By Tony Bailey and Clint Harrison
When Mother Nature doesn’t cooperate with gentle, weekly rains later in the growing season, irrigation comes to the rescue. It’s important to get the most out of your irrigation system by ensuring the mechanics are working properly. But don’t overlook your soils. Whether you irrigate or not, make sure your soils are functioning to use all water sources. That’s how you improve your overall water use efficiency — whether water is provided naturally or by irrigation.
Irrigation can be very expensive. Make sure all water is getting to the crop’s roots, where it can be used. If you experience irrigation-induced erosion or water standing in fields, the cause is often lack of water infiltration into soil rather than too much water being applied.
Using less tillage and including cover crops improves infiltration, builds aggregate stability, reduces soil compaction and increases soil organic matter.
Lack of aggregate stability will also lead to soil crusting, which further reduces infiltration. Soil compaction doesn’t allow water to move as easily through the soil profile.
Conservation practice pluses
Increasing soil organic matter by tilling less and using cover crops also improves water-holding capacity. One percent organic matter in the top 6 inches holds thousands of gallons of water per acre. What would an additional 1% soil organic matter mean to your crop and late-season water needs?
Water that doesn’t run off is stored in the field for later use. With the increase in extreme weather events, this becomes important for all cropping systems and improves overall water-use efficiency.
Evaporation is another form of water loss. There are a wide variety of drop nozzles and high-efficiency nozzles that can be used to reduce evaporation loss.
It’s also recommended that you utilize residues on the soil surface to act as a protective barrier, reducing evapotranspiration. They also reduce runoff and improve infiltration.
Better pivot performance
Consider completing a uniformity test on your irrigation pivot. This test shows where too little or too much water is applied. Testing is accomplished by placing catch cans at specific distances under the whole system and running the system for a specified time to see how much water is applied.
It’s possible some parts of the system could underapply by 20% while other parts overapply by 20%. That is a 40% swing from the planned application rate. While this extreme swing is unlikely, if it happened, it would lead to more interesting crop circles than already expected.
Another tool for your irrigation toolbox is a soil moisture probe. Soil moisture probes can be used to help schedule applications based on current field conditions. They can also help identify if you’re getting the intended amount of water to the root zone.
Is water getting into the soil or just running off? There are different types of probes on the market. Work with a reputable dealer to find the best probe for you.
Consider using soil moisture probes to conduct a test on your operation. Place one probe in soils that are tilled with no cover crops. Place another probe in soils that have had little to no disturbance, have cover crops and are in a soil health management system. Review the data and see which system gets the most water to the roots.
During the drought of 2012, the Natural Resources Conservation Service worked with a landowner who said, “We have invested in irrigation over the years to prepare for summers like 2012.” He added: “In a field that had not yet been converted to no-till and cover crops, we could only apply a half inch of water before it began to run off. Where we had three years of no-till and two years of cover crops, we could put over 2 inches of water on without runoff … and that field made 230 bushels of corn per acre!” Now, that’s water use efficiency.
If you irrigate, making certain your irrigation system is performing at its maximum capability is important. Improving water infiltration, reducing runoff and increasing water-holding capacity of the soil will improve the overall water use efficiency of irrigation and rainwater, and your overall profits.
Bailey is a state conservation agronomist with NRCS. Harrison is an NRCS district conservationist. They write on behalf of the Indiana Conservation Partnership.