INTERVALO HÍDRICO ÓTIMO COMO INDICADOR DE QUALIDADE FÍSICA DE UM LATOSSOLO VERMELHO, APÓS 26 ANOS DE ADOÇÃO DE SISTEMAS DE INTEGRAÇÃO LAVOURA-PECUÁRIA

Abstract

The least limiting water range (IHO) is an indicator of soil physical quality widely attested in the literature, but its efficiency is still questioned. In addition, the adoption of this indicator in integrated systems of long-term agricultural production, with more than 20 years, is still scarce. In this sense, the objective was to evaluate the least limiting water range as an indicator of physical quality in a Red Latosol Distrophic soil submitted to systems of preparation and integrated management of production, after 26 years of implantation, as well as the influence of resistance adjustments to critical penetration in soil water relations. The experiment was carried out in an area whose systems were implemented in 1991, at Embrapa Cerrados, in Planaltina - DF. Eight treatments were evaluated for soil preparation and management systems with four replications, including: Continuous pasture with grass and animal grazing (PAST); Integrated crop-livestock system, crop phase conventional tillage (SIL-C); Integrated crop-livestock system, crop phase under no-till (SIL-D); Integrated livestock-crop systems, pasture phase with animal grazing under no-till (SIP-D); Continuous crop under conventional tillage (LAV-C); Continuous crop under no-tillage (LAV-D); Native Cerrado (CN); Handling corridor (COR). Deformed and undisturbed soil samples were collected in three layers, 0.00-0.05; 0.05-0.10 and 0.10-0.20 m, and there were evaluated the density, porosity, soil water retention curve (CRA) and penetration resistance (CRP) for subsequent elaboration of the IHO. In addition to the fragmented layers, the single layer was considered 0.00-0.20 m, using all samples. For this, the SAS statistical program was used in the adjustment of CRA and CRP models. For critical reflection of IHO efficiency in the soil physical quality evaluation, the criterion was the use of the critical penetration resistance (PR) value, in all treatments of 2.0 MPa, since this value is widely adopted, independent of the use history and soil management and, for comparison purposes, variable according to the intrinsic characteristics of each management evaluated and considering, therefore, the cited literature, in which the PR values for the conventional system is 1.5 MPa; 2.0 MPa for non-conservation systems and 3.5 MPa for conservation systems. It was observed that the CRA and CRP presented in-depth equality, so the IHO, in the initial layers, had specific behaviors for each treatment in relation to its critical limits, but in depth (0,10-0,20 m), they were similar to the IHO boundaries of said layer. Animal trampling systems showed limitations to IHO with critical RP of 2.0 MPa, however, the same was not observed when adopting RP of 3.5 MPa. The lowest soil densities were observed in the surface layer, the result of which can be attributed to the greater presence of organic matter in this layer, except for LAV-C and COR.