A team of USDA-ARS researchers at the University of Nebraska-Lincoln is conducting a relay cropping trial in cooperation with several producers in south central Nebraska. This evaluation was started in 2002 with 150 acres in cooperation with one farmer, and was expanded to about 1,500 acres with four cooperating farmers in 2003.
First year results with the seed corn-wheat-soybean rotation showed that the wheat crop yielded 68 bushels per acre and removed 130 lb nitrogen per acre from the soil (about 90 lb nitrogen per acre in grain) that could have leached beneath the root zone. The wheat produced about 2 tons of residue per acre, which will help build soil organic matter content and control erosion. In addition, profit increased by about $100 per acre. This was even after accounting for a 15% reduction in soybean yields (which averaged 55 bushels per acre).
Wheat yields in 2003 ranged from 55 to 75 bushels per acre. In many areas, the yield monitor showed yields may have exceeded 90 bushels per acre.
Producers observed that the isolation areas around the perimeter of seed fields (about 90 feet wide) sometimes yielded up to 20% more than in the bulk field where seed corn was previously grown. These isolation areas were planted to wheat, soybean, or sorghum the previous year. Reasons for greater wheat yields in the border areas are unknown, but could hold the key to enhanced production and profitability from relay -cropping.
Possible explanations may include are:
- herbicide carryover after seed corn,
- nitrogen immobilization by the corn residue,
- seedbed and planting differences,
- different levels of residual nitrogen (nitrate-N) in the bulk field compared with the border area,
- and disease interactions.
Producers noted that plants in the border areas were more vigorous in the early growth stages and more erect at harvest.