Three weeks after your timely planting, a haboob sandblasts your cotton. Do you hold or fold? Even with such an event, there is the possibility of a healthy yield depending on your level of acceptable final plant population.
“It’s critical to determine the overall population of healthy plants,” says Mississippi cotton specialist Darrin Dodds. “If a grower has an overall healthy plant population of at least 15,000 plants per acre, Mississippi State University data shows the crop still has maximum yield potential. If you keep an evenly spaced, healthy plant population of 15,000, you can expect to make as an optimal yield as if you had 45,000 plants. Our data shows yields are level from 50,000 to 15,000 plants (per acre) population.”
However, Dodds quickly adds a caveat: The 15,000-plant population must be evenly spaced. “A 15,000-plant population on a 38-inch row averages about a plant every foot-row. You can’t have a 100-foot section of row that has a plant every 4 inches and have a 50-foot section of row that has a plant every 3 feet,” he explains. “Yield reduction come(s) from 2 and 3-foot skips.”
Time Is Critical. Keeping a stand is especially critical if a questionable crop is at the back end of the desired planting window. For example, if you planted mid- to late May, and something like thrips or sand hammers the stand three weeks later, you really need to keep your existing stand if at all feasible.
“You cannot put a price on time,” Dodds says. “You’ve lost three weeks and the expense of planting, and three weeks on the back end of the season,” he explains. “When you consider replanting, also consider the back end of the crop, because at some point in time, you’ll run out of heat units, your days will get shorter, and fall rains will come. If 2017 showed us anything, it showed that we can’t always count on good weather at the back end of the crop.
“Cotton is very resilient and can withstand low populations, and still make a tremendous crop. If you have plants that are relatively evenly spaced and have a minimum of 15,000 plants per acre, manage your crop for maximum yield as you would in a normal plant-population scenario.”
Maintain Yield Goal. Once growers decide to keep their stand, they need to maximize production of their remaining plants in order to keep up their yield goals. For example, do not change the nitrogen application rate. “The seeds in the bolls are the primary sink for nitrogen in the cotton plant,” Dodds says. “If your yield goal has not changed, then your nitrogen application rate should not change.”
Additionally, allow the plant to dictate the plant growth regulator (PGR) strategy. “In areas with low plant populations, cotton will fill in these gaps--if they are less than 2 to 3 feet,” Dodds says. “This outward growth may somewhat limit vertical growth compared to what you may see in fields with normal plant populations. However, if you see internode length--check internode length between the fourth and fifth node down from the top of the plant--exceeding 2.5 inches, a PGR application is needed.”
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