System fertilization improves soil quality and increases primary production in an integrated crop-livestock system

Managing fertilization in integrated crop-livestock systems (ICLS) during periods of low nutrient export, known as system fertilization, can optimize nutrient use by enhancing the soil's biochemical and physical-hydric properties. However, interdisciplinary studies on processes that improve input utilization in ICLS remain scarce. This study aimed to assess the relationships between the efficiencies of different nutrient management strategies in ICLS and pure crop systems (PCS) and the biochemical and physical-hydric quality of soil. Two fertilization strategies (system fertilization and crop fertilization) and two cropping systems (ICLS and PCS) were evaluated in a randomized block design with three replicates. In the PCS, soybean was grown followed by ryegrass as a cover crop. In the ICLS, sheep grazed on the ryegrass. In the crop fertilization, phosphorus and potassium were applied to the soybean planting, and nitrogen was applied in the ryegrass establishment. Nitrogen, phosphorus, and potassium were applied during ryegrass establishment in the system fertilization. Soil quality indexes were calculated using fourteen physical-hydric and biochemical soil indicators, and primary production and nutrient utilization efficiency were evaluated. System fertilization in ICLS enhanced the soil functions of water storage and availability for plants, structural stability, and resistance to degradation. System fertilization in ICLS improved the soil quality by 14% over PCS and 13% over crop fertilization in ICLS. Notably, this optimized system yielded the highest primary production. These findings underscore the pivotal role of system fertilization in ICLS to boost food production and enhance soil ecosystem services without increasing the consumption of external fertilizers. They advocate for a strategic shift towards system-level fertilization in integrated systems, and demonstrate for the first time in ICLS, the delicate balance between nutrient management, soil health, and sustainable productivity.