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Title: Biomass production, nutritional and mineral content of desiccation-sensitive and desiccation-tolerant species of sporobolus under multiple irrigation regimes

Author
item YOBI, A - University Of Nevada
item WONE, B - University Of Nevada
item SCHLAUCH, K.A - University Of Nevada
item PERRYMAN, B - University Of Nevada
item Oliver, Melvin
item CUSHMAN, J.C - University Of Nevada

Submitted to: Journal of Agronomy and Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2012
Publication Date: 9/1/2013
Citation: Yobi, A., Wone, B., Schlauch, K., Perryman, B., Oliver, M.J., Cushman, J. 2013. Biomass production, nutritional and mineral content of desiccation-sensitive and desiccation-tolerant species of sporobolus under multiple irrigation regimes. Journal of Agronomy and Crop Science. 199:309-320.

Interpretive Summary: Water supplies for agriculture are a major factor in limiting crop and livestock production in many areas of the U.S. that are classified as arid or semi-arid in climate and land usage. Livestock production is particularly sensitive to water shortages as many operations utilize open rangeland where forage is scarce or has to be shipped in from forage growing operations. In light of this it is advantageous to develop forage species that have suitable biomass productions, enough to support a cattle operation, but can do so on much less water than current forage species. It was with this goal that we undertook an evaluation of a new selection of grass species, that have the ability to thrive in drier conditions, for fresh and dry biomass production and for seed productivity. We looked at three species of the Sporobolus group of grasses, one that can survive total drying of its vegetative tissues, one that is relatively drought tolerant, and one that normally produces large quantities of leaves (biomass) under three different irrigation regimes (high, medium, and low) at a site in the desert southwest. All three species produced biomass of sufficient quality to be used as a source of feed for livestock and all three used significantly less water than the standard forage species (Timothy Grass or Alfalfa). The most drought tolerant of the three species, one that can survive total drying, was the least productive both in biomass production and in seed productivity suggesting that it was the energy requirement needed to fuel the ability to survive drying that inhibited the performance of the grass as a forage species. The other two grasses, Sporobolus pyramidilis and Sporobolus fimbriatus, with their ability to grow on very low water inputs make them prime candidates for the development of new forage crops that will serve farmers and ranchers in the semi-arid and arid regions of the U.S. where irrigation resources are limited.

Technical Abstract: The development of low-water-input forages of high quality would be useful for expanding or improving the water use efficiency of livestock production in semi-arid and arid regions. In this study, three Sporobolus species, the desiccation tolerant (DT) species, S. stapfianus Gandoger, and two desiccation sensitive (DS) species, S. pyramidalis and S. fimbriatus (Trin.) Nees. (Poaceae) were evaluated for fresh and dry aerial biomass production and seed productivity under three different irrigation regimes. S. stapfianus displayed the least biomass production, whereas S. pyramidalis and S. fimbriatus produced up to 4.4-and 11.6-fold more biomass, respectively, at the highest irrigation rate of 12.33 m3 (0.01 acre feet). S. fimbriatus and to a lesser extent S. pyramidalis, showed significant increases in biomass production in response to increased irrigation rates, whereas S. stapfianus did not. As with biomass production, S. pyramidalis and S. fimbriatus exhibited greater seed production than S. stapfianus. Furthermore, S. pyramidalis and S. fimbriatus exhibited up to 3.5-fold and 5.1-fold greater seed production, respectively, in response to increased irrigation rates than S. stapfianus, which showed no significant increases in seed production in response to increased irrigation. The observed inverse relationship between biomass and seed productivity and water demand is likely tied to the metabolic demands associated with the DT phenotype, which redirects metabolic resources away from growth and into pathways essential for survival and recovery from the desiccated state. Detailed evaluation of the forage potential for all three Sporobolus species indicated crude protein and fiber contents were comparable to those of Timothy, a forage grass grown widely in the Great Basin in the Western United States. In terms of micronutrients, all elements investigated were present in amounts that exceeded the minimum requirements of beef cattle, without surpassing tolerable limits, with the exception of zinc, which appeared low in all three Sporobolus species. The low-water requirements displayed by these species, combined with their acceptable forage qualities, indicates that these grasses have the potential to serve farmers and ranchers in semi-arid and arid regions of the Western U.S. where irrigation resources are limited.