Productivity, economics and nitrogen-use efficiency of sweet corn (Zea mays saccharata) as influenced by planting geometry and nitrogen fertilization

A field experiment was conducted during rainy season of 2007 and 2008 at Wadura, Sopore, to study the effect of crop geometry (60 cm 15 cm, 60 cm 20 cm, 60 cm 25 cm, 60 cm 30 cm) and nitrogen levels (0, 30, 60, 90, 120 and 150 kg N/ha) on yield, yield attributes, nitrogen use efficiency, crop productivity, economics and nitro- gen balance of sweet corn ( Zea mays saccharata Sturt). Plant height, weight of green cobs, number of kernel/cob, 1,000-kernel weight and kernel recovery increased as the inter-plant spacing was increased from 15 to 30 cm, while the number of cobs/ha, plant dry weight and bareness increased with a decrease inter-plant spacing from 30 cm to 15 cm. The maximum cob yield was recorded at 60 cm 20 cm spacing which was higher than 60 cm 25 cm planting geometry. A decrease in planting spacing from 60 cm 20 cm to 60 cm 15 cm caused 33.2% reduc- tion in cob yield. The kernel yield and crop productivity, crop profitability, net returns, nitrogen uptake and nitrogen use efficiency were also higher at 60 cm 20 cm planting spacing. Increasing nitrogen levels upto 120 kg/ha showed marked improvement in plant height, plant dry weight, number of cobs/ha, number of kernels/cob, 1000- kernel weight, green cob weight and kernel recovery, which consequently improved the yield and return. While Barrenness in cobs also declined with increasing nitrogen levels. Highest nitrogen uptake, total availability and ac- tual residual soil nitrogen contents were observed at 150 kg N/ha. Increasing nitrogen levels progressively re- duced agronomic and physiological nitrogen use efficiency. A level of 125.7 kg N/ha was found to be economic optimum with green cob yield of 14.21 t/ha and a response of 7.55 t/ha. The response to optimum level of N was found to be 60.09 kg green cob/kg N applied. Hence, crop geometry of 60 cm 20 cm with nitrogen level of 120 kg/ha should be adopted to obtain the maximum green cob yield and net profit from sweet corn in Kashmir valley.