PCG EMAIL SERVICES: Americot Cotton Field Report - September 2013

PCG Email Services pcg_email_service at plainscotton.org
Thu Aug 29 10:06:30 CDT 2013


The Cotton Field Report

An in-season, monthly agronomic report provided by the Americot, Inc. field team.

September, 2013

Fiber Development

The primary goal of cotton growers across the Belt is to produce pounds of lint.  Likewise, the primary goal of breeders and seed companies is to develop varieties that have high yield potential.  Other agronomic characteristics, such as fruiting and growth habit, leaf hair, as well as disease, insect and nematode tolerances, affect a grower’s variety choice.  However, after the field has been harvested and the seedcotton has been ginned, all attention rightly turns to fiber quality, which greatly determines the price per pound of lint.  Since fiber quality is of such monetary importance, it should be considered not only during variety selection, but also when in-season management decisions are made.  The physiology of fiber quality development and how different regions of the Cotton Belt could potentially see these traits express in 2013 are discussed below.

Chronology of Fiber Development

Cotton lint is a trichome, or plant hair, and is very similar in structure to leaf hair.  These single-celled fibers begin developing on the day of flowering, and start to elongate within a day of anthesis or pollination.  Lengthening continues for about 21 days after flowering.  Just like any other plant cell, first cell expansion (elongation in this case) occurs, then cell wall thickening.  At about 17 days after flowering, this cell wall thickening begins, one layer per day, much like rings of a tree.  The thickness of the rings is determined by the availability of carbohydrates, of which the lint we harvest is nearly completely comprised, and is measured as micronaire.  Thickening continues as long as there are available carbohydrates and adequate temperature and water for proper cell function.  Fiber strength is developed along this same timeline, since the strength is related to the size of cellulose molecules and molecular bonds that are formed between the deposited layers of cell wall, much like how layers are glued together at different angles to form a sheet of plywood.  Figure 1 shows the timeline of length, strength and micronaire development in days after flowering, as well as heat units (HU) after flowering.  Typically, the process takes 50 days or 800 heat units to complete, plus another 10 days or so for the boll to dry enough to invert and dehisce, or open.  Fiber quality is at its highest in a newly opened boll that has dried down.  After that point, fiber quality can only deteriorate due to weathering or mechanical handling from harvest machinery, ginning equipment or textile mill equipment.



Fiber Length

The fiber cell elongates much like a long, skinny balloon does, over a 21- to 25-day period following flowering.  What causes it to elongate is turgor pressure, which is influenced by plant water status and plant solute concentration, especially potassium (K), so fertility status is important.  Any deficit in either of these two important elongation factors can cause short fiber.  However, fiber length is also heavily influenced by genetics, so variety selection is key for achieving long staple.  To achieve longer staple, select a variety with long staple characteristic, since fiber length is a highly heritable trait.  However, length is also heavily influenced by growing environment, so to achieve longer staple, moderate temperatures and limited stresses, especially from drought and fertility (Figure 2).  Conversely, causes of shorter staple include variety selection, high temperatures, K deficiency, and drought stress.



Most areas of the Cotton Belt had favorable conditions for length development in 2013.  However, South Texas was very hot and very dry in 2013 during bloom, and could see some short staple values in their recaps.  Similarly, some of the early and mid-season set bolls in the Midsouth/Southeast could be of shorter staple, since the prolonged cloudy weather may have slowed photosynthesis such that fewer carbohydrates were available to the elongating fiber.  In this case, however, the top crop should offset overall staple with better conditions in those regions in the latter bloom stage. 

Micronaire

Micronaire is measured by HVI by forcing air through a sample; the more surface area (i.e., from finer fiber), the lower the reading, and the less surface area (i.e., from coarser fiber) will cause the reading to be higher.  Because HVI micronaire is both a measure of fiber fineness and fiber maturity, we cannot separate the two (although researchers can via AFIS measurements).  Mills desire fine, mature fiber; however, typically fine fiber, defined by HVI micronaire, is immature fiber that does not uptake dye as readily.  Mature fiber typically has higher micronaire readings, but the coarseness of those high-mic fibers does not spin as well, since mills cannot spin fine yarns with high numbers of fibers/cross section, a parameter important for yarn strength and uniformity of yarn thickness.  As such, micronaire is a tricky and somewhat elusive characteristic for growers to deal with.  To further complicate this, micronaire is very highly influenced by the environment and is only somewhat heritable.  So, management in the field and weather conditions are much more important than variety selection for micronaire.

