Getting maximum benefits from cereals do not lie in reducing N-rate and its number of splits but lowering cost per unit cereal production through higher yields. Field experiments were conducted on maize (Zea mays L.) at the New Developmental research Farm of NWFP (Northwest Frontier Province) Agricultural University Peshawar-Pakistan during 2002-03 and 2003-04 in order to investigate effects of variable rates of N and its time of application on the partial factor productivity (PFPN), agronomic efficiency (AEN), net returns (NR), value-cost ratio (VCR) and marginal returns (MR). The 2 x 3 x 6 factorial experiment was designed 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) applied to main plots, while six split application of N in different proportions were applied to subplots in two equal (T1), three equal (T2), three unequal (T3), four equal (T4), five equal (T5) and five unequal splits (T6) at sowing and with 1st, 2nd, 3rd and 4th irrigation at two wk intervals. Maize ranked first with maximum PFPN, AEN, NR, VCR and MR at higher than at lower plant density, and the increase in all these parameters studied in the experiments was more in 2003-04 as compared to 2002-03. Both PFPN and AEN showed negative relationship with increase in N rates and the cast that vary, but NR, VCR and MR showed positive relationship with increase in N rates and the cost that vary. Among time of N application, maximum PFPN, AEN, NR, VCR and MR were calculated when N was applied in five equal splits (T5) almost comparable with T4 and T6 but was more economical when compared with T1, T2, and T3. In conclusion, the findings suggest that growing maize at D2 applied with N3 in four to five splits is more economical in the wheat-maize cropping system of NWFP.
