Effects of Organic and Biological Fertilizers on Growth and Nutrient Content of Spinach (Spinacea oleracea L.)

In order to investigate the effects of organic and biological fertilizers on growth characteristics and nutrient content of spinach (Spinacea oleracea L.), two experiments carried out under organic farming conditions at Mohaghegh Ardabili University, Iran during 2013. In the first experiment, to determine the optimal levels of organic fertilizers, vermicompost, compost, washed and unwashed spent mushroom compost with the ratios of 10, 20, 30, 40 and 50 percent by volume and control media based on a complete randomized design with four replicates were used. The results showed that the highest vegetative growth parameters were obtained in plants grown in medium containing 30 % vermicompost, 10 % consumed mushroom compost and 10 % unwashed consumed mushroom compost. The second experiment was carried out in a factorial arrangement in a completely randomized design with four replications. At first, spinach seeds of P1, P10 and P19 strains of Pseudomonas putida and strains R69, R150 and R159 from Pseudomonas fluorescens (first factor levels) were inoculated. Subsequently, inoculated and uninoculated seeds were planted in optimum substrates consisted of volume ratio of 30 % vermicompost, and the washed and unwashed consumed mushroom compost each with a 10 % volume ratio (second factor levels). The results revealed that the effect of organic and biological fertilizers on growth indices and nutrient content of spinach was significantly different in compare to the control. The highest plant height, chlorophyll content, leaf area, leaf fresh weight, leaf dry weight, total dry weight and the highest amount of nitrogen, calcium and potassium were observed in plants inoculated with R150 strain of P. fluorescens and 30 % vermicompost in the planting bed. Application of non-leached mushroom compost residue, vermicompost and leached mushroom compost residue and plant growth promoting bacteria had significant effects on growth indices and nutrient content of spinach. Among different plant growth promoting bacteria, P. fluorescens R150 strain had more effect on the studied traits.