Adubação nitrogenada, fosfatada e emissões de metano e óxido nitroso na cultura do arroz irrigado por sulco

Abstract

Soybean cultivation in lowlands provides improvement in soil chemical and microbiological attributes, however, one of the main limitations for legume cultivation in this environment is water excess. Thus, a viable alternative for both crops is the use of the furrow-ridge system, which provides uniformity and high performance of the soybean crop, avoiding water excesses and plant death. Subsequently, the cultivation of irrigated rice in the furrow-ridge system will not form a uniform water depth and this impacts the redox condition of the soil and the dynamics and availability of nutrients in the soil, in particular nitrogen and phosphorus. In addition to the impact on nutrient availability, the variation in soil redox conditions along the length of the rice irrigation furrow should promote variations in the potential for methane (CH4) emissions and intensify the nitrification and denitrification processes, which have the oxide nitrous (N2O) as an intermediate product. Thus, the objective of this work was to evaluate ammonia volatilization, yield components, methane and nitrous oxide emission and grain yield of irrigated rice in a furrow-ridge system in rotation with soybean under nitrogen and phosphorus levels. The experiment was carried out under field conditions at the Ricetec Experimental Station, crop 2020/21 in Capão do Leão, RS, taking advantage of the furrows and ridges infrastructure established for soybeans cultivated in rotation in the previous season. A rice hybrid XP117 RiceTec with a cycle of 130 days was used. The experiment consisted of a 3 x 4 double factorial, where factor 1 consisted of the portion of the along the irrigationfurrows (upper, intermediate and lower) and factor 2, the dose of N (0, 60, 120 and 180 kg ha -1) and P2O5 (0, 30, 60, 120 kg ha-1) for irrigated rice. Furrow irrigated rice is more responsive to nitrogen fertilization in the lower portion of the furrow and less responsive to phosphorus due to the greater availability of the nutrient in the soil. The total N2O emission associated with rice cultivation is higher in the upper portion of the crop, in contrast, the CH4 emission is higher in the lower portion of the crop, where the soil is kept flooded. Thus, furrow irrigation reduces the emission of greenhouse gases, constituting a promising alternative to reduce the partial Global Warming Potential in rice production systems in southern Brazil.