A reduction in performance will occur if nutrient imbalances exist, both with respect to deficiency (deficiency imbalance) and excess (excess imbalance).
As a result of the general removal of mineral nutrients from the soil profile via harvest, and leaching or water runoff, nutrient replenishment is generally required. Thus, maintaining nutrient balances entails the supply of mineral nutrients in correct proportions and at opportune times. Excess imbalance is also important since nutrient excess may increase susceptibility to diseases.
The effect of some nutrients on development and maturity of cotton may lead to protection against diseases. Phosphorus, for instance, can moderate excessive shoot growth and therefore reduce susceptibility to leaf spot infections. The opposite is observed with high nitrogen levels, which increases shoot growth and delays plant senescence, creating conditions for infection.
Some nutrients "strengthen" plant tissues, such as calcium and potassium, while others make them more tender and thus more sensitive (e.g. high nitrogen rates).
Mechanisms of physiological resistance by nutrients has been related to the amino acids regulation and protein synthesis. Nitrogen normally determines amino acids composition, whereas zinc and others interact with nitrogen to regulate amino acids, amides and protein concentration.
Cotton resistance to Fusarium wilt is also associated to zinc, increasing ascorbic acid and carbohydrate production.
Premature senescence in cotton is related to plant potassium levels, regardless of potassium supply. Lack of potassium uptake can be due to environmental stress, such as flooding, cold, cloudy days and soil compaction, which all interfere in cotton's capacity to absorb potassium – required in large amounts - between flowering and boll filling. Premature senescence causes the bolls open earlier, which hurts fiber quality. This risk can be reduced by foliar applications of potassium where low levels of soil K are detected.
Creating the right nutrient management strategy in Cotton production is not a “one-size-fits-all” prescription. Cotton is grown in vastly different environments with differing soil conditions and yield potentials. Any nutrient program needs to be designed for these variables. But where do you start? Find these answers and more in this free webinar by Cotton Grower.