Manejo do trevo persa e da adubação nitrogenada para o arroz irrigado: dinâmica de nutrientes no solo e resposta de plantas

Abstract

Brazilian rice production predominates in the south of the country. In this region, most lowland soils cultivated with irrigated rice traditionally remain fallow in the autumn/winter period, due to its hydromorphism and difficulty to find cover plants that adapt to this characteristic. In recent years, there has been an increase in the adoption of Persian clover (Trifolium resupinatum L.). However, little is known about the benefits that this winter legume can bring to the system. In this sense, the objective of this work was to evaluate in Chapter 1: the availability of nutrients in the soil, plant nutrition and the productivity of irrigated rice grains in succession to the Persian clover in the autumn/winter period in a Albaqualf; and, in Chapter 2: to evaluate the effect of times of chemical management of the persian clover on the development components of the irrigated rice and the availability of nutrients in the soil solution. The following treatments were used: Chapter 1: under field conditions, persian clover and fallow, composed of 4 doses of N, being: 0, 60, 120, 180 kg N ha-1 and Chapter 2: Greenhouse experiment with persian clover and fallow, with 4 times of chemical management, (0, 15, 30, 45) days before sowing of irrigated rice, with two doses of N, 0 and 150 kg N ha-1 . The cultivation of persian clover in the winter period increases the availability of mineral N in the soil, reducing by 23% the dose of maximum economic efficiency of N for the rice hybrid established in succession. The chemical management of persian clover 45 days before rice sowing reduced the amount of dry matter in the autumn/winter period by 58%, while its chemical management closer to rice sowing results in a higher mineral N content in the solution. from soil. The cultivation of this legume increases the availability of mineral N in the soil solution by 108% in the vegetative period of rice development. The longest intervals of chemical management also increased the phosphorus and potassium content in the soil solution in the vegetative period of rice plant development. Thus, the use of the winter legume in irrigated rice production systems in southern Brazil is a promising alternative, as it has adaptation to excess water, high biomass production capacity and contributes to the contribution of N to the soil with minor effects need for nitrogen fertilization in rice. This context allows for greater economic profitability to rice farmers and less potential impact on the environment due to the lower N input.