Irrigation Termination in Cotton
The time of year has arrived that growers are getting the itch to terminate irrigation applications in cotton. In a normal year, cracked bolls are present at the present calender date; however, cracked bolls are currently the exception rather than the rule. Cracked bolls have been observed in the Rolling Fork area of the Delta and Macon area in the Hills. There are assuredly more fields with open bolls than these; however, the point being that there are very few at this point in time that are beginning to open.
The recommendation from the Mississippi State University Extension service with respect to irrigation termination in cotton is as follows. For fields that are furrow irrigation, irrigation termination should proceed once first cracked boll appears. Some prefer to furrow irrigate a week to ten days after the onset of first cracked boll. This may be beneficial in some cases but it is also risky. Once bolls begin to crack, irrigation applications can result in increased occurrence of hardlock or boll rot. I am not willing to risk my bottom crop to fill out a small portion of my top crop.
For those the irrigate using pivot systems, our recommendation is to terminate irrigation 10 days after first cracked boll. Pivot irrigation does not deliver the volume of water compared to furrow irrigation hence the later date of termination. Certainly watering with an overhead system when bolls are cracking can lead to hardlock and/or bollrot as discussed above. However, the likelihood of doing so is reduced.
Do not terminate irrigation based on the calender date. Take a good, hard look at your crop and let it tell you what to do. If you are 10 days to 2 weeks from first cracked boll and rain is nowhere in sight, an irrigation application is warranted.