Irrigation can be helpful when Mother Nature doesn’t cooperate. It’s important to get the most out of your irrigation system by ensuring the mechanics are working properly, but it’s also important not to overlook your soils. Tony Bailey says you should make sure your soils are fine-tuned to use all water sources, whether natural or irrigated. That’s key to improving your overall water use efficiency.
Bailey is a district conservationist with the Natural Resources Conservation Service in Indiana. He suggests completing a uniformity test on your pivot. A uniformity test shows where too little or too much water is being applied.
Testing is accomplished by placing catch cans at specific distances under the whole system and running the system for a specified period of time to see how much water is applied. It’s possible for some parts of the system to underapply by 20% and some parts to overapply by 20%. That equals a 40% swing from the planned application rate. While it is unlikely that this extreme swing would happen with the same system, if it were to happen, it would most certainly lead to more interesting crop circles than what were already expected.
Irrigation and infiltration
If you experience irrigation-induced erosion or standing water, it’s more likely caused by the lack of infiltration of water into your soil than too much water being applied, Bailey says. 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 crusting is a particular problem in springs like 2017, when young seedlings, especially soybeans, are trying to emerge.
Soil compaction doesn’t allow water to move as easily through the soil profile, Bailey notes. Increasing soil organic matter with less tillage and cover crops also improves the water holding capacity of soils. Each 1% of soil organic matter in the top 6 inches of soil holds about 27,000 gallons of water per acre.
More organic matter
What would an additional 1% of soil organic matter mean to your crop and late-season water needs? With increased extreme weather events, it means the water that doesn’t run off is stored in the field for later use by the crop, Bailey emphasizes. This is important for all cropping systems, and improves your overall water use efficiency.
In 2012, Bailey worked with a landowner who had invested in irrigation over the years to prepare for summers like 2012. The farmer noted that in a field that had not yet been converted to no-till and cover crops, he could only apply a half inch of water before it began to run off.
Where he had three years’ worth of no-till and two years’ of cover crops, he could put on over 2 inches of water without runoff. That field made 230 bushels of corn per acre.
If you irrigate, making certain that 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 from both irrigation and rain, Bailey concludes.