In recent years, in order to enhance the health of agroecosystems, concerns for ecological inputs especially to produce medicinal plants, has increased. In order to evaluate effects of winter crops on PGPRs activities and soil nitrogen content in simultaneous application of organic manures and biological fertilizer in a low input production system of Cucurbita pepo under minimum tillage condition, a split split plot experiment based on RCBD design with three replications was conducted in 2009-10 growing season in Research Farm of Ferdowsi University of Mashhad, Iran. Four different types of organic manures (cow, sheep, chicken and vermicompost) plus control, inoculation and no-inoculation with nitroxin (as biological fertilizer containing of Azotobacter sp., Azospirillum sp.) and cultivation and no-cultivation of winter cover crops (Lathyrus sativus and Trifulium resopinatum), assigned to main plots, sub plots and sub-sub plots, respectively. The results showed that all organic manures except the chicken manure, increased the fruit yield, compared to control. Inoculation with nitroxin and cover crop cultivation resulted in increased fruit number and fruit yield, respectively, meanwhile improved soil nitrogen content was happened. Simultaneous application of vermicompost and nitroxin, increased significantly seed yield compared to single use of these factors. In both condition of cultivation and no-cultivation of winter crop, all organic manures increased seed proyein content, compared to control. The triple interaction effect of treatments was significant as the best result of vermicompost application resulted when simultaneously applied with cover crop and nitroxin. The effects of organic manures and cover crops on soil EC and pH were not significant, but nitroxin reduced soil pH amount of 0.6. Soil EC showed a positive linear correlation with soil pH. In general, the results showed simultaneously application of organic manures, a biological fertilizer and winter cover crops resulted in beneficial interactions, moreover improved soil fertility and finally produced an optimum, healthy and agrochemicals-free yield of summer squash in a low input and ecofriendly cropping system aligned with long term guidelines of sustainable agriculture.

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