Nutrient Cycling by Cover Species and Yield of Soybean Grains in a Clayey Oxisol Under No-Tillage System

The objective of this work was to evaluate the impact of changes in soil management and crop rotation on a clayey Oxisol under no-tillage system in nutrient cycling and soybean yield. The experiment was conducted in the 2014/2015 harvest, at the Agronomic Institute of Parana (IAPAR), at the Experimental Station of Santa Tereza do Oeste, in a clayey Oxisol, in a completely randomized design with four replicates. The management systems evaluated were: no-tillage system (control), no-tillage system with scarification (NTSS) and no-tillage system with gypsum application (NTSG), and six treatments involving crop rotation with species reclaimers of structure: pearl millet, dwarf pigeon pea, sunn hemp, pigeon pea, rattlebox and velvet bean. The attributes/chemical characteristics of the soil were evaluated: phosphorus (P), calcium (Ca2+), magnesium (Mg2+), potassium (K+), organic carbon (C), soil acidity (pH), aluminum (Al3+), potential acidity (H++Al3+), base sum (BS), cation exchange capacity (CEC), base saturation (V), aluminum saturation (Al*) in the layers 0-0.05, 0.05-0.10, 0.10-0.20 and 0.20-0.40 m, after the application of treatments and cultivation of soil cover species. Statistical analysis was performed by analysis of variance (ANOVA) and the means of the treatments compared by the Tukey test at 5 % of significance. The pigeon pea provided higher phosphorus cycling (63.67 mg dm-3), velvet bean, larger magnesium cycling (4.25 cmolc dm-3) and higher values of organic carbon (27.67 g dm-3) in the layer of 0.05-0.10 m. The yield of grains, number of plants per meter and mass of 100 soybean grains did not present significant differences among the evaluated treatments.