Methods of planting and irrigation at various levels of nitrogen affect the seed yield and water use efficiency in transplanted oilseed rape (Brassica napus L.)

The ridge planting of cotton at row spacing of 67.5 cm is widely used in the southwest region of Indian Punjab. Generally, transplanted oilseed rape (Brassica napus) fits well to grow after the harvest of cotton. Transplanting reduces days to maturity and results in higher seed yield. The present study was undertaken to determine if rape could be transplanted onto the cotton ridges thereby saving time and resources. The field experiments were conducted for 3 years with four methods of planting, three methods of irrigation and three levels of N (100, 125 and 150 kg/ha). The four methods for transplanting were: flat with 45 cm row spacing, flat with 67.5 cm row spacing, 67.5 cm ridge and bed planting. The three methods of irrigation were: flooding for flat with 45 and 67.5 cm row spacing; each furrow and each bed irrigation for ridge and bed planting; ridge with alternate furrow irrigation. The results revealed that increase in N from 100 to 150 kg/ha increased the seed yield significantly during 2 years. For 3 years, ridge transplanting reduced, on average, water applied by 30% for each furrow and 47% for alternate furrow irrigation as compared to 45 cm row spacing in flat method without any loss in seed yield. The corresponding increase in WUE was 27 and 34%. In bed planting, there was a 35% saving in water resulting in 32% increase in WUE. It is concluded that after harvest of cotton that the same ridges can be used for transplanting oilseed rape thereby reducing the quantity of irrigation water applied as well as the energy otherwise required for preparing the seed bed.