Atributos químicos após dezenove aplicações de dejeto líquido de suínos em argissolo sob plantio direto

Abstract

The use of pig slurry as a source of nutrients can affect the conditions of acidity and nutrient availability, altering the environment for crop development. The objective of this study was to evaluate changes in chemical properties of an Alfisol after 95 months of cultivation and 19 applications of pig slurry, conducted under no-tillage system. The experiment was installed in May 2000, an experimental area under no-tillage at the Federal University of Santa Maria, and conducted until January 2008. The experimental design was a randomized block design with three replications. Were performed nineteen surface applications of 0, 20, 40 and 80 m3 ha-1 of pig slurry during the experiment and in the end, were collected samples of soil layers of 0-2, 2-4, 4 -6, 6-8, 8-10, 10-12, 12-14, 14-16, 16-18, 18-20, 20-25, 25-30, 30-35, 35-40, 40-50 and 50-60 cm depth. The soil was collected with the aid of a spade cut-off, air dried, milled manually with the aid of a roller and passed through a sieve with 2 mm mesh and reserved. It was determined the pH values in water (1:1), SMP, the levels of exchangeable Al, Ca, Mg and K. With the data obtained were calculated the sum of bases, base saturation and Al saturation, CEC pH7, CEC effective and potential acidity (H + Al). Were also determined the total contents of N, P and K, levels of mineral N, available P and soil organic matter. The successive application of pig slurry promoted increase in pH values in water up to 8 cm of soil, however, no change in potential acidity. Also caused increased levels of exchangeable Ca and Mg in the surface layers of soil, reflecting an increase in the values of sum of bases, base saturation and decreasing Al saturation. Furthermore, the applications over time caused an increase in levels of soil organic matter, reflecting in increased levels of total N to a depth of 30 cm. Applications of manure resulted in increased levels of available P and exchangeable K to a depth of 60 cm, while for the total P increases were observed up to 30 cm depth. The changes observed in soil chemical properties provides better environment for root development of crops due to lower acidity and higher nutrient availability in soil solution. However, one must be careful in extrapolating these results to different soils, although the phenomena are similar, they occur in different magnitudes depending on soil characteristics.