Integrated crop-livestock systems result in less nitrate leaching than ungrazed crop systems in North Florida

Integrated crop-livestock systems provide an array of benefits to agricultural systems, including a reduction in nitrogen (N) leaching. A farm approach to integrate crops and livestock is the adoption of grazed cover crops. Moreover, the addition of perennial grasses into crop rotations may improve soil organic matter and decrease N leaching. However, the effect of grazing intensity in such systems is not fully understood. This 3-year study investigated short-term effects of cover crop planting (cover and no cover), cropping system (no grazing, integrated crop-livestock [ICL], and sod-based rotation [SBR]), grazing intensity (heavy, moderate, and light grazing), and cool-season N fertilization (0, 34, and 90 kg N ha(-1)) on NO3-N and NH4-N concentration in leachate, and cumulative N leaching by using 1.5-m deep drain gauges. The ICL was a cool-season cover crop-cotton (Gossypium hirsutum L.) rotation, whereas SBR was a cool-season cover crop-bahiagrass (Paspalum notatum Flugge) rotation. There was a treatment x year x season for cumulative N leaching (p = 0.035). Further contrast analysis indicated that cover crops decreased cumulative N leaching compared to no cover (18 vs. 32 kg N ha(-1) season(-1)). Nitrogen leaching was lesser for grazed compared to nongrazed systems (14 vs. 30 kg N ha(-1) season(-1)). Treatments containing bahiagrass had lesser NO3-N concentration in leachate (7 vs. 11 mg L-1) and cumulative N leaching (8 vs. 20 kg N ha(-1) season(-1)) compared to ICL systems. Adding cover crops can reduce cumulative N leaching in crop-livestock systems; moreover, warm-season perennial forages can further enhance this benefit.