Potato crops in
Michigan are grown on sandy, well-drained, low organic matter soils and are typically in short 2- or 3-year rotations with cereal grains or other vegetables. These potato cropping systems are subjected to intensive tillage and minimal plant residue return. All these factors have led to grower concerns about soil organic matter decline and soil degradation. Farmers and agronomists in Michigan are expanding the use of winter cover crops to enhance quantity and quality of annual organic matter inputs. In 2001 a cover crop diversity in potato rotation sequence experiment was established on coarse soils at two sites in Southwest and central Michigan. In this experiment, spring biomass of fall-seeded winter rye, hairy vetch and rye-hairy vetch biculture cover crops were measured for 8 rotation-cover crop combinations. Springtime winter cover crop biomass has ranged from 500 to 7000 kg/ha during the 6-year project. Commercial potato fields in Michigan were sampled just prior to spring tillage to estimate fall-seeded cover crop biomass and tissue quality produced under on-farm environmental conditions. Spring cover crops on 10 fields from 6 farms averaged 900 kg/ha over 2 years. A third field experiment was conducted to evaluate biomass accumulation and quality curves for fall-seeded winter rye, hairy vetch and rye-hairy vetch biculture. Compared to monoculture cover crops, the biculture consistently produced the highest amount and quality (N-enrichment) of biomass across a range of environments.