Field Crop 2024, Vol.7, No.2, 79-92 http://cropscipublisher.com/index.php/fc 86 7 Soil Fertility and IAP 7.1 Importance of soil fertility Soil fertility is a critical factor in determining crop yield and overall agricultural productivity. It influences the availability of essential nutrients required for plant growth and development. High soil fertility ensures that crops receive adequate nutrients, leading to better growth, higher yields, and improved quality of produce. Conversely, low soil fertility can limit crop productivity and nutrient use efficiency (NUE), necessitating the implementation of effective soil management practices to enhance soil health and fertility (Zhou et al., 2019;Wang et al., 2020; Sailaza and Kannamreddy, 2020). 7.2 Addressing soil fertility issues Addressing soil fertility issues involves the adoption of integrated nutrient management practices that combine organic and inorganic fertilizers to improve soil health and nutrient availability. For instance, the application of farmyard manure (FYM) along with recommended doses of fertilizers has been shown to enhance soil organic carbon content, increase soil nutrient levels, and improve crop yields (Sailaza and Kannamreddy, 2020; Asaye et al., 2022; Nisar et al., 2022). Additionally, the use of biochar and compost in conjunction with inorganic fertilizers can significantly enhance soil fertility, especially in alkaline soils, by improving soil structure, nutrient retention, and microbial activity (El-Syed et al., 2023). Long-term integrated soil-crop system management (ISSM) strategies that combine organic and inorganic fertilizers have also been effective in maintaining high crop yields and NUE while reducing environmental impacts (Wang et al., 2020). 7.3 Relationship between soil fertility and IAP effectiveness The effectiveness of Integrated Agronomic Practices (IAP) is closely linked to the underlying soil fertility conditions. Studies have shown that IAP, which includes optimal planting density, split fertilizer application, and subsoiling tillage, can significantly increase maize grain yield and NUE, particularly in fields with high soil fertility (HSF) (Zhou et al., 2019). In HSF conditions, IAP promotes greater dry matter and nitrogen accumulation, leading to higher yields compared to low soil fertility (LSF) fields. However, even in LSF fields, IAP can still enhance crop performance by improving root length and soil mineral nitrogen content, although the yield gains may be less pronounced (Zhou et al., 2019). Furthermore, integrated nutrient management practices that combine organic and inorganic inputs can improve soil fertility over time, thereby enhancing the long-term effectiveness of IAP in various soil conditions (Sailaza and Kannamreddy, 2020; Asaye et al., 2022; Nisar et al., 2022). By addressing soil fertility issues through integrated nutrient management and adopting IAP, farmers can achieve sustainable increases in crop yield and NUE, contributing to improved food security and environmental sustainability. 8 Environmental Impact of IAP 8.1 Environmental benefits Integrated Agronomic Practices (IAP) have demonstrated significant environmental benefits, particularly in terms of reducing nitrogen (N) losses and greenhouse gas emissions. For instance, the Nutrient Expert (NE) system, a form of IAP, has been shown to reduce reactive N losses and greenhouse gas emissions by 46.9% and 37.2% for maize, respectively, compared to traditional farmers' practices (FP) (Wang et al., 2020a). Additionally, the Integrated Soil-Crop System Management (ISSM) strategy, which combines inorganic and organic fertilizers, has achieved lower N losses and greenhouse gas emissions while maintaining high maize yields (Wang et al., 2020b). These practices not only enhance nutrient use efficiency but also contribute to a cleaner environment by minimizing the environmental footprint of agricultural activities. 8.2 Long-term Sustainability The long-term sustainability of IAP is evident from various studies that highlight its ability to maintain high crop yields and improve nutrient use efficiency over extended periods. For example, an 11-year field study in Northeast China demonstrated that ISSM could sustain high maize yields and NUE with significantly lower environmental costs compared to traditional practices. Similarly, the use of biochar integrated with nutrient application has been
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