The effect of iron nano-chelate fertilizer on yield, yield components and seed protein content of bean (Phaseolus vulgaris L.) under drought stress

Bean (Phaseolus vulgaris L.) is the second most important legume plant after soybean, accounting for a major share of the diet of more than 300 million people worldwide. However, bean cultivation is always faced with several limitations, among these production limited factors, drought stress is the most important factor and has a considerable effect in reducing the production of this crop. One of the harmful effects of drought stress is disturbing the nutritional balance in the plant, so that due to drought stress, the mobility of nutrients in the soil is reduced and the absorption and transfer of substances to the plant is impaired. Studies show that nano-iron chelate fertilizer has a moderating effect against changes in drought, salinity, acidity and temperature and leads to improved plant growth. Hence, the present study was conducted to investigate of the role of nano fertilizer on increasing drought resistance of bean in Jiroft region.
 
A split-plot layout based on a randomized complete block design with three replications conducted in a farm located in Tohan village of Jiroft city during 2015-2016. The main factor was the drought stress with three levels included: no stress, stress in vegetative growth stages and stress in reproductive growth stages. Sub-factor consisted of different amounts of nano-iron chelate fertilizer at three levels of 0, 5 and 10 kg.ha-1. In this study, stem height, number of branches per plant, number of pods per plant, number of seed per pod, 100 seeds weight, seed yield, biological yield, seed protein content and protein yield traits were measured. The obtained data were exposed to analysis of variance (ANOVA). Means comparison was done using Duncan's multiple range test using SAS software. Correlation coefficients between traits were calculated with SAS software.
 
According to the results, no stress treatment and application of 10 kg.ha-1 of iron nano-chelate fertilizer led to the highest value of stem height, number of branches per plant, number of pods per plant, 100 seeds weight, seed yield, biological yield, seed protein content and protein yield. However, for the above traits, no statistically significant difference was observed between 10 and 5 kg.ha-1 of fertilizer in no stress condition. Also, the occurrence of stress in both stages of vegetative and reproductive growth reduced the studied traits, so that the lowest value of stem height, number of branches and number of pods per plant were obtained from the occurrence of stress in vegetative growth stage, and the lowest amounts of number of seed per pod, 100 seeds weight, seed yield, biological yield and seed protein yield were obtained from the occurrence of stress in the reproductive growth stage. Among the studied traits, only the percentage of seed protein with stress treatments showed a significant increase that this increase was greater in stress in the reproductive growth stage. It should also be noted that the application of 10 and 5 kg.ha-1 of iron nano-chelate fertilizer, respectively, in comparison with the treatment without fertilizer, in the occurrence of stress in both stages of plant growth moderates the effects of stress for all traits except seed protein percentage.
 
The results of this study showed that stress occurrence at any stage of growth reduces the growth and yield of the bean plant. This reduction will be more on the seed and biological yield of the plant if occurrence of stress is in the reproductive stages of the plant. Application of nano-chelate fertilizers in each one of the conditions without stress, stress in vegetative growth stage and stress in reproductive growth stage in comparison with not using this type of fertilizer will have a positive effect on growth characteristics and plant yield. There was no statistically significant difference between the application of 10 and 5 kg.ha-1 of iron nano-chelate fertilizer for seed and biological yield of bean in each one of the no stress and stress conditions.