نوع مقاله : مقاله پژوهشی
نویسندگان
1 دانش‌آموخته دکتری، گروه علوم و مهندسی آب، دانشکده آب و خاک، دانشگاه علوم کشاورزی و منابع طبیعی گرگان، گرگان، ایران
2 دانشیار، گروه علوم و مهندسی آب، دانشکده آب و خاک، دانشگاه علوم کشاورزی و منابع طبیعی گرگان، گرگان، ایران
3 استادیار پژوهش، موسسه تحقیقات برنج کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، رشت، ایران
4 استاد، گروه مهندسی آب، واحد لاهیجان، دانشگاه آزاد اسلامی، لاهیجان، ایران
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Introduction: Irrigated rice, as one of the most important cereals worldwide and a crop with high water requirements, is increasingly exposed to risks of water scarcity, low nitrogen use efficiency, and environmental impacts resulting from excessive fertilizer application. In this context, proper management of irrigation and fertilization, as well as the distinction between green water (soil moisture derived from rainfall) and blue water (withdrawn from surface and groundwater sources), combined with the application of process-based models such as ORYZA2000, can play a significant role in enhancing productivity and reducing pressure on natural resources. The aim of this study was to evaluate the effects of irrigation and nitrogen management on rice yield and green and blue water productivity indices using the ORYZA2000 model.
Materials and Methods: The experiment was conducted as split plots in a randomized complete block design with three replications and 16 treatments over two cropping years at the Rice Research Institute of Iran, Rasht, Iran. The main factor was four irrigation regimes (permanent flooding, irrigation 1, 3, and 5 days after surface water disappearance) and the subfactor was four nitrogen levels (0, 60, 90, and 120 kg.ha⁻¹). The hybrid rice ‘Bahar’ was used, due to its high yield potential and good adaptability to the climatic conditions of Guilan province, and grain yield, biomass, leaf area index, and nitrogen uptake were measured. The ORYZA2000 model was used for calibration and validation, and then, the results of water balance simulation were used to estimate blue and green water productivity indices as well as the components of the water balance.
Results and Discussion: The results indicated that the highest grain yield (7.2 t.ha-1) was obtained with 120 kg.ha-1 nitrogen and irrigation three days after surface water disappearance. The ORYZA2000 model successfully simulated grain yield, biomass, total nitrogen, grain nitrogen, and leaf area index with normalized root mean square error (NRMSE) of 7-12%, 6-12%, 8-15%, 9-10%, and 14-29%, respectively. The model efficiency for all indices, except leaf area index, was higher than 0.65. The coefficient of determination (R²) for all indices was also higher than 0.70, indicating a good fit between the measured and simulated data. The highest two-year average values of simulated water productivity indices were obtained with the 120 kg.ha-1 nitrogen + irrigation three days after surface water disappearance. Separating the productivity indices into green and blue components showed that this treatment was the maximum for most blue and green water productivity indices, but the highest green water productivity and green water transpiration productivity indices were obtained with the 120 kg.ha-1 nitrogen + irrigation five days after surface water disappearance and 120 kg.ha-1 nitrogen + permanent flooding, respectively.
Conclusion: Irrigation and nitrogen management plays a key role in improving rice yield and irrigation water productivity. The ORYZA2000 model demonstrated high accuracy in simulating management scenarios and analyzing water balance components, and thus can serve as a valuable decision-support tool in water and fertilizer resource policy-making for rice-growing regions.
کلیدواژه‌ها [English]
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