Nitrogen dynamics of cover crops with sorghum for increased sustainability

Project Overview

Project Type: Graduate Student
Funds awarded in 2013: $10,997.00
Projected End Date: 12/31/2015
Grant Recipient: University of Florida
Region: Southern
State: Florida
Graduate Student:
Major Professor:
Dr. John Erickson
University of Florida

Annual Reports


  • Agronomic: sorghum (milo), sugarbeets


  • Crop Production: application rate management, catch crops, continuous cropping, cover crops, crop rotation, fallow, nutrient cycling, organic fertilizers, tissue analysis
  • Education and Training: mentoring
  • Energy: bioenergy and biofuels
  • Production Systems: agroecosystems, holistic management
  • Soil Management: green manures, nutrient mineralization, organic matter, soil chemistry, soil quality/health
  • Sustainable Communities: local and regional food systems

    Proposal abstract:

    Plant nutrition is a major component of crop production, and nitrogen is the most commonly applied nutrient in much of the Southeast.  However, nitrogen fertilization practices often rely on chemical fertilizers which are produced from limited resources and can be expensive for producers. Additionally, nitrogen is susceptible to rapid leaching from the sandier soils of the region. Cover crops produced in rotation with a primary crop offer an option to provide an organic nitrogen source to the soil for use by the primary crop, and have multiple ancillary benefits. Sorghum has a high nitrogen use efficiency and is grown in the Southeast for a variety of uses, including as silage for livestock production, grain for human and animal consumption, and sugar for syrup and feed. This project will investigate the effects of winter cover crops on nitrogen availability and cycling to subsequent sorghum crops, and effects on sorghum yields. A multi-year field experiment with two nitrogen fertilization rates in sorghum and five winter covers will be established. Soil nitrogen will be quantified at the beginning and end of the study, and nitrogen availability in the rooting zone of each crop will be monitored with ion-exchange resin. Tissue nitrogen will be measured for each crop at maturity. By monitoring total nitrogen in the crops as well as nitrogen returned to the soil and available for subsequent crops,  it is expected that external fertilizer inputs can be substantially reduced, particularly with leguminous covers, while still maintaining high sorghum yields and increasing sustainability.

    Project objectives from proposal:

    Ascertain yields of sorghum grown under high and low fertility in rotation with winter cover crops.

    Measure plant tissue nitrogen concentrations for each crop produced in the rotation.


    Quantify monthly availability of nitrogen in the rooting zone of sorghum and winter cover crops, and correlate with crop yields and tissue nitrogen concentrations.


    Monitor soil nitrogen and organic matter, and ascertain effects of cover crop rotations on changes in soil nitrogen pools and organic matter content.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.