To study the response of summer squash as a medicinal plant, two manure application time and utilization of different biofertilizers, split plot arrangement of factors based on randomized complete block design with three replications was used in 2008-09 growing season. Two manure application time (autumn and spring) were allocated to main plots and four biofertilizers including 1- Nitragin (containing Azotobacter sp., Azospirillum sp. and Pseudomonas sp.), 2- phosphate solubilizing bacteria PSB (containing Pseudomonas sp. and Bacillus sp.), 3- Nitragin+PSB, 4-control, were assigned to sub plots. The results showed the significant effect of spring manure application on fruit and seed yield. Nitragin increased fruit and seed yield, significantly. The superiority of spring manure application was revealed on seed and fruit number. A positive correlation (R2 = 0.92) was found between fruit and seed yield with a linear trend in the range of 10 to 20 t ha-1 and leveling off at the above 20 t ha-1 fruit yields. The seed oil and protein content were not affected by treatments, however, the biofertilizers increased oil and protein yield compared to control. At a glance, the biofertilizers could be an appropriate alternative for chemical fertilizers to achieve ecological production of summer squash.

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