ارتقای عملکرد و بهره‌وری مصرف آب گیاه کدو سبز تحت سطوح مختلف کاربرد آب و کود نیتروژنه

در شرایط کمبود رطوبت خاک که جذب عناصر غذایی (به‌ویژه نیتروژن) تحت تاثیر قرار می‌گیرد، لزوم برقراری تناسب بین نیتروژن مصرفی و فراهمی رطوبت در خاک ضروری است. از این‌رو تعیین سطح بهینه کودی برای رسیدن به عملکرد زیاد گیاه یکی از اهداف مهم این پژوهش است. کدو سبز به‌صورت عمده در منطقه ساری کشت شده و تاکنون پژوهشی در مورد تاثیر نهاده‌های کشاورزی بر این گیاه انجام نشده است. بنابراین در این پژوهش تاثیر تنش خشکی و کود نیتروژنه بر عملکرد و بهره‌وری مصرف آب کدو سبز، در سال زراعی 1395 در شهرستان ساری بررسی شد. آزمایش به‌صورت کرت‌های خردشده در قالب طرح بلوک‌های کامل تصادفی در سه تکرار به اجرا درآمد. فاکتور اصلی با چهار سطح 25، 50، 75 و 100 درصد نیاز آبی و فاکتور فرعی با سه سطح صفر، 100 و 200 کیلوگرم در هکتار کود نیتروژنه (اوره) بود. صفات اندازه‌گیری‌شده شامل طول، عرض و وزن تک میوه، وزن کل بوته، تعداد برگ، وزن تازه، وزن خشک و سطح برگ، عملکرد کل محصول و بهره‌وری مصرف آب بودند. نتایج نشان داد بیش‌ترین عملکرد محصول، وزن تازه و خشک، عرض و تعداد برگ، و وزن کل بوته مربوط به تیمار با 100 درصد نیاز آبی و 200 کیلوگرم در هکتار کود نیتروژنه بود. بیش‌ترین وزن تک میوه و عرض میوه مربوط به تیمار 75 درصد نیاز آبی و 200 کیلوگرم در هکتار کود نیتروژنه است. بیش‌ترین بهره‌وری مصرف آب مربوط به تیمار با 75 درصد نیاز آبی و مصرف 200 کیلوگرم در هکتار نیتروژن بوده است. با توجه به این‌که با کاهش 25 درصدی مصرف آب 12 درصد کاهش عملکرد و بیش از 30 درصد افزایش بهره‌وری مصرف آب حاصل شد، می‌توان تیمار 75 درصد نیاز آبی و 200 کیلوگرم در هکتار کود نیتروژنه را به عنوان بهترین تیمار در شرایط محدویت آب معرفی کرد.

improving yield and water use productivity of green squash under different levels of water and nitrogen fertilizer application

abstractin the low soil moisture conditions, which affect the absorption of nutrients (especially nitrogen), it is necessary to establish a balance between the nitrogen consumption and the soil water availability to plant. therefore, determining the optimal level of fertilizer to achieve high plant performance is one of the important goals of the research. green squash is cultivated in the sari region and no research has been done about the effect of agricultural inputs on this plant. therefore, in this research, the effect of drought stress and nitrogen fertilizer on the yield and water use productivity of green squash was studied in 2015 in sari city. the experiment was in the form of split plots with complete randomized blocks design in three replications. the treatments included four irrigation levels of 25, 50, 75 and 100% of the required water as the main treatment and three levels of zero, 100 and 200 kg/ha of nitrogen fertilizer (urea). the measured traits included length, width and weight of single fruit, total plant weight, number of leaves, leaf fresh and dry weights, leaf area, total yield and water use productivity. the results showed that the highest yield, fresh and dry weights, width and number of leaves, total weight of the plant were related to the combination of 100% water requirement and 200 kg/ha of nitrogen. the highest single fruit weight and fruit width were observed in the treatment of 75% water requirement and 200 kg/ha of nitrogen. the highest water use productivity was related to the treatment with 25% water requirement and 200 kg/ha nitrogen. considering that a 25% reduction in water consumption resulted in 12% reduction in yield and more than 30% increase in water use productivity, the 75% water requirement and 200 kg/ha nitrogen can be introduced as the best treatment in the water-limited conditions.background and objective: in the water-limited conditions, the root uptake of soil nutrients, especially nitrogen, decreases. therefore, it is necessary to establish a suitable balance between the soil water availability to plant and fertilizer application to avoid excessive nitrogen consumption. allocating optimal amounts of irrigation and water to increase the efficiency of water and nitrogen consumption is important for farmers. the optimum use of irrigation water leads to maximum crop production, achieving maximum profit, reducing the amount of deep percolation of water, and better farm management in saline conditions (mousavi et al., 2013). although green squash is grown extensively in mazandaran province, few researches have been done regarding the optimization of water and nitrogen fertilizer application for this plant. therefore, this research was conducted to study the effect of drought stress and nitrogen on some physiological characteristics, yield and water use productivity of green squash in sari region.methods: the experiment was in the form of split plots with complete randomized blocks design in three replications. the treatments included four irrigation levels of 25, 50, 75 and 100% of the required water as the main treatment and three levels of zero, 100 and 200 kg/ha of nitrogen fertilizer (urea) as secondary treatment. irrigation treatment was applied after observing the first fruit; all treatments were fully irrigated before. nitrogen fertilizer was applied in three stages, one third at the beginning of the growing season, one third at the time of flowering and one third at the beginning of fruiting. finally, plant traits and water use productivity were measured. the statistical analysis was done using mstatc-c statistical software and the means were compared using duncan’s multi-range test at the 5% level of probability.results: the analysis of variance showed that the interaction effect of treatments on the growth and reproductive characteristics of green squash was significant. the vegetative traits such as number of leaves and leaf weight were the highest in the combination of 100% water requirement and 200 kg/ha of nitrogen fertilizer. plant reproductive traits such as yield were also affected by water stress and fertilizer. the highest yield was obtained in the combination of 100% water requirement and 200 kg/ha of nitrogen fertilizer, and the lowest value was obtained in the combination of severe water stress and zero nitrogen fertilizer. the water use productivity increased with an increase in water stress and fertilizer use. the highest water use productivity (i.e., 21.52 kg/m3) was observed in the combination of 200 kg/ha nitrogen and low irrigation treatment. the improvement of water use productivity by increasing the nitrogen consumption can be attributed to the increase in yield, because the water consumption was the same for all fertilizer levels. increasing the nitrogen application, by enhancing the net photosynthesis, resulted in an increase in biomass (raun and johnson, 1999).conclusions: in the studied area, the interaction of drought stress and nitrogen fertilizer had a significant effect on all measured traits except for the number and area of leaves. the deficit of water and nitrogen decreased the yield by reducing the yield components. in the favorable irrigation conditions, the highest yield was obtained at the highest level of nitrogen fertilizer (i.e., 200 kg/ha). the highest productivity was obtained in the combinations of 25, 50 and 75% water requirement and maximum nitrogen use. according to the results of plant traits and water use productivity, the combination of 75% water requirement and maximum use of nitrogen fertilizer (i.e., 200 kg/ha) can be considered the best treatment in this experiment.references:1. mousavi, s.g.r., seghatoleslami, m.j., ansarinia, e., javadi, h., 2013. the effect of water deficit stress and nitrogen fertilizer on yield and water use effeciency of calendula officinalis l. j. medic. arom. plant. 28(3), 493–508. (in persian with english abstract)2. raun, w.r., johnson, g.v., 1999. improving nitrogen use efficiency for cereal production. agron. j. 91, 357–363.