Effect of vermicompost levels on morphologic traits and nutrient concentration of chickpea (Cicer arietinum L. cv. Pirouz) under water stress

Introduction Water shortage is the main factor that limits growth in dry environments. Tolerant plant is able to absorb water from the soil even in conditions of limited availability so plants achieve maximum efficiency in terms of growth and productivity. Studies have shown that drought stress alone is the reason for 50 percent reduction in chickpea yield. In Iran, this problem is more serious, as chickpea is often traditionally cultivated at the end of the rainy season. The rapid growth stage of this plant coincides with the time in which the level of moisture in the soil decreases significantly. Therefore, the use of bio-fertilizers seems to be effective for drought condition. Vermicompost production is a method of converting organic waste into usable material in which species of earthworm are employed to stabilize organic waste. Vermicompost is produced by the decomposition of organic material using non-thermal interaction between earthworms and microorganisms. Vermicompost is rich in humic compounds and researchers speculate that the hormone-like activities of humic substances play a role in amelioration of water stress. In comparison with other organic fertilizers, vermicompost consists of high levels of nutrients such as N, P, K, Ca and Mg, as well as micronutrients such as Fe, Zn, Cu and Mn. Agricultural land in Iran is facing water shortage and chickpea is an economically valuable crop that has a significant role in the human diet. The present study was done with the following aims: (1) to determine the effect of vermicompost in reducing the effects of water stress in chickpea plants; (2) to determine the best mixture of vermicompost fertilizer and soil in the greenhouse. Materials and methods A factorial experiment with a completely randomized design and three replications was conducted. The first treatment prepared four ratios of vermicompost (VC) and soil as follows: control (100% soil); 10% VC + 90% soil; 20% VC + 80% soil; 30% VC + 70% soil. The second treatment was water stress as follows: control (non-stress; 100% of field capacity); moderate water stress (75% of field capacity); severe water stress (25% of field capacity). Chickpea seeds were soaked in water for 24 h and then planted four to a pot. The pots were kept under a photoperiod of 25ºC (12.5 h), and 15ºC (11.5 h), day and night, respectively. The samples were harvested approximately 45 d after planting (podding stage). The shoots and roots were separated and morphological traits of plant height, number of leaves, number of pod, root area, root diameter and dry weight of shoots and roots were measured. Na, Ca and K concentrations of leaves and roots were determined using the method cited in Chapman and Patt (1961). Results and Discussion Result showed that under non-stress, vermicompost fertilizer resulted in a significant increase in all studied traits. Under moderate stress, application of vermicompost significantly increased plant height (19%), number of leave (23%) and pod (32%), root area (23%) and root volume (69%), K (37%), Ca (54% and 30%) concentrations in leaves and roots. Under severe stress, addition vermicompost to soil at 30% level led to significant increase on number of leave (22%) and pod (33%), root diameter (48%), K (45% and 36%), Ca (63% and 33%) concentrations in leaves and roots. Vermicompost containing high levels of nutrients, plant hormones, and with good water storage capacity leads to improved uptake of nutrients that serves to reduce the detrimental effects of drought stress. The increase in plant height, root traits, number of pods and leafs are the result of the stimulation of auxin-like substances, humic and fulvic acids produced during vermicompost consumption. It appears that the use of vermicompost provides better conditions for water and nutrient absorption and allowing plants to spend less energy for root growth. Conclusion The results of this study show that under non-stress and moderate conditions, application of vermicompost can improve chickpea growth. Vermicompost facilitates an increased uptake of mineral nutrients such as K and Ca from the soil under conditions of water stress. According to the results of this study, using of vermicompost and soil mixture recommended to ameliorate the negative effects of water stress.