بررسی روش آبیاری پالسی بر عملکرد گندم رقم حیدری در مدت زمان‌های مختلف آبیاری

Today, the water crisis is a fundamental challenge to sustainable agriculture. Uneven water distribution, improper use of water resources, and inefficient irrigation methods are among the primary factors threatening water security. These issues are particularly critical in arid and semi-arid regions, such as Iran, where a significant portion of agricultural production relies on wheat. As a strategic global crop, wheat provides approximately 36% of the world's food, dietary proteins, and over half of human carbohydrate needs. However, population growth and climate change have heightened the necessity to improve wheat production methods. Designing efficient irrigation programs that optimize water use while maintaining high yields is of paramount importance. Pulse (intermittent) irrigation, a modern method gaining attention in recent years, applies water in specific cycles, enhancing soil aeration and reducing continuous soil saturation, thereby improving root growth and nutrient uptake. These benefits are particularly relevant in drip irrigation systems, widely adopted in arid regions due to their precision and reduced water loss. Given the increasing use of drip irrigation in wheat cultivation and the lack of comprehensive data on the effects of pulse irrigation in this system, this study aimed to investigate the impact of pulse irrigation on water use efficiency and wheat performance under varying irrigation durations. The primary objective was to identify a practical approach to enhance water productivity and wheat yield under water-scarce conditions.
Materials and Methods
The experiment was conducted during the 2021-2022 cropping season in Mashhad, Iran, a region characterized by arid and semi-arid climatic conditions due to its geographical location (longitude 737688, latitude 4011582) and elevation of 1006 meters above sea level, making it suitable for evaluating efficient irrigation methods. The study was designed as a split-plot experiment based on a randomized complete block design with three replications. Two main factors were examined: the number of irrigation pulses (one, two, and three pulses) as the main factor and irrigation duration (12, 15, and 18 hours) as the sub-factor. Each experimental plot, covering 30 m² (10 × 3 m), consisted of five rows of wheat (cv. Heydari) planted at 60 cm row spacing and 2-3 cm depth. Buffer rows were planted to minimize edge effects.
Soil characteristics were determined through random sampling at two depths (0-25 and 25-50 cm). The soil had a clay-silt-sand texture with specified nitrogen, phosphorus, potassium, and electrical conductivity levels, as presented in the results table. Irrigation was applied based on crop water requirements at 6-day intervals, with irrigation depth calculated using pre-irrigation soil moisture measurements. Soil samples were collected from three depths (0-25, 25-50, and 50-75 cm) to determine gravimetric and volumetric moisture content using standard equations. Gross irrigation depth was adjusted based on the 90% efficiency of the drip irrigation system. Evaporation pan data were also used to compare soil moisture and adjust irrigation. Fertilization was based on soil test results, and weeds were controlled using appropriate herbicides. At full maturity, performance indicators, including plant height, thousand-grain weight, number of grains per spike, spike weight, grain yield, and water use efficiency, were measured and analyzed.
Results
Analysis of variance revealed that both irrigation duration and the number of pulses, individually and interactively, significantly affected wheat yield, yield components, and water use efficiency at 1% and 5% probability levels. Among the treatments, the highest grain yield (7839.6 kg/ha) was recorded in the 18-hour irrigation treatment with three pulses, while the lowest yield (5992.7 kg/ha) was observed in the 12-hour irrigation with one pulse. These results highlight the superiority of the three-pulse method, which increased grain yield by 13.6% and 26.18% compared to two and one pulses, respectively.
Regarding water use efficiency, the highest value (1.053 kg/m³) was achieved in the 12-hour irrigation with three pulses, while the lowest (0.827 kg/m³) was recorded in the 18-hour irrigation with one pulse. These findings indicate that the three-pulse method improved water use efficiency by 32.6% and 43.18% compared to two and one pulses, respectively. Analysis of yield components showed significant increases in the number of grains per spike, thousand-grain weight, and spike weight in treatments with more pulses and longer irrigation durations, particularly in the 18-hour, three-pulse treatment, underscoring the positive impact of intermittent irrigation cycles on plant growth and development.
Conclusion
The study demonstrated that the effects of water filling and depletion phases in soil depend on irrigation duration and the number of pulses. Shorter pulse durations enhance the impact of these phases on irrigation performance indicators, attributed to reduced water losses and improved soil aeration in the pulse irrigation method. For optimal design and management of drip irrigation systems, understanding the thresholds of water distribution uniformity and potential application efficiency under varying pulse conditions is essential. This study confirmed that the three-pulse intermittent irrigation method significantly enhances grain yield and water use efficiency of wheat (cv. Heydari) by improving yield components such as the number of grains per spike and thousand-grain weight. The three-pulse method, by providing intermittent irrigation cycles, allows sufficient time for soil aeration, reducing continuous saturation and creating favorable conditions for root growth and water and nutrient uptake. Compared to continuous or single-pulse irrigation, this method contributes to water savings and increased productivity. The results showed that the three-pulse method with 18-hour irrigation achieved the highest grain yield (7839.6 kg/ha), while with 12-hour irrigation, it recorded the highest water use efficiency (1.053 kg/m³). This method saved approximately 20-25% of water compared to continuous irrigation, owing to reduced water losses and improved soil aeration.
Implementing the three-pulse irrigation method on a large scale has high potential for improving yield and water savings from a management perspective. However, its success depends on robust infrastructure (automation, pumping, filtration), workforce training, and salinity management. In small to medium-sized farms, implementation is relatively straightforward, but in large-scale operations, high initial costs and the need for continuous monitoring and zoning pose challenges that can be addressed with technical and financial support. These findings suggest that three-pulse irrigation is an effective strategy for enhancing water productivity and sustainable wheat production under water-scarce conditions, particularly in arid regions with limited water and suitable soil conditions, such as Mashhad.