Yield and Forage Quality of Perennial Grasses Under Limited to Full Irrigation in a Semi-Arid Climate.

The impending cap on ethanol production from grains in 2015 from the Energy Independence and Security Act/Renewable Fuels Standard (EISA/RFS) will require the production of more cellulosic materials to meet future ethanol demands. Much of the High Plains faces reduced irrigation amounts in the future due to recurring drought, regional water compacts, reduced reservoir supplies and ground water allocations. The goal of this experiment was to determine the production potential of perennial cool season (CS) and warm season (WS) grasses and determine if forage quality was affected by irrigation level. Plots were established in 2009 under a linear move irrigation systems on a a Tripp fine sandy loam soil at Scottsbluff, NE and on a Keith silt loam near Sidney, NE. CS grasses included orchard grass, a wheatgrass mixture and a brome mixture. WS grasses included switchgrass, big bluestem plus Indiangrass and a mixture of the three grasses. Maximum CS yields in 2010 ranged from 9 to 12 Mg ha^-1. Yields of WS grasses were generally less than 55% of CS grasses. CS yield during 2011 at Scottsbluff reached 15.7 Mg ha^-1. WS production in 2011 was 60% higher than 2010 but maximum yield was 11.2 Mg ha^-1 or 30% less than best CS. In 2012, drought severely limited yields of dryland and the lowest irrigation level. Forage quality of CS grasses was higher than WS grasses.  Drought reduced quality.  Irrigation response data will be discussed. CS grasses may offer an advantage over WS grasses under limited water in the High Plains region with normal rainfall. Data for the 2012 drought year will be presented as fall harvest will occur in September.