What is in this article?:
- Water crisis developing in Georgia corn crop
- Formula for minimum loss
• Any stress now guarantees some yield loss depending on the length of the plant stress and its growth stage.
• Irrigating to meet the crop demand is difficult given the evapotranspiration rates of corn and the current available water supply.
• Moisture stress has the most adverse effect on corn yields when it occurs two weeks before and two to three weeks after pollination.
Formula for minimum loss
If you know you only have enough water for four irrigations at the time of tasseling, then apply water as described, but after the second irrigation, add a two-day delay between the second and third irrigation and three days between the third and fourth irrigations. This will get you through the critical time with a minimum of loss.
Yield loss due to a water shortage is mitigated the further the kernels develop and mature prior to the stress as long as the soil profile is fully charged at the time water shortage occurs. That is why we say it’s best to use the majority of your water during this critical stage.
After 18 days-plus past the tassel stage, the kernel number is set and the milk stage begins. Drought stress during this time period will reduce kernel size and lead to some yield loss.
Studies have shown that the yield reduction is due mostly to kernel weight loss. At this point, a continuous two-day delay in irrigation applications will not severely damage your yield. Studies have shown a 5 to 20 percent loss can be expected. In this case, if you apply 1 inch every third day as described above, you may stretch to the fifth day without severely affecting yield.
If enough water is available, maintain this schedule. The further the crop matures the longer the less water is required to finish the crop.
In cases of very limited water, consider the following conservation suggestions. The goals of these conservation practices are to use the limited water supply in the most profitable way for the most return on your investment.
• Consider shutting off the end gun. End guns are major outlets of pressure and water and often irrigate non-crop areas (roads, pine trees, etc). Also, the areas under the end guns generally have much lower yield potential particularly under current conditions.
• Sacrifice the lower yield potential areas (end guns areas, soils with nematodes or nutritional problems etc). Minimize the amount of time the pivot walks through or over non-crop areas.
• Evaporative losses for two 0.5 inch applications are greater than for a 1-inch application, therefore, make your irrigation applications as much as possible prior to the point of run-off.
• In cases of shared water sources for separate fields, focus on the corn that is in the critical 18-day period we have discussed.
These are, hopefully, helpful suggestions to maximize your return during this critical drought. Each situation will be different and results will vary for each strategy taken.