By By Todd Whitney and Ben Beckman
Irrigating Forages
Forages vary greatly in water-use efficiency defined as pounds of forage produced per inch of water applied. In general, warm-season (C-4) forage crops are more water-use efficient than cool-season (C-3) crops. Further, annual forages use water more efficiently than perennial forages. Although legumes like alfalfa are very drought tolerant, they tend to be less water efficient than grasses.
When moisture is plentiful, water-use efficiency for warm-season annual sudangrass and sorghum-sudangrass hybrids ranges from 2.0 to 3.5 inches of water per ton of yield. Efficiency of cool-season oats is estimated at 3.5 to 4.5 inches of water required per ton of production. Comparatively, alfalfa needs 4 to 6 inches of water per ton or cutting.
Switching from harvesting corn as dried grain to corn silage can also increase overall irrigation water use efficiency, since the silage corn can be harvested at the R4 dough stage, or 30-40 days earlier than traditional grain harvest. Silage yields can peg 28 tons per acre while lowering overall total water usage by 7 inches per acre.
Where water supplies may be restricted, millet may be the preferred forage option for improving water use efficiency. However, potential total biomass production of millet will likely be less than other drought-tolerant forage options. In UNL forage research at North Platte, millet produced 2 tons per acre with 2.2 inches of irrigation water, while applying more than 4.5 inches of irrigation water did not increase millet forage yields above 3.5 tons per acre.
Source : unl.edu