Reproductive Performance and Fiber Quality Responses of Cotton to Potassium Nutrition

Potassium (K) acts as osmoticum to balance the turgor pressure and regulate opening and closing of stomata and balances the exchange of anions. It is a key element in enzyme activation and physiological functions of the cells. It also influences the transportation of photoassimilates from leaves to other plant parts and restricts fruit production to a greater extent. Potassium deficiency affects cotton growth and development and fiber properties.

An experiment was conducted in an outdoor pot culture facility by imposing four potassium stress treatments (100%, 40%, 20% and 0% of optimum K level) prior to flowering during 2010 and 2011 growing season. Upland cotton cultivar, TM-1, was seeded in the pots comprised of fine sand as rooting medium. Flowers and bolls were tagged daily to estimate boll maturation period (BMP). Leaf samples were collected every four days from flowering to maturity to estimate leaf K content. Plant height and node numbers were recorded from emergence to 21 days after treatment. Photosynthesis and stomatal conductance were measured weekly from day of treatment imposition to physiological maturity at an interval of seven days. Stem, leaf, and boll dry-component weights, and boll numbers were recorded at the end of the experiment in each year. From each boll, the lint samples were collected and grouped based on average leaf potassium concentration during BMP, and fiber quality parameters were recorded for each group in each treatment.

The results showed that at high K deficient (0 K) condition, total biomass declined by 27% and 28% in years 2010 and 2011, respectively. Significantly, lower numbers of bolls were retained per plant at 0 K stress treatment during both the years. Leaf photosynthesis (r2 = 0.92) and stomatal conductance (r2 = 0.80) declined with declining leaf K levels. Fiber length, strength, micronaire, and uniformity declined linearly with decrease in leaf K content. Weaker fibers with medium length were produced under K-deficient conditions with micronaire values in the discount range. Fiber uniformity, however, did not decline with decrease in leaf K.

In conclusion, the identified plant leaf K status-specific fiber functional relationships should be helpful to assist management practices during cotton growing season. Also, leaf K-specific indices for fiber properties should be useful for developing sub-models for cotton fiber development and can be incorporated into cotton simulation models to improve management practices under present and future climatic conditions.

Article by Suresh Lokhande and K. Raja Reddy, from Mississippi State University, Mississippi State, MS, USA.

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