Mixing it up: The potential benefits of cultivar mixtures under conservation tillage practices in organic agriculture (REVIEW)

Abstract

Current agricultural practises cause soil degradation: Tillage causes soil disturbance and chemical pesticides and fertiliser use pollute the soil. Conservation tillage practises reduce soil disturbance and leave at least 30% percent of the soil surface covered with residue as a protection layer against erosion. Under no-till practises the soil cover is completely preserved. Organic agriculture limits soil pollution by banning chemical inputs. In agricultural settings where conservation tillage and organic agriculture practises are combined, barely any conventional method is left to manage the threats on crops of pest attacks, pathogen infections, and weed competition that cause yield declines. This review hypothesised that making use of cultivar mixtures in a field brings in the functional diversity that can partly make up for the biotic stress resistance loss that these soil conserving practises generate. This literature review shows that cultivar mixtures turn out to negatively affect pest herbivorous attacks, pathogen infections, and weed dominance, relative to their monoculture stands. This increases yields in soil conserving practises settings. Not all crops in a field need to carry the same resistance trait for it to have an effect on the overall disease severity in the field. Therefore, there is no need to breed a cultivar with many resistance traits in combination with high yield and quality performance traits, which would otherwise be rather difficult and time consuming. Cultivar mixtures might not create full resistance against aforementioned biotic stresses. However, this review concludes that increased yields relative to monoculture stands in soil conserving practises settings and less economic inputs spent on chemical pesticides and tillage might make this an agricultural and economic beneficial option.