DETERMINATION OF THE ECONOMIC AND PHYSIC OPTIMAL NITROGEN RATES FOR THE CORN CROP WITH THREE RESPONSE MODEL, AZUERO, PANAMA, 2000-2002.

Abstract

A corn plantation experiment was carried out on 15 sites of the Azuero Region during 2000 to 2002. The objective of this experiment was to determinate the optimal nitrogen level, with a density of 6.25 plants/m² and a Nitrogen distribution of 10% at the planting date, 40% at 20 days after planting (dap) and 50% at 37 dap. A Complete Randomized Block Design with four replications was used. The evaluated treatments were nitrogen rates from 0 to 350 kg N/ha, the experimental plots counted by five rows of 5.2 m of length. For the calculation of optimal Nitrogen rate, it was considered the Minimal Return Rate of 15%, a price of B/.0.187/kg of corn and a cost of B/.0.65/kg of N (application cost was included). Three methods were evaluated to estimate the economic optimal linear in each one of the sites (Linear-Plateau, Quadratic-Plateau and Quadratic model). The Line-Plateau model when overestimating the near yields to the N quantity of change it spread to calculate very low rates. On the contrary, the Quadratic Model estimated very high rates. The Quadratic-Plateau Model it turned out to be the one that but it was ajusted to the results in field; consequently, it was identified as the most appropriate economic Nitrogen rate. The response to the application of this element was very varied where were sites where there were not response and sites where the best economic rates were around the 200 kg N.