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ARS Home » Plains Area » Temple, Texas » Grassland Soil and Water Research Laboratory » Research » Publications at this Location » Publication #349970
Title: Inter-annual precipitation variability decreases switchgrass productivity from arid to mesic environments

Author
item REICHMANN, LARA - University Of California
item Collins, Harold
item Jin, Virginia
item JOHNSON, MARI-VAUGHN - Natural Resources Conservation Service (NRCS, USDA)
item Kiniry, James
item Mitchell, Robert - Rob
item Polley, Herbert
item Fay, Philip

Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2018
Publication Date: 6/19/2018
Publication URL: http://handle.nal.usda.gov/10113/6082490
Citation: Reichmann, L.G., Collins, H.P., Jin, V.L., Johnson, M.V., Kiniry, J.R., Mitchell, R., Polley, H.W., Fay, P.A. 2018. Inter-annual precipitation variability decreases switchgrass productivity from arid to mesic environments. BioEnergy Research. 11(3):614-622. https://doi.org/10.1007/s12155-018-9922-3.
DOI: https://doi.org/10.1007/s12155-018-9922-3

Interpretive Summary: Perennial grasses, such as switchgrass, are high in cellulose and an important source of renewable bioenergy. Rainfall amount and its variability among years and among sites, has undefined influences on the fertilizer response of switchgrass productivity. Likewise, global climate models predict changes in rainfall patterns towards lower and increasingly variable soil water availability in several productive areas worldwide. This should have major impacts on the production of biofuel crops. We analyzed annual values for switchgrass production from 48 publications with numerous locations, soil types, switchgrass cultivars, and fertilizer inputs. Lowland ecotypes had doubled production with N rates > 131 kg N per ha per yr, but upland ecotypes showed only 50% increases. The optimum N rate was 30 to 60 kg N per ha per yr for both groups of ecotypes, after which biomass gain per unit of N added decreased. Growing season rainfall, long-term mean annual rainfall and inter-annual rainfall variability differentially affected lowland and upland productivity, depending on the N level. Productivity responses to mean annual rainfall and growing season rainfall were similar for both upland and lowland ecotypes at low N rates. When N increased beyond 60 kg N per ha per yr, lowland ecotypes had a greater growth response to mean annual rainfall than upland ecotypes. Productivity increased with increasing growing season rainfall and mean annual rainfall, and had a positive linear response to mean annual rainfall ranging from 600 to 1200 mm per yr. The N fertilization effect increased at higher levels of mean annual rainfall, more so in lowland than in upland ecotypes. After accounting for mean annual rainfall, sites with higher intern-annual rainfall variability had lower switchgrass productivity than sites with lower intern-annual rainfall variability. In lowland ecotypes, N fertilization mitigated the negative effect of intern-annual rainfall variability on productivity. Higher precipitation increased switchgrass yield more consistently among upland than lowland ecotypes. Increased inter-annual variation in precipitation reduced production of both ecotypes. Predicted changes in the amount and timing of precipitation thus likely will exert greater influence on production of upland than lowland ecotypes of switchgrass.

Technical Abstract: Cellulosic biofuels are an important source of renewable biomass within the alternative energy portfolio. Switchgrass (Panicum virgatum L.), a perennial C4 grass native to North America, is widely studied as a biofuel feedstock for its consistently high yields and minimal input requirements. The influences of precipitation amount and temporal variability on the fertilizer response of switchgrass productivity are not fully understood. Moreover, global climate models predict changes in rainfall patterns towards lower and increasingly variable soil water availability in several productive areas worldwide, which may impact net primary production of biofuel crops. We conducted a meta-analysis of aboveground net primary production of switchgrass from 48 publications encompassing 82 different locations, 11 soil types, 52 switchgrass cultivars, fertilizer inputs between 0 to 896 kg N ha-1 yr-1, and 1 to 6 years of annual productivity measures repeated on the same stand. Productivity of the lowland ecotype doubled with N rates > 131 kg N ha-1 yr-1, but upland ecotype productivity increased only by 50%. Results showed an optimum N rate of 30 to 60 kg N ha-1 yr-1 for both ecotypes, after which biomass gain per unit of N added decreased. Growing season precipitation (GSPPT), long-term mean annual precipitation (MAP) and inter-annual precipitation variability (inter-PPTvar) differentially affected lowland and upland productivity, depending on the N level. Productivity responses to MAP and GSPPT were similar for both upland and lowland ecotypes at none or low N rates. When N increased beyond 60 kg N ha-1 yr-1, lowland cultivars had a greater growth response to MAP than uplands. Productivity increased with increasing GSPPT and MAP, and had a positive linear response to MAP ranging from 600 to 1200 mm yr-1 MAP. The N fertilization effect increased at higher levels of MAP, more so in lowland than in upland ecotypes. One-third of the variability in switchgrass production was accounted for by inter-PPTvar. After accounting for MAP, sites with higher inter-PPTvar had lower switchgrass productivity than sites with lower inter-PPTvar. In lowland ecotypes, N fertilization mitigated the negative effect of inter-PPTvar on productivity. Higher precipitation increased switchgrass yield more consistently among upland than lowland ecotypes. Increased inter-annual variation in precipitation reduced production of both ecotypes. Predicted changes in the amount and timing of precipitation thus likely will exert greater influence on production of upland than lowland ecotypes of switchgrass.