What is in this article?:
• Cotton that is stressed early in the season actually does a little bit better later in the season,”
• As water efficiency becomes increasingly important, cotton producers need to know when a plant needs water the most, and when it doesn’t
Shooting for a balance
“Therefore, the shoots and the leaves will decrease their growth. And, depending on drought stress and the time of year, you can have increased or decreased retention in specific nodes on the cotton plant. If we have adequate water, we have much better balance between the roots and the top of the plant, and our fruit production tends to be limited by the next limiting factor, whether it’s fertility or something else,” he says.
But if there is excessive water, other problems arise, says Ritchie. “Our root system doesn’t develop as well because the plant doesn’t sense there’s any real need to invest in the root system. We tend to have taller plants, a higher leaf area index, and we tend to have decreased fruit retention earlier in the season.”
If there is too much water, then there will be excess vegetative growth, says Ritchie.
“If you have adequate water, the plant still will be actively growing during the production season, and you’ll have a much easier time controlling the growth chemically.
“You can skip some of that chemical control if you supply inadequate water. The plants generally will be shorter with less leaf area. They’re also going to have less photosynthesis, and you can run into fruit shedding. Unless you really have something that’ll make up for that period of drought, overall, you’ll have less yield potential if you’re unable to get adequate water to the plant.”
Leaf water content is going to affect several functions of the leaves, says Ritchie, primarily orientation, expansion, and the structure within the leaf. It’s also going to affect the opening of stomates and transpiration.
“If you decrease transpiration, that’s great from a water-saving standpoint for the plant, but from the standpoint of plant temperature, it’s bad, and from the standpoint of incoming carbon dioxide, it’s bad. The plant can’t really do much when it is water stressed, and it’ll cause a lot of other problems.”
With water stress, leaf expansion immediately stops and photosynthesis will eventually slow down and stop, says Ritchie. Early in the season, plants are going to be more prone to leaf wilting and in showing water stress than later in the season.
“The nice thing about having these stress signals is that now we have a way of knowing what the plant is doing during the season and hopefully be able to fix it in a timely manner.”
Once a grower knows when to water, then he needs to focus on making it as efficient as possible with irrigation, he says.