Irrigation Now and in the Future

There is no doubt that water–both its management and wise use–is now and will continue to be a critical factor in determining the future of agricultural productivity and subsequent food security in the U.S. and the world. After all, no present crop can be produced without the amount of water that is needed and used for its [hopefully optimum] production. There is no doubt that food security is important for the world’s population, but first there must be water security to ensure that the production of food needed to ensure that food security can be accomplished.

It is common knowledge that Midsouth producers who irrigate crops rely on groundwater from the Mississippi River Valley Alluvial Aquifer [MRVAA]. Over the last 2-3 decades, increased irrigation in the region has resulted in a significant decline in the water level in this shallow aquifer, and this decline has generated concern to the point that remedial measures are being proferred, discussed, and used. However, these water-saving technologies must be used by all irrigators in the region for them to be effective in reducing or stopping the decline in the aquifer level.

In Feb. 2019, the Council for Agricultural Science and Technology [CAST] published Issue Paper 63 titled “Aquifer Depletion and Potential Impacts on Long-Term Irrigated Agricultural Productivity” that reviews the causes and consequences of groundwater depletion. Pertinent excerpts from that paper can be accessed here.

The most obvious solution to decreasing aquifer depletion is to extract less groundwater from it. Since agriculture is the single largest user of groundwater in the U.S., it follows that a reduction in groundwater pumpage for crop irrigation could decrease groundwater depletion. A network of automated weather stations such as that described and tested in the article found here and used in the article found here could be combined with research-based crop coefficients [click here] to estimate crop water requirements. This would allow irrigation applications to more accurately match crop water needs without over-application of water and crop yield loss, thus resulting in decreased withdrawal from an aquifer.

There are available tools that can be used to result in more efficient irrigation of Midsouth crops. These include 1) using Pipe Planner to design a system to furrow-irrigate a crop field, 2) using soil moisture sensors [click here and here] to schedule irrigation, 3) using surge valves/surge irrigation [click here and here] to intermittently irrigate adjacent field areas, and 4) employing a tailwater recovery system to ensure that no applied irrigation water leaves a field. Agronomic practices such as early planting of early-maturing soybean varieties can be used to reduce the number of irrigation events.

Additional tools have been/are being developed for use by irrigators to increase irrigation efficiency. They include:

  • Overhead irrigation of a crop should be started at a wetter soil moisture than if using furrow irrigation so that a cumulative water deficit does not cause drought stress in the crop;
  • Raising the height of elevation buildups in a run of poly pipe used to furrow-irrigate a crop from an upper turn row with a significant elevation decline from the water source to the end of the poly pipe;
  • Matching subsurface tillage to soil texture of a field to optimize infiltration of both rainfall and applied irrigation water; and
  • Closely matching the timing of irrigation termination to a crop’s maturity timeline so that unnecessary irrigation is not applied.

Click here for a White Paper on this website that provides results from research that show the worth of using water-saving technologies when irrigating. Click here for an article on this website that addresses the potential development of soybean varieties with a genetic trait that will allow them to partially withstand drought stress.

The facts are clear. The continued population growth in the U.S. and world and the subsequent increasing demand for more food means that irrigation of cropland will increase the stresses on maintaining sustainable water resources. This in turn will increase reliance on groundwater sources as a supply for this increased need for water, which will then result in groundwater depletion. For agriculture, this continued decline in water tables will result in decreasing yield of wells used to provide irrigation water to crops, and create the need to drill more expensive deeper wells that will cost more to operate.

Click here for the Soybean Irrigation Guide from MSPB that is posted on this website, and here to access a White Paper titled “Soybean Water Relations and Irrigation”. Accessing the White Paper will allow access to detailed information about the myriad water conservation tools that can and should to increase irrigation efficiency.

Composed by Larry G. Heatherly, June 2024, larryh91746@gmail.com

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