Legumes

In fall 2008, we planted 14 legume varieties, including berseem clover, subterranean clover, sweet clover, crimson clover, hairy vetch, common vetch, winter pea and blue lupine. This study was planted at Piedmont and Tidewater Research Stations, as well as four farms from Tyner to Mt. Ulla, NC. Each farm was kind enough to host a field gathering one evening during planting season to allow people to see the no-till/roll kill technique early in the growing season. At both research stations we had 3 roll dates at 2-week intervals to roll-kill each cover crop and immediately plant corn (AgVenture AV 8262, 110-112 day maturity) into the mulch. The various roll dates were conducted to assess variety maturity and susceptibility to kill at the time of corn planting. Our 1st roll date occurred mid-April, where none of the cover crop varieties were successfully killed. Our 2nd roll date was early May, which killed the crimson clover varieties, and one hairy vetch – AU Earlycover. We had poor corn stands in the crimson clovers at the Tidewater Research Station for this roll date, presumably due to cutworm. Our 3rd roll date was mid-May, providing kill for another hairy vetch variety – AU Merit. All crimson clovers had completed flowering by this point, and these plots experienced the most reseeding during the summer, although affect on yield has yet to be determined.

Regarding the other varieties, both the sweet and berseem clovers started to flower after we finished planting corn. We were able to get decent corn stands in the last roll date for the berseem clover, but no success with the sweet clover. The subterranean clover died on its own within 2 weeks following the 3rd roll date. Blue lupine was subject to winterkill at all locations. We recently hand harvested the corn and have not finished processing samples, so yield results are not yet available.

In addition to assessing agronomic options in this system, there is additional work being conducted by the Soil Fertility Management in Organic Cropping Systems research group to look at nitrogen availability to the corn crop over the 12 weeks following legume kill. During this first year of the study, this data was gathered on one crimson clover and one hairy vetch variety along with control plots receiving no nitrogen or 150 lb N (as UAN)/A. Preliminary results show that most nitrate from the hairy vetch crop became available to the corn crop between 4 and 6 weeks after roll-kill, but that the crimson clover mulch may have caused some reduced nitrate availability (immobilization) when compared to an unfertilized plot.

Rye

We also looked at this no-till system for rye varieties being rolled and planted into soybean. There were 6 varieties, including both southern and northern. There were 2 roll dates for the rye, immediately planted into soybean (NC Roy, maturity group 6). The 1st roll-kill occurred in mid-May, with the 2nd Regardless of roll date, all rye varieties were killed successfully. We were anticipating the northern varieties to stand back up at the earlier roll date, based on observations from similar planting dates during the previous year, however this did not occur. As of early September, pod set at both research stations looks great.