Work out dap requirement instantly with clear inputs, formula shown and shareable results.
Di-ammonium phosphate is 18-46-0, so it is sized on the phosphate requirement: DAP = P2O5 need / 0.46. It also delivers 18% nitrogen, and that nitrogen must be credited against the N plan by deducting the equivalent urea, otherwise the crop is over-fertilised with N.
DAP quantity
DAP (kg) = P2O5 required / 0.46
Nitrogen credit
N supplied = DAP x 0.18; urea deduction = N supplied / 0.46
Phosphate lost in runoff drives eutrophication of lakes and rivers. Do not exceed soil-test recommendations and keep applications away from watercourses.
As a basal dose placed near the seed row at sowing. Phosphate moves very little in soil, so broadcasting it on the surface leaves much of it out of reach of young roots.
Yes — SSP is 16% P2O5 plus sulphur and calcium, so you need about 2.9 times the weight of DAP for the same phosphate, and the nitrogen credit disappears.