- Specialists Speaking -
Late Crop Needs To Be Managed
A lot of management goes into a successful cotton crop. Variety selection, proper fertilization, water and weed management, timely applications of growth regulators, insect control and other factors all affect boll set and maturity of the crop and final yield. One thing that we often overlook is the impact of rotations.
All producers know the value of rotations on crop yield and pest control. It is often easier to control certain weeds in some crops than in others. However, little information is available on the best crops to rotate with and to determine if a profit can be made with the other crops with which we rotate.
A long-term study being conducted at the University of Florida’s North Florida Research and Education Center (NFREC) in Quincy has shown the value of having a perennial grass in rotation with both cotton and peanuts. After eight years of comparing two years of cotton followed by peanuts, using an oat cover crop as compared with two years of bahiagrass followed by peanuts and then cotton with an oat cover crop, yields of the non-irrigated cotton and peanuts were higher than irrigated cotton and peanuts without bahiagrass.
Organic matter has increased by 0.1 percent per year in the bahiagrass rotation. The increase in organic matter has resulted in fewer nitrogen needs in the cotton, and yields of 1,700 pounds per acre of lint were made with 60 pounds per acre of nitrogen in the bahia-rotated cotton. Even though we are using the best conservation tillage technology methods available, there is no management available to make the conventional rotation equal to the rotation with bahiagrass.
The majority of Louisiana’s cotton crop is well past the midway point as of July 15. Since April 15, we have accumulated more than 1,700 DD60s (of the 2,400 to 2,600 needed from planting to harvest), well above the normal for this time period. The total DD60 accumulation is somewhat misleading. However, because about 10 percent of these DDs are from temperatures well above optimal, some of the DDs in June and July did not contribute to accelerated crop development.
We are accumulating DDs at the rate of 25-plus per day, so the April-planted cotton will be ready for defoliation in early August. The irrigated acreage and small percentage of fields that received adequate rainfall have excellent yield potential. However, only about 15 percent of cotton acreage received adequate rain in June, mostly in the central region of the state. Most of the state had four to six weeks with no rainfall.
Non-irrigated cotton fields were heavily stressed, first by excessive rainfall in April and early May and then by very hot and dry conditions in June and July. Large acreages of cotton with limited plant height and yield potential have already reached cutout and, although the rain will help to fill out bolls, the cotton plants will not be able to recover fully from the drought stress. The combination of early wet weather followed by extended dry weather also left plants with very shallow root systems in some fields. This has shown up in July as severely drought-stressed plants. A long overdue rain that covered about 80 percent of the cotton acreage occurred on July 6.
We are now in a more normal weather pattern with regular afternoon rains occurring somewhere in the state. A complicating factor with this year’s crop will be regrowth after rainfall. The amount of second growth will depend on several factors – growth stage, boll load and remaining nutrient availability, primarily nitrogen – at the time the crop received rainfall. If more rain occurs, decisions will have to be made on how (or whether) to manage the early crop and later-set bolls resulting from the belated rainfall.
End-of-the-year decisions will be more difficult this season due to the dry weather that we have had for the last month. Many areas are only forecast to receive isolated showers for the next 10 days. Many of the late-planted, non-irrigated cotton fields have blooms appearing in the top of the plant. This is unusual for early July. It is also very easy now to spot the cotton growing outside of the pivot circle.
We will have fewer uniform fields due to the weather conditions throughout the growing season. The Crop Progress and Condition Report for the week ending July 12 shows that 17 percent of our crop is rated poor, 38 percent fair, 41 percent good and four percent excellent. Although we are 10 to 12 days later than normal, we are seeing some fields with a good boll load. The final yield will be determined this year by the length of the growing season.
We will have some drought-stressed cotton as we head into the final weeks of the season. Timing of defoliation will be more difficult due to the spot planting in many fields. Producers are reminded that insects will need to be controlled and that irrigation will make a huge difference this year. With the hotter temperatures, we are accumulating more heat units but with the night temperatures in the mid-70s the cotton does not have as much ability to recover.
It will be a race to the finish for many Arkansas cotton producers in August. At least 30 to 40 percent of the crop is two to three weeks late with much of that acreage in northeast Arkansas. Our yields on this acreage will be determined in August and September.
