Production Potential and Nitrogen Fractionation of Sugarcane- Based Cropping System as Influenced by Planting Materials and Nitrogen Nutrition

摘要

A field experiment was conducted during the spring season of 2013-2017 at Pusa to assess the effect of various planting materials (three bud setts, poly bag raised settlings and bud chip raised settlings) and nitrogen levels (0, 75, 100, 125 and 150% N/ha) on productivity and nitrogen fractionation of sugarcane (Saccharum spp. hybrid complex) plant-ratoon system. Amongst the planting materials, three bud setts and poly bag raised settlings both being at par produced higher dry matter and cane diameter compared with bud chip raised settlings in plant and ratoon crops. The maximum sugarcane yield (83.5 and 76.2 t/ha) was recorded under three bud setts which was found at par with poly bag raised settlings in plant and ratoon crops, respectively. Three bud setts gave significantly higher net returns, B:C ratio and N uptake over others, with greater N-use efficiency (167.2 and 147.9 kg cane/kg N applied) and apparent N recovery (59.1 and 49.7%) in plant and ratoon crops, respectively. The higher nitrogen levels were associated with higher growth, yield attributes and yield of plant and ratoon crops of sugarcane than those of lower nitrogen levels. The highest cane yield (92.9 and 84.4 t/ha), net returns (Rs. 1,43,900 and 1,45,300 /ha; 1US$=INR similar to 70.00) and B:C ratio (1.57 and 2.08) were obtained with 150% of recommended N, which was statistically at par with 125% of recommended N and significantly higher over lower levels in plant and ratoon cane, respectively. Similar trend was also observed for N uptake. The maximum N-use efficiency (176.3 and 149.2 kg cane/kg N applied) and apparent N recovery (58.6 and 50.5%) were observed at 125% of recommended N, and thereafter, it decreased with the increase in the N level in plant and ratoon crops, respectively. The relative contents of these fractions were in order: non-hydrolysable N amino acid-N unidentified -N hydrolysable NH4+ -N exchangeable NH4+ -N hexoseamine -N NO3- -N. All the fractions except NO3- -N were in dynamic equilibrium as indicated by significant and positive correlation amongst them. Correlation studies between plant parameters of sugarcane and soil N fractions indicated that the yield of sugarcane and sugar yield were significantly and positively correlated with all N fractions except NO3- -N.