Analysis of spatial variability of pH, P and K in red latosoil cultivated in direct planting system

Adriane Brill Thum 1,Getulio Cerioli 1 and Maurício Roberto Veronez 2
1 Civil Engineering, Vale do Rio dos Sinos University, 
São Leopoldo - RS, Brazil, Avenida Unisinos, 950 – CEP: 93022-000 
Tel.: 051 35911100 Extension 1769 Fax: 051 35908177 
adrianebt@unisinos.br
2 Post-Graduation Program in Geology, Vale do Rio dos Sinos University, 
São Leopoldo - RS, Brazil, Avenida Unisinos, 950 – CEP: 93022-000 
Tel.: 051 35911100 Extension 1769 Fax: 051 35908177 
veronez@unisinos.br

Abstract
The concern about the environmental quality,  together with new technologies, like the Geographic Information Systems – GIS has been helping many sectors, including agriculture. The digital mapping that is being done from  the harvesting of field  work, with machines equipped with mass sensors and GPS receptors, allows geographic identification of proper places for great productivity. To this technique it is given the name of precision agriculture. With this, it is possible to analyze the specific factors of each site, allowing the maximization of its productive potential. The increase in productivity in cultivated field works only happens with the knowledge of the attributes of the soil and its characterization in specific areas within the cultivated glebe. In direct planting system, the superficial application through casting limestone and traditional fertilizers done in the sowing line, provide vertical and horizontal variability of some attributes of the soil, fact that may cause great variation of nutrient contents with low mobility of the soil, even in samples collected a few centimeters from each other. Through the panorama depicted above, the  aim of this research is to evaluate the variability of phosphorus and potassium contents, and pH of the soil from samples collected from 0 to 10 cm and 10 to 20 cm depth. The study was carried out in a glebe which has been cultivated for twelve years with direct planting system that is part of a land in the countryside of Lagoa Vermelha, Rio Grande do Sul State, Brazil. The exact geographic locations of the sampling points and the geostatistical treatment  allowed the definition of spatial variability and the nutrient dispersion around the analyzed area. The preparation of variograms in order to quantify the reach of each sample together with the kriging technique made the drawing of thematic maps from the analyzed attributes possible. Results have shown that in the study area there is a necessity of pH correction of the soil in specific places and the geostatistical analysis proved the impossibility of phosphorus and potassium application in variable quantities.

Keywords: analysis, spatial variability, geostatistics

In: Caetano, M. and Painho, M. (eds). Proceedings of the 7th International Symposium on Spatial Accuracy Assessment in Natural Resources and Environmental Sciences, 5 – 7 July 2006, Lisboa, Instituto Geográfico Português

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