Influence of liquid organic fertilizer on growth, cadmium and macronutrients uptake of Spinach (Spinacea oleracea L.) in a cadmium polluted soil

Background and objectives: The study of heavy metals is particularly important because they are not decomposable and also have harmful physiological effects on organisms even at low concentrations. Cadmium is a heavy metal which may entered water, soil, plants and ultimately the human and animal's food chain from various sources, and it can cause serious damages. Biological fertilizers are consisted of concentrated population of beneficial microorganisms or their metabolic products that introduced into soil to improve soil fertility and plant nutrition in sustainable agriculture. Vermicompost and its derived aqua products (i.e. vermiwash and tea vermicompost) are as biofertilizers. Vermiwash is a complex of materials which are excreted from both earthworm substrate and their body. Vermiwash is rich in vitamins, hormones, enzymes, macro- and micronutrients which can help plants for efficient growth. vermiwash, could be used an organic liquid fertilizer as foliar spray in agriculture. The aim of this study was to evaluate the effect of liquid organic fertilizer on growth, cadmium and macronutrients uptake of Spinach in a cadmium polluted soil.
Materials and methods: A greenhouse experiment was conducted with factorial arrangement in a completely randomized design with two factors and tree replications in a cadmium contaminated calcareous soil. Treatments were consisted of four levels of vermiwash (0, 25, 50 and 100 ml per kg of soil) and four levels of cadmium (control (5), 10 20 and 40 mg Cd kg-1. Before cultivation soil was used and its characteristics along with vermicompost were analyzed by standard methods. Seeds of spinach (Spinacea oleracea L.var. inermis) were planted in pots. After eight weeks of planting, wet and dry weights, concentrations and uptake of nitrogen, potassium, phosphorus and cadmium of plant were measured.
Results: The results of this study indicated that vermiwash is effective in improving of growth and yield of plant. The lowest dry weight was observed in control (without vermiwash) and the level of 40 mg Cd per kg of soil and the highest of them was observed in 50 ml vermiwash and the level of 40 mg Cd per kg of soil. In all Cd levels, the concentration and uptake of nitrogen and phosphorus by plants were increased. Vermiwash had no significant effect on cadmium and potassium concentration of plant.
Conclusion: Vermiwash application increased yield and macronutrient uptake by Spinach in Cd contaminated soil. Vemiwash could be used as a plant growth fertilizer. Further investigations will be useful and recommended in field condition.