Cotton Is Still small…..Do We Even Need to Think About Irrigation? (Collins & Edmisten)

— Written By
en Español / em Português

El inglés es el idioma de control de esta página. En la medida en que haya algún conflicto entre la traducción al inglés y la traducción, el inglés prevalece.

Al hacer clic en el enlace de traducción se activa un servicio de traducción gratuito para convertir la página al español. Al igual que con cualquier traducción por Internet, la conversión no es sensible al contexto y puede que no traduzca el texto en su significado original. NC State Extension no garantiza la exactitud del texto traducido. Por favor, tenga en cuenta que algunas aplicaciones y/o servicios pueden no funcionar como se espera cuando se traducen.


Inglês é o idioma de controle desta página. Na medida que haja algum conflito entre o texto original em Inglês e a tradução, o Inglês prevalece.

Ao clicar no link de tradução, um serviço gratuito de tradução será ativado para converter a página para o Português. Como em qualquer tradução pela internet, a conversão não é sensivel ao contexto e pode não ocorrer a tradução para o significado orginal. O serviço de Extensão da Carolina do Norte (NC State Extension) não garante a exatidão do texto traduzido. Por favor, observe que algumas funções ou serviços podem não funcionar como esperado após a tradução.


English is the controlling language of this page. To the extent there is any conflict between the English text and the translation, English controls.

Clicking on the translation link activates a free translation service to convert the page to Spanish. As with any Internet translation, the conversion is not context-sensitive and may not translate the text to its original meaning. NC State Extension does not guarantee the accuracy of the translated text. Please note that some applications and/or services may not function as expected when translated.

Collapse ▲

We really hope this article isnt 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 90’s for most of next week in alot of areas across the state, and the chances of rain or minimal to none. When temperatures reach this point, soil moisture begins depleting fairly rapidly, with more rapid depletion occuring in sandier soils.

But cotton is so young right now….We dont 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 dont 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 dont 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 4-5 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 doesnt 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 it’s highest point. But we have to set it up for success, during that time, by starting now. The squaring period certainly isnt 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 it’s 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 dont 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 hadnt already been lost. Likewise, these high yields could’ve been substantially higher, had the early season stress been alleviated.

Below 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 2nd week of squaring. Neglecting to irrigate during this particular week (see the red bar on the graph below), and allowing the crop to stress during this 2nd week of squaring, resulted in a YIELD LOSS of 400-600 lbs/A, DESPITE the fact that it was irrigated properly during the entire bloom period. When irrigated properly during this 2nd week of squaring (two irrigation events at 0.5″ each in this case) and during the bloom period, maximum yields were achieved (see the light blue bar in the graph below). This same result occurred in both an early and a late maturing variety. Therefore we can conclude that cotton doesnt need ALOT of water during squaring but it DOES NEED SOME.

If it doesnt need much water right now, then how much does it need?  As mentioned previously, squaring marks the point at which cotton need some water, and those demands will increase as the plant grows. Below is a very general model for irrigating cotton, and it illustrates general water demands for each week of development. In the absence of rains, these weekly rates should be split into 2-3 irrigation events and adjusted for any natural rainfall that occurs during any particular week of development. For example, if the water requirements during the first week of bloom is 1 inch, a grower should irrigate 0.5 inches twice during that week or 0.3 inches three times that week . Irrigations should be separated by 3-4 days (twice a week irrigation) or by 2-3 days (irrigating 3 times per week). This allows continuity of soil moisture and also allows for adjustments to be made if rainfall occurs, which could save you money and water. Keeping track of growth stages is also critical so that you dont get behind.

This model calls for 1 inch per week during squaring, and the same for the first week of bloom. Cotton likely doesnt need that amount, especially right now. It is more important to have some degree to meaningful soil moisture right now, than it is to apply a large amount of water through irrigation. For right now, cotton could likely use about 0.5 inch per week (two irrigations of 0.25 inches each). As the plant grows and approaches 1st bloom (approximately 3 weeks after first square when heat is adequate), weekly rates can be gradually increased to reach 1 inch per week as it enters the bloom period.

Take-home message: This is the time of year that most folks neglect to irrigate properly, simply because the plant is small and it is percieved to not need much water. Growers simply do not think about irrigating cotton at this point. It is true that cotton doesnt need much water right now, but it does need some. It is very rare to see yield penalties from failing to irrigate during this time of year, but it is also rare to encounter meaningful drought stress during this time of year. However, forecasted conditions over the next week or so could lead us into one of these rare scenarios when irrigating properly now can make a substantial difference in overall yields later.