Cotton Fertilization and Aphids
Posted by romeethredge on July 9, 2011
Late Planted and Uneven Stand Cotton Fertilization
Ray Hunter III (Little Man) is helping his daddy and I look at some dryland cotton that ended up coming up to a good stand, although somewhat uneven.
Dr Glen Harris, UGA Extension Crop Scientist, gives us some good information below concerning how to fertilize late-planted cotton and uneven stands.
Due to the extreme and exceptional drought in south Georgia, we have a lot of late-planted June cotton and fields with uneven stands this year. Some key points to remember when adjusting to this situation are:
1)Don’t try to rush the crop by overfertilizing with nitrogen – Unfortunately you can not fertilize your way out of a drought. I wish you could. And in fact, trying to rush a late-planted crop with extra N can actually backfire and delay maturity making matters even worse. Go with conservative sidedress N rates on dryland (50 to 60 lb N/a depending on how much preplant N was applied) according to yield goals. If the rain situation improves as the crop progresses, you can always make up some ground with foliar (up to 20 lb N/a if you use feed grade urea and are willing to foliar feed more than once).
2)Apply sidedress N on the early side – The normal ‘window” for sidedressing N is from first square to first bloom. For late planted cotton, especially dryland, you may want to hedge more toward first square than first bloom. Unfortunately, many preplant N applications were skipped and sidedress N is the first N fertilizer the cotton plant is receiving. Again, be cautious of applying too much N to late-planted cotton too early.
While it is true that most new cotton varieties fruit up earlier, and it makes sense they would need N earlier, there is also the strong possibility that you could interfere with the plant wanting to shift from vegetative mode to reproductive mode, that is, making it want to keep growing stalk instead of shifting to putting on bolls. On late-planted cotton you have less time to make the crop and usually can not afford this delay.
3)On uneven stands, fertilize to the majority and hopefully the oldest – I’ve seen a lot of fields, again dryland, where some cotton had enough moisture to come up early, but then another “flush” came up much later. It is not uncommon to have cotton plants that are near first square and others that have just emerged in the same field. The rule of thumb should be to time your sidedress N application according to which stage you have the most of in the field. This recommendation is easy to follow when you have mostly older (‘first square”) cotton, but is much trickier when you have “half and half”, especially if the “tall” cotton and “short” cotton are randomly mixed together and not in large patches. The only danger of sidedressing really young cotton is if you use liquid N and dribble a full rate directly on top or into the terminal. There is also a possibility of you sidedressing N close to very young cotton (2 to 3-leaf) and if it turns dry, you could get some salt injury.
4)Foliar N and K can help “get you through” (but not “do it all”) – Foliar feeding N and K should always be seen as a way to supplement a good soil applied fertilizer program. In times of limited soil moisture, it can be a good way to ‘tie you over” and get some nutrients into the plant when the plant may be struggling to take up nutrients through the roots. We have seen this (especially with K) on Georgia cotton before, where soil K levels are adequate but due to dry soil conditions, the plant goes almost K deficient during droughts. There are limits of course and it is not recommended to foliar feed anything if the crop is drought stressed to the point where it is “wilted by noon”. Also, it may be tempting to try to foliar feed N instead of sidedress until you see you have some true yield potential on drought-stressed dryland. However, this is not recommended. If a dryland crop is ready to sidedress i.e. at first square, I would recommend sidedressing N over foliar feeding.
Aphids are still a concern in cotton, although the beneficial fungus should take them out soon. Also, as you can see here on the left some white scymnus lady beetle larvae are doing their part at taking some out.