Alterations and spatial variability of soil fertility in successive years under no tillage system
This study was carried out in order to assess the spatial variability of some soil properties after adoption of no tillage system (NTS). A 19,200 m² plot was marked with a 20 x 20 m spacing grid. Crop yield and soil attributes, at 0-0.2 m deep layer, were measured in 63 points in 1985, 1987 and 1988. The spatial variability was assessed by semivariogram calculation using geostatistics. Soil base saturation index (BS) was interpolated by kriging and also, using a bivariate geostatistical method, the collocated cokriging (CLCK) using terrain elevation as ancillary data. Although, the coefficient of variation (Cv) for soil organic matter content decreased from 1985 (20.4%) to 1988 (10.7%), its mean value increased 32% in the same period. The soil fertility in 1985 was found to be more diverse (i.e. high Cv value), providing evidences that the clearing and subsequent no tillage cultivation increased soil homogeneity. Experimental semivariograms were best fitted to a spherical model. The cultivation under NTS improved the spatial continuity of the studied attributes at close distances. The range for most of the semivariograms of soil properties varied between 40 and 90 m. Kriged maps allowed distinguishing small areas with different chemical elements content. The CLCK approach resulted in maps with higher details and smoother contours in comparison to kriging and cokriging.
| Main Authors: | , , , , |
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| Format: | Digital revista |
| Language: | English |
| Published: |
Instituto Agronômico de Campinas
2010
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| Online Access: | http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052010000500005 |
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| Summary: | This study was carried out in order to assess the spatial variability of some soil properties after adoption of no tillage system (NTS). A 19,200 m² plot was marked with a 20 x 20 m spacing grid. Crop yield and soil attributes, at 0-0.2 m deep layer, were measured in 63 points in 1985, 1987 and 1988. The spatial variability was assessed by semivariogram calculation using geostatistics. Soil base saturation index (BS) was interpolated by kriging and also, using a bivariate geostatistical method, the collocated cokriging (CLCK) using terrain elevation as ancillary data. Although, the coefficient of variation (Cv) for soil organic matter content decreased from 1985 (20.4%) to 1988 (10.7%), its mean value increased 32% in the same period. The soil fertility in 1985 was found to be more diverse (i.e. high Cv value), providing evidences that the clearing and subsequent no tillage cultivation increased soil homogeneity. Experimental semivariograms were best fitted to a spherical model. The cultivation under NTS improved the spatial continuity of the studied attributes at close distances. The range for most of the semivariograms of soil properties varied between 40 and 90 m. Kriged maps allowed distinguishing small areas with different chemical elements content. The CLCK approach resulted in maps with higher details and smoother contours in comparison to kriging and cokriging. |
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