Improve Soil Productivity
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Opportunities For Summer Cover Crop Seeding
Source: Penn State University
By Sjoerd Duiker, Soil Management Specialist
July 3, 2012 -- Small grain harvest has started and some fields are still open after a challenging spring.
This is a golden opportunity for cover crop/summer forage seedings. The cover crops help protect soil from erosion, increase its resilience against soil compaction, boost the organic matter content, feed soil organisms, provide some weed control, produce the mulch for next year’s crop, hold and recycle nutrients, and can produce extra forage this fall or next spring.
Here are some options:
- Sorghum-Sudan grass. Forage sorghums, sorghum-sudangrass, and sudangrass established now can provide supplemental forage. Drill forage sorghums at 8–12 lbs/A, and sorghum-sudangrass or sudangrass at 25–30 lbs/A, 0.5–1”deep.
- Pearl millet. Excellent forage and very drought resistant. Drill at 15 lbs/A, 0.5” deep.
- Oats mixed with rye - Drill a mix of about 2 bu/A oats and 1.5 bu/A rye, 1-–2” deep. The oats produce more biomass for a fall forage harvest than rye. The rye doesn’t winterkill and will be present next spring when it can be terminated or harvested for silage. Establish late July/early August.
- Annual ryegrass - Annual ryegrass can be drilled at 15–20 lbs/A, 0.25–0.5” deep. Establish late July/early August to take a cut or graze this fall. If annual ryegrass goes into the winter with more than 4–6” of topgrowth it is likely to winterkill. If you want to have ryegrass only as a cover crop (no forage), establish it in the second half of August (central PA) or first part of September (south).
- Forage radish - If established late July/early August, the forage radish (also called ‘tillage radish’) puts on a lot of growth. The roots can grow 2” thick, 18” long. These roots drill holes in the soil which provide entryways for next year’s crop. The deeper rooting of the next crop is likely to make it more drought resistant. The forage radish can be grazed this fall. It winterkills in PA in December/January. Drill at 8–12 lbs/A, 0.25–0.5” deep. We recommend mixing with a cover crop that will provide mulch next year - oats if you want a dead mulch next spring, rye if you want a live cover in spring. If seeding with a companion, reduce forage radish seeding rate to 5 lbs/A. The brassica/cereal mix can be grazed in late fall.
- Hairy vetch/oat mix. Vetch is a winterhardy legume that can fix substantial amounts of nitrogen for next year’s crop. The oats provide protection for young vetch plants, increasing its winter survival, but don’t compete with vetch in the spring. If established too early, it puts on a lot of top growth and winterkills. For greatest success, I recommend establishing hairy vetch in the first half of August in the central part of the state, and in second half of August Sept 1 in the south. Drill approximately 20 lbs/A of vetch seed with 1 bu/A oats, 0.5–1” deep. This mix is not recommended for northern locations. Inocculate with pea/vetch rhizobium strain. Count on planting your late corn or forage sorghum in these fields next year. The vetch comes on slowly in the fall, but grows very fast in the spring. It can supply most of the nitrogen for a corn crop.
- Crimson clover. Crimson clover is a legume, and fixes substantial amounts of nitrogen, although not as much as hairy vetch. It grows fast in the fall and therefore does not profit much from a companion seeded with it. Just like vetch and annual ryegrass, it may winterkill if established too early in the fall. For greatest success, plant by Sept 1 in the central, and Sept 15 in the southern parts of the state. Drill 15 lbs/A of seed, 0.25–0.5” deep. It’s then likely to provide at least 80 lbs/A N for next years’ summer crop. Use crimson/berseem Rhizobium inocculant.
- Rye - while it is still early for rye establishment, it is worthwhile to get the seed in the barn to be ready whenever there is an opportunity after corn silage harvest. Seed 2 bu/A, 1–2” deep. ‘Aroostock’ is a variety well adapted to Pennsylvania winters.
- Red clover - Mix with oats to get a forage cutting this fall. Seed 10 lbs/A red clover, and 2 bu/A oat, 0.25” – 0.5” deep (avoid burrying the red clover seeds).
Make sure to eliminate all weeds before establishing the cover crop and wait with establishment until after a rain event.