Cover Crops May Help Mitigate Nutrient Losses, But Come with Trade-Offs

Strategic Insights -

Current research highlights the potential benefits and drawbacks of using cover crops in agriculture, particularly in subtropical sandy soils. According to a two-year experiment conducted by the University of Florida, cover crops may help mitigate nutrient losses from soils in agricultural cropping systems. However, the study also found that the breakdown of cover crop residues can increase soil inorganic N availability, potentially leading to greater N leaching. This trade-off between inorganic N production and N leaching is a key consideration for farmers and researchers working with cover crops in these systems.

Key Takeaways:

  • The study examined the effects of four cover crop treatments on soil inorganic N pools in sandy soils under a subtropical climate.
  • Results showed that cover crops increased soil inorganic N availability, but also increased the risk of N leaching, particularly with the sunn hemp treatment.
  • The study highlighted the importance of considering soil N dynamics when using cover crops in subtropical sandy soils.
  • The research was funded by the Center for Land Use Efficiency and the UF-FAS Center for Land Use Efficiency (CLUE).
  • Mary G. Lusk of the University of Florida was a key researcher on the project, along with collaborators Juma Bukomba and Gabriel Maltais-Landry.

Statistics:

  • The study consisted of a two-year experiment with four cover crop treatments: sunn hemp, sorghum sudangrass, a 50/50 mixture of sunn hemp and sorghum sudangrass, and a weed fallow control.
  • Soil samples were collected at three depths (0-15, 15-30, and 30-60 cm) and analyzed for extractable NO3--N and NH4+-N, as well as net N mineralization and nitrification rates.
  • N mineralization and nitrification rates increased under the cover crop plots compared to the control after cover crop termination, indicating increased soil inorganic N availability.
  • The sunn hemp treatment had the highest soil inorganic N after cover crop termination, but also resulted in more inorganic N at 30-60 cm compared to 15-30 cm, indicating increased risk of N leaching.

Sources:

  • NewsRx. New Findings from University of Florida Update Understanding of Cover Crops (Inorganic Nitrogen Dynamics Under Cover Crops In Florida's Sandy Soils). Agriculture Week. October 23, 2025; p 2179.
  • Inorganic Nitrogen Dynamics Under Cover Crops In Florida's Sandy Soils. Nutrient Cycling in Agroecosystems, 2025.