Soil water can be a limiting factor for dryland wheat production in Oklahoma. Five experiments on three different soils were conducted to determine the effect of placing residue (wheat straw and paper) layers beneath the soil surface on water conservation. Treatments included a control (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 tillage), 3 Mg ha-1 placed 6 cm below the surface, and 6 Mg ha-1 ground telephone book paper placed 1.5 cm beneath the surface. Water was applied to prepared pots, and water loss was determined on a daily basis. Pots were placed in growth chambers where daytime and nighttime temperatures were ramped to 32°C and 18°C, respectively. Water losses in the first 10 days were greater in all wheat straw inversion treatments when compared with zero-tillage. Water losses stabilized after 15 days in the 3− and 6-cm wheat straw inversion treatments, but zero-tillage continued to show significantly higher water loss. The 3 cm to 6 Mg ha-1 wheat straw inversion treatment had significantly lower water loss before reaching the wilting point when compared with zero-tillage in two of the three soils evaluated. Placing the wheat straw 3 cm beneath the surface reduced water loss when compared with 1.5− and 6-cm inversion.
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