چكيده لاتين :
Introduction
Oilseed pumpkin is a medicinal plant, and it seeds as well as some other parts of it are being utilized in treating an array of human diseases in Iran. Plant yield and its components are considered in plant production and the effect of water stress depends on plant type, harvested product, irrigation intervals and time of stress (Ali and Shui, 2009). Drought is one of the most common and important environmental stresses that may limit agricultural production worldwide. Despite the negative effects on yield, drought stress can enhance other stresses, to the especially nutrient deficit stress in plant (Kumbhar et al., 2007). Among food elements, nitrogen plays a very crucial role in the production power of crops and its deficit is one of the most important limiting factors to crop yield. Nutrient absorption is reduced under water deficiency conditions which causes proper proportion generation between water supply and fertilizer consumption that can reduce excessive consumption of nitrogen and this does not have any positive effect on seed yield in such conditions. Considering the plantʹs significance in the health products industry on the one hand, and the countrywide drought stresses and a lack of information on mineral nutrition of the oil seed pumpkin on the other hand, the aim of the present paper was to study the impact of different irrigation regimes and nitrogen levels on percentage of seed fatty acids, yield, water and nitrogen use efficiency of pumpkin.
Materials and methods
Field experiment was carried out as split plot based on complete randomized block design with three replications at the Bu-Ali Sina University in the growing season of 2013. Irrigation (320, 420, 600 and 900 mm. ha-1) was set as the main plots and nitrogen fertilizer (0, 130, 260, 390 and 520 kg urea.ha-1) was allocated in subplots. A furrow irrigation system was used for crop irrigation and irrigation treatments were applied after full establishment of the plants. Nitrogen fertilizer was applied at three stages of planting, flowering and fruiting. The evaluation traits included oleic acid, linoleic acid, fruit and seed yield, water use efficiency (WUE) and agronomic nitrogen use efficiency (ANUE). After physiological maturity, 1 m2 from each experimental unit was harvested to determine fruit and seed yields. Seed yield was calculated with 14% moisture at the harvest time. Seed fatty acids were determined using gas chromatography (GC). The WUE (kg.mm–1 water) was calculated for fruit and seed yield. Agronomic nitrogen efficiency (ANE) was calculated as the ratio of (Grain yield F – seed yield control) to N applied, where F equals fertilizer treatments (El-Gizawy, 2009). SAS procedures and programs were used for analysis of variance (ANOVA) calculations. The significance of the treatment’s effect was determined using F-test and to determine the significance of the difference between the means of the two treatments. Least significant differences (LSD) were estimated at the 5% probability level.
Results and discussion
Our findings indicated that the effects of irrigation and nitrogen on all traits were significant (p?0.01). Also, interaction of irrigation× nitrogen had a significant effect on all traits except WUE and ANUE. The highest values of linoleic fatty acid, fruit yield, seed yield and agronomic nitrogen use efficiency were achieved with the consumption of 600 mm water.ha-1 and application of 390 kg urea.ha-1. The lowest fruit and seed yield were obtained with the consumption of 320 mm water.ha-1 and nonapplication of urea. The highest water use efficiency for fruit and seed yield; 56.61 and 1.10 kg.mm-1, were obtained at 600 mm irrigation water ha-1. Between nitrogen levels, maximum and minimum WUE for fruit and seed yield, were achieved at treatments of 390 and 0 kg urea.ha-1, respectively. Also, maximum agronomic nitrogen efficiency belonged to 390 kg urea. It seems that water and nitrogen limitation during the growth period of the plants caused a decrease in fruit number per plant, seed number in fruit and seed weight through interruption in fertilization and reduction in plant growth period. The WUE was obviously reduced due to an increase in water consumption at irrigation level of 900, and a decrease in yield at irrigation level of 320 mm water.ha–1, respectively. With increasing N rates up to 390 kg urea.ha–1, WUE increased due to an increase in fruit and seed yield. Generally, based on the results of this research and by considering water and nitrogen use efficiency, irrigation of pumpkin plants with 600 mm water.ha-1 and consumption of 390 kg urea ha-1 are identified as suitable treatments.
Acknowledgments
We would like to thank the funding from the Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran.
References
Ali, M.D.H., and Shu, L.T. 2009. Potential evapotranspiration model for muda irrigation project, Malaysia. Water Resources Management 23: 57-69.
Kumbhar, A.M., Buriro, U.A., Oad, F.C., and Chachar, Q.I. 2007. Yield parameters and N-uptake of wheat under different fertility levels in legume rotation. Journal of Agricultural Technology 3: 323-333.
Pradhan, S., Chopra, U.K., Bandyopadhyay, K.K., Singh, R., Jain, A.K., and Ishwar, C. 2013. Effect of water and nitrogen management on water productivity and nitrogen use efficiency of wheat in a semi-arid environment. International Journal of Agriculture and Food Science Technology 7: 727-732.
