01460naa a2200145 a 450000100080000000500110000800800410001910000170006024501580007726000090023552010130024465000090125765000090126677300390127512798812025-04-22       1979    bl uuuu     u00u1 u    #d1 aUNGER, P. W.  aEffects of deep tillage and profile modification on soil properties, root growth, and crop yields in the United States and Canada.h[electronic resource]  c1979  aUnfavorable conditions of soil profiles, through their adverse effects on the growth, proliferation, and activity of roots, may severely limit the yield of crops at some locations in the United States and Canada. A review of the literature showed that deep tillage and modification of soils having unfavorable profiles may increase crop production by providing larger, more favorable zones of soil for the growth, proliferation, and activity of roots. The improved conditions may result from disrupting dense, high-strength horizons; leaching or burying salts or toxic materials; increasing the capacity of sandy soils to retain water; and reducing the erodibility of soil. When the horizons causing problems were adequately disrupted or altered, yields of crops were generally increased. Benefits from the treatments were greater when precipitation or irrigation were limited than when they were adequate. There are many soils on which no benefits can be expected from deep tillage and profile modification.  aRaiz  aSolo  tGeodermagv. 22, p. 275-295, 1979.