Agri-Brief: Cotton Petiole Analysis: A Useful Diagnostic Tool

AGRI-BRIEFS
AGRONOMIC NEWS ITEMS

From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335

Spring 1996, No. 8

COTTON PETIOLE ANALYSIS: A USEFUL DIAGNOSTIC TOOL

Petiole analysis is a useful tool in maintaining plant health, evaluating soil fertility programs...and guiding farmers and their advisors in making nutrient management decisions to support profitable crop yields. It is a practice worth using in high yield cotton production.

Petiole analysis allows crop advisors and farmers to monitor nutrient status in a timely manner, important in maintaining nutrient balance. Also, certain nutrients compete with each other while others are synergistic in terms of plant uptake.

Nitrogen deficiency, for instance, can result in small stalks and bolls or lead to increased boll shedding. Too much nitrogen can trigger excess vegetative growth, increase disease susceptibility, delay maturity, increase the frequency of boll rot and lead to lower lint quality.
Potassium enhances photosynthesis, late season boll fill, disease resistance and lint quality. Too much potassium antagonizes magnesium utilization from low magnesium testing soils.
Magnesium, the central element in the chlorophyll molecule, also serves to activate many enzyme systems and promotes seed formation.
Phosphorus, involved with energy transfer and storage, improves root and seedling establishment and stimulates seed and oil development.

Petiole analyses allow crop advisors to determine the nutrient status at weekly intervals and recommend corrective treatments where needed. It helps to evaluate factors such as:

the need for late season boron, potassium and/or nitrogen applications;
the effectiveness of previously applied fertilizer;
the potential for outbreaks of certain leaf spot diseases;
the risk of early cut-out;
potential harvest date.

Effective use of petiole analyses requires close attention to details. For best results several factors must be considered:

pre-arrangement for laboratory analyses and rapid return of test results, by electronic mail where possible;
adequate training of cotton scouts in the technique of proper plant and field sampling and handling of petiole samples;
time of day and time since irrigation affect petiole composition;
sampling of problem and normal areas for comparative purposes;
reliable laboratory result interpretation and sound agronomic recommendations for optimum profitability.

Cotton petiole analysis is growing in acceptance as a diagnostic tool that provides good opportunity to monitor the nutritional status of high yield cotton and provides an opportunity for in-season adjustments essential for top profits.