Abstract
Weeds represent a significant threat to crop yields and global food security. We analysed data on weed competition from the world's longest running agricultural experiment to ask whether potential yield losses from weeds have increased in response to management and environmental change since the advent of the Green Revolution in the 1960s. On plots where inorganic nitrogen fertiliser has been applied, potential yield losses from weeds have consistently increased since 1969. This was explained by a warming climate, measured as air temperature averaged over the growing season for the weeds, and a shift towards shorter crop cultivars. Weeds also reduced yield proportionally more on plots with higher rates of nitrogen which had higher yields when weeds were controlled; the relative benefit of herbicides was, therefore, proportional to potential crop yield. Reducing yield losses from weed competition is increasingly challenging because of the evolution of herbicide resistance. Our results demonstrate that weeds now represent a greater inherent threat to crop production than before the advent of herbicides and integrated, sustainable solutions to weed management are urgently needed to protect the high yield potential of modern crop genotypes.
Highlights
The dramatic increase in crop productivity since the 1960s associated with the Green Revolution has delivered plentiful, cheap food for much of the world's expanding population (Pingali, 2012)
Potential yield losses from weed competition significantly increased with time since 1969 (Figure 3d) with an indication that this is partly explained by differences between the cultivars (Figure 3b)
These spatial and temporal trends in yield loss, expressed as absolute t ha−1, may be a consequence of increases in the yield potential of more modern crop cultivars when grown with higher rates of nitrogen (Figure 3a,b)
Summary
The dramatic increase in crop productivity since the 1960s associated with the Green Revolution has delivered plentiful, cheap food for much of the world's expanding population (Pingali, 2012) These gains have largely been won through the enhanced yield potential of modern crop cultivars combined with the increased use of inorganic fertilisers (Borlaug, 2007; Evenson & Gollin, 2003). While herbicides have been the dominant driver of weed community dynamics in recent decades, it is likely that other changes in crop management (Baessler & Klotz, 2006; Fried et al, 2012; Storkey et al, 2012) and the environment (Peters et al, 2014) have had an impact on weed floras and weed competition Accounting for all these factors, we answer the question of whether weeds constitute a greater potential threat to yield than prior to the advent of herbicides
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