| Abstrakt: |
Tillage‐pans occur in many soils of the southeastern United States and usually decrease crop yields. Relative yield increases from subsoiling (deep tillage) as compared to a nonsubsoiled treatment have been variable among soils due to differences in soil properties. The primary objective of this investigation was to relate soil physical properties to relative yield increases of corn (Zea maysL.) due to subsoiling. Corn yields were measured for subsoiled and nonsubsoiled (disked twice) treatments during 1978, 1979, and 1980 at 12 locations in the North Carolina Coastal Plain region. Soil physical properties of the Ap and E or B horizons were characterized for each site, and included air‐filled porosity, cone index, saturated hydraulic conductivity, bulk density, ped mean weight‐diameter, and texture. Relative yield increases due to subsoiling ranged from 82.8 to −12.4%. Correlation relationships between relative yield increase and individual soil physical properties were greatest for the Ap horizons. Physical properties having high r values were very coarse plus coarse sand content (2.0–0.5 mm) (r= 0.90**), ped mean weight‐diameter (r= −0.72**), and saturated hydraulic conductivity (r= 0.85**). Cone index (mechanical impedance) was not significantly correlated with relative yield increases, possibly because of textural and structural differences among soils. A regression model based on very coarse plus coarse sand, and fine sand accounted for 93% of the variation in relative yield increase among the 12 sites studied. An economic model was used with the regression models to determine the most profitable tillage method at each site. |
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