Variabilidade espacial de atributos indicadores de acidez e resistência mecânica do solo à penetração na produção de raiz de mandioca

Abstract

Cassava (Manihot esculenta Crantz) is widely cultivated throughout all the national territory, but it is still a little technified activity, mainly in function to the heterogeneity of the soil system, since there is spatial dependence on the attributes that indicate the physical and chemical quality of the soil and these attributes influence in a localized way in the production. The objective of the present study was to characterize the spatial variability of the attributes indicating acidity and mechanical resistance of the soil to penetration, and its effects on cassava root production, with the purpose of estimating the chemical and physical soil changes at unsampled points and may indicating homogeneous zones for management efficiency. The study was carried out at Fazenda Freitas, located on Guanabara alleyway, in São Francisco city, Northeast of the Pará. The cultivation was submitted to spacing of 1m x 1m, under intercalated cultural treatments in weeding, herbicide application and fertilization. The georeferencing was performed to create the sample mesh, totaling 71 points of cassava soil and root collection at the depths of 0.00–0.20m, 0.20–0.40m and 0.40–0.60m and analysis of soil penetration resistance (RP) at depths 0.00–0.10m, 0.10–0.20m, 0.20–0.30m and 0.30–0.40m, and all samples were collected in regular mesh with a spacing of 22m. Soil analyzes were performed at the Soil Laboratory of the Federal Rural University of Amazonia, Capanema-PA campus, to determine pH in water, Al3 + and H + Al. Statistical data were analyzed by Pearson linear correlation and geostatistics were analyzed by semivariogram parameters and were estimated by ordinary kriging. Cassava root yield showed a significant low correlation (0.27) only with soil pH and no significant correlation for the other attributes. Soil pH showed significant linear correlation with Al3 + and H + Al content. The analysis of semivariograms showed spatial dependence for cassava root mass and most soil attributes in all studied layers, with the exception of exchangeable aluminum in layer 0.40–0.60m and RP in layer 0.30–0.40m from the ground. Cassava crop is tolerant to Al3 + and H + Al levels found in the soil and PR was not a limiting factor for root production. From the geostatistical analysis of the attributes of soil and plant, it was possible to characterize the spatial variability of the attributes indicating acidity and mechanical resistance of soil to penetration in cassava root production, providing subsidies to avoid waste and unnecessary costs with the application of fertilizers or correctives in a localized way, not only considering the medium values.