Monday, July 25, 2016

Getting a Fix on Nitrogen Levels in Cotton Plants

When you go for an annual check-up, the doctor often orders lab tests to check what’s going on inside your body. The results may suggest you need to take supplements to boost the vitamins and minerals that your body needs.

It’s the same thing with plants. You test plant tissues, find if there are any nutrient deficiencies or imbalance and then fix the problem

Earlier this month, field scout Carlos Silva headed into the fields to pick petioles, or leaf stems, for nitrate sampling.Taking the fifth or sixth petiole from the top of the plant, he collected a total of 50 leaf stems from three different areas of each field. The samples were sent to a lab for analysis, which involves chemically monitoring the nitrate-nitrogen and phosphorous content of the cotton petioles.Nitrogen and phosphorous are essential for healthy plant growth.

Finding the right nitrogen balance can be tricky. If there’s not enough nitrogen, the fruiting areas and potential yield suffer. Too much nitrogen can lead to excessive growth, increased problems with diseases, delayed maturity and reduced quality and yield.

Here is an example of nitrogen deficiency in a cotton plant.
Here’s what the BASIC Cotton Manual says: ‘Petiole analysis will indicate a need for nitrogen about two weeks prior to the appearance of plant symptoms. If petiole-nitrate application is low during the first three weeks of bloom, a soil application, a foliar application, or both, would be recommended. Urea has been found to be an effective and safe source of nitrogen to apply to a developing cotton plant. Leaf and petiole analyses are most reliable when moisture and other stress-related factors are not influencing growth.”

“The lab results are really useful for the growers,” Carlos says. Growers will use the data to make decisions on future fertilizer applications.

Growers are irrigating their cotton fields for the second time.
Meanwhile in the field, Carlos reports growers are starting to irrigate their cotton fields again. The plants are showing 11 to 12 fruiting branches and pest pressures are in check for now. But Carlos says growers will start keeping a close eye on aphids as bolls start cracking open in the coming weeks. He is finding aphid populations in about a quarter of the fields he monitors weekly

In alfalfa, the plants are about 15 to 18 inches high. In the next week or two, it will be time to harvest again. While worms and caterpillars remain a concern, growers have held back on treating their fields. Their thinking, Carlos says, is why spend money on chemicals when the next cutting is coming up soon.

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