Céline Pelosi

Agroecosystem management and biotic interactions: a review

Increasing the use of synthetic fertilisers and pesticides in agroecosystems has led to higher crop yields, accompanied by a decline in biodiversity at the levels of field, cropping system and farm. Biodiversity decline has been favoured by changes at landscape level such as regional farm specialisation, increases in field size, and the removal of hedgerows and woodlots. The loss of biodiversity in agroecosystems has increased the need for external inputs because beneficial functions are no longer provided by beneficial species as natural enemies of crop pests and ecosystem engineers. This trend has led to a strong reliance on petrochemicals in agroecosystems. However, many scientists have been arguing for more than two decades that this reliance on petrochemicals could be considerably reduced by a better use of biotic interactions. This article reviews options to increase beneficial biotic interactions in agroecosystems and to improve pest management and crop nutrition whilst decreasing petrochemical use. Four agronomic options are presented. First, it has been shown that the choice of cultivar, the sowing date and nitrogen fertilisation practices can be manipulated to prevent interactions between pests and crop, in either time or space. Nevertheless, the efficacy of these manipulations may be limited by pest adaptation. Second, beneficial biotic interactions may result from appropriate changes to the habitats of natural enemies and ecosystem engineers, mediated by soil and weed management. Here, knowledge is scarce, and indirect and complex effects are poorly understood. Third, changes achieved by crop diversification and, fourth, by landscape adaptation are promising. However, these practices also present drawbacks that may not necessarily be outweighed by beneficial effects. Overall, these four management approaches provide a powerful framework to develop sustainable agronomic practices.

Earthworm community in conventional, organic and direct seeding with living mulch cropping systems

The loss of biodiversity by intensification of agricultural practices is a major environmental issue that calls for the design of new cropping systems. For instance, negative effects of tillage on earthworm populations have been reported. However, few field studies have compared full cropping systems. Here, we assessed diversity, density and biomass of earthworm populations for 3 years. We use a combined method involving a diluted solution of allyl isothiocyanate to expel earthworms followed by hand sorting. In a long-term trial, we compared 3 systems: (1) a conventional system, (2) a direct seeding living mulch-based cropping system, named a living mulch cropping system, and (3) an organic system. These three cropping systems differed in terms of soil tillage, pesticide and nitrogen use, and crop biomass production. The results showed that measured variables, except diversity, varied depending on the year of sampling. Further, anecic and epigeic density was 3.2–7.2 times higher in the living mulch cropping system than in the conventional and organic systems. There were 3.4–12.5 times more anecic and epigeic earthworm biomass in the living mulch cropping system. The conventional and organic systems showed, respectively, 2.8 and 2.2 times more earthworm density, and 1.9 and 1.8 times more endogeic earthworm biomass than in the living mulch cropping system. Shannon-Wiener and equitability indices were superior in the living mulch cropping system compared with the conventional and organic systems. Cropping systems thus modified specific and functional diversity as well as earthworm community biomass. On the other hand, the organic and conventional systems did not differ in their earthworm density, biomass or diversity.