نوع مقاله : مقاله پژوهشی
نویسندگان
موسسه تحقیقات خاک و آب کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، کرج، ایران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Introduction: Agricultural systems in arid and semi-arid regions face significant challenges, including water scarcity, climate change, and inefficient resource management. Drip fertigation, which delivers water and fertilizers directly to the root zone, enhances resource use efficiency by synchronizing nutrient supply with crop demand. Understanding the dynamics of essential nutrients like phosphorus (P) and potassium (K) under this system is vital, as their behavior differs significantly. Phosphorus is relatively immobile in soil due to strong adsorption and precipitation reactions, particularly in calcareous soils. In contrast, potassium exhibits greater mobility, moving via both diffusion and mass flow. The distribution of these nutrients is influenced by the soil's wetting pattern, soil properties, irrigation regime, and crop root architecture.This field study investigates the spatiotemporal dynamics of P and K for two crops with contrasting root systems—maize and potato—under drip fertigation.
Objectives: This study aimed to: 1) Evaluate the horizontal and vertical distribution of soluble and available forms of P and K in the soil profile around maize and potato roots; 2) Compare the nutrient depletion profiles in the rhizosphere of both crops; and 3) Investigate the transformation of applied P and K into less mobile forms over time.
Materials and Methods: The research was carried out at the Soil and Water Research Institute in Karaj, Iran. The soil texture was clay loam with a calcareous nature (0.6% organic carbon, 9.4% calcium carbonate equivalent). Potato (Agria cultivar) was cultivated in a ridge-and-furrow system, while maize (Single Cross 704 hybrid) was planted in a strip pattern. The field was equipped with a surface drip irrigation system. Irrigation was applied twice weekly for 4 hours per session, delivering 4 liters per meter of drip tape. The fertilizer requirement (e.g., NPK), determined based on soil test results, was applied in two split doses. Fertigation commenced one hour after the start of irrigation and continued for three hours. Soil moisture was monitored twice daily using TDR sensors installed at various depths (10-50 cm). Following the first and second fertigation events, intensive soil sampling was performed at specific time intervals (4, 24, 98, 624, 1632 hours after each). Samples were taken at horizontal distances of 0, 5, 10, and 15 cm from the emitter and at vertical depth intervals of 0-5, 5-10, 10-15, 15-20, 25-30, and 30-40 cm using an auger, with two replicates per treatment (including a non-cropped control plot). The collected soil samples were analyzed and visualized for soluble P, available P (Olsen method), soluble K, exchangeable K, and non-exchangeable K.
Results: The results revealed distinctly different distribution patterns for potassium and phosphorus. The maximum accumulation for both elements was confined to a zone within 0-15 cm vertically and 0-35 cm horizontally from the drip emitter, closely following the advance of the soil wetting front. Phosphorus movement was limited. Maximum vertical and horizontal movement reached only 13 cm and 20 cm, respectively. Soluble P concentrations spiked shortly after fertigation and returned to baseline within five days. Available P showed greater horizontal dispersion than soluble P. Crop-specific differences were evident; maize restricted vertical P movement, while potato promoted lateral dispersion, reflecting their distinct root architectures and water uptake patterns. Potassium was significantly more mobile, moving up to 20 cm vertically and over 35 cm horizontally. The distributions of soluble and exchangeable K were highly correlated and dependent on moisture flow. Rapid K movement occurred initially when soil moisture was high. Crucially, K concentrations in the root zone of cropped plots were substantially lower than in the non-cropped control, demonstrating significant plant uptake.
Conclusion: This study demonstrates that the dynamics and distribution of phosphorus and potassium under drip fertigation are strongly influenced by soil properties, soil moisture, the specific crop and its root system. The practice of split fertigation with lower concentrations per application is highly recommended, particularly for crops with shallow root systems, as it synchronizes nutrient supply with root activity, thereby improving fertilizer use efficiency and mitigating environmental risks. The successful application of geostatistical interpolation to visualize these complex patterns underscores the potential of integrating simulation models like HYDRUS for optimizing fertigation management strategies, reducing the need for costly and time-intensive field trials. This research provides practical insights for enhancing nutrient management in drip-irrigated maize and potato systems in arid and semi-arid regions.
کلیدواژهها [English]
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