Implications of Agricultural Gypsum Doses in Physical-Hydric Attributes of a Typic Haplortox and on Root Growth and Soybean Productivity

The response to agricultural gypsum, as a conditioner of the root environment in depth, has been observed for most annual crops. These responses are attributed to the better distribution of roots of the crops in depth in the soil by the reduction of chemical impediments, caused by the exchangeable aluminum and calcium deficiency in these layers, which allows to the plants the use of greater volume of water when they occur summer. In this way, the objective of this study was to evaluate the effects of gypsum doses on physical-hydric attributes, root growth and soybean productivity. The experiment was conducted at the Agronomic Institute of Paraná (IAPAR) in Santa Tereza do Oeste-PR. The soil was classified as Typic Haplortox. Five doses of agricultural gypsum were evaluated: 0; 3; 6; 9 and 12 t ha-1, in outline randomized block design with six repetitions. Soil density, total porosity, macroporosity, microporosity and saturated hydraulic conductivity were evaluated at layers of 0.0-0.1; 0.1-0.2 and 0.2-0.3 m. Soybean productivity and root growth were also evaluated. Data were submitted to regression analysis. The physical attributes soil density, macroporosity and saturated hydraulic conductivity did not differ significantly with the application of the gypsum doses in the 0.0-0.1 and 0.2-0.3 m layers. However, in the 0.1-0.2 m layer, due to pressures imposed by the machines and agricultural implements deforming the soil, there were significant differences in the physical attributes of the density, macroporosity and saturated hydraulic conductivity. There was no significant difference in grain productivity and root growth of soybean.