⋅ BY KEITH EDMISTEN AND GUY COLLINS ⋅
COTTON EXTENSION SPECIALISTS — CROP AND SOIL SCIENCES
NORTH CAROLINA STATE UNIVERSITY
The key to successful cotton production in North Carolina is the adoption of a short-season management strategy. Cotton growers may equate short-season management strategy with the recently overworked “earliness” philosophy.
While earliness is a worthwhile goal in principle, particularly within a short-season management system, earliness alone may lead producers to adopt practices that unnecessarily limit yield and profit.
Even at the northern margins of the Cotton Belt, there is sufficient time to consistently produce yields in excess of three bales per acre or greater. “Timeliness” is the key component of a management strategy that is fluid enough to accomplish this yield level.
Earliness and timeliness frequently mean the same thing in North Carolina, although not always. There are few production practices that do not require some season-to-season and within-season modification to improve their effectiveness within a production system. For example, nitrogen fertilization must be adjusted for residue left by the preceding crop, as well as for the unique characteristics of the current soil and environment.
Variety selection depends on soil type, planting date and harvest scheduling, as well as yield and quality potential. The earliest variety may or may not be appropriate in a specific field. Plant growth regulators help a producer achieve earlier harvest, but sometimes that earlier harvest is not possible due to time constraints, picker availability or harvest schedule.
The key to successful cotton management is adapting the strategy to the specific situation. There are five specific goals important to producing a profitable crop in a short season production system:
Maximize Early Season Growth
Cotton farmers and researchers alike recognize the yield benefits that result from rapid early season development. Strong emergence of healthy seedlings that establish a uniform stand is the foundation enabling maximum early season growth. Once a stand is established, vegetative growth should be promoted through the judicious use of cultivation, fertilizers and agrichemicals.
Stimulate Early Flowering
Early flowering follows maximum early season growth. Commercially desirable varieties raised in North Carolina normally produce their first fruiting branch when the plants have between five and seven true leaves. A fruiting branch produces squares, or flower buds, that may become harvestable bolls. Flowering is delayed when physiological, chemical or insect-related stress retards square formation or causes square abscission (shedding).
Examine cotton plants with five to seven true leaves and note whether small squares, sometimes referred to as pinhead or match-head squares, are present on the plant. If they are, then your cotton is developing properly. If they are not, then you may need to alter your management plans to increase square formation and retention.
This situation may require you to apply Pix to reduce the likelihood of rank growth, delay nitrogen side-dressing, increase insect scouting and treatments to avoid further loss and avoid over-the-top treatments with injurious herbicides.
Prevent Rank Growth
Excessive vegetative or rank growth has historically been a common problem for cotton farmers, particularly in a rain belt like North Carolina. Problems associated with rank growth include (1) delayed maturity; (2) increased insect damage; (3) increased boll rot; (4) more difficult defoliation; and (5) decreased harvest efficiency. The indeterminate, perennial growth habit of cotton is partially responsible for this undesirable trait.
Unlike determinate, annual crops such as corn and small grains, cotton will support vegetative and reproductive growth simultaneously. Early season growth is dominated by vegetative growth. Once flowering and boll-loading begin, vegetative growth slows because bolls have preference over leaves and stems for available energy and nutrients.
When cutout occurs or cotton blooms out the top, the plant’s energy and nutrients from the leaves have been entirely directed to the bolls. Vegetative growth ceases until a sufficient number of bolls have matured enough to allow vegetative growth to resume. The development of cotton is a constantly changing balancing act.
Rank growth occurs when this balancing act is disturbed, and vegetative growth predominates over boll loading. This imbalance can happen in several ways. Abundant water and nitrogen accompanied by warm weather will support vigorous growth before bloom. As plant vigor and leaf area increase, available sunlight decreases for photosynthesis lower in the plant canopy.
Individual bolls are supported by leaves growing nearby. The earliest squares and bolls that form at nodes five through seven are fed by leaves that may not photosynthesize sufficient energy to support fruit growth. The result of this increased shading and decreased available energy is square and boll shed. Square and boll shed also may result from insect damage, pesticide damage or other environmental stress, such as drought or nutrient deficiencies.
Rank growth also can begin after the flowering starts. Whatever the cause, rank growth can snowball by reducing boll load and thereby increasing the potential energy available for further vegetative growth. In the past, farmers were ill-equipped to control rank growth.
The available solutions were to (1) plant on the sandiest drought-prone land, (2) withhold nitrogen, (3) avoid irrigation and (4) chop the tops out of rank cotton. Fortunately, with the availability of mepiquat chloride, the judicious use of nitrogen and timely insect control, we can largely avoid rank growth. In modern times, rainfall is usually the culprit of rank growth.
Protect Investments From Pests
To produce cotton profitably, pest control must be viewed as a wise investment, not just another cost. Typically, a new grower may see that weed, insect and disease management costs comprise a large and seemingly excessive part of production expenses. Therefore, a new producer may delay or avoid timely pest management. This delay is a serious mistake.
The tools available to minimize economic damage from pests are limited. Timeliness is the essence of effective pest management in cotton. Timely crop development is the first defense against pest damage. Perform those agronomic practices that promote cotton fruiting development. Cotton can better compete with pests if it is healthy and actively growing.
Some pesticide applications are inevitable because of the poor competitiveness of this tropical crop during the early part of the season, and the attractiveness of cotton to insects. The effectiveness of cotton pesticides is entirely dependent on timely application in a technically appropriate manner.
Veteran cotton producers can speak with experience about a field or crop that was lost because weeds, insects or diseases overran the cotton.
Harvest Quality Cotton
North Carolina cotton producers can expect some harvest delays because of rain and high humidity. In addition to delaying harvest, these environmental conditions can reduce lint quality and yield. Harvest delays may also result from the harvesting of other crops, particularly peanuts. Growers need to remember that these delays can, and frequently do, reduce the value of their cotton. Timely harvest will increase or maintain the value of an investment in cotton.
In many years, there is a temptation for growers to delay defoliation in the hopes of increasing yields. Growers in North Carolina need to remember that we seldom have the type of weather needed to increase yields after the first two weeks of October, unless warm weather is forecast for several days during the latter half of October.
For meaningful progress in upper boll maturity to occur, approximately 10 DD-60s per day or more would need to be accumulated. For this to occur, daytime highs should be 80 degrees Fahrenheit or higher and nighttime lows should be above 60 degrees. Daily highs below 70 degrees F and nightly lows below 50 degrees result in no heat unit accumulation, and thus no further meaningful maturity of unopened bolls.
Prolonged cooling trends are not uncommon in North Carolina once we reach mid-October. At this point, waiting on bolls to mature can become futile, if only a few or no heat units are forecast.
Even if a frost is not imminent, boll maturity slows down significantly, and progress towards maturity may take several weeks during late October, as opposed to a few days in late September. Meanwhile, cotton left in the field not only suffers losses in reduced quality but also in reduced yield because lint falls off the plant.
Losses exceeding 100 pounds of lint per acre over a six-week period have been observed in North Carolina, particularly in varieties with poor stormproof characteristics. In addition, days and hours suitable for harvest generally decline in the fall, and rains typically require more time to dry due to cooler weather, which could potentially limit the number of effective harvest days.
As a result, gaining a week for potential added growth in late September or early October may delay the final harvest of the season by a much longer period, which could increase the risk for yield loss of open bolls and degradation of fiber quality.