The Effects of Grazing in Integrated-Crop Livestock Systems of Different Intensity on Nitrogen and Phosphorus Cycling

Commodities

Practices

Rapid movement of nutrients like nitrogen and phosphorus in coarse-textured soils, common in the Southeast, results in leaching losses if not properly managed. Strategies to retain and recycle these nutrients are essential to improve farm profitability and long-term system stability. Integrated Crop-Livestock Systems (ICLS) are a promising alternative to conventional systems, as livestock adds complexity to agroecosystems, provides additional farm income sources, and contributes to lower nutrient losses. Livestock can be integrated through different approaches of variable intensity, although impacts on nutrient cycling remain poorly understood. The sod-based rotation (SBR) consists in converting the traditional three-year peanut-cotton-cotton rotation into a four-year rotation by adding two years of grazed bahiagrass in the summer. Alternatively, livestock can be integrated less intensively by grazing winter cover crops (GWCC) in the spring, which reduces grazing duration and avoids the removal of summer cash crop seasons. We propose to compare both ICLS types to conventional systems, using the coarse-textured soils in North Florida as a model system. We hypothesize that grazing with cattle accelerates nutrient recycling, enhances nitrogen availability, and reduces phosphorus legacy effects in the soil profile, with effects proportional to the duration of grazing (SBR > GWCC). We will evaluate soil N and P dynamics by measuring nutrient extractable pools across soil depths, assessing nutrient-cycling enzymatic activity, and quantifying mineralization. We will share key outcomes with a range of stakeholders to illustrate how ICLS can improve nutrient management and support the adoption of more resilient integrated farming systems in the region.

• Quantify biomass production, nutrient uptake and allocation among plant parts, and nutrient export for cotton in four different cropping systems: conventional peanut-cotton without cover crops, conventional peanut-cotton with ungrazed cover crops, GWCC, and SBR. For the GWCC system, determine the effect of three N input rates (33%, 67%, 100% of the recommended N rate) on cotton productivity and nutrient uptake.
• Identify differences in soil nutrient dynamics among the four cropping systems and the effects of grazing on extractable nutrients, enzymatic activity (two enzymes for N and one for P), and potential mineralizable nitrogen (PMN). In addition, compare methodological approaches used to measure N and P loss risks, i.e., by quantifying soil extractable pools at depth or by using anion-exchange resins.
• Identify relationships between soil nutrient cycling indicators and crop responses to determine which indicators are associated with improved nutrient efficiency, and thus which indicators are most advantageous to measure for North Florida growers, then share key outcomes with stakeholders through different outreach activities.