Irrigation Termination In Cotton

 DR. TYSON RAPER

KNOXVILLE, TENNESSEE

 Temperatures this week have really pushed our crop; node above white flower counts are crashing and bolls are hardening in our earliest crop well-up past the middle of the plant.  Many of those who have the option of irrigating their cotton have called this week to discuss if the rewards for irrigating outweigh the risks.  In this blog, I try to outline those discussions to help those in a similar situation.

This decision, in my opinion, breaks pretty clearly based on whether or not the crop was planted early (before May 6th) or late (between May 9th til June).  On our earliest planted acres, I suspect the response to irrigating will be negligible, as I believe most have enough available soil moisture to finish out this crop and cracked bolls will likely be easy to find in the immediate future (they are already showing up on some eroded hillsides).  To the counter argument(s) that, ‘rain is not in the forecast, my retention was low early, and/or my farm missed some of the big rains’- I might concede one or two irrigation events in the immediate future, but that would be all.  Humidity levels are very high and our July wet spell already led to boll rot/hard lock appearing low in the canopy.  I’m not concerned about any foliar disease on these earliest planted acres, but the risk of creating a perfect environment for boll rot or hard lock definitely outweighs the reward of filling out the last one or two positions this close to cracked boll.

For later planted cotton (8th-25th), I think I could make a pretty strong argument for irrigating.  Our forecast is void of any substantial rain events and although we have (or had earlier in the week) decent soil moisture, it is unlikely that this will carry us through the end of the season.  When irrigating, I would prefer the event to occur overnight and I would space irrigation events out to allow a thorough drying of the canopy between events.

Regardless of perceived need, terminate overhead irrigation events by cracked boll. ∆