Cover crops are indispensable in no-till production systems to build soil health, especially after corn silage harvest. Here are some reasons why:
1. A place to spread manure. In Pennsylvania, you need to have at least 25% residue cover to be able to spread legally between Dec 15 and Feb 28, any time the ground is frozen to 4” depth, or when the soil is snow-covered, meaning on corn silage ground you need to have a cover crop established to spread manure in this time window. A winter-surviving cover crop such as rye or wheat is especially effective.
2. Alleviate soil compaction caused by corn silage harvest. Typically, close to 100% of the field surface is compacted during corn silage harvest. Cover crop roots can help repair the damage. Research has shown that tap-rooted cover crops are especially effective to penetrate hard soil layers.
3. Control erosion. The soil is completely unprotected after corn silage harvest and the cover crop provides soil erosion protection. Cover crops help improve infiltration by protecting the soil from raindrop impact, limit soil splash, reduce surface sealing and also improve surface aggregate stability, thus keeping soil in place.
4. Reduce nitrate leaching. Cover crops are considered the most effective tool on farm fields to absorb nitrate that otherwise could be lost to groundwater.
5. Reduce phosphorus loss. Most phosphorus is typically lost with sediment. Cover crops are effective in reducing erosion and therefore reduce phosphorus loss too. Over winter cover crops, when frosted, can ‘leak’ soluble phosphorus that, if runoff occurs, can end up in surface waters, causing eutrophication. However, total phosphorus losses would be much higher without cover crops.
6. Provide emergency forage. Many parts of the state suffer from drought. A cover crop can provide emergency forage.
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One question that was raised is if it is even worthwhile to plant a cover crop when the soil is bone dry and there is no rain in the forecast. The problem is that after corn silage cover crops are really essential for the reasons mentioned. I would therefore recommend planting a low-cost cover crop that is winter hardy.
If you have bin-run wheat or barley you could use that. Rye is really fool-proof. I would plant the cover crop a bit deeper than normal, and would shy away from expensive cover crops that need to put on significant growth to make it through the winter.
These cover crops might not germinate for a while and might not put on enough growth for winter hardiness. Make sure the drill places the seed to the proper depth. It may even be worthwhile to wait for a shower so the soil softens up a bit.