When is it too late for Cover Crops?
This is a question I have been fielding frequently, and unfortunately, there is no perfect answer since I don’t have a crystal ball that predicts moisture and temperature accurately! There are several factors that play into when it is time to either switch to a different species or hold off on an application. Below are a few things to consider:
**For those north of I-80, you will need to reevaluate sooner, those south of 72, can add a week or so…
Goals – What do I hope to gain from my Cover Crop?
· Feed Value – if you are hoping to use a cereal grain or clover for some feed value, the economics may allow you to go later into the season with planting. Wheat and Triticale are typically planted until mid-October, and Cereal Rye has been successfully planted into November. It is worth noting that planting after mid-October will likely have some loss of yield due to lessened tillering and winter kill.
· Erosion Control – to maximize the reduction in wind and sheet erosion, it is beneficial to have a well-developed cover crop heading into winter. The earlier in fall that a crop is developed, the more likely it is to protect against wind erosion and runoff from it’s above ground forage, as well as using its root system to help protect from rill erosion. However, if there are areas that you are worried about runoff, gullies, or washouts, late is still better than never!
· Compaction Reduction – we are at the tail end of the window for turnips and radish to have time to break up compaction. Our first freeze (28⁰F overnight low) will typically kill most radish, rape and turnip species. The first freeze for Central Illinois is usually October 20th or so.
Above is a photo showing radish at different planting dates. The August 15th date is about the ideal size radish as it breaks up compaction, but doesn’t leave a large hole… There is still a benefit to the September radish, but it is likely to be less every day after September 15th…
· Nutrient Recycling – Crops that pull up nutrients closer to the surface are unlikely to be beneficial unless they will winter over and get spring growth. Oats, radish, and turnips will not likely have much time to provide benefit if they only have a 20-30 day window to establish. Crops that overwinter such as annual ryegrass, peas, vetch, clover, or cereal grains can be planted a little later (maybe until nearly October 1??) and provide some of the benefits in spring.
· Nitrogen Production – crimson & balansa clover and hairy vetch likely have until September 25th to be established and provide benefit. I would advise against peas much after September 20th. Peas typically are a little slower to establish, plus the higher cost of establishing makes them a more risky investment later in the season.
Equipment– How am I establishing my Cover Crop?
· Broadcast (Airplane or Spreader) – unless using a cereal grain, broadcast application after September 25th scares me. A broadcast application is critically dependent on rain to get established and germinating.
· Drilled or AirSeeded – I am more comfortable establishing a crop slightly past its normal window when we are actually getting the seed in the soil. This is likely to speed up germination and help establish a better root system.
Weather – When does the forecast change my plan?
· Moisture - I am more comfortable going a bit past the recommended date when there is a good chance of rain to help germination. When soils are dry and no rain is forecast, it becomes riskier…
· Temperature – The current 10-day forecast (as of 9/15/19) looks like about a week of warm temps, and then starting to cool down. If the forecast a week from now shows highs in the 60s, it is probably time to switch to only cereal grains*…
A crop that will winter kill is nearly out of time to be planted. Cereal grains (with the exception of oats) can still be planted for another month. For those looking to gain erosion control or feed value, the risk of later planting is more likely to be worth it. If you want to talk about your specific situation, give me a call at 309-255-3461 and we can discuss what may work!