Physiological Basis for Nitrogen Demand in Cotton.

Among the essential plant nutrients nitrogen (N) is required in the largest amounts. The physiological basis of N demand in cotton (Gossypium spp.) is a fundamental part of optimizing a crop management system with respect to N nutrition, fertilizer N efficiency (recovery), the management of vegetative and reproductive balance of the crop, crop maturity, lint yield, and even the economics and profit potentials. As we better understand the mechanisms associated with crop growth and development at the physiological and biochemical level we are better suited to manage our cotton production systems more efficiently (agronomically, economically, and environmentally). Considering the physiological basis of N demand for cotton (or any crop plant) there are several key aspects that include: N uptake from the soil solution into the plant (this includes ion absorption and assimilation of N), uptake patterns as a function of stage of growth, partitioning of N among plant parts, and important source-sink relationships for N within the plant. This paper provides a brief review and summary of the physiological basis of N demand in cotton.