Establishing a healthy stand of cotton is the first step toward a successful season. Cotton does not tolerate difficulties encountered during its first weeks of growth. An important accomplishment toward a successful season is achieved when cotton actually begins to grow the first true leaf. Advances in planting equipment, improved cultural practice techniques and technological improvements in seed quality and chemical protectants have enhanced the potential to obtain a healthy and uniform stand of seedling cotton. Nonetheless, lack of attention to detail, poor planting conditions or overconfidence is a formula for failure.
Getting a Good Start
Decisions regarding equipment, tillage systems and row spacing for cotton can be influenced at the farm level depending on rotation and other cultural practices employed. Other decisions such as variety selection and plant population can be field specific. Regardless of production strategies in place, substantial costs are often incurred by the producer before a seed has been planted. Doing the right thing at the right time is important. However, having a good plan does not ensure success as soil moisture and temperature levels influenced by weather conditions following planting can be unpredictable.
Equipment and Tillage Systems
Modern equipment offer growers a way to better match tillage systems to soils which allow for timelier soil preparations and planting in various soil types. For example, new planters are capable of precise placement of the seed. No-till, strip-till, and stale seedbed systems enable producers to plant when soil conditions are closer to optimum, rather than having to wait until fields can be tilled conventionally for planting. Additionally, winter cover crops are often used in no-till and strip-till systems to provide seedlings with protection from wind and sand. Establishing a uniform cover crop with few skips is important to ensure that the cover crop is weed-free and more easily terminated.
In most no-till and strip-till systems, burndown herbicide applications are made in early spring to facilitate planting into fields with a cover crop. A follow-up herbicide (post-plant pre-emergence) is often required at or immediately after planting to manage escapes and newly emerged vegetation. Early season insect pest problems, sometimes associated with cover crops such as wheat or rye, are often the result of pest populations increasing on broadleaf weeds found in the cover crop. Timely burn-down herbicide applications can be effective in eliminating the buildup of pests in weeds while continuing to allow cover crop residue to provide wind and sandblasting protection as well as preserve soil moisture for planting. After emergence, weed control is similar to that used in conventional tillage methods except that mechanical cultivation is avoided, if possible (National Cotton Council of America, 2007).
Stale seedbed producers prepare beds in the fall following harvest and leave them fallow until spring planting. The objective is to prevent planting delays that can occur when spring tillage is done on heavy soils. Tillage operations are avoided after the fields are bedded in the fall until planting time in the spring. Burndown herbicides are the sole means of native vegetation control. The lack of compaction from tillage operations improves soil structure and internal drainage which is often one of the most limiting factors for cotton on heavy soils. At planting, a thin layer of dry soil is removed from the top of the bed for optimum seed placement and planter operation. Producers sometimes can plant directly on the stale seedbed depending on moisture conditions.
Subsoiling fields that have plow pans can improve water and root penetration. This practice is generally done prior to fall bedding or in the spring before planting. Subsoiler shanks set to a depth of 16 to 18 inches will loosen compacted layers. Subsoilers are available that will address problem plow pans while minimizing disturbance to surface residues.
Reducing tillage trips in conventional systems can save fuel and lessen the potential for compacting soils. If fields are not rutted excessively at harvest, producers may re-shape the old beds for planting the following season if plow pans are not a problem. Excavating the cotton roots of the previous crop can provide clues as to the existence of a plow pan.
Cultural practices aimed to prevent the over-wintering of pink boll worms in some areas require the post-harvest destruction and incorporation of cotton stalks every fall. This requirement is mandated by law and every field is inspected to meet plow-down specifications. The adoption of reduced tillage practices has forced some changes in the degree of incorporation allowed. Stalks must be shredded and undercut to insure no spring regrowth will occur. The fall plow-down plus a legal planting date insures a 90 day host-free period to prevent the overwintering of this major cotton pest.
