EFFECT OF WHEAT-STRAW INVERSION ON SOIL-WATER CONSERVATION

Soil water can be a limiting factor for dryland wheat production in Ok lahoma, Five experiments on three different soils were conducted to de termine the effect of placing residue (wheat straw and paper) layers b eneath the soil surface on water conservation. Treatments included a c ontrol(no residue on the surface or inverted), 6 Mg ha(-1) wheat straw placed 1.5, 3, and 6 cm below the surface (wheat straw inversion), 6 Mg ha(-1) applied on the surface (simulation of zero-tillage), 6 Mg ha (-1) mixed with the surface 6 cm of soil (simulation of conventional t illage), 3 Mg ha(-1) placed 6 cm below the surface, and 6 Mg ha(-1) gr ound telephone book paper placed 1.5 cm beneath the surface. Water was applied to prepared pots, and water loss was determined on a daily ba sis. Pots were placed in growth chambers where daytime and nighttime t emperatures were ramped to 32 degrees C and 18 degrees C, respectively . Water losses in the first 10 days were greater in all wheat straw in version treatments when compared with zero-tillage. Water losses stabi lized after 15 days in the 3- and 6-cm wheat straw inversion treatment s, but zero-tillage continued to show significantly higher water loss. The 3 cm to 6 Mg ha(-1) wheat straw inversion treatment had significa ntly lower water loss before reaching the wilting point when compared with zero-tillage in two of the three soils evaluated. Placing the whe at straw 3 cm beneath the surface reduced water loss when compared wit h 1.5- and 6-cm inversion.