Managing Sorghum x Sudangrass and Sudangrass Hybrids As Double Crop Forage after Winter Wheat.

There is increasing interest among producers in the eastern Corn Belt to intensify forage production using annual forages within grain crop rotations. Our objective was to evaluate harvest management of two sudangrass, (Sorghum bicolor (L.) Moench ssp. drummondii (Nees ex Steud.) de Wet & Harlan, and two sorghum [Sorghum bicolor (L.) Moench] x sudangrass (S x S) hybrids when double-cropped for forage after winter wheat. Hybrids were no-till planted 19 July 2013 and subjected to four first harvest timings and two cutting heights. Harvest timings were (i) EARLY, first cut at 35 days after planting (DAP) and second cut 48 d later, (ii) MID, first cut at 47 DAP and second 36 d later, (iii) LATE single cut at 61 DAP, and (iv) very late (VL) single cut at 83 DAP. Two cutting heights, short (10 cm) and tall (20 cm) were imposed at the first harvest. There was a hybrid x cutting treatment interaction (P < 0.05) for dry matter yield and neutral detergent fiber (NDF) but not for NDF digestibility (NDFD); however, interactions were due primarily to changes in magnitude of differences. Total forage yield increased with delayed time of first cutting, but NDF increased and NDFD decreased. The EARLY-tall had greatest regrowth after the first harvest and highest yield at second harvest. Regrowth after first harvest in MID and LATE was poor so total yield from those treatments was similar or lower than in EARLY-tall. If double-cropped S x S or sudangrass hybrids in the eastern Corn Belt are harvested twice, the first harvest should be occur a month after planting with a high stubble height; however, a single harvest at 61 DAP produces more yield with similar NDF and NDF digestibility as the weighted average over two harvests of the EARLY treatment.