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

Abstract

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 90kg 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 Flüggé) rotation. There was a treatment × year × season for cumulative N leaching (p=0.035). Further contrast analysis indicated that cover crops decreased cumulative N leaching compared to no cover (18vs. 32kg N ha-1 season-1 ). Nitrogen leaching was lesser for grazed compared to nongrazed systems (14vs. 30kg N ha-1 season-1 ). Treatments containing bahiagrass had lesser NO3 -N concentration in leachate (7vs. 11mg L-1 ) and cumulative N leaching (8vs. 20kg 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.