Preemergence application of Roundup should be delayed until just before second crop seedlings are ready to emerge so more green plant growth can be contacted. Summary Doublecropping is a high risk cropping system in Nebraska. The risk increases from south to north as the growing season shortens and rainfall diminishes. Supplemental irrigation should be available for consistent success with doublecropping. Under strictly dryland conditions, do not attempt doublecropping if June has been dry and subsoil moisture is depleted.
Winter wheat is the best first crop for southern Nebraska.
In northern areas, whichever small grain is used should be harvested for forage to allow earlier planting of the second crop. Soybeans and sunflowers are the best second crops for southern areas. In the north where chinch bugs are less of a threat, corn, grain sorghum, or summer annual forages can be used as the second crop, in addition to soybeans. If planting sunflowers in northern areas, use an early maturity, dwarf hybrid. Kenneth R. Bolen, Director of Cooperative Extension, University of Nebraska, Institute of Agriculture and Natural Resources.