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Lancaster, OH | I worked with a guy here many of you will know, Dave Brandt, on various covers. We looked at vetch, clovers, peas and RRSB.
Without a doubt, the SB were the easiest to work with and plant into the next spring. The seed bed was exposed due to the standing stubble, warmed quickly and had the least slug damage in multiple locations, multiple years. If you have SCN, and I think most of us do, that is a downside to consider as well as the cost of the seed. Our goal was to use a maturity that would not fill pods as we wanted all the N below ground and not pulled up into proteins in the soybean. For central Ohio, that was a Group V-VIII and the later the better.
Next was the austrian winter pea. It came up and covered but froze off late in the winter so the seed bed again was pretty clean although not as clean as the beans because of the later glyp. treatment. Really did well in wetter soils and probably provided as high a yield benefit as any barring slug damage.
Vetch was also fun but was unnerving in that you didn't really know what you had until the late winter when it really took off. The downside here is that it had LOTS of growth which led to tough planting, slugs, etc. If you need lush cover in the spring or could feed it, this could be your cover crop.
Lastly, the clovers were the most dissappointing. They were easy to get, plant and establish but had all the downsides of vetch with less N benefit.
As for N credit, this was really hard to measure accurately. Some studies indicate organic N won't be released until the following year. Dave wanted to try to grow all his N which was unrealistic but a great goal. It seemed that with the RRSB, Vetch & Peas, adding more that 100 units of N had minimal benefit. These were conducted over a couple of years stripping the covers and planting across the strips and applying different N rates. After we got below 100 units of N, all of them dropped below the non-cover crop area at 150-180#. It was a case that the risk involved with dropping N rates very much was too great for the hard to predict reward.
I think it is important to note that the N credit is only one of the benefits of the cover crop. Basing the decision solely on that is very narrow. The tilth and OM increase that can be realized is likely as valuable but harder to put in a budget.
Hope this helps. | |
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My radish experiment
