As we approach the end of August, terminating cotton irrigation is on the mind of many folks. In cotton, we recommend terminating furrow irrigation at first cracked boll. If you anticipate bolls opening in the immediate future and have been dry for some time, a final irrigation event may be in order. However, once bolls begin to open, furrow irrigation is not recommended. Irrigation obviously introduces moisture under the crop canopy; however, if the canopy is dense and moisture is present when bolls are cracking, the chances for hard lock and/or bollrot are greatly increased. Some prefer to irrigate one additional time past first cracked boll but keep in mind that this is a risk/reward situation. While you may help fill out some of the uppermost fruit, you run the risk of rotting or hard locking some of the lower fruit on the plant.
For pivot irrigated cotton, we recommend terminating irrigation 7 to 10 days after first cracked boll. The reason for the discrepancy between furrow irrigation and pivot irrigation is due to the difference in volume of water delivered. As with furrow irrigated cotton, water from an overhead source after bolls begin to open may increase the chances of hard locking or rotting some of the fruit.