The objective of this research was to investigate the effects of three methods of deep tillage of compacted reclaimed mine soil on corn (Zea mays L.). Moldboard plowing (0.5-m depth), slip-plowing (0.7-and 1.0-m depths), and subsoiling (0.7- and 1.0-m depths) on test plots were compared with a no-deep-tillage check treatment. During the 1982 growing season, no significant differences in corn yield among the tillage treatments were observed. Instead, corn yields were strongly associated with the microtopography of harvest plots. Yields were reduced in concave positions where standing water had collected during critical periods of the growing season. The spatial variability of corn yields at the experimental site was characterized by geostatistical techniques. The weak expression of tillage-induced drift in the semivariograms that were constructed for different parts of the research area confirmed that tillage treatment effects on corn yield were insignificant. The semivariograms also revealed that spatial variability patterns of yield greatly varied for different regions of the site. An isarithmie corn yield map produced by kriging graphically illustrated the effect of microtopography on yield.
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