diff --git a/frontend/src/components/Applications/ApplicationPlanModal.js b/frontend/src/components/Applications/ApplicationPlanModal.js
index c9d4b01..f1a3ca6 100644
--- a/frontend/src/components/Applications/ApplicationPlanModal.js
+++ b/frontend/src/components/Applications/ApplicationPlanModal.js
@@ -275,15 +275,21 @@ const ApplicationPlanModal = ({
         return;
       }
 
+      // Build payload with correct field names and handle xor validation
       const payload = {
-        productId: currentProductForSettings.isShared ? currentProductForSettings.id : null,
-        userProductId: !currentProductForSettings.isShared ? currentProductForSettings.id : null,
         equipmentId: parseInt(selectedEquipmentId),
-        setting1: parseFloat(spreaderFormData.setting),
+        settingValue: spreaderFormData.setting.toString(), // Must be string according to schema
         rateDescription: spreaderFormData.rateDescription || null,
         notes: spreaderFormData.notes || null
       };
 
+      // Add either productId OR userProductId, not both (xor validation)
+      if (currentProductForSettings.isShared) {
+        payload.productId = currentProductForSettings.id;
+      } else {
+        payload.userProductId = currentProductForSettings.id;
+      }
+
       const response = await fetch('/api/product-spreader-settings', {
         method: 'POST',
         headers: {