Chemical soil attributes as affected by lime and phosphogypsum surface application in a recently established no-tillage system

There is interest to establish the no-tillage system in areas cultivated previously with conventional tillage or pasture, with surface liming after system establishment. This practice is possible provided that there are no physical obstacles for root growth. Phosphogypsum is an alternative to decrease Al3+ and increase base saturation (BS), mainly Ca2+ in the subsoil, and can be used complementary to liming. The objective of this study was to evaluate the changes in chemical soil attributes (pH CaCl2, H + Al, Al3+, Ca2+, Mg2+, S-SO42-, BS, and content of cationic micronutrients) as affected by lime and phosphogypsum surface application in a recently established no-tillage system in dry-winter region. The experiment was carried out on a dystroferric Haplorthox, in Botucatu County, Sao Paulo State, Brazil. A randomized complete block design, in split-plot scheme and four replications, was used. The plots consisted of four dolomitic limestone rates (0; 1,100; 2,700; and 4,300 kg ha(-1)), intended to reach a BS to 50, 70 and 90 %, respectively. The subplots were represented by the absence or presence of phosphogypsum application (2, 100 kg ha(-1)). Soil samples were collected 3, 6, 12, and 18 months after lime and phosphogypsum application, at depths of 0-0.05, 0.05-0.10, 0.10-0.20, 0.20-0.40, 0.40-0.60, and 0-0.20 m. Lime surface application reduced soil acidity and increased exchangeable Ca and Mg contents, mainly in the top soil layers. Phosphogypsum application promoted increasing exchangeable Ca and S-SO42- contents, and decreased exchangeable Al in the soil, favoring the effects of surface liming that influenced the. subsoil layers more. rapidly. Base saturation values obtained at a depth of 0-0.20 m with liming were lower than those estimated by BS method, mainly at the highest levels, even with phosphogypsum application. Surface liming did not influence micronutrient contents in the 0-0.20 m layer.