Skip to main content Accessibility help

Crop Biomass Not Species Richness Drives Weed Suppression in Warm-Season Annual Grass–Legume Intercrops in the Northeast

  • K. Ann Bybee-Finley (a1), Steven B. Mirsky (a2) and Matthew R. Ryan (a1)


Intercropping with functionally diverse crops can reduce the availability of resources that could otherwise be used by weeds. An experiment was conducted across 6 site-years in New York and Maryland in 2013 and 2014 to examine the effects of functional diversity and crop species richness on weed suppression. We compared four annual crop species that differed in stature and nitrogen acquisition traits: (1) pearl millet, (2) sorghum sudangrass, (3) cowpea, and (4) sunn hemp. Crops were seeded in monoculture and in three- and four-species mixtures using a replacement design in which monoculture seeding rates were divided by the number of species in the intercrop. Crop and weed biomass were sampled at ~45 and 90 d after planting. At the first sampling date, intercrops produced more crop biomass than monocultures in all but 1 site-year; however, weed biomass in intercrops was lower than monocultures in only 1 site-year. By the second sampling date, crop biomass was consistently greater in the intercrops than in the monocultures, and weed biomass was lower in the intercrops than in monocultures in 2 site-years. Although we observed several negative relationships between crop species richness and weed biomass, crop biomass was a more important factor than species richness for suppressing weeds. Despite the weak weed suppression from the two legumes compared with the two grasses, legume crops can provide other benefits, including increased forage quality, soil nitrogen for subsequent crops, and resources for pollinators if allowed to flower. On the other hand, if weed suppression is the top priority, our results suggest that monocultures of high biomass–producing grasses will provide more effective suppression at a lower seed cost than functionally diverse intercrops that include low biomass–producing legumes in warm-season intercrops.


Corresponding author

*Corresponding author’s E-mail:


Hide All

Associate Editor for this paper: John L. Lindquist, University of Nebraska.



