First 40 days critical for cotton plant

In the time it took Noah to batten down the hatches, plug the leaks and calm the livestock, a cotton plant develops much of its yield potential.

The first 40 days after putting a cotton seed in the ground are crucial, say specialists from across the U.S. Cotton Belt. Last year those specialists contributed to a First 40 Days Workshop, which brought scientists and crop consultants from throughout the Cotton Belt together to develop best management practices for the first 40 days in the life cycle of a cotton crop.

Two of those specialists, J.C. Banks, Oklahoma State University agronomist, and Craig Bednarz, University of Georgia plant pathologist, discussed findings from the workshop at the recent Belt Wide Cotton Conferences in San Antonio, Texas.

The five best management practices developed by the First 40 Workshop include:

  1. Good early season insect control,

  2. Seed and variety selection,

  3. Seedbed preparation, emergence and plant population,

  4. Weed control, and

  5. Nematode and seedling disease control.

Banks says workshop participants agreed that a cross-disciplined approach to early-season cotton management provides valuable production information. A key objective was identifying the ideal cotton plant after 40 days.

“The height to node ratio should be at least one to zero,” Banks says. “An eight-leaf plant should be at least 8 inches tall. At 40 days the optimum plant should have seven to eight nodes and two to three squares per plant.”

Healthy cotton plants at 40 days, Banks says, should have a root system 24 to 30 inches deep and healthy stems to overcome crusty soils.

Banks says growers should be wary of planting in cool soils and should plant high quality seed in a good seedbed. “In general, the best yields come from cotton planted in the early part of the planting season.”

A first consideration, he says, is selecting a variety that will provide the agronomic traits necessary for yield goals. He says yield is the first criterion in selecting a variety that offers the best chance for net profit. Following yield he lists fiber quality, earliness, pest resistance and technology (enhanced traits). He also cites diversity of genetics, seed quality, seed size, growth habit and seedling vigor as important factors in cotton plant health and yield potential.

Bednarz says now that cottonseed are sold as individual units, it is more critical for growers to select varieties to produce plants that contribute pounds and to avoid seed that scavenge resources without significantly contributing to yield.

Banks says growers, researchers, consultants and specialists also need to define seedling vigor to include:

  • Evaluating the correlation between seedling vigor and seed size,

  • Characterizing varieties for cold tolerance at planting,

  • Developing and characterizing varieties for drought tolerance,

  • Evaluating varietal characteristics influencing specific components of fiber quality,

  • And developing transgenic resistance to nematodes and other specific pests.

A uniformed, early stand also contributes to final yield. Workshop participants agreed that plant stand should be greater than 30,000 plants per acre and less than 60,000 per acre.

“Final stand should be uniform, with at least one plant per foot,” Banks says. “Farmers should strive for a minimum of stand gaps greater than 2 feet in adjacent rows.”

Bednarz says re-planting should be done only as a last resort.

Limiting stress early helps maintain yield potential. Specialists and consultants recommend good leaf color and form. “Control thrips and minimize damage from blowing soil,” Banks says.

Bednarz says some farmers place efficiency and simplicity over agronomic performance and sound management. “We believe some decisions made primarily for the sake of efficiency may result in losses in yield, quality and profitability,” he says.

Also, at-planting management decisions to reduce inputs for early season pest control can result in delayed maturity, higher overall production costs and reduced yield and quality.

Entomologists in the First 40 Days group recommend use of an at-planting systemic insecticide with long residual activity. Insect control systems highlighting automatic over-sprays for thrips can lead to aphid or mite infestations and should be avoided, Bednarz says.

“Some producers and consultants use automatic applications of pesticides for insurance,” Banks says, “but this may cause pest populations to explode later in the season.”

Cultural practices, especially pre-plant weed control in the field and field perimeters, improve insect control by eliminating host plants and breeding sites. For growers in the western end of the Cotton Belt, this is particularly important for lygus control, Bednarz points out.

Workshop participants also recommend early-season weed control, the fourth best management practice. Recommendations varied greatly from one end of the Belt to another, but the general consensus is to rotate weed control systems as often as possible and to incorporate residual herbicides into weed control systems.

In the lower South, Bednarz and others strongly recommend that growers stop sole reliance on glyphosate. He confirmed the findings in 2005 of glyphosate resistance in Palmer amaranth (pigweed) in Georgia, noting that this weed is a good example of “why” to avoid dependence on any one weed control system.

“New evidence,” he says, “indicates seedling cotton exposed to weed damage may never recover.” Therefore, the group recommends weed competition should be eliminated for at least the first 21 to 35 days, or to the 5-leaf stage. Bednarz says in one recent test cotton seedlings exposed to weed competition at the 5-leaf stage showed a 23 percent yield loss.

The fifth best management practice, nematode and seeding disease control, is a double-edged sword. “We all recognize lethal levels of seedling disease or nematode damage, but sub-lethal levels can be difficult to identify and often result in significant yield, quality and overall profitability losses,” Bednarz says.

Soil sampling should monitor both nematode species and populations. Depending on pressure and species of nematodes, crop rotation and/or nematicides should be used.

“It is much easier to maintain a nematode population at a manageable level than to reduce a nematode population that has been allowed to build to damaging levels,” Bednarz says.

Banks says research efforts should develop transgenic technology to control nematodes. He also recommends development of nematicides that will be convenient, and provide longer control or control across nematode species.

The group also recognized need for further research and diagnostic tool adoption.

Banks recommends GPS technology, yield monitors and site-specific applications as ways to maximize production and control costs.

The group also wants to see an early-season crop model that uses measurements in addition to degree-days. Possible measurements include: solar radiation, humidity and stress factors (wind and blowing sand damage).

Banks says cotton farmers need new herbicides. “The possibility of resistance to herbicides applied to transgenic crops increases the need for specific soil and foliar applied herbicides,” he says.

Other needs include development of management systems that cross disciplines. “And industry and academia need to work together to evaluate products and systems prior to introduction to producers.”

The group says the industry needs to correlate further the relationship between vegetative growth and yield, develop fertility recommendations for specific varieties or variety types and characterize the plant's capability to compensate for shock or stress.

Workshop recommendations indicate that cotton farmers need more tools for insect management — including new chemistry, landscape ecology and transgenic varieties for controlling plant bugs and thrips.

“We also agree that we need alternatives to control early season insects without encouraging populations of other insect pests later in the season,” Banks says.

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