Rate and Timing Of Nitrogen Application Influence Partial Factor Productivity and Agronomic NUE In Maize (Zea mays L) Planted At Low and High Densities On Calcareous Soil In Semiarid Conditions.

Field experiments were conducted to investigate impact of nitrogen (N) rate and time (splits) on partial factor productivity (PFP) and agronomic N use efficiency (NUE_A) of maize (Zea mays L.) at the New Developmental Research Farm of The University of Agriculture Peshawar-Pakistan, during two consecutive years in summer 2002 and 2003 under low and high plant densities. The 2 x 3 x 6 factorial experiment having two plant densities (D₁ = 60,000 and D₂ = 100,000 plants ha^-1) and three N levels (N₁ = 60, N₂ = 120 and N₃ = 180 kg N ha^-1) in the main plots, and six ways of N applications (viz. two equal, three equal, three unequal, four equal, five equal, and five unequal splits) in sub-plots. The PFP and NUE_A of maize were highest at high than at low plant density. The increase both in PFP and NUE_A was more during the second than first year. Both PFP and NUE_A showed negative relationship with increase in N rate. The highest PFP and NUE_A were obtained when N was applied in five equal splits but these results were comparable with treatments receiving N in four equal and five unequal splits.  These results suggest that application of N in four or five splits under high plant density increasing both PFP and NUE_A as well as grain yield of maize under calcareous soils.