cover crop

Mixed tillage radish cover crop 

VALLEY CITY, N.D. – Many producers are faced with a substantial amount of prevented plant (PP) acres this year and are looking to see how to best manage those acres during the remainder of the growing season.

Many are looking to seed cover crops on those prevented plant acres, but there are lot of things that need to be taken into consideration when deciding on which cover crops to use in certain situations, according to Abby Wick, NDSU Extension soil health specialist and coordinator of this series of café talks titled: “Cover Crops on PP.”

Three other NDSU Extension personnel made the trip to the event in Valley City; David Franzen, Extension soil specialist with a focus on fertility; Joe Ikley, Extension weed specialist; and Marisol Berti, Extension cover crop specialist. All four individuals had valuable insight for using cover crops for prevented plant acres.

Reasons for a cover crop

Farmers are not required to plant a cover crop on prevented plant acres, Franzen noted, but if you have normal to above normal moisture from now until next spring, you are much more liable to get back in the prevented plant program next year if you don’t plant cover crops than if you do.

“Your cover crop will use up a lot of water and your chances of being able to plant crop next year is a lot higher if you do plant a cover crop this year on the prevented plant acres,” Franzen said. “The cover crops will keep the soil from blowing and get it in condition so you can plant a crop next year.”

The advantages of planting a cover crop were shown back in 2014, when there was a significant amount of prevented plant acres, Wick explained. In her work she had different cover crops growing in some areas and as a check, they left a few of the test areas with no cover crops growing on them.

“We did moisture profiles throughout the soil on each of those plots, and it was amazing how you get this drying at the surface and then you have this bulge where there is a ton of moisture down below,” she said. “On those plots with just tillage, all we were doing is drying out the surface and we still had that bulge of moisture. However, with the cover crops, the moisture declined and we could see the roots were getting to three or four feet deep and using that moisture more evenly through the soil profile.”

For that reason, Wick suggests a cover crop mix should include some deep-rooted crops that will tap into the moisture supplies deeper in the soil.

Deciding on your mix of cover crops

Before deciding on what to plant for cover crop(s), a grower should go through a series of questions, according to Berti:

  • What crops would you like to plant?
  • When are you going to plant the cover crop?
  • When are you going to terminate the cover crop?
  • What are you going to do with that crop?
  • Are you going to hay or graze it?

“There is no simple answer,” she said. “You must go through the matrix of questions.”

In terms of weed control in cover crop acres, Ikley said it is easier to either make the crop selection on a grass or broadleaf basis. When both classes of plants are planted in a field, a herbicide program will take out not only the weeds you are trying to control, but also the cover crop. For instance, if your herbicide program is designed to eliminate broadleaf weeds, the broadleaf cover crop plants will also be eliminated.

“If you re doing a combination of crops, I will often say the weeds you have growing in the cover crop fields are just another three or four crops and you live with them,” Ikley said. “The simplest thing would be to plant a grass cover crop and take out the broadleaf weeds and not kill the cover crops. It is a lot easier to select either a grass or broadleaf cover crop and then build your weed control around that instead of having a diverse mixture and killing part of the cover crop with your weed control measures.”

Where does the nitrogen go?

Reason would suggest that if a 200-pound application of nitrogen was made last fall and the land was now in prevented plant, some of that nitrogen would appear next spring from the residue from the cover crop planted this year. But that is not the case, according to Franzen. Work has been done at NDSU for the past two years in this area, and as of yet, it is not known where this nitrogen goes. Work will continue to solve this mystery.

He suggested those who think they might have a nitrogen credit next spring go with a reduced nitrogen rate on the majority of the field, but then have a check strip with the amount of nitrogen the crop should need. Then, if the check strip is a brighter green, which shows the rest of the field is short of nitrogen and should receive an additional nitrogen application. However, if the check strip and the remainder of the field are similar, it means no additional nitrogen will be needed on the entire field.

Other factors to consider

Several other issues were raised during the discussions that covered a wide range of topics. Some of the main topics included:

1)      Due to the high demand for cover crop seed, some seed is now in short supply or even nonexistent. This applies to seed for German millet, because it can be used as a livestock feed and rye seed is hard to find in some areas. A few seed dealers were in attendance at the meeting and said this shortage will be temporary, as some of those crops in short supply will soon be harvested in other parts of the country and the seed made available.

2)      Those growers with a soybean cyst nematode (SCN) problem need to pay special attention to the crops they select in their cover crop mix. Crops they choose should not support SCN populations.

3)      Only certain crops will become established in a saline soil situation. Franzen said there are some barley and oat varieties that grow better in saline soils than others, but a list of those varieties is hard, if not impossible to find. However, in general, any barley or oat variety does better at establishing a stand in saline soils than other crops and should be considered for cover crops in those areas.

4)      Insurance issues need to be checked out in regards to prevented plant, since not following the insurance guidelines can result in a reduction in insurance payments.

Finally, Wick said growers need to watch and learn from their prevented plant cover crop experiences this summer and carry those findings over to the cover crops they grow in subsequent years.