Variabilidade espacial dos atributos do solo com horizonte a antrópico sob diferentes usos no sul do Amazonas

Abstract

Inadequate crop management compromise soil quality, affect crop production and cause environmental damage. Non-conservationist crop systems are deleterious to the soil-plant system, as they accentuate crop yield decline as a result of the quality of the physical, chemical and biological attributes of the soil. Soils with anthropogenic A horizon, known as Terra Preta de Índio (TPI), occur in many Amazonian regions. These soils generally present high fertility, in contrast to the acidic and less fertile soils common in the tropics. Thus, the objectives of this study were: i) to evaluate the spatial distribution of chemical attributes in the areas of Terra Preta de Índio (TPI) under three different soil uses (Brachiaria brizantha, Coffea canephora and Theobroma cacao) in the southern Amazonas state; ii) verify the degree of similarity of soil attributes of TPI areas under the different uses (Brachiaria brizantha, Coffea canephora and Theobroma cacao), using multivariate statistical techniques. Three areas of TPI were selected, where experimental grids were sampled with dimensions of 80x56m with spacing of 8x8m for the pasture area, dimensions of 100x42m with spacing of 10x6m for the coffee area, and dimensions of 88x42m with spacing of 8x6m for the cocoa area. The soils were sampled at the crossing points in the layers of 0-0.05m; 0.05-0.1m; and 0.1-0.2m, taking a total of 88 sampling points in each area. In the laboratory were determined: pH, Al3+, H+ Al, Ca, Mg, K, P, Organic Carbon and Carbon Stock, potential CTC, base saturation and aluminum saturation. Data were submitted to descriptive statistics, geostatistics and multivariate analysis. The results showed difference between the environments with presence of TPI. The geostatistical analysis allowed making inferences about the spatial behavior of the evaluated attributes in function of the use of the soil and the evaluated layer. The results confirm geostatistics as an efficient tool in interpreting the dynamics of soil chemical attributes. The multivariate analysis revealed a distinct variability pattern for the evaluated soil use systems, and the area with Brachiaria brizantha presented in the three evaluated layers a relation with attributes that indicate acidity, while the area with Theobroma cacao presented a relation with the attributes that indicates fertility.