Row Spacing
Altering row spacing from a wider conventional spacing of 38 to 40 inches to a narrow row pattern of 15 to 30 inches can offer an alternative approach to enhance earliness and help the crop make more efficient use of light in fields that typically grow smaller plants. Shifting row spacing may also allow producers, who grow grain crops, to use the same equipment across the entire farm. However, a shift in row spacing can represent a significant investment in new equipment if necessary to accommodate new row spacing.
Variety Selection and Seed Quality
Variety selection and seed quality have a lasting effect on the crop’s early-season vigor and on overall plant health which is critical in establishing high yield potentials. Less vigorous varieties are more susceptible to stresses caused by inadequate moisture, cool temperatures, thrips feeding, seedling diseases, nematodes and other pests. In addition, varieties exhibit varying levels of resistance or tolerance to high temperatures, diseases and pests, such as fusarium or verticillium wilt, root-knot nematode and bacterial blight. Consider planting resistant varieties, or those that have at least some tolerance when possible.
Yield still is the ultimate measure for a cotton crop, although the ever-increasing demand for higher fiber quality makes this factor a close second in priority. When selecting varieties for planting, don’t simply choose the top yielding variety at any single testing location or year, but look at the averages of several seasons. Varieties that consistently produce yields near the top are often easier to manage than those that produce at the top in some locations and in the middle or near the bottom at others. Also, some varieties perform more consistently across different seasonal conditions and locations (Sadras et al. 1997). Pay particular attention to yield ranking in irrigated as well as dryland locations. This will help identify varieties that may tolerate stress better than others.
Each variety has strengths and weaknesses. The challenge is to identify these characteristics and adjust management strategies to enhance strengths while minimizing the weaknesses. Ultimately, the best experience is based on first-hand, on-farm knowledge. Evaluate yield and quality parameters of unbiased testing programs to learn more about new varieties. Three-year averages are much more meaningful in evaluating the performance of a variety. If three-year averages do not exist for the varieties in which you are most interested, evaluation across locations can be useful.
Producers should try new varieties on some of their land. However, planting the entire farm in new varieties is not recommended. Plantings of new varieties should be limited to no more than 10 percent of the farm. Acreage of a variety may be expanded slightly if it performs well the first year. Consider planting the bulk of the farm to three or four proven varieties of differing maturity to reduce the risk of weather interactions and to spread harvest timings. Producers should always evaluate more than one year’s worth of data prior to planting more than trial acreage of a new variety on their farm. Be very cautious in terms of acres planted to newer varieties if multi-year testing is not available.
Select the highest quality seed for planting. Rapid field germination and emergence is best because it narrows the window for seedling diseases and minimizes the impact of pests. In addition to the standard warm germination test, a cool germination test is also recommended. When cool and warm germination numbers are added together, high-quality seed will have a vigor index of at least 160 (e.g., a warm germination value of 90 plus a cool germination value of 70 equals 160) (Table 1) (Hopper et al., 1988). Early planting into cool soils requires a high vigor index. When planting early, plant the best vigor index available in the variety you are planting. Under less than optimal conditions, it is inadvisable to plant cotton seed with a combined (warm and cool) germination percentage of less than 150 (Hake et al., 1996).
Table 1. Planting seed rating based on vigor index calculated by adding the standard warm germination and the cool germination test percentages (Hopper et al., 1988).
Rating
Vigor Index
(Standard + Cool germination)
Excellent
160 or greater
Good
140 to 159
Fair
120 to 139
Poor
Less than 120
Planting
Plant uniformly spaced seeds (drilled or hill-drop pattern) with good seed-to-soil contact in warm moist soil with temperatures of at least 60 to 65˚F. Planting with precision, not speed has a proven payoff. The trend in reduced seeding rates reflects the availability of precise planters and the producer’s desire to manage high-value seed costs by reducing the number of seeds per acre. An efficient, well-timed planting operation can result in a 10 to 25 percent savings of seed, seed treatment costs and if planting licensed seeds, technology fees (Robertson et al., 2007b).
