Cotton is Still Small…Do We Even Need to Think About Irrigation?


We really hope this article isn’t necessary, but the way the weather forecasts are shaping up, we are facing hot and dry conditions throughout this weekend and most of next week.

Temperatures are expected to be in the low 90s for most of next week in a lot of areas across the state, and the chances of rain are minimal to none. When temperatures reach this point, soil moisture begins depleting fairly rapidly, with more rapid depletion occurring in sandier soils.

But cotton is so young right now…we don’t need to think about irrigating cotton right now, do we? 

Well, that depends. If hot weather occurs without any rain, some irrigation is likely going to be warranted. Some folks believe that cotton should be stressed while it is young, and before it starts blooming, so that it can develop a strong root system. We understand this concept, but “stressed” is not the answer.

During the squaring period, we certainly don’t want to over-water cotton, but that would be difficult to do with irrigation. In fact, overwatering would require substantial rainfall resulting in waterlogging of soils, which is difficult to do with irrigation alone, in the absence of rain.

In such cases, shallow roots are likely to develop, which can cause problems for cotton later, so we certainly don’t want to over-water cotton right now. The current forecasts indicate that this is a very unlikely scenario right now.

We also do NOT want to stress cotton right now. There is a VERY FINE LINE between having just enough moisture to stimulate root growth and insufficient water to the point that adversities to plant growth AND YIELD are likely to occur. In times of hot weather and in the absence of rain, we are never more than four to five days away from a yield-impacting drought, and even sooner on sandy soils. These conditions are expected next week.

Our early planted cotton is beginning to develop squares, and more cotton will begin squaring next week. Squaring marks the point of increasing demand for many things, such as nutrients, and of course, water.

Cotton doesn’t need MUCH water right now, but it DOES need SOME. Water demands will increase as the plant grows, with peak demand occurring during mid-bloom when the number of developing bolls is at its highest point. But we have to set it up for success, during that time, by starting now. The squaring period certainly isn’t a period of high water demand, but that doesn’t mean that we can neglect it.

In the past, my cotton has rebounded very well in July or August, and I made high yields then. What’s different? 

Nothing is “different”. Cotton is known to be an “elastic” crop, so to speak, and its indeterminate nature allows for it to compensate for periods of stress. Cotton is also known to be a drought-tolerant crop, but this doesn’t mean that it’s not responsive to supplemental water (irrigation), especially when used to “bridge the gap” between rain events.

And this concept even applies to young cotton. It is rare to encounter yield-impacting drought stress on young cotton that is just entering the squaring phase. But research has CLEARLY demonstrated that YIELD PENALTIES CAN OCCUR as a result of hot, dry weather that occurs during this time of year.

As such, many growers have commented that they feel their crop rebounded when rains occurred during July and August. We don’t doubt that…cotton can certainly rebound and achieve high yields when sufficient rains resume following a period of drought.

What is not often realized, however, is how much yield is lost when early season stress occurs. Yes, high yields can still be achieved when rains during July and August bring cotton out of early season stress, but that doesn’t mean that some yield hadn’t already been lost. Likewise, these high yields could’ve been substantially higher had the early season stress been alleviated.

The Lint Yield graph included in this article is one such case that occurred when research was being done several years ago. This just so happened to be considered a “wet” year, but most of the heavy rains occurred during July and August.

In this particular case, rains were nearly sufficient to meet cotton demands for water during the first and third week of squaring, and rainfall was more than sufficient during the latter half of the bloom period. HOWEVER, hot and dry conditions occurred during the second week of squaring.

Neglecting to irrigate during this particular week (see the red bar on the graph) and allowing the crop to stress during this second week of squaring resulted in a YIELD LOSS of 400 lbs.- 600 lbs. per acre, DESPITE the fact that it was irrigated properly during the entire bloom period.

When irrigated properly during this second week of squaring (two irrigation events at a half inch each in this case) and during the bloom period, maximum yields were achieved (see the light blue bar in the graph). This same result occurred in both an early and a late-maturing variety. Therefore, we can conclude that cotton doesn’t need A LOT of water during squaring, but it DOES NEED SOME.

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