Conteúdo de água em um latossolo e a relação com a produtividade de grãos de soja sob plantio direto

Abstract

The productivity of plants increases when the water content in the soil is maintained at appropriate levels. Thus, in compacted soil, excess or reduced water content in the soil may limit the development of plants. Based on the methodology of least limiting water range (LLWR) is to find the value of critical bulk density (Bdcritical) when the LLWR = 0, that is, from which the development of the plants may be reduced. In this sense, aimed to evaluate the water content in an Oxisol in the explored profile by soybean roots during the crop cycle and check the frequency and intensity with which the water was out of the LLWR limits and also check if the values "Bdcritical" were limiting productivity under no-till soybeans 10 years. 117 disturbed soil samples were collected in an irregular mesh in layers of 0- 0.10; 0.10- 0.20; 0,20- 0,30 and 0,30- 0,40 m in stages V1, V2, V4, R1, R3, R5.3 and R7.2 of culture. Concomitant, plant samples were collected. It was found that on the basis of IHO graphics, limitations on the plant crop can be more intense in the layers of 0- 0.10 0.10- 0.20 m, especially if the soil is subjected to heavy rain or the absence of rain. However, there was not a negative correlation between the rate of relative water accumulation in the soil with leaf area index and the growth rate of the culture, and also there was not difference between the average soybean yield to values below and above the Bdcritical in layers of 0- 0.10 and 0.10- 0.20 m. Whatever the outcome, it is recommended to determine the variability of soil density, because the rainfall distribution can vary of a crop to another and the water content in the soil can stay out of the "LLWR" and that can be harmful especially in phase of soybean flowering.