By Sjoerd Willem Duiker
Cover crops provide organic cover and crop diversity, two of the three pillars of no-till production systems (the other one being limited soil disturbance). Cover crops are essential after corn silage harvest for soil erosion protection, soil compaction alleviation, soil organic matter, and soil health improvement, nutrient loss reduction through leaching and runoff, winter manure spreading, and optionally to use the cover crops as forage. They are also important after soybeans because this crop leaves very little crop residue for soil protection and is often considered a losing proposition for soil health. Although corn for grain leaves plenty of crop residue for erosion protection it is still a good idea to plant a cover crop if you can, to maintain a living root in the soil year-round. The rhizosphere is where most of the soil biological activity is concentrated, that is why this is an important principle of soil health management. Corn silage harvest has already started in the southern parts of Pennsylvania and very soon high moisture corn and early corn and soybeans will start too. For success with cover crops, timeliness is key so you should have the cover crop seed on hand and the drill ready to go with an operator in the seat when you start your harvest. It gives a lot of satisfaction to see the drill in a field that is being harvested!
There are many options for cover crop species to be planted in the south, while the options are getting fewer in the northern parts of the state as can be seen in the table below. You will notice no warm season annuals (such as millets, sorghum and sudangrass, cowpea, sunhemp, and buckwheat) are listed because temperatures are expected to be too cool for those. Some choices available in central and southern PA are annual ryegrass, crimson clover, hairy vetch, and rape – but it is already too late to plant those further north, where you are down to the winter-hardy cereals such as wheat, triticale, and rye. Other options for southern regions include oats and radish, which will winterkill, but with enough fertility, they can produce a lot of biomass before they do so. One note - The recommendations in the table are based on research done without manure or fertilizer. Our experience tells us that if a field has high fertility planting dates can be relaxed a bit – it is likely that 2 weeks later planting than what is listed in the table can still be successful in that scenario.
Planting date recommendations for fall-established cover crops in Pennsylvania
| ||Sole seeding rate (lbs/A)||Northern PA||Central PA||Southeastern PA|
|Annual ryegrass||15||Aug 15||Sept 1||Sept 15|
|Crimson clover||10||Not recommended||Sept 1||Sept 15|
|Hairy vetch||20||Aug 15||Sept 1||Sept 15|
|Rape||10||Aug 15||Sept 1||Sept 15|
|Barley||120||Aug 15||Sept 15||Oct 1|
|Wheat||120||Sept 15||Oct 1||Oct 15|
|Triticale||120||Oct 1||Oct 1||Oct 15|
|Cereal rye||120||Oct 1||Oct 1||Oct 15|
|Spring oats*||100||Aug 1||Aug 15||Sept 1|
|Forage radish*||7||Aug 1||Aug 15||Sept 1|
*Will winterkill throughout PennsylvaniaSource : psu.edu