Increase the seeding rate slightly when planting early into cooler soils. The minimum plant population in the final stand should be about two plants per foot of row for row spacing of 38 to 40 inch rows, or approximately 30,000 plants per acre. Research has shown that due to the compensating nature of cotton, uniform populations between 30,000 and 60,000 thousand plants per acre can produce similar yields (Siebert et al., 2006). In some regions where 30-inch rows are standard, higher populations 45,000 to 60,000 thousand plants per acre is the norm. Planting less than 2 seeds per foot of row on 38 to 40 inch rows can significantly delay maturity, as cotton tends to develop more bolls on outer positions and on higher nodes in less dense populations (Siebert et al., 2006). Consider the plant’s architecture, by variety, when adjusting planting rates. Plants with a tendency to produce more vegetative growth will perform better with lower plant populations. Planting density and environmental factors can affect final plant heights (Kerby et al., 1990, Sadras et al., 1997, Siebert et al., 2006).
Figure 1. Sensitivity to chilling injury in relationship to days after planting (NCC, 1996).
Soil and air temperatures should be at optimum levels when planting. A mid-morning soil temperature of 68˚F at the planting depth for three consecutive days and a favorable five-day forecast following planting is best, but not always realistic for early planting (Table 2) (Kerby et al., 1996). Soil temperatures below 50˚F have been associated with chilling injury of pre-emerged seedlings (Fig. 1) (Christiansen, 1964; Wanjura and Buxton, 1972). A favorable five-day forecast will help avoid potential chilling injury getting the seedling off to a good start which can pay dividends at the end of the season (Fig. 2).
Table 2. Temperature guidelines to determine favorability of a five-day forecast.
Outlook for Planting
Five Day DD60 Accumulation
Very Good
50 or greater
Good
26 to 49
Marginal
16 to 25
Poor
11 to 15
Very poor
10 or less
Figure 2. Impact of heat unit accumulation during the first five days after planting (NCC, 1996)
Although dependent on growing conditions, a delay in planting early in the planting window can have little impact on the date of flowering as cotton planted under optimum conditions will often catch up to earlier planted cotton that struggled with cool temperatures. Adequate soil temperature for a vigorous plant is critical. Make sure adequate soil moisture is available for optimum results and that seedbeds are firm to ensure good seed-to-soil contact.
Prior to planting it is important to create a pest-free seedbed environment. Pre-plant, burndown herbicide applications should be made at least three weeks prior to planting to ensure no green matter is on the seedbed (Fig. 3). Control all potential host plants/weeds in and around fields to eliminate sources of insect and mite pests. Most of the pest problems in cotton originate in other crops or on native vegetation surrounding cotton fields. Plant the highest quality seed variety available if planting conditions are less than favorable. The planting depth should be within the 0.25 to 1.5 inch range depending on soil characteristics to optimize emergence. For the duration of the season, it is very important to manage weedy host plants on field borders in an ongoing effort to reduce pest problems in adjacent cotton fields, but take care to avoid off-target pesticide problems.
Figure 3. Planting into pest-free seedbed environment with a terminated cover crop containing no green matter is recommended to avoid pests.
Replant decisions
Regardless of location, cotton producers have one experience in common – replanting – especially when they push the limits on earlier-than-advised planting. Experience has shown that planting early does not necessarily result in earliness. In many years, first fields planted are not necessarily the first fields ready for harvest.
Since the optimum soil temperature for cotton germination is near 85°F, it is understandable that soil temperatures less than 60˚F can lead to stand failure. Cold weather slows cotton growth, increasing its vulnerability to fungal pathogens which grow well at 65°F. The coldest soils are fine textured, poorly drained, flat-planted, light colored soils, which can lead to slow germination. The presence of sodium and other salts in these soils will slow germination even more, especially when soil calcium is low. When planting into cold soils it is imperative to use the highest quality seed. As seed size decreases, seed quality becomes more critical when planting in marginal conditions.
When determining if replanting is necessary, many factors should be considered. First, it is important to evaluate the current stand of plants that will survive (Fig. 4). This may not be evident for a few days after a storm if evaluating hail damage. Nonetheless, it is crucial to evaluate the population, uniformity and health of the existing stand. Establishing the occurrence of skips greater than three-foot in length, especially when this occurs simultaneously in adjacent rows is critical. The calendar date is also important. A thin stand is much more acceptable near the end of the planting window. The ability of cotton to adapt and maintain yield potential at lower plant populations is often underestimated. Most recommendations state, “If the decision to replant is difficult, then there are probably enough plants to keep the stand.” (Robertson and Lorenz, 2003)
Figure 4. Inspect both above and below ground plant tissue when evaluating damage.
Close attention to planting correctly the first time may prevent having to become familiar with replanting recommendations. Most advisors recommend that planting be delayed until mid-morning soil temperatures reach 68°F, 58°F California and Arizona, Kerby et al., 1989) at the desired planting depth for three consecutive days, and the five-day forecast calls for dry weather and a minimum of 25 DD60s (Robertson et al., 2007b).
Protecting the Plant
Producers should plant seed that has been treated with two or more fungicides, since most materials have activity against only one species of seedling disease pathogens. These materials also have different control mechanisms. Some protectants provide surface defense from disease organisms carried on the seed or in the nearby soil. Other products are systemic and are absorbed through the seed coat and then taken up by the seedling. Since practically all seed treatments are applied by a commercial seed processor, make sure recommended fungicides are being used that offer protection against more than one type of fungi.
Seed treatments can provide only so much protection as high rates might injure the seed. In fields with a history of seedling disease or in areas which can experience cool, wet conditions at planting, the use of one or more in-furrow fungicide may be recommended. Planting on raised beds can also improve soil warming and drainage, creating less favorable conditions for seedling disease.
Nematodes and insects/mites can compound the severity of seedling diseases by slowing plant growth. Plants suffering from foliar damage caused by insects/mites or root damage from nematodes are not able to grow as rapidly. Also consider that it may be the seedling disease that sets up the plant for more injury by nematodes and insect/mite pests.
Producers should choose an at-planting systemic insecticide/miticide capable of providing long residual efficacy. Some choose to omit systemic insecticides/miticides at planting because of the added expense and time requirements during the planting operation. However, problems may arise if adverse weather conditions prevent producers from making timely applications of foliar sprays, adding to the time the plant is subjected to insect/mite feeding.
Whether or not systemic products are used to protect the plants, cotton must be scouted in the early season for insects/mites or signs of their feeding (Fig. 5). Lack of soil moisture or a damaged root system can impact the efficacy of systemic products. When damage does occur above threshold levels, it is best to select insecticides/miticides that are not phytotoxic to the cotton seedling or harmful to beneficial insects. Cotton can overcome some damage by pests if the plant is actively growing. An example is thrips damage to cotton. Cotton is less susceptible to feeding by thrips after the plant has five true leaves and is growing vigorously (Layton and Reed, 1998). However, prior to this more tolerant stage, heavy earlier thrips feeding has been shown to be detrimental to early root development and final yields (Roberts and Rechel, 1996).
Figure 5. Illustration of three equal age plants with varying levels of thrips protection (NCC, 2007).
Adverse weather conditions in the early season can upset the best-laid weed control strategies. If pre-emergence herbicides are not activated due to lack of moisture or if excessive rains cause delays in applying post-directed or over-the-top herbicides in the early season, excessive weed competition can impact maturity, yield potential, and fiber value from contamination.
Establishing a healthy stand of cotton, which is free from damaging levels of pests, is the first step toward a successful season. As stated previously, cotton is a poor competitor during the early season. Weed, insect and disease pests often impact maturity and yield potential if left unchecked early in the season. Field scouting should be initiated at emergence, setting up the first line of defense, to protect the cotton crop during this vulnerable time of the season.
