Physical Properties and Organic Matter in Soils with High Soybean Yields
under No-till in the Brazilian Cerrado
Abstract
The present study was conducted in areas of large-scale soybean
cultivation under long-term no-till (NT). Soil samples from depths of
0.0-0.10 (L1), 0.10-0.20 (L2) and 0.20-0.40 m (L3) were obtained from 65
commercial farms characterized by a high soybean yield in the state of
Mato Grosso, Brazil. Oxisols were the predominant soils in these farms,
which were located within the Cerrado Biome, and the main textural
classes were loamy sand, sandy loam, sandy clay loam, sandy clay and
clay. The following physical properties of soil were measured:
penetration resistance, bulk density, particle density, total porosity,
field moisture capacity, saturation and residual moisture contents, soil
water retention curve (SWRC), inflection point, plant available water, n
and α parameters of the Van Genuchten equation, S index, and clay and
sand contents. In addition, the soil organic matter (SOM) and its
densimetric fractions were also determined. The average soybean yield of
the studied areas in the last three years was 4.13 Mg ha-1; however, 26
farms had yielded above 4.20 Mg ha-1. Only some of the physical
properties at L1 layer, including the penetration resistance, bulk
density and the porosity-related parameters, were significantly related
with the soybean yield. The SOM and its fractions were directly
influenced by the clay or sand contents. In conclusion, the areas with
higher productivity under long-term NT showed an adequate S index at
three studied layers with values of 0.11, 0.67 and 0.84 at L1, L2 and L3
layers, respectively.