Spatial variability patterns of wheat [Triticum aestivum] growth and soil properties in a small field as affected by tillage intensity
2002
Nakamoto, T. (Tokyo Univ. (Japan)) | Yamagishi, J. | Oyaizu, H. | Funahashi, T. | Richner, W.
The objective of this study was to obtain information about spatial heterogeneity as a basis for site-specific soil and crop management in small fields. The spatial variability patterns of wheat growth parameters and soil properties, e.g. nitrate, available phosphate, pH, and soil surface hardness, were investigated on a 0.25 ha field of Humic Andosol in 1998 - 1999. Two plots in the field had been tilled with different intensities since autumn 1997. A plot was minimum-tilled with a rotary tiller (MT) and the other plot was conventionally tilled with a moldboard plow and disc-harrowed (CT). Raw data, collected from 100 locations with 2.5 m*5 m spacing in each plot, were divided into trends (large-scale deterministic structure) and residuals (small-scale stochastic structure) by median polishing. Trends were more dominant in CT than in MT. The trend of wheat above-ground biomass at harvest was similar to those of soil nitrate and available phosphate. These trends were partly due to high variability across rows, possibly caused by the same traffic direction of farming operations for several years. The residual data, on the other hand, showed no correlation among the parameters. The spatial dependency of the residual data for soil properties, except for pH, was not apparent for distances larger than the minimum sampling distance (2.5m). It is concluded that modification of fertilizer application based on the trend data may improve the efficiency of fertilizer use while small- scale site-specific management based on the residual data may be practically difficult.
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