Neco 2017 Agricultural Science Question 7

A farmer has 10 ha of land. He can either grow maize continuously for two years, applying \(150\) kg N ha\(^{-1}\) fertilizer each year, or adopt a two‑year rotation of maize (year 1) and cowpea (year 2). Maize yields \(5\) t ha\(^{-1}\) and needs \(120\) kg N ha\(^{-1}\); cowpea yields \(2\) t ha\(^{-1}\) and fixes \(40\) kg N ha\(^{-1}\). Grain nitrogen contents are \(1.2\%\) for maize and \(2.5\%\) for cowpea. In the rotation, maize receives only \(80\) kg N ha\(^{-1}\) fertilizer in year 1 and cowpea receives no fertilizer in year 2. Calculate the total net nitrogen surplus (fertilizer + fixation - removal by harvest) over the two‑year period for each option and state which option gives the higher surplus.