Interpretive Summary: Due to climate change, drought and urban development, less water is available for agriculture in arid regions, and many farmers are searching for low-water alternatives to traditional crops. Advancements in biofuel technology should soon make it possible to convert perennial grass biomass into fuel. Perennial grasses use less water than many traditional crops and therefore offer a potential alternative for agriculture in arid regions. However, little is known about which perennial grasses can produce high quantity, high quality yields with minimal irrigation. We monitored biomass production, weed resistance and rooting characteristics of nine perennial grasses under multiple irrigation treatments in western Nevada. Under a low irrigation treatment, cool-season grasses produced more biomass and were more weed-resistant than warm-season grasses. Abundance of fine roots (but not large roots) was correlated with increased biomass and fewer weeds. Our work suggests that cool-season grasses (particularly Elytrigia elongata, Leymus cinereus, and other species with abundant fine roots) may be worthy of further attention as potential biofuel crops for arid regions of the western US.

Technical Abstract:
In arid regions, reductions in the amount of available agricultural water are fueling interest in alternative, low water-use crops. Perennial grasses have potential as low water-use biofuel crops. However, little is known about which perennial grasses can produce high quantity, high quality yields with minimal irrigation on formerly high-input agricultural fields in arid regions. We monitored biomass production, weed resistance, rooting depth, and root architecture of nine perennial grasses under multiple irrigation treatments in western Nevada. Under a low irrigation treatment (190 ± 30 mm water annually via rainfall and irrigation), cool-season grasses produced more biomass and were more weed-resistant than warm-season grasses. With additional irrigation (239 ± 40 mm water annually), warm- and cool-season grasses had similar biomass production, but cool-season species remained more weed-resistant. Among species within each grass type, we observed high variability in performance. Two cool-season species (Elytrigia elongata and Leymus cinereus) and one warm-season species (Bothriochloa ischaemum) performed better than the other tested species. Root depth was not correlated with biomass production, but species with deeper roots had fewer weeds. Abundance of fine roots (but not large roots) was correlated with increased biomass and fewer weeds. Both L. cinereus and E. elongata had deep root systems dominated by fine roots, while B. ischaemum had many fine roots in shallow soil but few roots in deeper soil. Cool-season grasses (particularly E. elongata, L. cinereus, and other species with abundant fine roots) may be worthy of further attention as potential biofuel crops for cold desert agriculture.