by: Chris Reberg-Horton and Julie Grossman
We do not have a lot of data yet, but wanted to give everyone an update on the project. The experiment was planted at seven locations last fall and the best five were chosen to continue with this spring. Fourteen different legumes were rolled and planted to corn and six cultivars of rye were rolled and planted to soybeans. Preliminary information on the correct time of roll for each cover crop is listed below.
Table 1. Roll times for legume cover crops.
Table 2. Roll times for rye (Secale cereal L.) cover crops.
Wrens 96
MatonII
| Mid |
Early May |
Aroostook |
| Late |
Mid to late May |
Rymin |
Wheeler
One unifying factor for most of the cover crops is that it must be heavily flowering to kill with the roller. For instance, in crimson clover, we estimate that flowers must be on average 80% up each head before the cover crop can be killed (Figure 1). Vetch must have a few green pods with unfilled seed on the lower stems, and rye needs to be in the milk stage of development. We are putting together a guide for knowing when these crops are ready to roll which will be available by next year. The subterranean clover was impossible to kill with the roller and died on its own sometime in late May after seeding out. Subterranean clover flowers underground, making it an ideal reseeder. Whether this is an advantage or disadvantage depends on the crop rotation.
All the rye cultivars grew well and flowering time has so far been the only distinguishing feature. Soybeans emerged well from the rye mulches and weeds have yet to break through. Given our positive experiences with this system last year, we are optimistic about the system, but not yet ready to recommend it. We hope to be able to recommend after this year’s yields come in.
It is too early to make predictions with the corn. We planted corn at three times at each of the stations, mid-April, late April/early May, and mid-May. While the roller did not kill any of the cover crops at the first planting date, some of the corn plots look surprisingly good. The middle planting date at Plymouth and the Hubers farm suffered severe stand problems. We suspect a combination of cutworms and birds. Other planting dates and locations had decent stand establishment.
We’ll update you with more about nitrogen in the cover crops in the next issue.
