COTTON WITH WET FEET
Management Considerations for Wet and Excessively Wet Cotton in 2013 (July 6th, 2013)
Jared Whitaker, Guy Collins, Glen Harris & Stanley Culpepper
Excessive amounts of rainfall have occurred in several areas of the cotton growing region in Georgia during the month of June. In many fields where this kind of rainfall has occurred, cotton has already been planted and seedling cotton is suffering. Cotton seedlings are highly sensitive to excessively wet soils. Not only is cotton in general a particularly sensitive plant, the seedling stage is the most sensitive to excessively wet soils. However, in most cases the soil profile dries out and growth and development is not delayed. In many cases this year, the shear amount of rainfall and continued frequency of rains have left soil in parts of some fields and entire fields in other cases waterlogged for days, if not weeks.
There are several things to consider when evaluating what, if anything, a grower should do while the soil is drying out. First things first, the soil does have to dry out for us to do most anything to the crop, since getting any equipment in the field will require it. Worrying about something we can’t do anything about can be wasted effort. By no means should we ignore the issue, but don’t get too rash until there is something that can be done. One thing that may happen is that portions of a field will remain waterlogged while most of the field is drying out. The question of when to start working a field may be based on when a particularly wet portion of the field dries. This kind of decision is something that should be considered on a case by case situation, but consider that these parts of the field may remain unworkable for the entire year and proceeding with field activities in the majority of the field while staying out of wet areas may be the way to go.
Waterlogged soils can cause cotton seedlings to respond in various ways. The visible effects will likely be related to how long the soil has been waterlogged and the age of the cotton. Generally speaking, waterlogged conditions reduce the crop growth rate by replacing the air in the soil with water, depriving the roots of oxygen. Since oxygen diffuses much more slowly through water than air, the roots soon become deprived of oxygen and are unable to maintain normal respiration. Respiration is a necessary plant process that the plant uses to provide energy and building blocks for growth. In general the respiration rates are highest in the terminal of the plant and the root tips.
As soils become more and more saturated and eventually become waterlogged, they are termed anaerobic and the effects on cotton plants may include chlorosis, yellowing, reduced shoot growth, reduced nutrient uptake, altered hormone levels, and other problems (many acres of cotton have symptoms of reddening leaves and stems being too wet, as well as typical nitrogen deficiency symptoms). So, if we consider the amount of rainfall which has occurred in some fields and the fact that soils have been waterlogged (or close to it) for an extended period of time the crop has most certainly gotten off to a slow and rough start. This will most certainly bring up management issues that may or may not be worth addressing and will likely create a scenario where growers are trying “fix the problem” or “bring the crop out of it”.
Below I’ve just listed questions that could be related to this issue and may help with grower questions or yours. As we all know, nothing is constant and very few things are certain in agriculture. These are some of our thoughts from existing literature, experience, and talking to folks who have dealt with this.
In general, we think that this issue will be something that just has to work itself out. As soon as the soil dries out, the crop should start to rebound and major alterations to management will not likely be warranted.
What’s going to fix this cotton? SUNSHINE AND DRY WEATHER The plant processes have been slowed and the plant needs time to recover. It will recover when oxygen levels reach normal in the soil and respiration can proceed as normal. Most of the symptoms that are present are related to the plant not growing, not a lack of something. In most cases, everything the plant needs is there it just needs to recover to start utilizing nutrients and producing new leaves and roots.
Will this cotton live? Our answer would have to wait until the field dries out, if the soil is no longer waterlogged, and the terminal is green and is starting to produce new leaves, then the logical answer would be that it has lived. If not, then it isn’t. That answer is pretty simple, but trying to decide while the soil is too wet to do anything is somewhat of a futile task. When the supply of oxygen is cut off to the plant, and the field is in standing water, the plant can die in as little as 36 hours. I don’t think this is always the case, but it could explain plant death. When the supply of oxygen is completely cut off, roots stop absorbing water, even when completely saturated with water, and eventually die. Cotton survival has been variable, as one would expect, but in general cotton which has produced several true leaves has fared much better than germinating cotton or cotton with less than two true leaves.
