Effects of legume-cereal cover crop mixtures on nitrogen management in sweet corn
Cover crop mixtures were evaluated as alternatives to fertilizer nitrogen (N) in sweet corn. Five legume species were investigated in three separate experiments from 1990 to 1993 at the UMass Research Farm in S. Deerfield, Mass. These were hairy vetch (Vicia villosa Roth), lana vetch (Vicia dasycarpa MacLeod), purple vetch (Vicia benghalensis L.), field pea (Pisum sativum spp. Arvense (L.) Poir) and white lupin (Lupinus albus L.).
Oat (Avena sativa L.) was used as a companion crop with all five legume species investigated. With conventional tillage, legumes seeded in combination with oats provided significant amounts of N to sweet corn seeded early the following spring. Hairy vetch was the only legume species to survive the winter in these trials. This made it the most effective of the legume species investigated since the regrowth in the spring accumulated more N compared to the legumes that did not survive the winter.
Research studies also evaluated hairy vetch interseeded with rye (Secale cereale L.). Results suggest that a combination of oat-vetch may be superior to rye-vetch due to the competition observed from rye in the spring. Oat would provide necessary erosion control since it germinates and grows faster than vetch in the fall and it would add more soil organic matter than the legume grown alone.
The pre-sidedress nitrate test and the SPAD-502 chlorophyll meter were evaluated as predictors of N needs in sweet corn. Soil samples and chlorophyll meter readings were taken in sweet corn following different cover crop treatments when the plants were approximately 30 cm high. The data were compared to relative yield of sweet corn. Neither the pre-sidedress nitrate test or a chlorophyll meter proved to be effective predictors of N needs in sweet corn. Most of the nitrate-N levels observed in this work were far below the critical levels of 20 to 30 mg NO$\sb3\sp-$-N/kg of soil established by other researchers. It is speculated that the majority of the mineralization of N from the soil-incorporated cover crop tissue took place before the pre-sidedress nitrate test samples were taken and therefore was not in the 0-30 cm soil depth. (Abstract shortened by UMI.)