Cover Crop Mixture Diversity and its Effects on Biomass Production, Weed Suppression, Soil Fertility, Soil Microbial Biomass and Community Structure, and Performance Stability

Project Overview

Project Type: Graduate Student
Funds awarded in 2013: $10,000.00
Projected End Date: 12/31/2015
Grant Recipient: University of Nebraska-Lincoln
Region: North Central
State: Nebraska
Graduate Student:
Faculty Advisor:
Charles Francis
Grain Place Foundation
Faculty Advisor:
Dr. Rhae Drijber
University of Nebraska-Lincoln
Dr. Leon Higley
University of Nebraska-Lincoln
Dr. John Lindquist
University of Nebraska-Lincoln

Annual Reports


  • Agronomic: barley, corn, soybeans, wheat


  • Crop Production: catch crops, cover crops, multiple cropping
  • Education and Training: on-farm/ranch research
  • Natural Resources/Environment: biodiversity
  • Pest Management: biological control, cultural control
  • Production Systems: general crop production
  • Soil Management: soil analysis


    This study evaluated the effect of cover crop mixture diversity on biomass productivity, weed suppression, nutrient cycling, soil microbial community characteristics, and stability of biomass productivity. Up to forty cover crop treatments—a no cover control, eighteen species in monoculture, and twenty-one mixtures—were planted at eleven sites in Nebraska. While increasing diversity was associated with increased average productivity it was not associated with increased potential productivity. While increasing cover crop mixture diversity was often correlated with increases in weed suppression, nutrient retention, soil microbial biomass, and stability, once variations in biomass productivity were controlled for, these apparent associations disappeared.


    The diversity-productivity hypothesis proposes that greater diversity should lead, on average, to greater total biomass productivity (Tilman, 2001). The diversity-invasibility hypothesis proposes that greater diversity should lead to increased resistance to invasion (Elton, 1958). 

    Both of these hypotheses are predicated on the hypothesis that more diverse systems capture more resources through niche complementarity than less diverse systems. It’s by capturing a greater amount of available resources it is thought that diverse mixtures might be both more productive and more resistant to invasion.

    The diversity-stability hypothesis proposes that more diverse systems are more stable systems (Tilman, 2001). This hypothesis is based on the idea that if one species fails in a certain context, another species might be able to compensate for it in a mixture.

    The increased abundance hypothesis proposes that increasing plant mixture diversity should increase soil microbial biomass while the altered microbial community hypothesis proposes that it should also alter soil microbial community structure predictably (Chapman and Newman, 2010). These hypotheses are predicated on the idea that the litter of different plants will provide different kinds of habitats and resources for soil microbes—supporting both more of them and a wider variety of them.

    The goal of this study was to test all of these hypotheses in the context of cover crop mixtures—that is, to ask the question: “Does increasing cover crop mixture diversity (1) increase average biomass productivity, (2) increase weed suppression, (3) increase nutrient uptake and therefore soil nutrient retention, (4) increase soil microbial biomass and alter soil microbial community structure predictably, and (5) increase the stability of biomass productivity?”

    Chapman, S. K., and G. S. Newman. 2010. Biodiversity at the plant-soil interface: microbial abundance and community structure respond to litter mixing. Oecologia 162:753-769.

    Elton, C.S. 1958. The ecology of invasions by plants and animals. Chapman and Hall, London, UK.

    Tilman, D. 2001. Functional Diversity. p. 109-121. In S. A. Levin (ed) Encyclopedia of Biodiversity, Vol. 3. Academic Press: Waltham, MA.

    Project objectives:

    The primary objective of this study was to evaluate the effect of cover crop mixture diversity on a variety of parameters pertaining to the function of a cover crop. Specifically, this study evaluated the effect of cover crop species and functional richness on productivity, weed suppression, nutrient cycling, soil microbial community structure and stability.

    The performance targets of this study were to share the findings of this study through presentation at academic conferences, presentation at farmer-oriented conferences, publication in scientific journals, and publication in popular press formats.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.