Cover crop biomass production is more important than diversity for weed suppression

Research output: Contribution to journalArticle

Abstract

Biotic resistance theory suggests that diverse cover crop mixes may be more effective at weed suppression than a cover crop monoculture. However, evidence for this has so far been inconsistent. To investigate, we designed a trial to explicitly test the role of cover crop diversity in weed suppression, through comparing eight cover crop mixes that varied in species diversity, functional diversity, and composition. Mixes contained either one, four or eight species, in equal proportions. Three mixes contained only cereal species, three contained only legumes, and two contained a mix of cereals, legumes and brassicas. Research was conducted on two farms in South Africa’s winter rainfall region, replicated over two years. Indicators of resource uptake by each mix in terms of light, soil nitrogen and water were measured at three time points throughout the season, approx. 50, 85 and 110 days after establishment (DAE). Aboveground biomass (dry weight) of cover crops and weeds within each mix was measured twice, at approximately 70 and 120 DAE. Regression analyses indicated that cover crop biomass was key to resource uptake and weed suppression, and that early-season nitrogen and later-season light availability had the strongest influence on weed biomass. Neither species diversity nor functional diversity affected resource uptake or weed suppression by cover crops. These results indicate that it is important to consider the competitiveness of individual species when designing cover crop mixes. Diverse mixes remain valuable to perform multiple functions, but may contribute to weed problems if composed of poorly competitive species.
LanguageEnglish
Pages(In-Press)
JournalCrop Science
Early online date24 Jan 2019
DOIs
StateE-pub ahead of print - 24 Jan 2019

Fingerprint

cover crops
Biomass
weed control
biomass production
Fabaceae
biomass
Nitrogen
Light
Brassica
South Africa
weeds
functional diversity
Soil
Regression Analysis
Weights and Measures
legumes
Water
Research
species diversity
Crop Production

Keywords

  • cover crops
  • weed management
  • diversity
  • competition
  • biotic resistance

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)

Cite this

@article{b9d0c82f5ba14a3eae3e829c1334de8a,
title = "Cover crop biomass production is more important than diversity for weed suppression",
abstract = "Biotic resistance theory suggests that diverse cover crop mixes may be more effective at weed suppression than a cover crop monoculture. However, evidence for this has so far been inconsistent. To investigate, we designed a trial to explicitly test the role of cover crop diversity in weed suppression, through comparing eight cover crop mixes that varied in species diversity, functional diversity, and composition. Mixes contained either one, four or eight species, in equal proportions. Three mixes contained only cereal species, three contained only legumes, and two contained a mix of cereals, legumes and brassicas. Research was conducted on two farms in South Africa’s winter rainfall region, replicated over two years. Indicators of resource uptake by each mix in terms of light, soil nitrogen and water were measured at three time points throughout the season, approx. 50, 85 and 110 days after establishment (DAE). Aboveground biomass (dry weight) of cover crops and weeds within each mix was measured twice, at approximately 70 and 120 DAE. Regression analyses indicated that cover crop biomass was key to resource uptake and weed suppression, and that early-season nitrogen and later-season light availability had the strongest influence on weed biomass. Neither species diversity nor functional diversity affected resource uptake or weed suppression by cover crops. These results indicate that it is important to consider the competitiveness of individual species when designing cover crop mixes. Diverse mixes remain valuable to perform multiple functions, but may contribute to weed problems if composed of poorly competitive species.",
keywords = "cover crops, weed management, diversity, competition, biotic resistance",
author = "Chloe MacLaren and Pieter Swanepoel and James Bennett and Julia Wright and Katharina Dehnen-Schmutz",
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AU - MacLaren,Chloe

AU - Swanepoel,Pieter

AU - Bennett,James

AU - Wright,Julia

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N2 - Biotic resistance theory suggests that diverse cover crop mixes may be more effective at weed suppression than a cover crop monoculture. However, evidence for this has so far been inconsistent. To investigate, we designed a trial to explicitly test the role of cover crop diversity in weed suppression, through comparing eight cover crop mixes that varied in species diversity, functional diversity, and composition. Mixes contained either one, four or eight species, in equal proportions. Three mixes contained only cereal species, three contained only legumes, and two contained a mix of cereals, legumes and brassicas. Research was conducted on two farms in South Africa’s winter rainfall region, replicated over two years. Indicators of resource uptake by each mix in terms of light, soil nitrogen and water were measured at three time points throughout the season, approx. 50, 85 and 110 days after establishment (DAE). Aboveground biomass (dry weight) of cover crops and weeds within each mix was measured twice, at approximately 70 and 120 DAE. Regression analyses indicated that cover crop biomass was key to resource uptake and weed suppression, and that early-season nitrogen and later-season light availability had the strongest influence on weed biomass. Neither species diversity nor functional diversity affected resource uptake or weed suppression by cover crops. These results indicate that it is important to consider the competitiveness of individual species when designing cover crop mixes. Diverse mixes remain valuable to perform multiple functions, but may contribute to weed problems if composed of poorly competitive species.

AB - Biotic resistance theory suggests that diverse cover crop mixes may be more effective at weed suppression than a cover crop monoculture. However, evidence for this has so far been inconsistent. To investigate, we designed a trial to explicitly test the role of cover crop diversity in weed suppression, through comparing eight cover crop mixes that varied in species diversity, functional diversity, and composition. Mixes contained either one, four or eight species, in equal proportions. Three mixes contained only cereal species, three contained only legumes, and two contained a mix of cereals, legumes and brassicas. Research was conducted on two farms in South Africa’s winter rainfall region, replicated over two years. Indicators of resource uptake by each mix in terms of light, soil nitrogen and water were measured at three time points throughout the season, approx. 50, 85 and 110 days after establishment (DAE). Aboveground biomass (dry weight) of cover crops and weeds within each mix was measured twice, at approximately 70 and 120 DAE. Regression analyses indicated that cover crop biomass was key to resource uptake and weed suppression, and that early-season nitrogen and later-season light availability had the strongest influence on weed biomass. Neither species diversity nor functional diversity affected resource uptake or weed suppression by cover crops. These results indicate that it is important to consider the competitiveness of individual species when designing cover crop mixes. Diverse mixes remain valuable to perform multiple functions, but may contribute to weed problems if composed of poorly competitive species.

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