Plant water and nutrient uptake depends on several factors, mainly on the soil depth explored by the roots. Some soil factors and processes can limit root growth. The objectives of this study were: (a) to quantify the relationships among corn root density with several soil properties and to identify which of these attributes restrict root growth in the Bt horizon and corn yield; (b) to measure the temporal variation of the soil water content to verify if plants extract water from the Bt horizon. The study was carried out with corn under no tillage during the 93/94 growing season at the Federal University of Santa Maria on a Typic Hapludalf soil. Porosity, bulk density, aerial space, texture, gravel, resistance to penetration, calcium + magnesium, saturation with aluminum, root density and corn yield were analyzed. Through the observation of the cultural profiles and root density, it was noticed that the horizon Bt restricted root growth, mainly in the profiles with shallow A horizon when compared to deep A horizon. The soil bulk density and resistance to penetration did not restrict root growth. Conversely, the gravel presence and the high saturation with exchangeable aluminum were the variables that strongly restrict root growth. Reduction of the moisture content of the Bt horizon was not observed during the corn growth, even under dry conditions, indicating that low root density probably prevented the plants to take up water in the Bt horizon. Corn yield was 23% lower in the profiles with shallow A horizon than in profiles with deep A horizon. This yield decrease was probably a function of the restriction to the root growth.
soil properties; water uptake; corn yield