Caracterização física de três solos do município de Areia, Paraíba.

Abstract

The objective of this work was to characterize, in terms of its physical properties, three soils representative of the city of Areia as a way of contributing, in part, to the rational planning of the agriculture of the area and in the preparation of plans of conservation of tenders tending to avoid their destruction by the effect of the water erosion. The soils studied correspond to the following associations: Soil 1. Yellow red podzolic, clayey texture, fceda stage subcaducifóia, flat relief. Soil 2. Latosol red yellow, clayey texture, sub-deciduous forest phase, strong relief corrugated. Soil 3. Podzolic red yellow, medium texture, chalky, subperenifolia forest phase. In order to reach the indicated objectives, the following determinations were made: texture, apparent density, real density, porosity, aggregate stability, field capacity, equivalent humidity, wilt point, organic matter and soil reaction. The results show that the three studied soils present medium textures in the first depths, increasing the clay content and, consequently, reducing the content of the sand fraction, as the depth increases. The stability of the aggregates reflects the influence of soil formation processes as well as their previous and current use and management. The highest value corresponds to Soil 2 (89.2%) and the lowest is Soil 3 (5 5, 4%). Soil 1 has intermediate aggregate stability between Soils 1 and 2 (74.4%). The values of equivalent moisture and 1/3 bar [% dry basis weight] presented by the three soils are moderate to slightly low, corresponding to the highest values ​​in soil 2. In general, the amount of water available to the plants is low when calculated in range of 0.33 - 15 bar suction, increasing appreciably when using 0.1 bar as the upper limit of available water. A high correlation was found (r = 0.83 **) between equivalent humidity and 0.33 b a r, suggesting that the old centrifugation method, which is faster and easier than 0.33 bar, can be used to estimate field capacity. Analyzing the pore distribution by their sizes, it is verified that the three soils have a proportion of macropores, and micropores that allow an adequate retention and movement of water and diffusion of gases for normal plant growth. The values ​​of infiltration (test done only in soil 1), in dry and humid soil, indicate that this soil presents good physical characteristics, which added to its almost flat topography, makes it advisable to incorporate it into an irrigated agriculture regime. In g e r a l, the organic matter content of all three soils is low and, of course, decreases with depth. The highest content is presented by Soil 1, however soils 2 and 3 show very similar contents between and, decreasing rapidly as the depth increases. Finally, in light of these results, it can be recommended that Soils 2 and 3, due to their topography and erosion past and present, are submitted to cultural systems that allow the conservation of the soil and the restoration of some of its characteristics that currently are in the process of being degraded. 0 Soil 1, on the other hand, can be grown without much restriction when both the nutrients and the content of organic matter are kept at shallow levels. It is considered of interest to conduct economic studies to determine the feasibility of incorporating regime of irrigated agriculture.