• One of the concerns with green chopping would be the potential for nitrates, particularly if the layby or side-dress nitrogen application already has been made.
• You need to leave 12 to 15 inches worth of stubble height if you’re going to green-chop.
A fourth option, says Hancock, is making silage out of the crop — probably one of the best options available.
“Silage is such a superior way of handling this because it reduces the nitrate concentration in the crop. It retains more of the quality and reduces the amount of time we’re required to handle the crop. In the process of fermentation, we could end up with a reduction in nitrates of up to 50 to 60 percent. So it’s important that we create conditions where the fermentation is well-supported.”
One of the challenges of putting up silage from a crop like this is that it still needs to be wilted, says Hancock.
“Even though this crop is drought-stressed, the moisture level is still going to be 85 to 90 percent, even if it’s beginning to turn brown and die back. We still need to wilt it to get down to an optimum of 64 to 70 percent moisture. That can be easily done with a mower conditioner, and windrowing behind the mower-conditioner. Usually, it’ll take a few hours for it to wilt down from 85 to 90 percent down to 65 to 70 percent.”
One option, he says, instead of chopping it for silage, is to make bale silage from it. This will make it easier to handle the crop. After windrowing behind a mower-conditioner, you can follow in behind with a baler and wrap it with plastic to create silage.
“In this system, we still advise that you raise the cutter bar. You still want to leave about 6 to 8 inches of stubble height. We’re trying to reduce nitrate levels as much as possible, especially if we’re feeding this into a dairy ration.”
Regardless of the silage system, it’s important to allow the crop to ferment for three to four weeks before you start feeding the crop if you suspect nitrates will be high.
“Regardless of how the crop is harvested, we still need to test the nitrates. Nitrates can cause some major animal problems, so what we need to do is to assess the nitrate level. There are field kits for doing this, but it’s important that we quantify exactly how many nitrates are there. That can be accomplished usually by taking it to a lab and running a nitrate analysis. When we develop a ration, we can dilute the forage down to a point to where it’s safe to feed to the animals.”
It’s important, says Hancock, to use a hay corer to take those samples as well. “The hay corer will give us a good random sample into the bale so that we get a good cross-section of stem, leaf and other material within that bale itself. It’s also important that we get a good representative sample throughout the entire field. Some areas of the field may be elevated in terms of nitrates whereas other areas may be low.”