Propriedades químicas do solo e resposta da sucessão trigo-milho-trigo sob plantio direto em função da calagem e da aplicação de doses de gesso

Abstract

The effects of lime and gypsum application on chemical attributes of an Oxisoil under no tillage system and also on wheat and corn nutrition and yield were evaluated during 2011-2013, in Guarapuava-PR. The experiment was conducted in a completely randomized blocks design, in a factorial scheme (2x4). The treatments comprehended two lime rates (no lime and the recommended rate to achieve a V = 70 %) and four gypsum rates (0, 2, 4, e 8 ton ha?¹) with four replicates. The soil sampling was performed after five months of lime application at 0-20 cm depth and at 0-80 cm depth after 10 and 17 months of lime application what means 5 and 12 months after gypsum application, respectively. The leaf nutrient content and crop yield were also evaluated. The results were submitted to variance and regression analysis. A lime effect occur on soil pH only in 0-10 cm layer on the first sampling. At second soil sampling the lime effect achieve the 10-20 cm layer. Gypsum rates also promoted a small effect on soil P levels at second and third samplings. The Al³+ levels decreased at 0-10 cm in the first two sampling with lime applications. Lime didn`t affect soil potential acidity (H+Al) in 0-10 and 10-20 cm layers at five months but at 10 and 17 months after lime application the H+Al levels decrease on these layers. The Ca²+ levels increase at 0-10 cm layer in first sampling. The second sampling showed a linear increase of Ca²+ level as function to gypsum application with or without lime. In third sampling the lime effect didn`t occur at 0-10 cm, but was observed at 10-20 cm depth. In the first sampling no effect of lime in soil Mg²+ levels occur but in second and third samplings an increase at 0-10 cm occur with or without lime. At third sampling, the behavior of gypsum rates in absence of lime was the same while in the presence of lime, beyond the decrease of soil Mg²+ levels at 0-10 cm layer and the increase in 10-20 e 20-40 cm, this increase achieve the 40-60 cm layer. There was a decrease in K+ levels at 0-10 and 10-20 cm layers in second and third sampling and an increase on S-SO42- levels in all layers sampled on second and third sampling. There was no effect of lime on wheat yield and on leaf macronutrients levels in 2011. To corn crop there was increase in leaf levels of N, P, Mg and S with lime + gypsum application and decrease in K. Isolated application of gypsum promoted a decrease in Mg leaf levels in corn. The corn yield increase linearly with application of lime + gypsum however when only gypsum was applied the yield was higher when compared with lime + gypsum application. For wheat (in 2012) no effect of lime, gypsum or the combination of both occurs in leaf levels of N, P and K. Levels of Ca, Mg and S increased linearly with lime, gypsum or with application of both. Yield of wheat increase only with lime + gypsum application.