Figure 3 lists some causes of high and low micronaire.  The 2013 season very likely produced situations and conditions conducive to both high and low mic, depending on the region. 



The High Plains could see low micronaire, a perpetual problem for the region, due to the lateness of the crop, and the proportion of the total boll load forced to develop under cooler conditions in the late bloom period going into cool conditions in the fall.  A warmer-than-average fall is predicted for the region, however; warmer temperatures will tend to favor higher micronaire values, which in the High Plains, will be a benefit. 

Many growers have questions about when to terminate irrigation to not only optimize yield, but also to make certain to avoid low micronaire discounts.  As a general rule, irrigation should continue until first cracked boll, especially if yield potential is very good (i.e., avoid the temptation to “save” irrigation when you have a high-yielding crop).  However, consideration must be given to soil texture; if the field has heavy soil with high water retention, growers may opt to terminate irrigation sooner than first cracked boll in order to deplete soil moisture to avoid juvenile leaf growth that could complicate crop termination.  If, however, the field is a lighter soil texture that does not retain moisture as well, maintain soil moisture until first cracked boll.  Doing so will help increase micronaire in the upper portion of the canopy and will increase the chance of avoiding a low micronaire discount for the crop.

The Midsouth and Southeast crops are also late, and a high proportion of bolls will be developed late in the bloom stage.  Both regions have been subjected to prolonged cool and cloudy conditions.  The fall temperatures will greatly determine overall micronaire values.  Many areas have a strong bottom crop, then shed the middle crop, and the top positions may be too late to be harvestable.  In this case, we would expect high micronaire for the crop, since a few bolls at the bottom of the plant will have all the carbohydrates produced by leaves in the middle and top portions of the canopy.  Other areas shed their bottom and middle crop, but produced a sizable top crop that will be harvestable.  In this case, we would expect normal to low micronaire, depending on fall temperatures – if we have a warm fall, then normal micronaires would be expected; if we have a cool fall, then we would expect low micronaire, as those fibers would not get the chance to fully mature. 

Finally, harvest preparation can greatly influence micronaire.  If a boll opener or defoliant is applied too early, micronaire development can be arrested and low micronaire can result.  Conversely, if those products are applied too late, high micronaire can result.  By applying defoliants when nodes above cracked boll (NACB) is 4, growers can avoid adversely affecting micronaire (and optimize yield and harvest timing as well).  NACB is determined by counting the number of nodes between the highest first-position cracked boll and the highest first-position harvestable boll.

Micronaire can be very unpredictable, and can cause substantial discounts.  By observing your boll load and environmental conditions, you can at least be informed about what micronaire levels to expect and what degree of discounts to potentially experience.

Strength

Fiber strength is developed by the molecular bonds between layers of the cell wall as they are deposited on a daily basis, again, much like the glue between layers of a sheet of plywood.    Of all the fiber properties measured by HVI, fiber strength is the most heritable trait, meaning that variety selection is key.  However, there are some environmental and weather factors that affect strength. 

Generally, high yielding environments allow varieties to also express high strength values, so yield and strength are very correlated.  Low strength can be associated with extremes in temperature that reduce carbohydrate supply, drought stress during boll development, or potassium deficiency.  Any weathering after boll opening by microorganisms tends to reduce strength, since fungal growth on the surface of the fiber cell will weaken the lint.  And finally, aggressive ginning or other post-harvest handling involving heat can potentially weaken fiber (Figure 4).



As mentioned previously, the key factor managing fiber strength is choosing a variety with high strength characteristics.  Once a variety is planted, in-season management for high strength closely matches that for high yield management, followed by timely harvest to avoid any in-field weathering.

Summary

Variety selection and proper in-season and post-harvest management are important to achieve the genetic potential for fiber properties.  Fiber quality is very complicated, since each fruiting site along the indeterminate cotton plant’s structure develops in its own timeframe and microenvironment.  Knowing when the predominate portion of the crop was developed, and where within the canopy the majority of the harvestable bolls are will help growers and consultants when making decisions about harvest aid applications and harvest logistics, and will help build realistic expectations for fiber quality.

