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Tillage Effects on Winter Wheat Production where the Irrigated and Dryland Crops are Alternated¹

While adequately irrigated winter wheat (Triticum aestivum L.) yields are relatively high, drylaml wheat yields in the southern Great Plains are only about 700 kg/ha with continu6us cropping and about 1,000 kg/ha on a harvested-area basis after fallow. This study was conducted to determine if yields could be increased where irrigated and dryland wheat crops are alternated on the same plots. Tillage effects were also studied.

In this study, continuous winter wheat production was evaluated with respect to grain and residue yields and soil water storage, use, and use-efficiency. Wheat crops were alternately grown on Pullman clay loam [fine, mixed, thermic family of Torrertic Paleustolls (Mollisols)] with or without irrigation on disk, sweep, or no-tillage plots, and continuously on dryland and irrigated plots with sweep and disk tillage, respectively. Dryland wheat with sweep tillage yielded 2,250 kg/ha where the irrigated and dryland crops were alternated and 2,080 kg/ha on continuous dryland plots, a significant yield increase. For irrigated wheat with disk tillage, yields were similar where irrigated and dryland crops were alternated or where continuously irrigated.

For the tillage evaluations, dryland wheat yields with sweep and disk tillage were similar, averaging 2,250 and 2,330 kg/ha, respectively. Yields for both were significantly higher than the 2,120-kg/ha no-tillage average. Irrigated wheat yielded 4,650 with sweep, 4,390 with disk, and 4,220 kg/ha with no-tillage in the tillage evaluation. The differences were significant. By comparisons, dryland wheat yielded significantly more grain with sweep or disk tillage in the irrigated and dryland system than in the continuous dryland system (with sweep tillage). With irrigation, wheat yielded significantly more with sweep tillage in the alternate system than with disk tillage in the continuous and alternate systems.

Considering the combined system and tillage effects, the best treatments were sweep tillage for irrigated wheat and disk or sweep tillage for dryland wheat. Using sweep and disk tillage for irrigated and dryland wheat, respectively, where the crops are alternated increased average grain yields 10.3% over the average for the continuous irrigated and continuous dryland treatments. The greater grain yield occurred with 8.4% more soil water use, but only 2.3% more total water use. Wateruse efficiency was 8.5% greater where irrigated and dryland crops were alternated than where irrigated and dry]and crops were grown continuously. The irrigated and dryland alternate system offers a potential for greater and more water-efficient grain production than that possible where equal areas are continuously cropped to irrigated or dryland wheat.

Key Words: Irrigated wheat • Dryland wheat • Soil water use • Soil water storage • Water-use efficiency • Precipitation-storage efficiency • No-tillage • Disk tillage • Sweep tillage • Triticum aestivum L.

² Soil Scientist, USDA Southwestern Great Plains Research Center, Bushland, TX 79012.

Received for publication March 10, 1977.

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