Evaluation of agronomic and economic effects of nitrogen and phosphorus additions to green pepper with drip fertigation

Drip fertigation is an effective way in splitting soluble fertilizer application to simultaneously meet water and nutrient demands of multi-harvested green pepper (Capsicum annuum L.). However, fruit yield and the profitability of green pepper can be constrained, if nutrients are either insufficiently or excessively supplied. A 3-yr experiment was conducted to assess both agronomic and economic effects of fertilizer N and P addition for green pepper grown under drip fertigation. Both fruit yields, including total and marketable, and net economic return responded quadratically to fertilizer N rate. The 3-yr average maximum marketable yield of 38 Mg ha-1 was achieved at the N rate of 227 kg N ha-1 The economic optimum N rate was identical to the one required for the production of maximum marketable yield, due to the large price ratio of green pepper to fertilizer N. Nitrogen use efficiency and N agronomic efficiency decreased as N rate increased. The amount of fertilizer N required for production of each megagram of marketable fruit yield increased with the level of yield, with an average of 6.0 kg N Mg-1 fruit across the 3 yr at the maximum marketable yield. Fertilizer P did not affect selected variables, except for both total and marketable fruit yields that increased linearly with increases in P rate in one of the 3 yr. The results suggested that an increase in the optimum N rate to 227 kg N ha-1 is needed to maximize the profitability of green pepper production with drip fertigation. © 2010 by the American Society of Agronomy.