Water withdrawal for irrigation from the Mississippi River Valley Alluvial Aquifer (MRVAA) is occurring at a rate that is depleting the aquifer–i.e., it is not sustainable. Therefore, methods to increase the efficiency of irrigation water application to crops, especially soybeans, are required to curb this over-withdrawal.
Conventional continuous flow furrow irrigation (CONV) is the predominant delivery system for 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 which 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.
Surge irrigation (SURGE) is a technique that improves furrow irrigation efficiency on these 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.
Click here for a White Paper on this website that provides details and links to resources about SURGE use with furrow irrigation systems.
A June 2020 post titled “Surge Valves Update” by Drew Gholson and Dan Roach on the MCS blog site provides the specifics of using this water-saving technology on both silt loam and clay soils. Pertinent points from that article follow.
• By using surge valves, producers can expect 1) reduced surface runoff, 2) reduced deep percolation loss of water, and 3) application efficiencies that are about 25% greater than using conventional furrow irrigation techniques.
• The first step in deciding on the correct surge valve to install is to select the proper valve based on the well or riser output. A chart in the above MCS blog article is provided to assist in this decision.
• For a silt loam soil, 1) determine the out time from past experience, 2) set the advance cycle, 3) record the time for irrigation water to actually reach the tail ditch, and 4) use the PHAUCET/Pipe Planner printout to determine the soaking time, and adjust if needed.
• For a cracking clay soil, 1) refer to the PHAUCET/Pipe Planner printout for the time required to apply 3 acre-inches of water and set the advance cycle accordingly, 2) use the surge valve only in the advance mode and use the custom tab to adjust the total number of cycles per side, ensuring that the value is never less than 3 (see the table of recommended settings in the above MCS blog article) , and 3) do not operate in soak mode.
Using surge valves along with Pipe Planner and soil moisture sensors will assuredly increase furrow irrigation efficiency and save time and money according to results from MSPB-funded research shown in the article here.
Composed by Larry G. Heatherly, July 2020, firstname.lastname@example.org