Relationship between weed diversity and crop productivity affected by resource availability and imbalance

Abstract

Sustainable farming systems need to balance crop production with the conservation of weed diversity to maintain the ecosystem services provided by these species. To this aim is relevant to characterize the relationship between weed diversity and crop production. This relationship could be affected by weed diversity response to both resource availability and resource imbalance. We assessed whether increasing the supply of limiting resources reduces weed diversity and functional divergence of weed communities, and whether greatest values of these variables occur when multiple resources are supplied at balanced ratios. We further analyzed whether higher weed diversity allow a reduction in weed-crop competition. We used data collected in 2014 from a long-term experiment (Broadwalk, Rothamsted, UK) in which plots were cropped with wheat and subjected to a fertilization treatment. Treatments varied in both resource abundance and imbalance due to different combinations of nutrients applied at contrasting doses. In each plot we computed weed species richness (S), community diversity (eH’) and functional divergence using SESFDis (with 6 traits). We recorded the number of nutrients added, as well as resource availability and imbalance using previously developed formulas. Our results showed that S and eH’ were not related to resource availability but decreased as more nutrients were added. The increase in the availability of resources led to higher functional divergence in weed communities, but SESFDis was not related to resource imbalance. On the contrary eH’ was higher in plots where resources were supplied more balanced. Higher values of S, eH’ and SESFDis reduced yield loss.