Response of morphological traits, yield and yield components of pumpkin (Cucurbita pepo L.) to the integrated management of irrigation intervals and nitrogen fertilizers

Oilseed pumpkin is an introduced medicinal plant, the seeds as well as some other organs of which are being utilized in treating an array of human diseases in Iran. Considering the plant's significance in the health product's industry on the one hand, and the countrywide drought stresses and a lack of information on mineral nutrition of oilseed pumpkin, the study aimed to assess the effects irrigation interval and different levels of nitrogen fertilizer on same of morphological traits, yield components and seed yield of this medicinal plant of this useful medicinal plant.
This experiment was studied as split plot based on randomized complete block design with three replications at the Research Farm of Bu-Ali Sina University in during growing season of 2012-2013. Irrigation intervals (6, 9, 12 and 15 days) as main plots and nitrogen levels (0, 60, 120, 180 and 240 kg N ha-1) were considered as sub-plots. Furrow irrigation system was used for crop irrigation and irrigation treatments were applied after full establishment of plants. Nitrogen fertilizer was applied at three stages of planting, flowering and fruting. The evaluation traits included plant length, node number/plant, branch number/main stem, leaf number/plant, fruit number/plant, seed number/fruit, 100 seed weight, seed yield and chlorophyll meter reading.
Results showed that the effects of treatments were significant on plant length, nod and branch number/main stem, leaf and fruit number/plant, seed number/fruit, 100-seed weight, grain yield and chlorophyll index of pumpkin. Also, interaction of treatments had significant effect on all traits except branch number/main stem and seed number/fruit. Maximum and minimum traits as well as grain yield in averaging of 84.84 and 25.26 g m-2, were achieved at 180 kg N in 6 days irrigation interval and non supplying N in 15 days irrigation interval treatments, respectively. Treatment of 180 kg N in 6 days irrigation interval did not differ with treatment of 180 kg N in 9 days irrigation interval. Drought stress occurrence and nutrient deficiency, especially nitrogen during development stages especially reproductive stages caused decreasing in yield components and eventually seed yield through reduction in chlorophyll content, reduction in photosynthesis period and material translocation resulted from current photosynthesis and also reduction of proportion of supplied remobilization of materials.
Generally, results of this experiment showed that the highest grain yield was obtained in the treatment of irrigation interval of 6 days with accompanying consumption 180 kg N, but there was no significant difference between the mentioned treatment and the treatment of irrigation interval 9 days and 180 kg N. So, it can be concluded that irrigation interval of 9 days and application of 180 kg N ha-1 can produce satisfactory yield besides water saving and reduction in production cost particularly from to nitrogen fertilizers.