Is this crop worth it now? If the plants aren’t dead and are actively growing in the near future, then in all likelihood it’s worth it. So, in most cases proceed as normal. One thought here is what to do if some or portions of the field are drowned out. Talking to insurance providers and experts may help with the financial makings of this decision. If a part of the field was dry enough to get back going, it would make sense to farm the drier parts, but it may depend on the insurance side of it and the protection and coverage available.
What are the potential lingering effects? Excessive moisture causes seedling cotton to develop smaller leaves and shorter internodes, resulting in stunted growth. Once excessive moisture is gone, normal growth should start, but the effects may be noticeable for much longer. One potential issue with waterlogged seedling cotton is the dramatic reduction is root growth. In normal conditions root development may proceed at a rate of 0.5 to 2.0 inches per day; however wet and waterlogged conditions will greatly reduce root growth. This may cause the crop to be more prone to drought later in the year. Other than irrigation to alleviate drought stress, this is a problem that could potentially hurt yield. One other issue is that development could be delayed such that the crop could be managed like it was planted much later than it really was. For instance, waterlogging could slow growth to the point in which cotton planted much later could actually be further along and management should reflect this.
Can I cultivate the middles and help it out? In some soils, excessive rainfall events tend to pack soil and “seal” it. When these conditions occur, drying of the soil may proceed slower and there is a potential for cultivation to loosen soil and allow oxygen to reach the roots faster and help the crop start to develop normally. Since root development was restricted during wet conditions, cultivation could actually prune roots if the sweeps are set too low. One could dig around to see where in fact the major portions of the root zone are before considering cultivation. In most cases where soils are excessively wet for an extended period of time, lateral roots may be very close to the soil surface and pruning them may set us back even further, especially if the tap root has not developed as it should.
Should I try foliar fertilization? Most research indicates that foliar feeding with nutrients or applying plant growth products will not provide much benefit to young, stressed cotton. These applications may leave the grower feeling like it helped (based on slight color differences, or slightly more growth) but a yield response is unlikely. The cotton crop is likely suffering from the ability to take up nutrients rather than the lack of nutrients. Also a stressed cotton plant struggling to grow, with photosynthesis impaired, it will likely have a more difficult time also taking up foliar nutrients. Foliar fertilization can also potentially burn the crop, which is generally not needed in these cases.
What about Pix or PGRs from now on? I would delay any initial thoughts to apply PGRs to cotton coming out of this situation. Even with aggressive varieties, I would be hesitant to inhibit vegetative growth. Watch the internode lengths and be sure that the crop needs an application before just going out and doing it because its time. The growth rate of the plant can be seen in the internodes, if they are still “tight”, then the crop still needs to get going. If the internodes have started expanding and the crop is getting some height on it, then we can do something, especially if after side-dress N and after bloom. This crop needs to grow, and doesn’t need any slowing of vegetative growth.
What about side-dress nitrogen? Regarding timing, we know that the typical time for side-dressing N is from 1st square to 1st bloom, if cotton in this scenario is drying out and starting to grow, it may not hurt to start a little early or at least be on the early end. If the cotton has already reached 1st square, go as soon as possible. If cotton is already blooming, again go as soon as possible. With regards to rates, it may be more appropriate to go with a lower rate than normal for a couple of reasons. Reducing the amount of nitrogen may help with proper growth and development of this “late” crop. Too much nitrogen may cause too much vegetative growth that may not in turn relate to more cotton yield because of the reduced amount of time to mature. Also, if reduced rates are used up front, then there is still an opportunity to come back with some through a pivot or foliar later on.
What about weed control? Weeds are likely going to be bigger than usual in fields that we have been kept out of. When we can get in the field, make sure that we are making the appropriate decisions on herbicide selection. Regarding weed control, all should be the same. Regarding herbicide injury, it may be a different story. Any tank-mixture that can burn the cotton crop could delay development further and an attempt should be made to avoid it. This will most likely be related to the application of Staple, Warrant or Dual mixed in with Roundup or Liberty, especially liberty on Phytogen Widestrike cotton. However, weed control is extremely important in any cotton field and this may not be avoidable. Potential problems that can be avoided should be additional tank-mix partners (other than herbicides) that are not necessary. These include additional adjuvants, water conditioners, ammonium sulfate, and other foliar fertilizer mixtures that could increase chance of injury, especially when mixed with Dual, Warrant, or Staple. Unless absolutely necessary, consider leaving these out of the tank.