Soybean yield and quality a function oflime and gypsum applications

Effects of lime and gypsum applications on the quality of soybeans grown under no-till (NT) are not well defined yet. A field trial established in 1998 on a dystrophic clayey Rhodic Hapludox, at Ponta Grossa, State of Paraná, Brazil, evaluated grain yield and soybean quality based on oil, protein and nutrient content, after lime and gypsum applications under NT, in a randomized complete block design (n = 3), split-plot experiment. In the main plots, the treatments with dolomitic lime were: control (no lime), split application of lime on the surface (three yearly applications of 1.5 Mg ha¹), surface lime (4.5 Mg ha¹), and incorporated lime (4.5 Mg ha¹). Subplots received four different rates of gypsum: 0, 3, 6, and 9 Mg ha-1. The soybean crop was evaluated in the agricultural years of 20022003 and 20032004. After 58 months, the correction of acidity through surface liming, with full or split rates, was more pronounced in the top layer (00.05 m) and there was greater reaction at the depths of 0.050.10 and 0.100.20 m when lime was incorporated. Surface or incorporated liming had no effect on grain yield, soybean oil and protein content. Gypsum improved chemical subsoil conditions, raising pH (0.01 mol L-1 CaCl2) as well as Ca2+ and S-SO4(2-) contents; it also caused exchangeable Mg2+ leaching in the soil profile. The application of gypsum did not affect grain yield, yet it improved soybean quality through an increase in protein and S contents, in 20032004, and in grain P, K and Ca, in the two cropping years. The use of gypsum in NT soybeans can be especially important for fields of seeds production. Os efeitos da aplicação de calcário e gesso na qualidade da soja cultivada em plantio direto não são muito conhecidos. O experimento foi instalado em 1998 em um Latossolo Vermelho distrófico textura argilosa, em Ponta Grossa (PR), com o objetivo de avaliar a produção de soja e a concentração de óleo, proteína e nutrientes nos grãos, após a aplicação de calcário e gesso em plantio direto. O delineamento experimental utilizado foi o de blocos completos ao acaso em parcelas subdivididas, com três repetições. Nas parcelas, os tratamentos com calcário dolomítico foram: testemunha (sem calcário), calcário parcelado na superfície (três aplicações anuais de 1,5 Mg ha-1), calcário na superfície (4,5 Mg ha-1) e calcário incorporado (4,5 Mg ha-1). As subparcelas receberam quatro doses de gesso: 0, 3, 6 e 9 Mg ha-1. A cultura da soja foi avaliada nos anos agrícolas de 2002200