UPLAND RICE IN ROTATION WITH SOYBEAN

Abstract

The objective of this study was to evaluate the performance of upland rice grown in soils of continued soybean cultivation, under different tillage systems and nutrient doses, and the effects of these treatments on the subsequent soybean yield. The treatments were three doses of macronutrients (zero, 100 kg.ha^-1, and 300 kg.ha^-1 of commercial formula 4-30-16), without or with micronutrient fertilization (20 kg.ha^-1 of zinc sulfate, 50 kg.ha^-1 of FTE BR 12, and 50 kg.ha^-1 of iron sulfate). The experiments were carried out under three soil tillage systems (heavy disk harrow, chisel plow, and moldboard plow). A joint analysis showed that the moldboard plow system provided average rice grain yield of 3077 kg.ha^-1, 9% and 26% higher than those of chisel plow (2823 kg.ha^-1), and heavy disk harrow (2440 kg.ha^-1), respectively. Macro and micronutrient treatments did not significantly affect rice grain yield. The different soil tillage systems and nutrient doses applied to rice crop did not significantly affect soil macro and micronutrient levels and pH, nor did it affect the soybean yield when the crop was planted in the same area in the succeeding year. Average soybean yield was approximately 2600 kg.ha^-1. As far as profitability and sustainability are concerned, it was recommended that rice grown after soybean crop, under moldboard plowing, should be fertilized with 100 kg.ha^-1 of commercial formula 4-30-16, without micronutrient fertilization.

KEY-WORDS: Moldboard plow; chisel plow; heavy disk harrow; macronutrient; micronutrient.