Abstract

This study investigates how soil organic matter and the physical and microbiological attributes affect soybean yield in two distinct crop environments (high and low productivity) in southern Brazil, during a crop season with the occurrence of a severe hydric restriction. Soil samples stratified by depth were collected to evaluate the chemical (organic matter), physical (root penetration resistance and growth), and microbiological (enzymatic activity) attributes. Soil organic matter was higher in the high productivity environment, both in shallow and deep soil profiles. The resistance to soil penetration was higher in the low productivity environment after 0.15 m, with values exceeding 2.5 MPa (critical value). For root growth (volume, surface area, and dry mass), these values were higher in the high productivity environment at depths of 0-0.10 and 0.20-0.30 m. The activity of beta-glucosidase and arylsulfatase enzymes was also higher in the high productivity environment. The average difference in soybean grain yield was 39% between the environments, at 2188 kg ha^-1 (high yield) and 1563 kg ha^-1 (low yield). In this sense, the findings reinforce that surface and deep organic matter stocks will be the best alternative to reduce soybean yield losses in years with severe water.

Key words: Water restriction, production environments, organic matter, compaction, root growth, enzymatic activity.