If you have any questions or would like to discuss Americot or NexGen varieties, call Dr. Ken Legé at 806.773.7014.

 

SOUTHWEST:

Northern High Plains of Texas, as well as southwestern and south central Kansas and Oklahoma.  The cotton crop through late August in most of my area progressed well to slightly behind with average day and night time temperatures.   In certain areas, rain continued to bless us in August. North of I-40, and most regions, producers are trying to control excessive growth with PGR's. In the areas of Silverton and Wellington, Texas, and Oklahoma, most irrigated fields are around 3rd to 4th node above white bloom.  Most fields need to be at cut-out near September 1.

Dryland fields are a mixed bag. Several fields have been or are being failed at this time. Some fields are stressed and cut-out, some are very good, and some are late planted and behind. A good September and October will be needed for many good irrigated and late planted dryland fields in all regions to mature and finish.  I have observed very good square retention on most irrigated fields.  Hail storms recently took out some excellent cotton fields in the northern Texas Panhandle. 

Terminating water management is now upon us.  Making the perfect decision here is a tough call.  Just remember, a bloom needs around 800 to 900 heat units to mature, or 50 to 60 days of an average of 15 heat units a day.  

Call Jerry Montgomery at 806.577.8011 for any NexGen questions or if you would like for him to come see your field.  

 

The five-county area of Lubbock, Lynn, Crosby, Garza and Dickens counties.  The irrigated cotton in my area is loading up and is responding well to the August rains.  We could use another rain, but hopefully rainfall will hold off once we get through the second week of September so it will not slow down defoliation.  A few growers will try to start defoliating in early October, but most will do so later in the month because the crop is about a week to 10 days behind normal. 

Of course, our dryland cotton is a different story.  We probably lost at least half of the dryland crop to the drought.  We do have some good dryland cotton, but it’s spotty.   

If you have questions about your Americot/NexGen varieties and how they’re growing off, call Scott Stockton at 806.790.7749.

 

The Triangle Area (from Lubbock to Muleshoe to Hereford). The cotton that is left in the Triangle Area of West Texas is in most cases very good.  Irrigated and dryland cotton fields have the potential to make exceptional yields IF our September and October weather is favorable for crop development.  The irrigated cotton has almost completely passed the hard cut-out stage.  Depending on the amount of irrigation in the field, we started cut-out by August 15 in most fields.  There are some later fields that did reach cut-out the week ending on August 24, but even these later fields have raced toward finishing their bloom period in good shape. 

The dryland cotton that remains in the fields is in very good shape; it’s just a little late.  These fields will still need a rain and warm temperatures in September, but could be very productive.

Insects have not been a problem in most cotton fields this year.  We can probably thank the amount of corn and grain sorghum planted in the area for attracting any worm eggs that have hatched.  Thankfully for cotton, the worms have preferred the grain crops.  Producers need to watch for lygus and other plant bugs in the irrigated cotton, but we are nearing the hard boll stage when the insect can no longer inflict damage. 

For the irrigated producer, the question now is how long to continue to irrigate.  The general rule is to irrigate good production until first cracked boll and that should be about 500 heat units after cut-out (5 nodes above white flower).   Depending on the day and night time highs and lows, that would be about 30 days, but any irrigation or rain should hold the crop since the plant is using less water at this stage.  If you have late cotton or farm in a shorter growing season like in Deaf Smith County, you should gradually start to reduce the irrigation without causing severe wilting during the day. This is one of the most difficult management decisions in cotton.  The right answer will be known in mid-September.

If you have questions about your Americot/NexGen varieties and how they’re growing off, call Gary Sanders at 806.777.4534.

 

MIDSOUTH:

Arkansas, Mississippi and Louisiana.  Growers’ concerns for September include terminating irrigation, scouting and treating plant bugs, and timing defoliation. 

Determining our last irrigation involves a delicate balance; we need to maximize the yield of the top crop while avoiding boll rot. The effective cut-out date in the North Delta is August 9 to10, and the South Delta is August 10 to 15.  We’re now experiencing warm, sunny weather and we can push those dates if the warm weather continues through September.  Confer with your consultant and university Extension to determine your last irrigation on a field-by-field basis.

