Root growth is affected by mechanical soil resistance and affects the crop yield potential. This study evaluated the soil penetration resistance on a clayey Oxisol under distinct no-tillage cropping systems. The experiment was carried out at the technological field of Cotrijui in southern Brazil. The soil was a Haplorthox with a clay content of 0.68 kg kg-1 and it has been under four no-tillage cropping systems: succession soybean/wheat; corn/black oat/corn + velvet bean/wheat/soybean/wheat; velvet bean/wheat/soybean/ wheat/soybean/black oat; and crotalaria/wheat/soybean/black oat/corn/wheat. Soil penetration resistance (PR), soil moisture, and soil bulk density were evaluated at different times and soil depths. For all four cropping systems on this clayey Oxisol under no-tillage, the highest compaction state was observed at about 0.1 m depth and the lowest in the surface layer (0 to 0.07 m). The PR showed great temporal variation and was associated with soil moisture for each soil bulk density or compaction state. PR values restrictive for plant root growth were found at depths varying from 0.03 to 0.23 m, at soil moistures between 0.14 and 0.28 kg kg-1. The effect of inclusion of warm-season cover crops, which have an aggressive rooting system responsible for biological pore formation, was not observed for the studied time.
no-tillage; compaction; biopores; roots; mechanical properties
