Canopy temperature of high-nitrogen water-stressed cotton

Abstract

Australian cotton (Gossypium hirsutum L.) farmers are adopting canopy temperature (Tc)‐based irrigation scheduling as a decision support tool to improve on‐farm production. High N supply, characteristic of the high‐yielding, furrow‐irrigated cotton system of Australia, might alter cotton Tc with implications for irrigation. We examined growth, physiological, and biochemical traits and changes in Tc of well‐watered and water‐stressed cotton plants supplied with high to excessive levels of N under glasshouse conditions. We also examined Tc, lint yield, and fiber quality of furrow‐irrigated cotton crop supplied with high N. In the glasshouse and under well‐watered conditions, high N supply stimulated plant growth and increased stomatal conductance and photosynthesis, resulting in cooler Tc. Under water deficit stress, high N also stimulated growth, increasing plant water demand and thus vulnerability to water stress, which manifested as warmer Tc. Water‐stressed plants supplied high N also showed reduced stomatal conductance, lower leaf water potential, and greater accumulation of leaf and xylem sap abscisic acid. Furrow‐irrigated crops supplied higher N also had higher Tc, but there was no gain in lint yield and fiber quality. The influence of high N on cotton Tc suggests that the need for accurate and reliable Tc‐based irrigation scheduling is paramount.