Hide All
Akemo, MC, Regnier, EE, Bennett, MA (2000) Weed suppression in spring-sown rye (Secale cereale)–pea (Pisum sativum) cover crop mixes. Weed Technol 14:545549
Balkcom, KS, Reeves, DW (2005) Sunn-hemp utilized as a legume cover crop for corn production. Agron J 97:26
Ball-Coelho, B, Bruin, A, Roy, R, Riga, E (2001) Forage pearl millet and marigold as rotation crops for biological control of root-lesion nematodes in potato. 95:282292
Bastiaans, L, Paolini, R, Baumann, DT (2008) Focus on ecological weed management: what is hindering adoption? Weed Res 48:481491
Baumann, DT, Bastiaans, L, Kropff, MJ (2001) Competition and crop performance in a leek–celery intercropping system. Crop Sci 41:764774
Baumann, DT, Kropff, MJ, Bastiaans, L (2000) Intercropping leeks to suppress weeds. Weed Res 40:359374
Brainard, DC, Bellinder, RR, Kumar, V (2011) Grass–legume mixtures and soil fertility affect cover crop performance and weed seed production. Weed Technol 25:473479
Burdon, JJ, Thrall, PH, Ericson, AL (2006) The current and future dynamics of disease in plant communities. Annu Rev Phytopathol 44:1939
Bybee-Finley, KA, Mirsky, SB, Ryan, MR (2016) Functional diversity in summer annual grass and legume intercrops in the northeastern United States. Crop Sci 56:2775
Cardinale, BJ, Matulich, KL, Hooper, DU, Byrnes, JE, Duffy, E, Gamfeldt, L, Balvanera, P, O’Connor, MI, Gonzalez, A (2011) The functional role of producer diversity in ecosystems. Am J Bot 98:572592
Creamer, NG, Baldwin, KR (2000) An evaluation of summer cover crops for use in vegetable production systems in North Carolina. HortScience 35:600603
Creamer, NG, Bennett, M, Stinner, B (1997) Evaluation of cover crop mixtures for use in vegetable production systems. HortScience 32:866870
Curto, G, Dallavalle, E, Santi, R, Casadei, N, D’Avino, L, Lazzeri, L (2015) The potential of Crotalaria juncea L. as a summer green manure crop in comparison to Brassicaceae catch crops for management of Meloidogyne incognita in the Mediterranean area. Eur J Plant Pathol 142:829841
Dalerum, F, Cameron, EZ, Kunkel, K, Somers, MJ (2010) Interactive effects of species richness and species traits on functional diversity and redundancy. Theor Ecol 5:129139
Davis, D, Oelke, E, Oplinger, E, Doll, J, Hanson, C, Putnam, D (1991). Cowpea. In Alternative Field Crops Manual. Madison, WI: University of Wisconsin Cooperative Extension,
Dı́az, S, Cabido, M (2001) Vive la différence: plant functional diversity matters to ecosystem processes. Trends Ecol Evol 16:646655
[FAO] Food and Agriculture Organization of the United Nations (n.d.) Crotalaria juncea. Accessed December 4, 2014
Hauggaard-Nielsen, H, Ambus, P, Jensen, ES (2001) Interspecific competition, N use and interference with weeds in pea–barley intercropping. Field Crops Res 70:101109
Hayden, ZD, Brainard, DC, Henshaw, B, Ngouajio, M (2012) Winter annual weed suppression in rye-vetch cover crop mixtures. Weed Technol 26:818825
Haynes, RJ (1980) Competitive aspects of the grass-legume association. Pages 227261 in NC Brady, ed. Advances in Agronomy. New York, NY: Academic Press
Hooper, DU, Vitousek, PM (1998) Effects of plant composition and diversity on nutrient cycling. Ecol Monogr 68:121149
Ketterings, QM, Cherney, JH, Godwin, G, Kilcer, TF, Barney, P, Beer, S (2007) Nitrogen management of brown midrib sorghum × sudangrass in the northeastern USA. Agron J 99:1345
Kilcer, TF, Ketterings, QM, Cherney, JH, Cerosaletti, P, Barney, P (2005) Optimum stand height for forage brown midrib sorghum × sudangrass in North-eastern USA. J Agron Crop Sci 191:3540
Knops, J, Tilman, D, Haddad, N, Naeem, S, Mitchell, C, Haarstad, J, Ritchie, M., Howe, K, Reich, P, Siemann, E, Groth, J (1999) Effects of plant species richness on invasion dynamics, disease outbreaks, insect abundances and diversity. Ecol Lett 2:286293
Lee, D, Wayne, H, Buntin, GD, Dozier, W, Timper, P, Wilson, J (2017) Pearl millet for grain. Athens, GA: University of Georgia Cooperative Extension
Levine, JM, HilleRisLambers, J (2009) The importance of niches for the maintenance of species diversity. Nature 461:254257
Liebman, M, Dyck, E (1993) Crop rotation and intercropping strategies for weed management. Ecol Appl 3:92
