By NANCY BORKHOLDER
Purdue Extension Elkhart County
Just a few days ago, it seemed the rain was not going to stop. The talk is about how quickly our soils have dried out. We are approximately 1.5 to 2 inches behind the normal rainfall for the growing season at this point.
We learned back in 2012 that an early season drought can be tough on a crop. The young seedlings will expend energy to send out roots to search for water and then the plants stop growing. While no one likes to apply irrigation water this early, it may be necessary in 2016.
The good news is there is still moisture available deep in the soil in most fields. However, the seedlings need some water in the upper portions of the soil to give them the strength and vigor to find that deeper water.
In fields where a cover crop such as rye or wheat was recently harvested as a forage, much of the moisture stored in the top 3 to 4 feet of soil was “harvested” by the cover crop. You may need to apply 3 inches of water to rehydrate the soil profile down to the 3 or 4 foot level. In many cases, you might want to split that application if the soils are vulnerable to runoff.
Crop residues on the soil surface tend to reduce evaporation-transpiration rates. In fields with no-till or high residue reduced tillage, you can apply 0.5 inch of water to wet the soil profile to about 6 inch depth. That 0.5 inch of water will be used up in approximately 5 days given the current evaporation-transpiration rates.
Plowed fields with little or no crop residue on the surface will allow more water to evaporate than a reduced tillage field. An application of 0.75 to 1 inch might be required to wet the soil to provide 5 days’ worth of water.
Hopefully, rains predicted the next few days will come through for us. As temperatures rise this summer and crop roots grow deeper, we will see the need to increase the amount of water that is applied to our fields, approaching 1 to 1.5 inches in a single pass of the irrigation system.