1. Dep. of Agronomy, Horticulture and Plant Sciences South Dakota State Univ. Brookings SD 57007 USA
2. Current address: Dep. of Crop Sciences Univ. of Illinois Urbana IL 61801 USA
3. Dep. of Agricultural and Biological Engineering Univ. of Florida Gainesville FL 32611 USA
4. Institute for Sustainable Food Systems Univ. of Florida Gainesville FL 32611 USA