Zn fertilization improves water use efficiency, grain yield and seed Zn content in chickpea

In a number of the major chickpea-growing areas in the world, rainfed crops of chickpeas are often grown on soils with low available zinc (Zn). Consequently, chickpea crops can be challenged by soil water deficits and Zn deficiency coincidentally during the growing season. The interaction between these stresses was examined in two glasshouse experiments using genotypes differing in Zn efficiency. Water stress was imposed during podding. Increasing the level of Zn resulted in large and significant increases in vegetative growth up to podding. Applying Zn increased grain yields when the plants were well watered, but not under water stress, except for the Zn-efficient and drought-resistant genotype ICC-4958. Harvest indices were generally reduced as the supply of Zn and water increased. Applying Zn increased water use and water use efficiency of chickpea. Yields were reduced by water stress, largely due to fewer pods set per plant. Losses from water stress were greatest at the highest level of Zn, which was attributed to the limited soil volume afforded by the pots and the rapid development of stress in the larger plants grown at adequate levels of Zn. However, at each level of Zn, the loss in yield from water stress tended to be less in a Zn-efficient genotype. The major factor determining the distribution of Zn in the plant was the supply of Zn, while differences due to water stress and genotype were relatively small. Two-thirds of the Zn present in the plant at maturity was accumulated after the start of podding and this was little affected by water stress. The proportion of Zn in the roots of Zn-deficient plants was less than that in Zn-adequate plants. As the Zn supply increased, Zn accumulation was higher in leaves than in the stem and reproductive parts, due to combined effect of both higher Zn concentration and higher dry matter. At maturity, senesced leaves and pod walls had relatively lower concentrations of Zn compared to leaves and pods at the start of podding in all Zn treatments. In contrast, the Zn content in the stem either increased or remained unchanged. At maturity, Zn accumulation in plant organs generally increased with increasing Zn supply, but the largest proportion of Zn was found in the seeds, which is a beneficial nutritional trait for human nutrition.