Neco 2020 Geography Question 11

An agriculturalist rotates three crops over a three‑year cycle: maize, soybean and wheat. The average nutrient removal per hectare for each crop is: - Maize: 120 kg N, 40 kg P₂O₅, 30 kg K₂O - Soybean: 60 kg N is fixed from the atmosphere, so the net removal is 30 kg N; it also removes 20 kg P₂O₅ and 15 kg K₂O - Wheat: 80 kg N, 35 kg P₂O₅, 25 kg K₂O Each year the farmer applies \(150\) kg ha\(^{-1}\) of a mixed fertilizer that contains \(15\)% N, \(10\)% P₂O₅ and \(12\)% K₂O. Over the three‑year cycle the farmer wants the net soil nitrogen balance to be zero (i.e., total nitrogen removal equals total nitrogen added). Determine the amount of pure nitrogen fertilizer (100 % N) that must be applied in the maize year to achieve this balance. Also compute the total cost if the mixed fertilizer costs \(\text{₦}400\) per kg and the pure nitrogen fertilizer costs \(\text{₦}900\) per kg.