Molecular Soil Biology 2024, Vol.15, No.5, 216-226 http://bioscipublisher.com/index.php/msb 223 climate of Salto, Uruguay, supplemental irrigation during the reproductive stage (R1-R8) was found to increase soybean yield by up to 35% compared to rainfed conditions. However, the economic benefit of this practice was contingent on soybean prices being above $350 per ton. When prices fell below this threshold or when rainfall was stable, rainfed conditions were more economically viable (Montoya et al., 2017). In the Loess Plateau of China, a two-year study comparing drip irrigation (DI) and flood irrigation (FI) found that DI combined with 80% field capacity irrigation and 750 kg/hm2 fertilization yielded the highest economic benefits. This combination improved soil moisture and nutrient content, leading to increased crop yields and overall profitability (Luo et al., 2023). Similarly, in Japan's low rainfall regions, drip irrigation was shown to prevent yield decreases in dry years, thereby stabilizing income for farmers (Chomsang et al., 2021). 7.2 Financial implications of fertilization strategies Fertilization strategies also play a crucial role in the economic outcomes of soybean farming. In the arid regions of Northwest China, a study demonstrated that nitrogen (N) fertilization had a more significant impact on soybean yield compared to phosphorus (P) and potassium (K). The optimal fertilization combination for maximizing yield and quality traits was found to be 411.62~418.39 kg/ha N, 153.97~251.03 kg/ha P2O5, and 117.77-144.73 kg/ha K2O. This optimized fertilization strategy not only enhanced yield but also improved the cost-efficiency of fertilizer use (Li et al., 2022). In the Indian mid-Himalaya, long-term fertilization with a combination of farmyard manure (FYM) and recommended doses of NPK fertilizers significantly increased soybean yield under both rainfed and supplementary irrigation conditions. The highest economic returns were observed with the combined application of FYM and NPK, highlighting the cost-efficiency of integrating organic and inorganic fertilizers (Panday et al., 2018). Moreover, in the steppe zone of Central Ciscaucasia, the application of mineral fertilizers in combination with biological nitrogen (rhizotorfin) was found to be economically feasible. The highest profitability was achieved with the application of N12P52 and pre-sowing inoculation with rhizotorfin, resulting in a profitability rate of 68.8% (Shabaldas et al., 2020). 8 Challenges and Future Perspectives 8.1 Environmental and economic constraints Water scarcity and soil degradation are significant challenges in soybean cultivation. Water stress, often exacerbated by soil salinity, severely limits plant productivity and soil fertility, leading to reduced yields and increased oxidative damage in plants (Osman et al., 2021). Additionally, inappropriate water and fertilizer management can lead to soil degradation and groundwater pollution, further complicating sustainable agricultural practices (Yan et al., 2021). Economic considerations also play a crucial role; for instance, in regions like Uruguay, the profitability of supplemental irrigation is highly dependent on soybean market prices, making it a less viable option when prices are low or rainfall is stable (Montoya et al., 2017). Therefore, balancing the economic costs with environmental sustainability is essential for long-term agricultural success. 8.2 Technological advances in irrigation and fertilization Technological advancements such as precision agriculture and smart irrigation systems offer promising solutions to the challenges of irrigation and fertilization. Precision agriculture techniques, including the use of soil moisture sensors and crop coefficients, can optimize water use efficiency and ensure that irrigation is applied only when necessary, thereby conserving water resources (Montoya et al., 2017). Smart irrigation systems, which can adjust water application based on real-time data, further enhance water use efficiency and crop yield (Yang et al., 2022). Additionally, the integration of plant growth-promoting microbes (PGPMs) and nanoparticles has shown potential in mitigating the adverse effects of water stress and soil salinity, thereby improving soybean growth and productivity under challenging conditions (Osman et al., 2021).
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