Introduction: Water deficit is the major limiting factor in agriculture crops production, and one of the negative effects of water stress on growth and crop production is micronutrient uptake reduction by plant root. In the other side considering population rising and increased demand for food and providing food security, legumes are the most important source of protein in human nutrition. In this regard, the objective of this research was to investigate the effect of foliar application of micronutrients (Zn and Fe) on some growth characteristics and yield of cowpea under drought stress conditions.
Materials and Methods: This experiment was carried out as a split plot in randomized complete block design with three replications in a field located in shooshtar city, during the growing season of 2014-2015. Water stress at three levels (control, cut off irrigation in 50% flowering and 50% pod formation stages) were assigned as main plots and micronutrients foliar application in four levels (control, Zn foliar application (1.5 ml/lit), Fe foliar application (2 ml/lit) and mixture of two elements) were randomized in sub-plots. Elements spray was done two times at 60 and 75 day after planting. Studied traits were leaf area index, leaf number, leaf dry weight, dry weight of stem, height of first pod insertion, number of nodules on main stem, number of secondary-lateral branches, stem diameter and grain yield.
Results: Results indicated that the drought stress at flowering and podding stages decreased all investigated trait. Obviously, drought stress had more effect on podding stage than flowering stage. Number of leaf, dry weight of leaf, height of first pod insertion, number of nodules on main stem and stem diameter were decreased in drought stress at podding stage by 50, 36, 29, 44 and 18 percent in comparison to control (normal irrigation), respectively. Also, the results showed that foliar application of micronutrients increased significantly abovementioned traits. The effect of two elements mixture was more than single application of each element. The results of interaction effects of water stress and foliar application indicated that the minimum leaf area index, dry weight of stem, number of secondary-lateral branches and grain yield was obtained in no foliar application of micronutrients and cutting irrigation at podding stage. Also, the results indicated usage of two elements combination in normal and drought stress at flowering and podding stages increased the grain yield by 19, 15 and 36 percent compared to control (no spray) treatment, respectively.
Conclusion: Generally, however foliar application of Fe and Zn caused to growth and yield increasing, but in drought stress mixture of the two elements had a better impact for minimizing stress effects. Therefore, according to the limitations of soil Zn and Fe in arid and semi-arid area, spray application is an applied method to increase of micronutrients level in plants which can improve the impact of water deficit on growth and yield of cowpea.
Keywords: Drought, Micronutrients, Spray, Properties, Cowpea