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Surge Irrigation for Improved Irrigation Efficiency

During the past several years, the MSPB funded the RISER project (click here for project final report) that was conducted under the leadership of Dr. Jason Krutz, now the Director of the Miss. Water Resources Research Institute. This project investigated various technologies or best management practices (BMP’s) that potentially can be used to increase irrigation efficiency and thus minimize or stop the decline in the water level of the Mississippi River Valley Alluvial Aquifer (MRVAA), which is the primary water source for Delta-wide crop irrigation.

Conventional continuous flow furrow irrigation (CONV) is the predominant delivery system for furrow irrigation water that is applied to soybeans grown on the clay-textured soils in the Midsouth. This water delivery is done through lay-flat polyethylene tubing that is attached to a well or riser, and then laid perpendicular to the furrows at the upper end of a field. Holes are then punched in the tubing to allow the continuous flow of water down each furrow. Even though this method allows rapid delivery of water down the furrows, its application efficiency is low. This low efficiency is attributed to deep percolation losses (infiltration exceeds irrigation requirement), tail water runoff at the end of the furrows, and slow wetting advance time.

A technology that was investigated in the RISER project as an alternative to CONV is surge irrigation (SURGE), which is a technique that may improve furrow irrigation efficiency on clay-textured soils. During SURGE, water is applied intermittently to furrows on each side of the water inlet by alternating a series of relatively short on and off time periods. This intermittent water application is accomplished by using a programmed automated valve which automatically cycles irrigation water between the two sides of the inlet, and results in water moving to the end of irrigated furrows quicker than when applied by continuous flow.

In a published article by Wood et al. (CFTM Aug. 2017), results from a three-year (2013-2015) study that investigated SURGE in furrow-irrigated soybeans grown on a clay soil are presented. A summary of that research and its results follows.

•   The objective of the research was to determine the effect of SURGE vs. CONV on 1) amount of irrigation water applied to soybeans, 2) soybean seed yield, 3) irrigation water use efficiency (IWUE), and 4) net return above irrigation costs when used on clay-textured soils in the Delta.

•   Studies were conducted for 3 years (2013-2015) at Stoneville, Miss. on Sharkey clay soil.

•   The research consisted of paired fields, with the same MG IV soybean variety planted on the same date within each year on each field.

•   Computerized hole selection (PHAUCET) was used for both CONV and SURGE applications.

•   Irrigation water was applied to both CONV and SURGE fields when the average soil water potential in the 0- to 24-inch soil depth was between -75 and -100 centibars.

•   Irrigation events were considered complete when water reached the end of 90% of the furrows. Irrigation was terminated when soybeans reached the R6.5 growth stage.

•   Water applied per SURGE event and total water appled with SURGE during the season were reduced by 22% and 24%, respectively, compared to CONV.

•   Water savings with SURGE vs. CONV increased by 2% per 100 ft. as row length increased from 540 to 1800 ft.

•   Soybean seed yield averaged 66 bu/acre with both CONV and SURGE applications.

•   SURGE improved IWUE by 29% relative to CONV.

•   Net returns above irrigation costs were not different between CONV and SURGE regardless of diesel fuel cost or pumping depth. Thus, the additional costs associated with SURGE are offset by reduced water application with SURGE.

•   Conclusions from this research are: 1) A significant portion of the overdraft from the MRVAA can be eliminated by SURGE adoption; 2) SURGE vs. CONV will improve IWUE by soybeans grown on clay-textured soils in the Midsouth without sacrificing yield; 3) SURGE vs. CONV will reduce the time required to irrigate a site devoted to soybeans; and 4) Midsouth soybean producers can adopt SURGE on the shrink-swell clay soils in the region without adversely affecting on-farm profitability because the water savings due to SURGE use will compensate for the increased capital investment required for its implementation.

The issue, then, is not how soybean producers can reduce their use of irrigation water, but rather when will they realize that SURGE and other water saving technologies discussed/presented on this website must be adopted now and not later if the MRVAA is to continue as a viable source of irrigation water. To delay will certainly limit the future of irrigation of all crops in the Midsouth.

Composed by Larry G. Heatherly, Apr. 2020, larryheatherly@bellsouth.net