name "Examplium"))
+      (define examplium-nitrate
+        (update-nutrient! examplium #:name "Examplium Nitrate"))
+      (check-equal? (length (get-nutrients)) 2)
+      (check-equal? (nutrient-name examplium-nitrate) "Examplium Nitrate")
+      (check-equal? (nutrient-formula examplium-nitrate) "Ex"))
+
+    (test-case "Update nutrient formula"
+      (define examplium-nitrate (get-nutrient #:name "Examplium Nitrate"))
+      (define examplium-sulfate
+        (update-nutrient! examplium-nitrate #:formula "ExSO4"))
+      (check-equal? (length (get-nutrients)) 2)
+      (check-equal? (nutrient-name examplium-sulfate) "Examplium Nitrate")
+      (check-equal? (nutrient-formula examplium-sulfate) "ExSO4"))
+
+    (test-case "Update nutrient name and formula"
+      (define examplium-nitrate
+        (get-nutrient #:name "Examplium Nitrate"))
+      (define examplium-sulfate
+        (update-nutrient! examplium-nitrate
+                          #:name "Examplium Sulfate"
+                          #:formula "ExNO3"))
+      (check-equal? (length (get-nutrients)) 2)
+      (check-equal? (nutrient-name examplium-sulfate) "Examplium Sulfate")
+      (check-equal? (nutrient-formula examplium-sulfate) "ExNO3"))
+
+    (test-case "Delete nutrient"
+      (define examplium-sulfate (get-nutrient #:name "Examplium Sulfate"))
+      (delete-nutrient! examplium-sulfate)
+      (check-equal? (length (get-nutrients)) 1)
+      (define ignorium (get-nutrient #:name "Ignorium"))
+      (delete-nutrient! ignorium)
+      (check-equal? (length (get-nutrients)) 0)))))
diff --git a/views.rkt b/views.rkt
new file mode 100644
index 0000000..d78c370
--- /dev/null
+++ b/views.rkt
@@ -0,0 +1,152 @@
+#lang racket
+
+(provide index-page
+         new-measurement-page
+         fallback-page)
+
+(require web-server/formlets
+         "formlets.rkt"
+         "models/nutrient.rkt"
+         "models/nutrient-measurement.rkt")
+
+
+(define (page-template title body-xexpr)
+  `(html
+    (head
+     (meta ([charset "utf-8"]))
+     (meta ([name "viewport"] [content "width=device-width, initial-scale=1"]))
+     (title ,title)
+     ;; Bootstrap CSS
+     (link ([href "https://cdn.jsdelivr.net/npm/bootstrap@5.3.3/dist/css/bootstrap.min.css"]
+            [rel "stylesheet"]
+            [integrity "sha384-QWTKZyjpPEjISv5WaRU9OFeRpok6YctnYmDr5pNlyT2bRjXh0JMhjY6hW+ALEwIH"]
+            [crossorigin "anonymous"])))
+    (body
+     ,navbar
+     (div ([class "container"])
+          ,@body-xexpr)
+     ;; Bootstrap JS bundle
+     (script ([src "https://cdn.jsdelivr.net/npm/bootstrap@5.3.3/dist/js/bootstrap.bundle.min.js"]
+              [integrity "sha384-YvpcrYf0tY3lHB60NNkmXc5s9fDVZLESaAA55NDzOxhy9GkcIdslK1eN7N6jIeHz"]
+              [crossorigin "anonymous"])))))
+
+
+;; Page components
+
+(define navbar
+  '(nav ([class "navbar"])
+        (div ([class "container-fluid"])
+             (a ([class "navbar-brand"] [href "/"]) "FAPG")
+             (button ([class "navbar-toggler"]
+                      [type "button"]
+                      [data-bs-toggle "collapse"]
+                      [data-bs-target "#navbarNav"]
+                      [aria-controls "navbarNav"]
+                      [aria-expanded "false"]
+                      [aria-label "Toggle navigation"])
+                     (span ([class "navbar-toggler-icon"])))
+             (div ([class "collapse navbar-collapse"] [id "navbarNav"])
+                  (ul ([class "navbar-nav"])
+                      (li ([class "nav-item"])
+                          (a ([class "nav-link active"]
+                              [aria-current "page"]
+                              [href "/"])
+                             "Home"))
+                      (li ([class "nav-item"])
+                          (a ([class "nav-link"]
+                              [href "/about"])
+                             "About"))
+                      (li ([class "nav-item"])
+                          (a ([class "nav-link"]
+                              [href "/contact"])
