Atributos físicos de um latossolo sob gramíneas em experimento de longa duração no brejo paraibano

Abstract

The substitution of native vegetation by perennial pastures has caused an imbalance in the agroecosystem, having as a result of the degradation of these soils, Besides that, the use of grasses has become an alternative to circumvent this problem. Thus, the objective of this work was to evaluate physical attributes in an Latossolo (Oxisol) under grasses in a long-term experiment in the Brejo Paraibano. The experiment was installed in the experimental area of Centro de Ciências Agrárias in sand-PB (6°58'12''S; 35°41'15''W and altitude of 620 m). The experimental design was randomized blocks, with five treatments one more, and with four replications. The treatments were the following: T1-Brachiaria decumbens (BD), T2-Brachiaria brizantha (BB), T3-Brachiaria humidicola (BH), T4-MG5 Brachiaria brizantha cv Victory (BBMG5), T5-without coverage (SC) and native forest (MT). Were collected in the center of each plot disturbed and undisturbed samples of layers of 0.0-0.10, 0.10-0.20 and 0.20-0.30 m depth. The physical characterizations were performed at the Laboratory of Soil Physics (LFS) of the Universidade Federal da Paraíba, for determining the following variables: Granulometry, available water, permanent wilting point, soil bulk density and particle porosity (total, macro, micro and aeration), degree of compaction, weighted average diameter of aggregates dry and wet, stability of aggregates, saturated hydraulic conductivity, organic carbon, the carbon stock, resistance to penetration, current moisture. The analysis of variance and the averages were compared by the Tukey test, Pearson correlation and principal components analysis, the level of (p<0.05). The treatment MT was superior to the others to field capacity in the 0.0-0.10 m, where he obtained 0.275 m³ m³ and total organic carbon in the layer of 0.20-0.30 m, where was obtained 37.9 g kg-1. The BB treatment was superior to the other treatments for water available in the 0.0-0.10 m, where was obtained 0.083 m³ m³, already for layer of 0.10-0.20 m the treatments SC obtained 0.095 m³ m³. The treatment BB obtained the best results for the stock of carbon in the layer of 0.10-0.20 m, where was obtained 53.2 g kg-1. As the correlation values, in the 0.0-0.10 m layer, we obtained MI/PT (0.90), Qfc/Ds (-0.79), in the layer of 0.10-0.20 m obtained GC/PT (1.00) and DS/EN (-1.00), in the layer of 0.20-0.30 m obtained θAD/Qfc (0.89) and GC/PT (-1.00). In the analysis of principal components, in the 0.0-0.10 m layer, the MO, CO and EC obtained the best results (0.483), and the layer of 0.10-0.20 m, CO and MO obtained the best results (0.448), and the layer of 0.20-0.30 m to MA has obtained the best result (-0,457). After 13 years of system implantation there was improvement in θCC, θAD, COT and EC, and the other variables were not significant over time.