ABSTRACT
To reduce acidity in no-till systems, lime is broadcast on the soil surface without incorporation. Two experiments were carried out, one in a clayey Latossolo Vermelho Distrófico (Rhodic Hapludox) and another in a sandy loam Neossolo Litólico Húmico (Lithic Hapludoll), to test the hypothesis that the source and particle size of lime influence soil reaction in the short term, and crop response to surface liming under a no-till system. A randomized complete block design was used in a 2 × 2 × 4 factorial arrangement with three replications for each experiment. The treatments consisted of two sources of lime, calcitic (25-50 g kg-1 MgO) and dolomitic (160-180 g kg-1 MgO); two ranges of effective calcium carbonate equivalent (ECCE) of lime material, range B (ECCE 60-75 %) and range D (ECCE>90 %); and four rates of lime on the surface, one control treatment without lime and three rates estimated to raise the base saturation of the topsoil (0.00-0.20 m) to 50, 70, and 90 %. In both experiments, lime was surface applied in August 2010. During the spring-summer season in 2010/11 and 2011/12, corn and soybean were grown on the Latossolo Vermelho Distrófico, and soybean and corn on the Neossolo Litólico Húmico, respectively. Surface application of lime in both soils after 12 months led to reduction in soil acidity mainly in the 0.00-0.05 m layer and, to a lesser extent, in the 0.05-0.10 m layer. Calcitic lime at higher rates and lime composed of finer particles showed a greater reduction in acidity in the soil surface layers. Surface liming increased the Ca-leaf content, especially with the use of calcitic lime, and Mg-leaf content, mainly with the use of dolomitic lime. It also reduced Mn and Zn contents in the leaves, regardless of the source of lime, in the corn and soybean crops. Grain yields of corn and soybean in both the clayey Latossolo Vermelho Distrófico and the sandy loam Neossolo Litólico Húmico increased with increasing lime rates, but were not affected by the sources and ECCE ranges of lime. The surface application of lime is an effective and important practice to maximize crop grain yields under no-till systems, regardless of magnesium content and particle size of the lime.
soil acidity; aluminum; calcium; reactivity of lime; effective calcium carbonate equivalent (ECCE)
