Top vs. Bottom Crop…Deciding Which Crop to Chase (Collins & Edmisten)
As expected, the prolonged dry and hot weather that occurred in many areas in North Carolina has not only affected yield potential but has also complicated decisions for the 2020 crop. There have been quite a few calls this week from growers on this very issue. In many areas of the state, the July heat and drought sent the crop into a very premature cutout. Had this stress been alleviated quickly by rainfall, we probably would’ve never known much of a difference from normal. However, the stress was not alleviated until Hurricane Isaias in very early August, and luckily we have had timely rains since then. We’ve always said that July sets it up, August makes the crop, and the Fall either preserves it or loses it. So far, this holds true for 2020.
The prolonged July drought in many areas resulted in a distinct and noticeable break between the bottom crop and a potential top crop, except for areas of the state that just happened to catch one or two rains right on time during July. This was expected in regions where the drought was prolonged in July, but began to recover once August rains resumed. Simply put, the crop went into cutout, and stayed there a while, retaining the earlier set bolls and shed the younger ones. When rains resumed, the crop filled out what bolls it had to some degree then terminal growth resumed and new younger bolls began forming. Therefore, there is no “normal” fruiting pattern where there is a constant and smooth progression from the bottom of the plant to the top in terms of boll age and development. Rather, we have an early and mature bottom crop with a distinct fruiting gap, above which is a much younger and immature top crop. So which one do we chase?
This is a very tough decision, and until we can predict longterm weather, we’ll never be 100 percent accurate in this decision. Below are a few considerations that will hopefully simplify these decisions, with some pros and cons to each scenario.
- The first thing to do is to quantify the potential value of both the bottom crop and the top crop. As of right now, it will be easier to evaluate the bottom crop because those bolls are most mature and are unlikely to be lost to abortion by now (unless insect problems occur). Generally speaking, our last effective bloom date was early this week for the Northern half of the state, and late this week or early next week for the Southern half of the state, so we can begin to evaluate the top crop now. In a couple of weeks, we can evaluate the top crop with a little more precision, because fruit that recently bloomed (over last weekend or early this week for example) may or may not be retained due to boll load and the plant needing to abort smaller bolls to account for available resources. Regardless, we need to know how much each crop is worth. When doing so, it’s important to know how much money you have invested in your crop and a good estimate of remaining expenses (harvest aids, harvesting, bale wrap, ginning, etc.) and the prices you are likely to receive for your cotton. You also need to revisit your crop insurance policy to determine that value that it covers and IF it will cover you, depending on how you have your farms divided. These figures are needed to determine your break-even yield. Keep in mind our general rule of thumb that 12 mature bolls per foot of row is roughly equal to 1 bale per acre (on 36-inch rows).
One example: if you have a 600-700 lb/A bottom crop and another 200 lbs/A potential top crop, naturally you would want to chase the bottom crop. You need to be willing to risk the top crop, but you probably wont lose all of it. In this case, you may want to harvest some of the top crop, but you cant afford to wait indefinitely on that top crop. Wait as long as you can while you have decent heat unit accumulation and WATCH THE WEATHER!. Keep in mind that the bottom crop in this scenario is likely to open much earlier than the top, and exposed lint is vunerable to major losses if tropical storms come our way. Be ready to defoliate and harvest in a timely manner to capture the bottom crop and hopefully harvest some of the top crop. Using higher rates of ethephon in your defoliation mixtures may help a few of the top bolls to open in time to be harvested along with the bottom crop. Although we don’t always have the luxury to precise pathways of tropical storms 2 weeks out, if you find yourself in this situation, you need to defoliate and harvest the bottom crop before any tropical weather arrives. The only scenario where you shouldn’t is if a number of your bottom bolls are still closed when a tropical storm moves through. In this case, leave it alone and defoliated after the storm passes. A closed boll is a protected boll. Flooding from such storms is always a concern but theres little we can do about it. An open boll is vunerable and will likely be lost or hardlocked, flooded or not. Now imagine the reverse scenario, where you have a 200-300 lb/A bottom crop and another 600-700 potential top crop. As mentioned earlier, we can begin to assess the top crop now, but these assessments will be more precise in a couple of weeks once we know which recent blooms/young bolls will be retained or aborted. In this case, you’d need to be willing to risk the bottom crop in order to chase the top crop. You are more likely to lose the bottom crop to hardlock, or weathering losses if a tropical storm passes through after the bottom crop opens, compared to losing the top crop in the previous scenario. Inevitably, you would need to push this crop later, and delay defoliation, to perhaps just prior to first frost depending on the top crop’s value. Still, even in this case, watch the weather. You will probably need to defoliate before a frost occurs, using a high rate of ethephon, or products like Finish or CottonQuik if defoliating in cooler weather. Try to take action at least 2-3 days ahead of a likely frost in order to get the proper degree of ethylene buildup inside these bolls. If you have already defoliated, most or all the leaves are off the plant, but some bolls are hardened but just wont open, you can try using paraquat to hopefully pop some open before a frost occurs.The worst, and most complicated, scenario is half and half, where your bottom and top crop are equal contributors to potential yields. In this case, you would really need to have an accurate long-term weather prediction in order to make the best decision. Regardless, it never hurts to watch the 2-week weather forecasts that we do have available, and if you see a particular break or change in the weather occuring in your area, especially in regard to hurricanes or temperature trends, you may want to take action while you can.
- Regardless of your scenario, it would behoove nearly everyone in the state to evaluate their fields right now. Using some flagging tape, flag the uppermost node that has a recent bloom as seen in the illustrations below (should be a bloom tag and/or young boll at this point). Sidenote: make sure to remove this tape before harvest to avoid plastic contamination issues. If rains continue, and there is some in the forecast for this weekend, we are likely to see blooming continue in a few areas. Bloom made beyond this point (Northern half of the state) or beyond early next week (Southern half of the state) are not likely to contribute to yield, and are likely to be what we often call regrowth bolls. The more uniform your fields are, the easier this flagging exercise will be. However in North Carolina, every field has some variation, thus resulting in variation in crop growth, therefore you will need to flag a few plants in each representative part of the field. In a few weeks, this exercise will help you to know which bolls have a reasonable chance of being harvested (bolls formed on nodes below the tape) and which ones will not (bolls formed on nodes above the tape). Without this, you will likely be scratching your head during the Fall, wondering how long to wait on some bolls. Depending on your scenario, this wondering and waiting could cost you unnecessarily.