Corn Production in Kura Clover Living Mulch Without Herbicides.

At the University of Wisconsin-Madison, a corn (Zea mays L.) kura clover (Trifolium ambiguum Bieb.) living mulch was developed that provides a permanent ground cover, reduces soil erosion, requires no nitrogen fertilizer input, and reduces nitrate movement to groundwater. This system currently requires herbicide inputs similar to conventional corn production. An experiment was conducted at two locations in Wisconsin over 2 years to investigate replacements to herbicides acceptable in USDA certified organic production by examining corn yield response (grain and whole plant) to the frequency of these suppression events. Strip tillage was imposed in a well-established kura clover stand in late April. One month later, the entire plot area was mowed and the tilled strips were propane flamed, creating a stale seedbed. Corn was then no-till planted into the strips. Inter-row kura clover suppression was accomplished with different frequencies of mowing and flaming (1, 2, or 3 mowing or flaming events imposed biweekly or weekly respectively starting after planting) and were compared to a control treatment of killed kura clover. Whole plant corn yield, harvested at 50% kernel milkline as for silage, ranged from 11.2 to 14.3 Mg ha-1 in living mulch treatments and yielded 51 to 65% of the control. Corn grain yield in the living mulch treatments ranged from 8.4 to 10.1 Mg ha-1, yielding 60 to 70% of the control. Unusually erratic precipitation patterns contributed to very dry periods where corn water stress in the living mulch treatments was observed, and was a main contributor to reduced yields. Although we have found many challenges to controlling competition in this system without herbicides, the yield loss may be compensated for by the near double price per bushel of organic corn grain and silage compared to conventionally grown corn.