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July 2, 2014 Cotton Scouting Notes

July 2, 2014 Cotton Scouting Notes

General Conditions

Cotton growth is good yet most fields are slightly behind in terms of crop growth stage. Typically, early bloom occurs some time between July 1st and July 8th within this area. Approximately 40% of fields are on target to meet this but the remaining fields are likely to be 10-14 days later. Given the scattered rainfall providing ample soil water for growth, this is not likely to be a yield limiting factor. However, it does indicate a greater potential benefit from a slightly more aggressive plant growth regulator application regime to encourage early maturity.

Weed control, application of the remainder of nitrogen and application of plant growth regulators continues to be the primary and correct management actions. However, with a pending tropical storm system approaching, the following comments are offered in advance.

MANAGEMENT AFTER A TROPICAL STORM

Arthur’s path is projected to impact this region some time Friday, July 4th. Arthur’s timing is much earlier than we have experienced in a while. The following comments are made in advance Arthur in hope to aid management.

Excessive Rainfall and Leaching

Excessive rainfall may be detrimental in several ways. First is the impact of leaching rains. Rapidly falling rainfall may leach nitrogen (N), sulfur (S) and potassium (K) from the upper soil surface. As such, corrections for leaching may be necessary if the depth to clay of soils is more than 12 inches. Keep in mind that excessive rainfall amount does not equate to leaching rainfall. Leaching occurs only when water percolates through the soil. Very heavy rainfall that is often experienced during tropical storms often falls on soils that are already saturated. Thus, rainfall moves as surface flow over fields rather than downward into the soil profile. If this is the case, refer to the section below discussing saturated soils rather than leaching correction.

Regrettably, experience is perhaps the best management regarding the amount of nutrients to be replaced after leaching rainfall. Soil type, varietal performance, crop stage and prior nutrient application should be considered. However, even when excessive rains have occurred in the past, seldom have growers reported or have I observed plant response from more than 15-20 lbs./ac of actual nitrogen and 5-8 lbs. of actual sulfur. Corrections of nutrients greater than this is not usually warranted. Lastly, additions of K are seldom needed. Most soil K index values are high to very high. While some potassium may move deeper within the soil profile, cotton roots are often deep enough to still utilize existing soil K.

Excessive Rainfall and Saturated Soils

Water saturated soils create oxygen depletion, root decay and loss of nitrogen from denitrification. Usually, plants yellow and wilt and root systems grow shallow within the soil. Additionally, should the cotton bloom reach the top terminal position, plants may not resume growth for several weeks. Thus, whenever, possible, aim to drain fields or saturated areas within 24-48 hours. If this is not possible, consider adding 10-15 lbs./ac of actual nitrogen (with sulfur preferred) as soon as soil conditions permit. Do not add more than this rate or excessive cotton growth may occur.

Experienced producer realize that foliar materials applied under soil saturated conditions offer little to no benefit. Foliar fertilizers will be ineffective since plant nutrient uptake will not occur when leaves are wilted and soils are saturated. Too, foliar materials will only supply a few days worth of nutrients. Soil drainage will provide a greater benefit than foliar fertilizer applications.

Lastly do not adjust for leaching if soils are simply saturated. (This is especially critical for soils with a clay layer of 12 inches or less. Adjusting for leaching losses when they actually did not occur adds excessive nitrogen to the soils potentially creating excessive cotton growth). The main point is that saturated soils are often more detrimental than leaching loss of nutrients simply because they damage plant growth for an extended amount of time. Addition of excessive nutrients will NOT restore the plant to good health. As we have experienced in the past, cotton is rather tolerant of the water and will resume growth when soils drain and oxygen returns to the soil-plant system. The deep-rooted cotton plant seldom requires much additional nitrogen to produce a good crop.

Wind Blown Cotton

Regardless of whether we experience leaching rainfall, excessively wet soils, or both, wind blown cotton can be difficult to manage. Initially, plants will not respond to management other than drainage of water from poorly drained areas simply because the roots, stems and leaves are damaged from wind and wind blown debris. After a few days, plant will begin to recover and should respond to management decision.

Fortunately, at the time of this post, the cotton stage of growth is prior to or at first bloom. Some fruit shed may occur but we have ample time to recover and make high yields. However, two issues that will need to be addressed are weed control and plant growth regulator utilization.

Lodged plants do not shade the row. Thus the sunlight and ample soil moisture allows weeds to emerge. Producers that recently applied a pre-emergence herbicide should reap some benefit but even this may not be ample to prevent new weeds from emerging over time. Over the top applications of appropriate herbicides fitting the correct cotton tolerance (glyphosate or glufosinate) may be necessary. Make sure to follow the pesticide label regarding rate and timing.

The decision to apply or not to apply a plant growth is a bit more difficult to evaluate. Plant growth often slows considerably after storms but rebounds with new growth suddenly. Lodged plants may also begin to grow abnormal fruting branches since many are now growing upward rather than parallel to the ground. Shaded branches may abort existing fruiting structures. (Lodged plants, wet soils, high humidity and poor sunlight often results in loss of the fruit on the portion of the plant closest to the ground). All of these situations typically indicate a need for an aggressive plant growth regulator rate. Conversely, if plants do not show this type of growth, nitrogen has not been recently applied or soil remains water saturated, an aggressive plant growth applicator rates is not needed or recommended.

Additional post and information will be provided as soon as possible after evaluation of crops and departure of the tropical storm system.