Crop Yield Response to Precision Deep Tillage

Experimental precision deep tillage was applied at 3 sites in central Kentucky with relatively welldrained silt loam soils in no-till crop production with fields divided into 0.4 ha (1 ac) grid cells using DGPS mapping. Assessment of soil compaction by machinery traffic was made using multiple soil cone penetrometer measurements. Corn, wheat and soybeans yields were depressed in grid cells with CIavg > 1.5 MPa prior to application of tillage treatments at sites 1 and 3, whereas at site 2, where most of the highest average CI-values ranged from 1.44 to 1.49 MPa, the opposite was true. In general, deep tillage resulted in yield improvement in compacted grid cells relative to compacted cells receiving no deep tillage, increasing to approximately the same yields as cells with CIavg < 1.5 MPa . Cells receiving maximum depth (40 cm) tillage generally had higher yields than cells tilled to the maximum depth at which CIavg > 1.5 MPa (precision deep tillage) at sites 1 and 3, however, the reverse was true for double-crop soybeans subjected to limited rainfall. At site 2, tilled cells had higher yields than non-tilled cells, with precision tillage showing the maximum relative yield.