Effect of continuous application of fertilizer nutrients on the long term productivity of a rice cropping system

Abstract

Field experiments conducted for a period of seven years to study the effect of continuous application of fertilizer nutrients on the long term productivity of a rice based cropping system revealed that nitrogen application increased grain yield in all the seasons for a period of seven years. Both the physical and economic optimum dose of N decreased @ 4.06 and 3.7% per season, respectively. Nitrogen application @ zero and 120 kg/ha per season continuously over a period of five years, decreased the grain yield @ 1.47 and 1.28 g/ha/year, respectively. But application of N @ 40 kg/ha during the same period increased grain yield 6 1.22 q/ha/year. The productivity of plots applied with N @ 80 kg/ha remained stable. The study clearly revealed the possibility of skipping P for four years and K for seven years in soils containing medium amounts of these nutrients. Application of N at optimum dose is important to maintain the long term productivity of a rice based cropping system involving rice-rice-fallow.