Neco 2020 Agricultural Science Question 4

Soil test results for a field are: available nitrogen \(20\) kg ha\(^{-1}\), phosphorus \(8\) kg ha\(^{-1}\) (as \(P_2O_5\)), and potassium \(15\) kg ha\(^{-1}\) (as \(K_2O\)). The target maize crop requires \(150\) kg ha\(^{-1}\) N, \(60\) kg ha\(^{-1}\) \(P_2O_5\), and \(80\) kg ha\(^{-1}\) \(K_2O\).\n\nFertiliser options are: urea (46% N), single superphosphate (20% \(P_2O_5\)), muriate of potash (60% \(K_2O\)), and a blended NPK fertiliser 20‑10‑15 (percent by weight).\n\nDetermine the amounts (kg ha\(^{-1}\)) of the blended NPK, urea, single superphosphate and muriate of potash that should be applied to meet the crop nutrient requirements exactly while minimising the total fertiliser applied.