Mapping soil micronutrients in a 63 ha low productivity pasture in Rondonia, Nova Vida Ranch
Carlos
Clemente
Cerri, Centro de Energia Nuclear na Agricultura (CENA), Universidade de Sao Paulo (USP), cerri@cena.usp.br
(Presenting)
Martial
Bernoux, Institut de Recherche pour le Développement (IRD), mbernoux@cena.usp.br
Carlos
Clemente
Cerri, CENA-USP, cerri@cena.usp.br
Marisa
Cássia
Piccolo, CENA-USP, mpiccolo@cena.usp.br
Brigitte
J.
Feigl, CENA-USP, beduardo@cena.usp.br
Jerry
M.
Melillo, The Ecosystems Center, Marine Biological Laboratory, jmelillo@mbl.edu
Soils vary widely in their micronutrient content and in their ability to supply micronutrients in quantities sufficient for optimal grass growth. Therefore, rational management of micronutrient fertility and toxicity requires an understanding of how total soil micronutrients vary across the field. A variety of approaches have been used to survey and map the geographic distribution of soil micronutrient content at scales ranging from global to sites within single production fields. The present study investigates the spatial variation of soil micronutrients in a 63 ha pasture area located at Nova Vida Ranch, Rondonia, Brazil. A regular 100 m grid was used for collecting a total of 195 soil samples at the 0-10, 10-20 and 20-30 cm layers. Soil samples were analyzed for Zn, Cu, Fe, Mn contents and also pH, total C, total N, P, K, Ca, Mg, and Al. Conventional statistical methods and geostatistics were performed in order to analyze soil properties spatial dependence. The spatial structure of the studied nutrients was analyzed and variogram models with a nugget component and two spatial components were found to fit the experimental results. Semivariograms were best fitted by spherical and exponential models. Two types of validation (cross and external) were conducted, indicating a lack of bias for the used prediction models. Contour maps made by block kriging allowed to identify micro-regions with significantly high or low extractable nutrient contents. Maps of total soil micronutrient content can show where low micronutrient concentrations may cause deficiencies in plants and in the livestock that subsist on them.
Submetido por Carlos Eduardo P Cerri em 17-MAR-2004