Bloom Period Considerations

ARIZONA

Much of the crop around the state is well into the bloom cycle and will be approaching peak bloom within the next few weeks to a month. Peak bloom also often coincides with the onset of our monsoon season. High moisture levels in the atmosphere can lead to high nighttime temperatures, causing the plant to encounter heat stress. This may lead to aborted fruiting forms, typically in very young (one- to three-day-old) bolls.

Heat stress levels are monitored at all Arizona Meteorological Network (AZMET) locations around the state. That data can be accessed at http://cals.arizona.edu/azmet. Research has shown that level 2 (L2) heat stress experienced by the crop over a period of several days may result in significant fruit shed, particularly if that L2 heat stress coincides with the peak bloom crop development stage.

This scenario of excessive fruit loss under a well-managed crop with respect to fertility and irrigation can very easily lead to excessive vegetative growth. Monitoring crop development, fruit load and vigor help in assessing the crop’s potential to develop excessive growth. Indices created at the University of Arizona from thousands of observations can provide a baseline for an expected or “normal” height-to-node ratio and fruit retention.

Comparing observed conditions in the field to established baselines assists in making decisions for plant growth regulator applications and perhaps mid-season fertilizer applications. To access these baselines and descriptions of how they may be used to effectively manage growth and development go to http://cals.arizona.edu/crops.

ARKANSAS

So far, this season has been one of the most difficult I have experienced in Arkansas. The crop is steadily improving but at a much slower rate than most would like to see. The status of our cotton plants at first flower reveals much about the past and gives us an indication of what we must do down the road to end up where we want to be.

Ideally, 60 days after planting we will find nine to 10 first-position fruit above the first white flower. This verifies we have the foundation to establish and develop high yield and fiber quality potentials. Going into first flower, our goal is to maintain 80 percent retention. Problems directly impacting yield and profit are associated with extremely high retention rates as well as low fruit retention. Going into flowering with extremely high retention rates can set you up for failure if any problems are encountered as the margin for error is small when retention is high.

Maintaining a balance between vegetative and reproductive growth helps to optimize earliness and preserve yield and fiber potential. Irrigation initiation and timing plays a dominant role in this balance. Using sensors and scheduling tools along with programs such as Pipe Planner will help improve irrigation water-use efficiency and profitability. An effective fruiting window of three weeks between first flower and cutout (NAWF=5) will provide the yield and earliness Arkansas cotton producers in desire.

FLORIDA

July is a critical time for setting bolls for earliness in cotton. Most cotton begins blooming in early July and blooms through August. It is important to ensure that adequate moisture and fertility are available to set a good crop in the first two-four weeks of bloom.

Getting an early boll set helps reduce the amount of vegetative growth and the amount of growth regulator needed. Growth regulators are applied to create the best canopy size for crop management and to promote earliness.

Our research has shown that no nitrogen is needed after the third week of bloom (late July), and later applications may extend vegetative growth and management of insects, diseases, etc. Nitrogen applications made between squaring and first bloom have resulted in highest yield. Later applications (after the third week of bloom) tend to lower yields if there is a good boll set and may delay harvest. It is natural for petiole nitrate levels to drop as the crop matures.

GEORGIA

By the time you read this, it should be early to mid-July. Many Georgia producers planted cotton during the past two weeks of April or early May. For those growers, the cotton crop should be at roughly first flower to peak bloom development stage and may be approaching canopy closure on some irrigated acres. This is a good thing because it indicates the crop has produced adequate leaf area and the canopy architecture required to support a substantial boll load. While farmers should be careful to avoid drought stress at any crop development stage, the impact of missing a needed irrigation at this time can have the most drastic impacts on yield. Why?

1) Phenological sensitivity: Most published data indicate the cotton crop is more sensitive to drought during early flowering than later developmental periods or prior to flowering.
2) Atmospheric demand: Periods of high vapor pressure deficit (hot, dry air) place more evaporative demand on the crop and accelerate the rate of water use.
3) Leaf area: Once canopy closure occurs, the main route by which the cotton crop loses water to the atmosphere is through numerous microscopic pores (stomata) on leaf surfaces. Because there can be more than three times the amount of leaf area as soil area at canopy closure, the water-use rate at this stage is much higher than at earlier stages prior to canopy closure.

What’s the takeaway? Plant factors and environmental factors necessitate that the cotton crop approaches peak water use at a time during the growing season when it is particularly sensitive to drought stress. Additionally, many of the coarse-textured soils of the Coastal Plain have limited water-holding capacity. Thus, farmers should be diligent in using proven, science-based methods for irrigation management to minimize stress and maximize productivity and water-use efficiency.

To access resources related to cotton irrigation in Georgia and other cotton production topics, go to www.ugacotton.com.

