Teores foliares de nutrientes na soja sob diferentes culturas de cobertura e estratégias de adubação

Abstract

The use of cover crops associated with different fertilization strategies constitutes an important tool for the sustainability of agricultural systems under no-tillage. The objective of this study was to evaluate the leaf contents of nitrogen, phosphorus, potassium, calcium, and magnesium in soybean cultivated in succession to different cover crops and subjected to different fertilization strategies. The experiment was conducted at the experimental area of the Federal University of the Frontier South (UFFS), Erechim-RS Campus, in a randomized block design, in a 2 × 9 factorial scheme, with four replications. Two fertilization strategies were evaluated (fertilization at soybean sowing and system fertilization) and nine soil cover treatments: Black Oat (AVP); Rye (CENT); Vetch (ERV); AVP + CENT; AVP + ERV; CENT + ERV; AVP + CENT + ERV; commercial MIX, and Fallow. During the R2 phenological stage of soybean, trifoliate leaves were collected to determine the leaf contents of nitrogen, phosphorus, potassium, calcium, and magnesium. The data were submitted to analysis of variance and the means were compared by Tukey's test at 5% probability. The results demonstrated that the leaf nutrient contents were influenced by the cover crops and fertilization strategies. Higher leaf nitrogen contents in soybean occur with the use of single AVP associated with fertilization at sowing, or with the commercial MIX associated with system fertilization. The highest leaf contents of phosphorus and potassium occur in the commercial MIX, Fallow, and AVP + CENT + ERV consortium treatments. System fertilization promoted higher leaf contents of calcium and especially magnesium compared to fertilization carried out at sowing. It is concluded that the leaf nutrient contents in soybean respond jointly to cover crops and fertilization strategies, highlighting system fertilization as an efficient strategy to optimize the mineral nutrition of the crop.