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Title: Biomass production and nutrient removal by switchgrass under irrigation

Author
item KIMURA, EMI - Washington State University
item Collins, Harold
item FRANSEN, STEVE - Washington State University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/8/2014
Publication Date: 1/13/2015
Publication URL: http://handle.nal.usda.gov/10113/61010
Citation: Kimura, E., Collins, H.P., Fransen, S. 2015. Biomass production and nutrient removal by switchgrass under irrigation. Agronomy Journal. 107(1):204-210.

Interpretive Summary: Perennial herbaceous plants can improve soil quality, enhance nutrient cycling, improve wildlife habitat, and sequester C. Switchgrass has potential as a bioenergy crop due to its high above- and below-ground biomass, ability to grow on marginal lands and seemingly low demand for agricultural inputs. Switchgrass production under irrigation in the Columbia Basin of the PNW is a viable bioenergy feedstock with aboveground biomass yields averaging over five years, 21, 20, and 17 Mg DM ha-1 yr-1 at low N rate and 25, 20, and 18 Mg DM ha-1 yr-1 at high N rates for the Kanlow, Shawnee, and Cave in Rock, respectively. Higher N input increased macro- and micronutrients uptake by Kanlow over the course of this study enhancing annual biomass production over either upland switchgrass cultivars. Under irrigated conditions in the PNW at 46° N latitude, the lowland cultivar Kanlow is the superior switchgrass cultivar when managed under a two harvest per season regime.To maintain long-term switchgrass productivity under irrigation and a two cut system, all cultivars must be adequately fertilized to supplement the high macro and micronutrient removal rates.

Technical Abstract: Switchgrass has been identified to supply a major portion of U.S. energy needs when used as a fuel. Assessments of the export of essential plant nutrients are needed to determine impacts on soil fertility that will influence fertilizer recommendations since the nutrients contained in the above ground biomass will be removed from the field when processed as a bioenergy feedstock. The objective of this study was to determine the influence of N fertilization rates (112 and 224 kg N ha-1 yr-1) on the biomass production, nutrient removal, and nutrient concentration of three cultivars of switchgrass grown under irrigation in the lower Columbia Basin of the Pacific Northwest. Aboveground biomass yields averaged over five years of 23.0, 19.9, and 17.7 Mg dry matter ha-1 y-1 for Kanlow, Shawnee, and Cave in Rock, respectively. Kanlow cv. increased biomass yield at the 224 kg ha-1 N rate compared to two upland cultivars. The annual removal of macronutrients from the field averaged 237 kg N ha-1, 37 kg P ha-1, 326 kg K ha-1, 15 kg S ha-1, 68 kg Ca ha-1, and 43 kg Mg ha-1 among cultivars. Switchgrass produced 93 kg of biomass per 1 kg of N, and S may play a key role in maintaining the yield under a high N regime. Micronutrients (B, Mn, Cu, and Zn) removed at harvest averaged less than 1 kg ha-1 among cultivars, while Fe removal was 3.4 kg ha-1. Increased yields and enhanced uptake of essential nutrients especially after reaching stand maturity in the third year of production resulted in high nutrient removal with the biomass harvest.