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United States Department of Agriculture

Agricultural Research Service

Research Project: MANAGING AND MODELING DEFICIT IRRIGATION AND LIMITED RAINFALL FOR CROP PRODUCTION IN SEMI-ARID REGIONS

Location: Wind Erosion and Water Conservation Research

Title: Circular Planting to Enhance Rainfall Capture in Dryland Cropping Systems at a Landscape Scale

Authors
item Lascano, Robert
item Nelson, Randall -

Submitted to: Trade Journal Publication
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 27, 2014
Publication Date: N/A

Interpretive Summary: The water table of the Ogallala Aquifer in the Southern Texas High Plains is declining as predicted and is some years at a faster rate than others. This decline is directly proportional to the amount of rainfall and associated drought and in dry years translates to more water pumped from the aquifer in order to accommodate the water needed to establish an economic harvest. Because of drought and increases in the energy-cost to pump water from the aquifer the amount of land area used towards dryland production has increased. Further, economists predict than this shift towards more dryland production will increase both in rate and in magnitude. From a research view a partial solution to alleviate the economic lost that will come from producing less crop yield per unit land area is to increase the amount of rainfall use efficiency (RUE). What is RUE? In first analysis, RUE is the amount of rainfall that is stored in the soil and is not loss to runoff. For example, a 2-inch rainfall will have a RUE equal to 50% if 1 inch of this water is stored and the other 1-inch is lost due to runoff. An increase of RUE from 50 to 75% means that only 0.5 inches of this storm is lost due to runoff. General knowledge indicates that about 50% of the rainfall received in this area is lost due to runoff and this loss increases with increasing rates of rainfall. We have hypothesized that a solution to increase RUE is to plant dryland crops in a circular pattern as done under center-pivot irrigation. The circles across the landscape provide a contour that will increase ponding time of rainfall and thus more infiltration and less runoff. We tested our hypothesis using the Precision Agricultural Landscape Modeling System (PALMS) model to simulate a circular planting in a dryland cropping system and to evaluate the impact on the surface water balance, mainly runoff and infiltration, across the landscape. Field studies, on predominantly sandy soils were conducted during 2007, 2008 and 2009 on four commercial dryland fields, ranging in size from 26 to 64 ha, in Dawson County, TX to measure soil water content and crop response to circular planting patterns. Values of soil water content indicated less runoff from fields planted in circular patterns occurring during large, intense rainstorms. The PALMS simulations indicated longer ponding time and increased infiltration in fields planted in a circular pattern, most notably in locations with significant topographic relief. We conclude that planting crops in a circular pattern is a viable option under dryland production.

Technical Abstract: Declining availability of irrigation-water from the Ogallala Aquifer in the Southern High Plains of Texas has caused a shift to more dryland production and we need to increase rainfall use efficiency with minimal expense to producers. We hypothesized that planting dryland crops -13in in a circular pattern would increase surface roughness, ponding time, and subsequent rainfall infiltration compared to conventional straight rows. The objective was to use the Precision Agricultural Landscape Modeling System (PALMS) to simulate a circular planting in a dryland cropping system and evaluate the impact on the surface water balance, mainly runoff and infiltration, across the landscape. Field studies, on predominantly sandy soils were conducted during 2007, 2008 and 2009 on four commercial dryland fields, ranging in size from 26 to 64 ha, in Dawson County, TX to measure soil water content and crop response to circular planting patterns. Measured soil water content from all locations and years yielded 421 values that when compared to corresponding simulated values produced a linear regression with slope of 0.88, r2 of 0.86 and RMSE of 0.038 m3 m-3. This agreement was used to infer that simulated components of the surface water balance were correct. Values of soil water content indicated less runoff from fields planted in circular patterns occurring during large, intense rainstorms. The PALMS simulations indicated longer ponding time and increased infiltration in fields planted in a circle, most notably in locations with significant topographic relief. We conclude that circular planting is a viable option under dryland production.

Last Modified: 12/20/2014
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