+                             "Contact")))))))
+
+
+;; Page helpers
+
+(define (round n number)
+  (~r number #:precision n))
+
+
+;; Pages
+
+(define (index-page measurements)
+  (page-template
+   "Ferti"
+   `((h1 ([class "display-1 mb-3"]) "Ferti")
+     (a ([class "btn btn-primary mb-3"] [href "/target/new"]) "Créer une cible")
+     (table ([class "table"])
+            (tr (th "Nutriment")
+                (th ([class "text-end"]) "Dernière Cible")
+                (th ([class "text-end"]) "Dernier Relevé")
+                (th ([class "text-end"]) "Delta (%)"))
+            ,@(for/list ([n (get-nutrients)])
+                (define latest-target (+ (get-latest-nutrient-measurement-value n) 1))
+                (define latest-value (get-latest-nutrient-measurement-value n))
+                (define delta (* 100
+                                 (/ (- latest-target latest-value)
+                                    latest-target)))
+                `(tr (td ,(nutrient-name n))
+                     (td ([class "text-end"]) ,(round 2 latest-target))
+                     (td ([class "text-end"]) ,(round 2 latest-value))
+                     (td ([class "text-end"]) ,(round 1 delta)))))
+
+     (a ([class "btn btn-primary mb-3"] [href "/measurement/new"]) "Ajouter un relevé")
+     (table ([class "table table-striped"])
+            (tr (th "Date")
+                (th ([class "text-end"]) "N")
+                (th ([class "text-end"]) "P")
+                (th ([class "text-end"]) "K"))
+            ,@(for/list ([m measurements])
+                (define measured-on (nutrient-measurement-measured-on m))
+                (define-values (n p k)
+                  (apply values
+                         (for/list ([nutrient '("Nitrate Nitrogen" "Phosphorus" "Potassium")])
+                           (define n (get-nutrient #:name nutrient))
+                           (define mnv (get-nutrient-measurement-value m n))
+                           (if (real? mnv)
+                               (round 2 mnv)
+                               "—"))))
+                `(tr (td ,measured-on)
+                     (td ([class "text-end font-monospace"]) ,n)
+                     (td ([class "text-end font-monospace"]) ,p)
+                     (td ([class "text-end font-monospace"]) ,k)))))))
+
+(define (new-measurement-page)
+  (page-template
+   "Nouveau relevé"
+   `((h1 ([class "display-1 mb-3"]) "Nouveau relevé")
+     (div ([class "mb-3"] [style "max-width: 30em"])
+          (form
+           ([action "/measurement/create"]
+            [method "POST"])
+           ,@(formlet-display (measurements-formlet)))))))
+
+(define (fallback-page request-code)
+  (page-template
+   (format "Réponse: ~a" request-code)
+   `((h1 ([class "display-1 text-danger"]) ,(number->string request-code))
+     (p ,(fallback-message request-code))
+     (a ([href "/"]) "Revenir à la page d'accueil"))))
+
+(define (fallback-message request-code)
+  (string-join
+   `("Bonjour, je suis votre serveur."
+     ,(format "J'ai répondu '~a'" request-code)
+     "et"
+     ,(case (string-ref (number->string request-code) 0)
+        [(#\4) "c'est de votre faute, malheureusement."]
+        [(#\5) "c'est de ma faute, pardonnez-moi."]
+        [else "je ne sais pas qui est en tort."])
+     ,(case request-code
+        ;; Client errors
+        [(400) "Votre requête ne fait pas sens."]
+        [(401) "Vous n'avez pas vérifié votre identité."]
+        [(403) "Vous n'avez pas le droit de consulter cette page."]
+        [(404) "Vous avez demandé de consulter une page qui n'existe pas."]
+        ;; Server errors
+        [(500) "Je suis dans une situation que je ne sais pas gérer, et ne peux vous en dire davantage."]
+        [(502) "Un tiers ne m'a pas transmis les informations nécessaires pour répondre à votre requête."]
+        [(503) "Je ne peux pas vous aider, il se peut que je sois momentanément surchargé. Revenez plus tard."]
+        ;; Fallback message
+        [else (format "Je ne sais pas encore interpréter le code ~a." request-code)]))))