LOUISIANA

The Louisiana cotton crop looks very promising. DD60s accumulated for the past 60 days are above average compared to the historical average for this time period. Thrips pressure was extremely heavy this year. Soil moisture is very good in most parts of the state.

As of June 10, most of the cotton fields are squaring. Plant growth regulator applications will be going out to manage plant height and excess vegetative growth. Earlier planted fields in central Louisiana will be approaching first bloom in 10 to 14 days. Since squaring began, insect pressure from aphids, fleahoppers and plant bugs has been low throughout most parts of the state. Square set is looking good with fields having 80 to 85 percent square retention or higher.

As Louisiana cotton fields reach early bloom, an effective method for farmers to determine vigor, or the amount of horsepower the cotton plant has, is to count the number of nodes above white flower (NAWF). NAWF is measured by counting the number of nodes above the lowest first position white flower on the cotton plant. The last node to be counted at the top of the plant will be the uppermost node that has an unfurled main stem leaf larger than a quarter (greater than 1 inch diameter).

Factors that influence NAWF at early bloom are maturity differences in varieties, soil moisture conditions, insect pressure and disease. At early bloom, NAWF can be at five or six under drought-stressed conditions to 10 or more under optimum growing conditions. Fewer NAWF at early bloom indicates that an early cutout is eminent and there is potential for low lint yields. Higher NAWF counts of nine or 10 indicate the plant has ample horsepower and the potential for an excellent crop.

MISSISSIPPI

What a difference a year makes. In 2016, a large portion of the state saw nearly a month of dry weather after planting. In 2017, we have a significant number of acres planted in June due to prolonged rainfall in May. As of the middle of June, Mississippi had some fields with blooms present and others with seed just planted. The spring of 2017 ranks as one of the most challenging I have seen in the past 10 years.

In addition to challenging weather, off-target dicamba movement has certainly been a hot topic this growing season. When it comes to dicamba drift, it takes a much larger dose to injure cotton compared to soybean. However, non-dicamba-tolerant cotton is certainly not immune to dicamba.

Furthermore, I am very skeptical of any product claiming to help crops grow out of dicamba injury. Prior to applying ANY product to crops injured from off-target dicamba movement, demand to see reputable data that will support claims of helping the crop grow out of injury. To the best of my knowledge, the best thing for crops suffering from injury of this type is time and good growing conditions (including warm weather and adequate moisture). To quote an unnamed source: “Do not let others profit off of your misery.”

MISSOURI

Missouri cotton producers have certainly had their share of weather problems. Flooding in late April and early May resulted in cotton being planted past the optimum planting date. The Missouri Crop Progress and Condition Report provides the breakdown. By May 14, only 48 percent of the cotton had been planted; May 21 showed 68 percent planted; May 28 reported only 85 percent planted, and 95 percent planted by June 5.

The crop condition, according to the June 11 report, was 2 percent very poor, 15 percent poor, 36 percent fair, 41 percent good and 6 percent excellent.

It’s hard to predict the outcome of this year’s crop, but I see all stages and a wide range of plants even within the same field. Each year, I observe cotton emerging even under the best conditions and wonder how it will develop. This year will definitely be a management challenge. I know of some fields that were spot planted up to three times. We have some failed acreage, and I am not sure at present about prevented planting.

Some yellowing has occurred, which is more likely due to loss of nitrogen or sulphur or both. With the rainfall amounts we have received so far and more expected, producers need to use plant growth regulators to keep vegetation under control. The greatest benefit of growth regulators is to set squares and maintain earliness.

NORTH CAROLINA

We have completed three years of research comparing tillage systems in North Carolina. There are several conclusions I think have the most practical implications for cotton producers. First, strip-tillage completed two weeks prior to planting was always as good as, or better than strip-tillage done at planting. Strip-tillage two to three weeks prior to planting gives farmers the option to not disturb residual herbicide activity at planting.

Secondly, strip-tillage conducted in the fall reduced soil resistance to root growth for two years without additional strip-tillage and was similar to annual strip-tillage. Soil resistance after three years was only slightly higher than annual strip-tillage and was considerably lower than continuous no-till. Finally, comparisons between conventional (rip and bedded) versus strip-tillage (no beds) were made in 17 environments.

Bedding used to be common in North Carolina but is not as prevalent now as producers have shifted to reduced-tillage systems in response to herbicide-resistant transgenic varieties. There was no difference in yield due to bedding in 15 out of 17 of the environments. In two of the locations, bedding resulted in higher yields than planting flat with strip-till. The increase in yield due to bedding in these two environments ranged from 100 to 250 pounds of lint per acre and was due to excessive moisture.

OKLAHOMA

As of this writing June 8, Oklahoma cotton producers are still busy finishing up planting on mostly dryland fields. Some of our irrigated acres had to be replanted due to high intensity rainfall events in the third week of May. Overall, the crop is in pretty good shape for this time of year. Planted acreage will be very large in our state this year. We have producers who are new to cotton and some who have planted cotton for the first time in many years.

