Establishment and Persistence of Legumes in SwitchgrassBiomass and Forage/Biomass Production Systems

K. Warwick1, F. Allen1, P. Keyser2, G. Bates1, D. Tyler3, P. Lambdin4, C. Harper2 (1)Department of Plant Sciences (2) Department of Forestry, Wildlife, & Fisheries (3)Biosystems Engineering and Soil Science (4)Entomology and Plant Pathology

University of Tennessee

Abstract

Switchgrass is being used as a biofuel feedstock for ethanol production on marginal, as well as, crop land. Legumes may be interseeded into switchgrass to improve available N in the soil, reduce fertilizer costs, and enhance switchgrass yield and forage quality. The objective of this research is to develop legume management strategies for switchgrass production systems that are economically and ecologically sustainable for biomass and forage production. A total of seven cool and warm-season legumes were examined for two years at the research and education centers East Tennessee (Knoxville), Plateau (Crossville) and Milan. The cool-season legumes were alfalfa, Medicago sativa cv “Evermore”; red clover, Trifolium pretense cv “Cinnamon Plus”; crimson clover, Trifolium incarnatum; common vetch, Vicia sativa; and hairy vetch, Vicia villosa. The warm-season legumes included in the study were Illinois bundle flower, Desmanthus illinoensis; and partridge pea, Chamaechrista fasciculata. The legumes were interseeded into established 2 y old switchgrass (cv. ‘Alamo’) and monitored for establishment, self-reseeding, and N contribution as determined by increases in yield.

Objectives

Identify selected cool- & warm-season legumes that can be grown with switchgrass (SG) for biomass/forage systemsTo determine switchgrass/legume forage quality for the two-cut integrated forage/ biomass approach. Determine nitrogen contribution of common and hairy vetch grown with switchgrass and its affect on yield.

Materials/MethodsExp Design: Randomized Complete BlockReplications: 3 per locationLocations: East TN Research & Education Center (ETREC)

Plateau Research & Education Center (PREC) Research and Education Center at Milan (RECM)

See Fig. 4

Results

Characteristics Measured

Experiment Descriptions

Exp One: One Cut (Biomass) Harvest (Fall)ETREC, PREC, RECM

Nitrogen Treatments60 lbs/ac N0 lbs/ac N (control)Alf + 67 kg/ha NRC + 67 kg/ha NCC + 67 kg/ha N*HV + 67 kg/ha N*IBF + 67 kg/ha N*PP + 67 kg/ha N*135 kg/ha N*

Legume TreatmentsAlfalfa (ALF) (13.46 kg seed ha-1) Crimson Clover (CC) (6.73 kg seed ha-1 ) Hairy Vetch (HV) (6.73 kg seed ha-1 ) Illinois Bundle Flower (IBF)(8.97 kg seed ha-1 ) Red Clover (RC) (8.97 kg seed ha-1 ) Partridge Pea (PP) (13.46 kg seed ha -1)

*Treatments only at RECM

ExpTwo: Two-Cut Forage (Summer)/ Biomass (Fall) Harvest

ETREC & PRECNitrogen Treatments67 + 67 kg/ha N67 kg/ha N0 kg/ha N (control)

Legume TreatmentsSame as Experiment One

Exp Three: N Fixation in Common & Hairy Vetch ETREC

Stand densities (Vogel and Masters, 2001) & plant hts on count dates Forage yields and quality (2-cut system) 2009-10Biomass yields (1&2-cut systems) 2009N fixation rates of Common and Hairy Vetch (Danso, 1995; Peoples et al., 2009)

Common VetchHairy Vetch0+0 kg/ha NWheat- Control plant

Quantify Nitrogen Fixation RatesN2 fixed= (Vetch N) – (Wheat N)Plant N= (Plant DM) x (%N) 100 (Danso, 1995; Peoples et al., 2009)

