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United States Department of Agriculture

Agricultural Research Service

Title: Water Use in a Modified Summer Fallow System on Semiarid Northern Great Plains

Authors
item Aase, J
item Pikul Jr, Joseph

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 24, 1999
Publication Date: N/A

Interpretive Summary: Wheat (Triticum aestivum L.) is the major crop on semiarid northern Great Plains of the U.S.A. Attempts to introduce alternate crops have had limited success. Alternate fallow-crop rotation is the most common cultural practice. Our objective was to investigate soil water availability and crop water use when fallow was included once in four- year rotations that included deep rooted crops in a study 11 km north of Culbertson, Montana. We used spring and winter wheat, barley, a legume/grain forage crop, buckwheat, sunflower, and safflower. Safflower and sunflower used ca. 20 inches of water, more water than any of the other crops used. The greatest water use efficiency (economic yield per unit of water used) was captured by the annual forage crop. The legume/grain forage mix, in addition to aiding in potential soil improvement, also yields a high quality forage and seems to fit well in a rotation with the typical spring wheat grown on the northern Great Plains. In addition, it appears that deep rooted crops, such as safflower and sunflower, can have a place in crop rotations on the semiarid northern Great Plains. But one must be prepared for variable yields and accept possible reduced yields for the following crop and also for an occasional crop failure not associated with drought. Crop and soil management for alternative crops differ from that of small grain management, requiring some adaptation of management practices.

Technical Abstract: Wheat (Triticum aestivum L.) is the major crop on semiarid northern Great Plains. Attempts to introduce alternate crops have had limited success. Alternate fallow-crop rotation is the most common cultural practice. Our objective was to investigate soil water availability and crop water use in four-year rotations including fallow and deep rooted crops. The study was on Williams loam (fine-loamy mixed, Typic Argiboroll) 11 km north of Culbertson, Montana. Plots, replicated four times in randomized blocks, were 12 x 15 m. Rotations were: 1) fallow, sunflower (Helianthus annuus L.), barley (Hordeum vulgare L), winter wheat; 2) fallow, safflower (Carthamus tinctorious L.), barley, winter wheat; 3) fallow, buckwheat (Fagopyrum esculentum Moench.), annual legume/grain forage crop, spring wheat; 4) fallow, buckwheat, annual legume/grain forage crop, winter wheat; 5) fallow, spring wheat; 6) continuous spring wheat. Soil water to 1.8 m depth was determined near time of seeding and of harvest by neutron attenuation. The soil reached an upper drained limit of 20 to 25% water in a 1.8 m profile, equating to 450 mm water. Safflower and sunflower used ca. 500 mm water, more water than any other crop. The forage crop had the greatest water use efficiency. Except following safflower and sunflower, soil water every spring was near the upper drained limit. Deep rooted crops can have a place in rotations on the semiarid northern Great Plains. But one must prepare for variable yields and potential reduced yields following deep rooted crops, and for an occasional crop failure. Crop and soil management for alternative crops differ from that of small grain management, requiring adaptation of management practices.

Last Modified: 9/23/2014
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