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United States Department of Agriculture

Agricultural Research Service

Research Project: Improved Soil Managment Practices for Tilled Summer Fallow in the Pacific Northwest

Location: Soil and Water Conservation Research

Title: Surface effects on water storage under dryland summer fallow, a lysimeter study

Author
item Wuest, Stewart

Submitted to: Vadose Zone Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary: Small changes in short and long term soil water storage can have large effects on crop productivity in semi-arid climates. To optimize tillage and residue management, we need to measure evaporation from a range of treatments on contrasting soil types. Most weighing lysimeters are expensive and labor intensive, so small lysimeters were tested for use in comparing evaporation over the summer in a dry climate. The depth of loose soil, the presence of clods, and other factors were tested. The lysimeters were capable of distinguishing fine gradations in mulch depth and surface residue treatments. Crop residue on the soil surface had little influence on evaporation during long, dry periods, but had a substantial effect on retention of water immediately after rainfall, especially as rainfall increased and temperatures decreased in early autumn. Results will be used to recommend ways to increase soil water storage of water for crop growth.

Technical Abstract: Small changes in short and long term soil water storage can have large effects on crop productivity in semi-arid climates. To optimize tillage and residue management, we need to measure evaporation from a range of treatments on contrasting soil types. Sixty low-cost, low-maintenance lysimeters were constructed from 26-liter buckets and installed in-ground. Summer fallow soil management options were mimicked by packing soil uniformly to the surface (no-till), putting a loose layer of fine soil on top of the packed base (tilled) or placing a mixture of clods and fine soil on top of the base (conservation tillage). The lysimeters were capable of distinguishing fine gradations in mulch depth and surface residue treatments. Crop residue on the soil surface had little influence on evaporation during long, dry periods, but had a substantial effect on retention of water immediately after rainfall, especially as rainfall increased and temperatures decreased in early autumn. The depth of a loose soil mulch over the dense sub-soil had an incremental effect on reducing evaporation over summer, and this was not affected much if the loose soil contained a mixture of clods and fine soil. Lower density soil sometimes stored more water after rainfall, which contradicts observations that denser, no-till soils often recharge faster than tilled soils after a dry summer. The results indicate high levels of surface residue might be more important than tillage or no-tillage in the proportion of early autumn rain stored versus evaporated.

Last Modified: 07/21/2017
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