Thursday, May 10, 2018

How Growers Determine if a Cotton Stand is Too Weak, Too Strong or Just Right

With nice, warm weather enveloping the Valley, cotton fields are turning into a faint sea of green as seedlings start popping out of the ground.

Growers will assess how well the cotton crop is developing.
Field scout Damien Jelen reports crop emergence is looking good the first couple of weeks of the month. The sunny, 80-degree weather is spurring growth. “We’re seeing pretty good cotton stands,” he says.

That’s good news. This is an important time for cotton because the first 30 to 40 days after planting gives growers a clue about the crop at harvest time. UC Integrated Pest Management says everything that occurs after the cotton stand is established will either maintain or decrease yields.

A healthy cotton seedling basking in the warm sun.
So it’s important for growers to assess stand development at this time. Damien will be doing his own census to provide a second set of eyes for growers who do their own assessments. The goal is to determine if the stand is too weak, perfect or growing too vigorously.

UC IPM offers these tips to estimate the plant population:

·         * Take at least four measurements from several representative areas of the field and average the results.
·         * Find the length of a row that represents 1/1000th of an acre for various row widths. (see chart below)
·         * In the field, count the total number of plants in the 1/1000th acre area and multiply by 1,000.

Length of row representing 1/1000 of an acre for various row widths
Row width (inches)
1/1000 (row feet)
The optimal rate is 40,000 to 60,000 plants per acre (PPA). The stand is considered weak if the rate is below 30,000 PPA. The stand is growing excessively if the rate is more than 60,000 PPA.

Here is an example of a weak cotton stand.
Growers need to thin out the crop if it is growing too vigorously. For a weak stand, growers need to determine if there are any seedling diseases or damage from insects. Often, growers will replant an area experiencing a weak stand.

In addition to stand assessment, growers also need to monitor for spider mites, aphids and thrips,start tracking degree day accumulation to monitor plant growth and survey for weeds in the field. Growers should watch for soil diseases such as Race 4 Fusarium, a nasty ailment that spreads easily and can plague big swaths of plants.

While these practices might be time consuming, the hard work will pay off at harvest time.

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