Liebman, M, Mohler, CL, Staver, CP (2001) Ecological Management of Agricultural Weeds. London, UK: Cambridge University Press. 546 p
Lin, BB (2011) Resilience in agriculture through crop diversification: adaptive management for environmental change. BioScience 61:183193
McGiffen, M, Ehlers, J, Aguiar, J (2012) Cowpea (Vigna unguiculata) cover crop. Cover Crops Database. Accessed July 11, 2017
Miller, FR, Stroup, JA (2003) Brown midrib forage sorghum, sudangrass, and corn: what is the potential? Pages 143151 in Proceedings of the 33rd California Alfalfa and Forage Symposium. Davis, CA: Department of Agronomy and Range Science Extension University of California, Davis
Mohler, CL, Liebman, M (1987) Weed productivity and composition in sole crops and intercrops of barley and field pea. J Appl Ecol 24:685699
Myers, RL (2002) Pearl millet: a new grain option for sandy soils or other moisture-limited conditions. Columbia, MO: Jefferson Institute
Newman, Y, Jennings, JV, Blount, A (2010) Pearl millet (Pennisetum glaucum): overview and management.
Picasso, V, Brummer, E, Liebman, M, Dixon, P, Wilsey, B (2008) Crop species diversity affects productivity and weed suppression in perennial polycultures under two management strategies. Crop Sci 48:331
Poffenbarger, H, Mirsky, S, Teasdale, J, Spargo, J, Cavigelli, M, Kramer, M (2015) Nitrogen competition between corn and weeds in soils under organic and conventional management. Weed Sci 63:461476
Rao, SC, Northup, BK (2009) Capabilities of four novel warm-season legumes in the southern Great Plains: biomass and forage quality. Crop Sci 49:10961102
Riday, H, Albrecht, KA (2008) Intercropping tropical vine legumes and maize for silage in temperate climates. J Sustain Agric 32:425438
Sanderson, M, Skinner, R, Barker, D, Edwards, G, Tracy, B, Wedin, D (2004) Plant species diversity and management of temperate forage and grazing land ecosystems. Crop Sci 44:11321144
Scherber, C, Mwangi, P, Temperton, V, Roscher, C, Schumacher, J, Schmid, B, Weisser, W (2005) Effects of plant diversity on invertebrate herbivory in experimental grassland. Oecologia 147:489500
Schipanski, M, Drinkwater, L (2012) Nitrogen fixation in annual and perennial legume–grass mixtures across a fertility gradient. Plant Soil 357:147159
Schwinning, S, Parsons, A (1996) Analysis of the coexistence mechanisms for grasses and legumes in grazing systems. J Ecol 84:799813
Sheahan, C (2014) Plant Guide for Pearl Millet (Pennisetum glaucum). Cape May, NJ: USDA-Natural Resources Conservation Service, Cape May Plant Materials Center. 4 p
Snapp, S, Swinton, S, Labarta, R, Mutch, D, Black, J, Leep, R, Nyiraneza, J, O’Neil, K (2005) Evaluating cover crops for benefits, costs and performance within cropping system niches. Agron J 97:322332
[SARE] Sustainable Agriculture Research & Education (2012) Managing Cover Crops Profitably. 3rd edn. College Park, MD: SARE. 244 p
Szumigalski, A, Van Acker, R (2005) Weed suppression and crop production in annual intercrops. Weed Sci 53:813825
Teasdale, J (1996) Contribution of cover crops to weed management in sustainable agricultural systems. J Prod Agric 9:475479
Tilman, D, Reich, P, Knops, J, Wedin, D, Mielke, T, Lehman, C (2001) Diversity and productivity in a long-term grassland experiment. Science 294:843845
Trannin, WS, Urquiaga, S, Guerra, G, Ibijbijen, J, Cadisch, G (2000) Interspecies competition and N transfer in a tropical grass–legume mixture. Biol Fertil Soils 32:441448
Vandermeer, J (1989) Ecology of Intercropping. Cambridge, UK: Cambridge University Press. 237 p
Waide, R, Willig, M, Steiner, C, Mittelbach, G, Gough, L, Dodson, S, Juday, G, Parmenter, R (1999) The relationship between productivity and species richness. Annu Rev Ecol Syst 30:257300
Weiner, J, Freckleton, R (2010) Constant final yield. Annu Rev Ecol Evol Syst 41:173192
Weston, L, Harmon, R, Mueller, S (1989) Allelopathic potential of sorghum–sudangrass hybrid (sudex). J Chem Ecol 15:18551865
Willer, H, Yussefi, M, Sorensen, N (2010) The World of Organic Agriculture: Statistics and Emerging Trends 2008. London: Earthscan. 268 p
Wright, T, Wheeler, E, McKinlay, J (1998) Forage Sorghum–Sudan Grass. Accessed: September 16, 2014



Altmetric attention score

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed