It’s hard to believe it’s already time to plant cotton again, but the season is upon us. As we make preparations for planting the 2013 cotton crop, there are many important things to consider. Since so much is invested in a cotton crop it is absolutely imperative that we protect this investment by taking all precautionary measures to establish an optimal stand with good seedling vigor. Although we cannot control the environment, (which is often the most important factor in stand establishment), there are a few things we can control in order to promote and establish an optimal stand. Most areas in Georgia have experienced adequate rainfall throughout the winter and early spring, which has replenished sub-soil moisture in most fields. This hopefully will help get the 2013 crop off to a good start; however, as we have seen before, soil moisture can be depleted quickly if hot and dry conditions occur. Once our normal planting window (late-April through June 15th) begins and conditions (both temperatures and moisture) are suitable, many growers will likely begin planting, especially in dryland fields with proper moisture in the planting zone. Irrigated fields are generally planted throughout all times within our planting window, due to the flexibility that irrigation provides. In most cases, our June planted cotton tends to be double-cropped behind winter small grains. Regardless, when planting cotton planted between June 1st and June 15th, rapid stand establishment and undelayed growth and development are critical to ensure that adequate time exists to make a substantial crop. Therefore, irrigation is usually key in promoting rapid emergence and retention of critical fruit. We should also consider an operation’s planting capabilities (how long it takes to plant the entire crop) and plan properly to ensure the crop is planted within our normal planting window and in time to meet insurance cutoff dates.
Seed Quality – This is something that is often taken for granted during the rush to plant the crop. Seed quality can greatly influence germination, subsequent seedling vigor and ultimately overall stand establishment and final yield, especially when encountering adverse weather that can occur during the early portion of our planting window. When evaluating the germination of cotton seed, consideration should be given to both the warm (standard) and cool germination test percentages. Results from the warm germination test are more indicative of seed germination in near-optimal conditions. However, we may encounter less than optimal temperatures during the early portion of our planting window, thus the warm germ rating may not be the best measure of actual seed performance during such environmental conditions. The cool germ test is a better measure of germination and vigor in suboptimal conditions such as cool, wet weather. This information can often be provided by the dealer and/or the seed company. Cool germ percentages between 65 and 80 are considered to be good, while percentages greater than 80 are considered to be excellent. Seed with cool germ percentages ranging from 50 to 65 should be planted with extreme caution. Understanding both warm and cool germ test results, allows us to somewhat predict the potential for stand losses in various environmental conditions, and also provides a basis upon which seeding rate decisions or adjustments can be made in order to achieve optimal stands in these conditions. Additionally, protecting our seed by avoiding herbicide injury, maintaining proper soil pH, and ensuring protection against thrips, nematodes, and seedling diseases, are all considerations that are not to be ignored. Obtaining an optimal stand is extremely important, and even more so since it appears that seed for some varieties for 2013 are already limited, making replant options even more limited.
Planting Dates and Seeding Rates – Planting in optimal soil conditions is very important in achieving optimal germination and vigorous early-season growth. Although seed companies generally only bring high quality seed to the market, temperature and moisture play significant role in the establishment of the crop. We are currently coming out of a short mild cool spell. Many growers have probably planted in conditions similar to these in the past, without observing any adverse effects on germination or seedling vigor, especially when planting into well-drained and/or bedded soils. Despite its perennial and indeterminate nature, cotton is a very weak plant when it is young. Cotton seed and seedlings are very susceptible to injury resulting from both biotic and abiotic stresses, one of which is cool, wet conditions within a few days of planting. This is generally not a problem for most of our planting season, yet we are sometimes faced with cooler temperatures towards the early end of our planting window. The first five to seven days after seed imbibe water is generally the period when cotton is sensitive to cool temperatures, with the greatest sensitivity occurring during the first two to three days after imbibition. If we anticipate potential problems with germination and vigor, it is very important to avoid planting when cool, wet conditions occur or are expected soon after planting, and to adjust seeding rates to account for potential losses. Even though we may experience some high daytime temperatures, we must not forget the impact that low nighttime temperatures could have on germination and emergence. In general, cotton should be planted when soil temperatures are 65°F or greater and 30 to 50 DD60’s are expected to accumulate within five days of planting. However, the risk of poor germination and vigor increases when planting in soil temperatures less than 65°F. Growers are currently at the beginning of their planting season, therefore waiting a short time for suitable planting conditions is an option. The urge to plant into moisture in dryland fields often takes precedence over waiting for optimal soil temperatures for some growers. Close observation of expected rain events and high/low temperatures within five days of the anticipated planting date can aid growers in making these decisions. In addition, observing soil temperatures at the 2, 4, and 8-inch depths (www.georgiaweather.net), and any changes in soil temperatures that occur over several days, can provide useful information in determining when it is safe to plant. Temperatures at the 4 and 8-inch depths could also be an indicator of the warming capacity of the soil, or the likeliness of rapid cooling, when encountering a short-lived cool spell. Hopefully, the recent mildly cool spell will be the last.
Utilizing optimal seeding rates and planting depths are also very important in establishing a good stand. For cotton planted on 36 to 38-inch rows, planting at a rate of 2.5 seed per linear row foot, or a hill-dropped system consisting of 2 seed per hill with hills spaced 9 to 10 inches apart, is generally our standard planting rate (for 30-inch rows, this would equate to approximately 2.1 seed per linear row foot). This rate generally allows for optimal plant stands, growth, canopy architecture, maturity, and yield. Reducing seeding rates below this standard could lead to poor stands, delayed maturity, erratic and inconsistent plant growth, and possibly reduced yields, even if planting larger-seeded varieties (which can result in more consistent stands and higher vigor), and/or if planting conditions are favorable. If planting conditions are unfavorable, this rate could be slightly increased. Some growers may also want to utilize or capture available soil moisture by deep planting. Cotton in Georgia should be planted at depths between 0.75 and 1 inch but not greater than 1 inch. Planting on the shallower end of this spectrum is advised when encountering unfavorable soil or environmental conditions, or if surface crusting is likely. Deep planting in unfavorable soil temperatures, or in soils that tend to crust, could lead to germination and emergence problems. Planting at depths closer to 1 inch is only appropriate when planting in good soil moisture, warm soil temperatures, and in well-drained soils without the potential for crusting. One way in which growers can combat soil crusting is to run a rotary hoe over the seed bed after germination and before (or at) the point in which the plants emerge. This method is extremely effective in reducing potential stand losses due to soil crusting, but special considerations should be made to ensure this practice does not injure emerging plants (which may in fact reduce overall stands).
Evaluating Plant Stands and Replant Considerations – Plant stands should be evaluated very soon after emergence. Replant decisions are far more difficult to make as time elapses, and these decisions usually need to be made more quickly as the end of the planting season draws near. Every field situation seems to be different, and there are several factors to take into account, when considering saving or replanting a sub-optimal stand, such as costs (seed, fuel, labor, additional herbicides/insecticides, time, etc.), herbicide options or limitations, the status/health of the remaining stand, how much time is left in the season to plant, delays in maturity by replanting, and yield potential of particular fields, among others. Therefore, it is imperative to evaluate the crop and make these decisions promptly. Small, evenly spaced and infrequent gaps between plants may have little impact on maturity, architecture, or yield. Frequent gaps of 2-3 feet or larger however could significantly impact yield and could lead to delays in maturity, as the plants adjacent to these gaps could only compensate for space by forming more outer position and/or vegetative branches or bolls. Additionally, these plants may often produce very thick stalks to support the additional growth of vegetative branches, and if this type of plant structure is observed throughout the field, then harvest efficiency may also be affected.
Observing the size and frequency of these gaps compared to a mental “optimal stand” could help determine potential yield losses and the advantages/disadvantages of replanting. Previous research in Georgia suggests that replanting in June may be justified when 3-foot (or greater) skips occupy nearly 50% of planted acres, which is quite a substantial loss. One reason that such a substantial loss is required before replanting is justified is the economics of starting over, therefore it is important to reduce the risks of stand loss by planting when conditions are optimal and protecting seedlings (from insects, herbicide injury, diseases, nematodes, etc.) for several weeks after emergence. When evaluating a plant stand, take a mental note of stand losses and try to visualize what an optimal stand would look like. If planting 2.5 seed per foot on 36-inch rows, then you would expect to see a stand of approximately 2 plants per row foot. Comparing the stand losses to an optimal stand could provide insight on how much yield may be lost. Additionally, observing the size of gaps between plants may provide insight regarding potential effects on weed control, maturity and canopy architecture. When making visual estimations of stand loss, consider gaps larger than 3 feet as multiple gaps to determine the percentage of acreage that is comprised of 3-foot gaps. For example, if gaps of 6 feet are observed, then it should be considered as two 3-foot gaps. Secondly, evaluate the status or health of remaining plants. If significant thrips, seedling disease, and/or herbicide injury are observed when seedlings are relatively young, then additional yield may be lost, although this varies widely from situation to situation. Whether or not additional injury is observed in fields with skippy stands, it is always imperative that the remaining stand be protected from anything that could cause additional yield loss or delays in maturity. If a skippy stand is the result of hail damage, remember that seedlings can generally survive if one or both cotyledons and the terminal are still present in whole (preferably) and sometimes in part, although split terminals and delays in maturity are a common result of hail damage. If both cotyledons and the terminal have been destroyed, yield penalties can be expected. Also evaluate the strength of the main stalk in hail damaged situations, as hail can typically damage or bruise the main stem and affect the seedlings’ ability to recover and continue to grow. These observations should be made meticulously in order to make the best decision. Another factor to consider is yield potential of a particular field, based on field history and other factors (soil productivity, irrigated versus dryland, etc.) when deciding whether it is worth the extra effort and expense of replanting. Additionally, growers must decide whether or not a better stand can be achieved by replanting. Some fields may consistently present a challenge for stand establishment, or moisture may become deficient when growers intend to replant. In other words, consider the likelihood of obtaining a better stand if replanted. The necessity of replanting can only be determined through extensive evaluation and consideration of all factors. Although there are factors we cannot control, there are several factors that can be controlled to protect seedlings, so that replanting can be avoided.