EFFICIENCY OF NITROGEN USE IN RICE-WHEAT CROPPING SYSTEM IN SALT-AFFECTED SOILS WITH CONTRASTING TEXTURE

Considerable nitrogen (n) losses lead to lower n use-efficiency (nue) in salt-affected soils due to leaching and volatilization. a lysimeter experiment was conducted to determine nue in two salt-affected soils of different texture (clay loam and sandy clay loam), using various rates of n fertilizer. the experiment used a three replicate completely randomized design. the treatments included five n rates, three higher (15, 30 and 45%) and two lower (15 and 30%) than recommended rate of 125 kg ha^-1. additionally, gypsum was added at 50 and 100% of soil gypsum requirement (sgr) in both salt-affected soils. maximum paddy and straw yields were recorded for sandy clay loam saline-sodic soil collected from village 132, faisalabad (132s), using 45% higher n + gypsum at 100% sgr. whereas clay loam saline-sodic soil, from village 84, faisalabad (84s) at 30% higher n rate with gypsum at 50% sgr gave the highest paddy and straw yields. in general, the clay loam soil produced more paddy yield than the sandy clay loam soil at similar n fertilization. in the sandy clay loam soil, gypsum at 100% sgr along with a 30% higher n rate increased the grain and straw yields of wheat significantly (p < 0.05) compared to application of gypsum at only 50% sgr. nitrogen use efficiency was the highest with 45% higher n (n145) with gypsum applied @ 100% sgr compared to 50% sgr in severe salt-affected (sandy clay loam) soil during rice crop. from marginal clay loam saline-sodic soil, nue remained higher with n130 along with gypsum @ 100% sgr which was statistically on par with gypsum @ 50% sgr. it was concluded that nue remained highest with n130 and n145 with gypsum applied @ 100% sgr during rice crop from clay loam and sandy clay loam soils, respectively. moreover, nue was higher at recommended n fertilization when gypsum was applied at 100% sgr during wheat crop which was also attributed to improved soil chemical properties, i.e. phs, ece and sar.