Summary

    Alfalfa CC HV IBF PP RC SG

Year Exp #/m2 ht/cm #/m2 ht/cm #/m2 ht/cm #/m2 ht/cm #/m2 ht/cm #/m2 ht/cm ht/cm

2009One 14 4 18 8 9 21 5 3 6 8 20 8 68Two 20 3 18 10 8 13 6 2 9 7 21 9 58

2010One 0 0 5 27 2 36 1 2 2 16 10 27 100Two 0 7 5 24 3 37 1 1 2 15 21 50 58

BCC C BC BC

ABA

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CC HV PP RC 0N 67N 135N

DM

tonn

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Forage+Biomass (2-cut) Switchgrass Total DM 2009

ABAB

AB BAB

ABA

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CC HV PP RC RC+67 0N 67N

DM

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Biomass (1-cut) Switchgrass DM 2009

Figure 1. Legume count and plant heights across locations. Switchgrass height was not significantly different among treatments. Heights and counts taken on 13May09 & 24May10 at ETREC, 14May09 &25May10 at PREC, and 19May2009-10 at RECM.

Figure 2. Yield for single cut in biomass harvest system across all locations (ETREC, PREC, RECM) for 2009. There is no significant difference among legume treatments.

Figure 5. Yield of 1st and 2nd cut in the forage/biomass harvest system across both locations (ETREC, PREC) for 2009. There was no significant difference among legume treatments.

B B B B B B A

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CC HV PP RC 0N 67N 135N

DM

tonn

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Forage cut (1st of 2) Switchgrass DM 2009-10

Figure 3. Yield for 1st cut in the forage/biomass harvest system across both locations (ETREC, PREC) for 2009-10. There was no significant difference among legume and 67 kg N treatments.

  Legume Seeding Dates  ETREC PREC RECM

All legumes (warm & cool) 3/24/2009 3/31/2009 4/9/2009Cool-season legumes only 10/29/2009 10/22/2009 12/17/2009

Literature Cited

Danso, S. K. A. 1995. Assessment of biological nitrogen fixation. Fertility Research 42: 33–41.Peoples, M.B., M.J. Unkovich, and D.F. Herridge. 2009. Measuring symbiotic nitrogen fixation by legumes. In D.W. Emerich and H.B. Krishnan (Ed.) Nitrogen Fixation in Crop Production. Agronomy Monograph 52:125-170.Vogel K.P. and R.A. Masters. 2001. Frequency grid–a simple tool for measuring grassland establishment. Journal of Range Management 54: 653–655.

This project funded by:

Crimson Clover

Hairy Vetch

ALF and IBF germinated but did not persist in competition with switchgrass (Fig. 1) 0 N vs 67 N treatments across locations, years, and experiments were not significantly different (Fig. 2, 3, & 5)In the forage/biomass system, presence of legumes did not significantly alter forage quality among legumes treatments. Data not shown.Presence of legumes in 1-cut biomass system did not significantly alter SG yield from 67 N treatments except for RC (Fig. 2).In the forage system, there were no significant differences in SG yields among the legume treatments and 67 kg ha-1 N when averaged across both locations for two years (Fig. 3).In the forage/biomass system, total SG yield (forage + biomass) did not differ among legume treatments; however , HV and PP treatments were significantly lower than 67 and 135 kg ha-1 N when averaged across two locations in 2009 (Fig. 5).Insufficient time to determine reseeding and persistence of crimson and red clover, hairy vetch, and partridge pea in lowland switchgrass types such as ‘Alamo’.N fixation rates were similar for common and hairy vetch (2.1 & 2.2 kg ha-1, respectively) based on seeding rates and plant populations of this study. Given above N fixations rates and plant densities, we estimate that seeding rates of common and hairy vetch would need to be 14.5 & 13.6 kg ha-1, respectively to achieve 33.5 kg ha-1 N fixation rates.

Future Research

New study of 1x,1.5x, 2x of arrowleaf, ladino, and red clover; hairy vetch, and partridge pea has been initiated in 2010.

Figure 4. Tennessee research and education center. Indicated centers read left to right are RECM, PREC, ETREC. http://www.taes.utk.edu/centers/

Partridge Pea