Additionally, as corn dries down, plant bugs will migrate to green cotton.  Continue scouting for this pest and spray as needed.

Although most cotton in my area is several weeks away from defoliation, I do have some fields that will be defoliated in early September.  Remember, don’t be in too big of a hurry to defoliate, even though we’ll pick later than normal.  Mature out what you have and pick it! 

If you have questions about your Americot/NexGen varieties and how they’re growing off, call Chris Booker at 870.275.0586.

In the Missouri Bootheel and West Tennessee.  Typically, August 15 has been noted as our last effective bloom date, based on the average historical date of first frost for West Tennessee. Most insecticide applications can be terminated once we have accumulated 350 – DD60s from the Aug. 15 date, and we should be able to relax our treatment threshold once we have accumulated 250 – DD60s.

However, after speaking with several key independent crop consultants concerning the lateness of our cotton crop, many of them emphasize the need to protect this crop through the middle of September.  While all agree that we do not have a bumper crop in the field, many agree that we still have time and opportunity to make a very good crop. We are now experiencing some very good cotton producing weather, with daytime highs in the mid-90s and night-time lows in the mid-70s and we have finally broken the cycle of catching rainfall every other day. There is no rainfall in the 10-day forecast and we can now start accumulating some very good DD60 numbers to help move this crop toward physiologically cut-out.

The key take home message for our cotton producing farmers is: “Don’t give up on the crop”.  We can still make a very good cotton crop IF we have some typical September weather.

If you have questions about your Americot/NexGen varieties and how they’re growing off, call Rick Rebstock at 870.623.8570.
 

SOUTHEAST:

South Carolina, North Carolina and Virginia.  As I write this report (8/25), the sun is shining and it is expected to shine for the next 7-10 days.  For the last few weeks, it seems like if it wasn’t raining, it was cloudy and cool.  This has caused some extreme fruit shed in many places.  Low fertility levels caused by earlier leaching coupled with high fruit shed, make for a not so promising crop.  But it is not all doom and gloom.  It seems as though the cooler temperatures are keeping Target spot at bay, and I’ve seen some good looking cotton in places.  Most early-May planted cotton, on well-drained soils, looks pretty good.

Our main pests moving forward with this crop are stink bugs.  Levels are over the threshold in most cases, but it’s been a challenge to get in the field to spray them.  However, we need to protect the fruit.  Planes are helping out a lot, but most of them are booked up for weeks.  East Georgia and the coastal plain of South Carolina seem to be hardest hit, but this is definitely a regional disaster, and I’ve spent a lot of time on the phone lately relaying that message.  Many farmers will need some type of disaster funding to help pay the bills.

The next few weeks will be critical for this crop.  We need to protect our top crop from insects, and keep our fingers crossed that we can accumulate sufficient heat units, and that we get a laaaate frost.  In the meantime, it’s time for some football!!  Go Tigers!!

If you have questions about your Americot/NexGen varieties and how they’re growing, call Jeff Sandifer at 803.300.2530.   

 

Georgia, Florida and South Alabama. The Southeast cotton crop will be remembered as the year of the monsoon.  The much higher than average rainfall has brought many challenges; saturated fields habitually prevent growers from running ground rigs to apply materials such as insecticides, herbicides and plant growth regulators.

By the last week of August, growth stages ranged from second week of bloom to cut-out. Some early cotton has opened, and the current weather situation has growers considering applying more foliar fertilizer. Boll rot is expected to be a large problem, so growers are counting on the top crop to make the yield.

Stink bugs and white flies are creating a large problem with the abundance of moisture. When ground rigs are not able to make the passes, growers utilize crop dusters.

The abundance of rain has also depleted or weakened residual herbicides. Hoe crews are removing Palmer amaranth in many fields. Growers have made great headway managing this weed in the last few years, but the wet weather has allowed it to flourish this season. 

            Growers continue battling the detrimental effects of the cloudy, rainy weather and the crop’s slow growth, and are protecting and nurturing what they have on the plant, especially the top crop.  This year will be one for the books!

If you have questions about your Americot/NexGen varieties and how they’re growing, call Michael Williams at 229.454.4438.   

 

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