Consider Austrian winter peas following early vegetables
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
As vegetable crops come out of the ground, now is a good time to consider planting late summer and fall cover crops. Although N fertilizer prices have dropped since a year ago, legumes and legume-grass mixtures are still worth considering for their N fixation and soil-building potential. Legumes can also add diversity to cover crops in vegetable production systems where grass or mustard cover crops have been used extensively in the past. Such diversity can help break pest cycles and enhance soil microbial communities to improve vegetable crop growth. The ideal window for planting summer legume cover crops (e.g. cowpea or soybean) has now passed, but late summer and fall legumes (peas, hairy vetch) still have sufficient time to provide benefits.
Austrian winter peas
Austrian winter peas have good potential following vegetable harvest. Research and demonstration plots in northern climates have demonstrated that Austrian winter peas can produce substantial biomass when sown in August, before winter killing in late fall. Winter peas are more tolerant of cold temperatures than spring peas and are able to withstand temperatures down to 10° F for short durations (although prolonged exposure to temperatures below 20° F will kill them). Good background information on Austrian winter peas, and many other cover crops, can be found at www.sare.org/publications/covercrops/covercrops.pdf. For Midwest specific cover crop information, including information on Austrian winter peas see the KBS/MSU cover crop webpage: www.covercrops.msu.edu/species/index.html#pea
Possible N benefits
Austrian winter peas are reported to typically fix from 90 to 150 lbs N/A. In one study from Kansas, melons following Austrian winter peas (and no fertilization) had equivalent yields as melons fertilized with 63 to 90 lbs N/A. However, in Ohio, no benefits were detected in field corn following a late summer Austrian winter pea planting http://ohioline.osu.edu/sc166/sc166_29.html.
In Michigan demonstration plots conducted by extension educator Dan Hudson in Ingham county, Austrian winter peas sown after wheat harvest in early August produced 1.5 tons/acre of dry matter and contained over 130 lbs N/acre in above- ground tissue before winter kill (see full report at: www.ipm.msu.edu/cat09veg/8-12winterpeas.pdf). Active nodules were observed on roots of Austrian winter pea as late as mid-November when spring pea nodulation had subsided.
In Zone 5, the suggested window for Austrian winter pea planting is mid-August to mid-September, although benefits are likely to drop off quickly past the end of August. Because Austrian winter peas have smaller seeds than spring peas, lower seeding rates can be used to obtain the same density; typical seeding recommendations range from 30-60 lbs/A. Drilling at 0.5 to 1.0 inch depth can help reduce seed rate and seed costs. Pea seeding rates can be reduced by 0.25 to 0.5 in mixtures.
Combinations of Austrian winter pea with a small grain like oats or barley can also reduce seed rates and are thought to improve longevity in the spring. Results from studies of grass-legume mixtures in other crops suggest that N fixation is also enhanced when legumes are sown with grasses. However, competition from the grass can be a problem. Dan Hudson suggests keeping the oat seeding rate to a bushel/A or less to avoid suppressing winter peas in mixtures.
Research is underway to evaluate the optimal use of Austrian winter pea and other legumes and legume-grass combinations in vegetable production systems. Objectives include assessing optimal seeding rates of mixtures, evaluating N-fixation benefits and assessing effects of cover crops on weed suppression and soil health. For more information or suggestions of needed research in this area contact Dan Brainard at email@example.com.