Boll weevil eradication across most of the U.S. Cotton Belt, including Oklahoma, has been successful and is a major contributing factor to the continued profitability of cotton production. It has been a long, difficult and challenging task to rid our state and most of the Cotton Belt of this invasive species. For such a long time it negatively impacted our production. We all need to do our part to keep this pest from resurfacing.

Some new cotton producers may be unaware of the ongoing program. It is important for those who are not familiar with it to contact the Oklahoma Boll Weevil Organization to make sure their new fields are properly identified and trapped. Farmers also need to stay on top of weed control and any insect problems that might emerge.

Based on Altus long-term average Mesonet data for a May 10 irrigated cotton-planting date, July and August are typically our highest crop evapotranspiration months, coming in at about 8.4 inches and 9.1 inches, respectively. For southwest Oklahoma, average precipitation for July is 2.25 inches. For August it is about 2.75 inches. Therefore, these two months can be the “crunch time” for making or breaking a crop, with a potential moisture deficit of about 12 inches or so.

Some of this deficit can be provided by moisture in the soil profile. However, it shows how important July and August rainfall is in making a good crop. We have a lot more acres of dryland cotton this year. Over the past two years, we obtained good to excellent rainfall in these months in many areas. We hope to do this again in 2017.

TENNESSEE

Rains have been fairly frequent and substantial for most in Tennessee up until the second week in June. As I write this, there is only one substantial chance for rain over the next two weeks. Given the dry weather many will likely experience over the next few weeks, it will no-doubt be tempting to irrigate our pre-square or squaring cotton.

Although we definitely want to start the flowering period with adequate soil moisture and remain at that state through the boll-fill period, there have been very few documented cases of increased yields from irrigating pre-flower. Although some research has indicated pre-flower irrigations can increase yields under periods of severe stress, irrigation is rarely justified pre-square and should be uncommon pre-flower. Proper termination timing varies by production system. But by the time bolls crack, farmers should be considering shutting off the pump on most irrigated fields in Tennessee.

I brought up atmometers last year as an excellent tool for assisting irrigators in estimating the potential for the environment to drive water loss. This simple device gives insight into atmospheric demand across a large area. When coupled with a solid number for typical crop water use by growth stage, it can give you a good feel for how much water to apply.

As anyone who has attempted to irrigate a crop knows, the hardest part is figuring out how much you need and how much you have. Although atmometers are far from perfect, I firmly believe they are a great (inexpensive) place to start. The good news is advancements in technology like radar estimated rainfall and studies examining crop water use are moving us closer to having a complete picture of available water and plant demand.

TEXAS

With the exception of the dryland cotton in the Rio Grande Valley, the crop in South and East Texas is looking quite good with substantial fruit loads. One more good rain will be needed to really bring this yield potential to fruition in the Coastal Bend and Upper Gulf Coast, while the Blacklands will need a couple of good rains. The early June rains were a billion dollar event for our South Texas growers. The RGV missed much of the rain, and its dryland crop has low yield potential.

Insects have been persistent and bad in some areas but have been worse in years past. Farmers are keeping an eye on stink bugs because the numbers have been high in the grain crops.

In the Rolling Plains, the irrigated cotton is planted and off to a decent start with growth stages ranging from recently emerged to four-leaf stage. Many growers in the Rolling Plains had postponed planting their dryland crop waiting on a rain for adequate moisture. As of mid-June, about 50-70 percent of the dryland cotton in the Rolling Plains had been planted. The remaining acreage must be planted before June 20 to meet the final planting date deadline.

TEXAS

As of mid-June, the vast majority of cotton in the Texas High Plains has been planted and much of it has been in the ground for almost a month. Conditions during the early part of the planting season were favorable. And then hot, dry, windy conditions set in during late May, and there was little relief to be found for the first several weeks of the season. If significant rain still hasn’t been received across the entire region by the time this issue of Cotton Farming reaches you, then irrigation decisions will be fairly simple: If you’ve got water, use it.

Based on planting date alone, we’ll reach the bloom period across the High Plains in early to mid-July; however, the conditions that were present during the early part of the season slowed the growth and development of the crop, particularly in dryland fields. Squaring through four to five weeks after first bloom period is a critical time to avoid water stress. To ensure optimal fruit set and retention, supply the crop with adequate moisture.

In instances where controlling plant growth is a concern, proper irrigation and fertility management, along with the hot, dry conditions typical across the High Plains and high fruit retention, will provide the best plant growth regulation. If field history, variety, or excess rain or nitrogen create a situation where a plant growth regulator application is necessary, refer to the weather forecast to determine the best timing for this application. If conditions are such that slower growth will be occurring, use PGRs efficiently.