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Since tillage operations within the conventional plow depth alter soil physical properties (Cooper 1971). tillage below the usual 15 cm has often been advocated as a means of modifying subsoil conditions affecting crop growth. However, results in terms of crop yield response have been very variable (Burnett and Hauser 1967). In their extensive review of deep tillage experiments, these authors noted that yield increases resulting from deep tillage operations appeared restricted to situations where moisture was the yield- limiting factor. There the increased soil infiltration rate and aeration following inversion and fragmentation of the subsoil impervious layers resulted in greater water availability to the plants, and increased root growth. Soil compaction, as measured by bulk density, was generally reduced. Burnett and Hauser concluded that deep plowing was of no benefit where moisture was adequate, or soils were coarse textured. Two inferences could be made from their data: (1) that poorly or artificially drained soils would not respond to deep tillage (2) in view of the energy requirements for deep tillage (Larson 1967), deep tillage should be undertaken only where a favorable crop response is indicated.
effect of fall and spring plowing at three depths on soil bulk density, porosity and moisture in brookston clay
Bolton, E. F., Dirks, V. A. and M. M. McDonnell 1981. EFFECT OF FALL AND SPRING PLOWING AT THREE DEPTHS ON SOIL BULK DENSITY, POROSITY AND MOISTURE IN BROOKSTON CLAY. Canadian Agricultural Engineering 23(2):71-76.
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