If you look at the 30-year average temperatures for northeast Arkansas, our last effective bloom date, which is the date based on the probability of accumulating 850 heat units through the remainder of the season, is Aug. 9, using a 50 percent chance probability.
There will be many acres throughout the state that will not be at cutout (NAWF=5) by that date. Last effective bloom dates for the remainder of the state are Aug. 14 for central Arkansas and Aug. 17 for southeastern Arkansas. If we look at average temperatures over the past five years, these last effective bloom dates could be extended three to five days at each location. Establishing the dates of cutout is important in identifying the last group of bolls that will contribute significantly to yield and profit. It is this group of bolls and their development on which we base our end-of-season decisions. Unfortunately, in many fields in northeast Arkansas, this date may come before the plants have reached NAWF = 5.
With the rough start to the 2009 High Plains crop, we are hoping for a much better finish. The dryland struggled due to lack of rainfall, and then finally in late June many dryland areas received substantial moisture. What this means is that we will have a sizeable acreage of late dryland. Of course, we will still need to have some timely rains to help us out.
Although we lost a few acres due to various meteorological events, the irrigated crop is pretty much intact. It was planted in a timely manner, but due to a cool spell at the end of May, crop development lagged somewhat.
This likely means that we will once again need to squeeze out as much growing season as possible for a lot of our irrigated fields. Thoughts concerning end-of-season management inspire me to encourage producers to consider the following. I really like to keep tabs on nodes above white flower (NAWF) and the date where we reach “hard cutout.”
I define that as the date the crop reaches less than four to five nodes followed by “blooming out the top.” We can sometimes see irrigated crops stay around 5 NAWF for two to three weeks, depending on irrigation capacity and rainfall events. What we’re interested in here is the date when the crop drops below four to five and then goes to zero in a few more days. Based on long-term temperature data at Lubbock, we can still get about 850 heat units past this if it occurs before Aug. 15.
Tennessee producers will be contending with a late to extremely late crop this year. Several topics come to mind to get this crop out of the field in an economical and timely manner. First, manage rank growth and promote earliness by using plant growth regulators in a timely manner. Waiting too long will require more PGR to effectively slow cell elongation and will lead to increased PGR costs. Second, determining when to stop making inputs will be critical to maximizing profit.
In most years we can stop making insecticide inputs during the last two weeks of August. We will have some cotton that will begin blooming the first week of August, requiring an extended period to control plant bugs, stink bugs and worms. Scouts and producers will need to determine what bolls will fill and not chase “phantom” bolls that will never mature.
Based on average DD60 accumulations, don’t expect to fill a boll that flowers after Aug. 25. A flower needs 850 heat units to mature to a harvestable boll and protection from pests for 450 heat units past bloom. Potentially, we could be treating for pests until mid-September.
The cotton crop across Arizona varies in maturity from peak bloom to cutout. Decisions regarding crop termination have or will be made soon. This is a critical decision affecting many aspects of the final crop, including yield and fiber quality. The decision to terminate irrigations should be based on crop condition and progression toward and through cutout, which is defined as nodes above white flower of less than five.
Once cutout has been reached, a pivotal decision is made whether to terminate or carry the crop into the second cycle fruit set, attempting to develop and mature out a “top-crop.” Research has revealed potential issues associated with a top-crop, including high rates of square and small boll abortion in the upper canopy of the crop, potential for elevated fiber micronaire in the lower bolls resulting in fiber quality discounts, additional fertilizer and irrigation costs and the possibility of additional pest control costs.
These factors must be given consideration if a top crop is pursued. On the other hand, if a decision is made to terminate the crop, some key items should be taken into account that will affect that decision. Once cutout is reached, it is important to identify the last flower that you intend to mature out for harvest.
How Rough Was The Weather?
Conditions in Mississippi this season have been more difficult than many have seen in 30 years. Fertile cotton grounds that were besieged by water in May have seen very little rainfall since that time.
In fact, 2009 marked the fifth wettest June since 1892 in Mississippi and, as a result, nearly 40 percent of the crop was planted after May 25. However, as feared, we went from too wet to too dry in a span of about 10 days. In many areas, less than 1.5 inches of rainfall was received in June with July not shaping up to be much better.
However, cotton tends to be more drought tolerant than may of our other row crops, and if we catch a couple of breaks heading into fall, good yields are still possible.