|Allen R R,|
|Musick J T,|
|Schneider A D,|
Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 9, 1995
Publication Date: N/A
Interpretive Summary: Much of the irrigated winter wheat in the Southern High Plains is managed with furrow irrigation. Improved methods are needed to efficiently manage the irrigation water that is available because supplies are limited. Some land having 1% or more slope also has dense soil that accepts water slowly, causing irrigation water to runoff ends of fields. A one-time deep moldboard plowing 14 to 16 inches deep can mix dense soil layers and increase irrigation infiltration by about 25% during the first irrigation after tillage, which reduces runoff water lost from fields. After deep plowing and growing a crop, the soil surface may be recompacted from irrigation wetting and subsequent harvest equipment traffic. This can be corrected by moldboard plowing only about 8 inches deep to mix surface soil and crop residue before planting the next crop. This management option offers furrow irrigated growers an opportunity to improve irrigation water use efficiency by maintaining desirable irrigation water infiltration, and increasing wheat yields from 60 bushels per acre for conventional tillage to 75 bushels per acre with deep moldboard plowing.
Technical Abstract: Pullman clay loam (Torrertic Paleustolls) and related soils are the predominant soil types in the Southern High Plains. They are slowly permeable in their natural state, but respond to deeper than normal tillage to increase irrigation water intake. One-time deep moldboard plowing to 0.4, 0.6, and 0.8 m depths was done in 1966 to evaluate inversion and mixing of the slowly permeable Bt1 horizon with the Ap horizon. We report long term residual effects from the deep plowing after 25 years of cropping. Winter wheat [Triticum aestivum (L)] was grown during this 4-year test. After moldboard plowing to 0.2 m to restore surface tillage layer permeability, residual effects from the one-time deep plowing caused an average increase in intake of about 25% (129 to 163) mm for the 0.4 m plow depth compared with the 0.2 m check during the first irrigation after tillage. Irrigation intake increased by 40% (52 mm) with 0.6 m deep plowing, but there was no added increase for 0.8 m plowing. Average grain yields increased from 4.2 to 5.0 Mg/ha (19%) with 0.4 m or deeper plowing. Deep plowing increased soil water storage and apparent crop rooting to extract soil water, thus increasing water use efficiency about 8%.