SPATIAL VARIABILITY OF RESISTANCE TO PENETRATION IN SOIL UNDER SUGARCANE CROPS WITH DIFFERENT HARVEST METHODS

ABSTRACT The objective of this work was to evaluate the spatial variability of resistance to penetration in soil under sugarcane crops subjected to different harvest methods in the North Coast microregion of the state of Paraiba, Brazil. The study was conducted in a Typic Hapludult under sugarcane crops, at the farms Santa Emília-II and Maria da Luz-I of the company Miriri Food and Bioenergy S/A, in the municipalities of Rio Tinto and Capim, respectively, state of Paraíba, Brazil. Three sugarcane areas with different harvest methods (manual, mechanized, and manual/mechanized) were selected. The sampling was done in plots of 100 × 100 m, using a grid of 20 × 20 m, covering planting rows and interrows; each intersection point of the grid was georeferenced, and the soil mechanic resistance to penetration was evaluated with the aid of an impact penetrometer (IAA/Planalsucar-Stolf) up to the depth of 0-0.6 m. Soil disturbed and undisturbed samples from the 0.0-0.1 and 0.1-0.2 m layers were collected for analyses of soil moisture, texture, clay dispersed in water, flocculation degree. A pure nugget effect was found in the 0.0-0.1 and 0.4-0.5 m soil layers in the rows of the areas with manual/mechanized harvest. The spherical model was found for most conditions evaluated. The results for the areas were similar, with amplitude of 25-49 m, indicating that the harvest management had no effect on the soil resistance to penetration. No compacted areas were found, and the spatial dependency of the resistance to penetration was characterized as moderate to strong. RESUMO O objetivo deste trabalho foi avaliar a variabilidade espacial da resistência a penetração em solo sob diferentes condições de colheita de cana-de-açúcar na microrregião do Litoral Norte paraibano. O estudo foi realizado em Argissolo Acinzentado cultivado com cana-de-açúcar, nas fazendas Santa Emília II e Maria da Luz I, pertencentes à Usina Miriri e Bioenergia S/A, nos municípios de Rio Tinto e Capim, estado da Paraíba no Brasil. Selecionou-se três áreas: Colheita manual; Colheita mecanizada e; Colheita manual e mecanizada. As coletas se procederam em parcelas de 100 x 100 m, sob grid de amostragem de 20 x 20 m, contemplando linhas e entrelinhas de plantio, sendo cada ponto de cruzamento da malha amostral georreferenciado, e levantada a sua resistência mecânica à penetração com auxílio de um penetrômetro de impacto modelo IAA/Planausucar-Stolf na profundidade de 0-0,6 m. Foi procedida coleta de amostra