Intercropping oats with annual clovers : effects on yields and aspects of biodiversity

Sammanfattning: The use of fertilizers, pesticides and herbicides has contributed to greatly increase the crop yields per hectare. Humanity has become reliant on artificial inputs overshadowing usage of resources from ecosystem services that we continue to weaken further, by using agricultural practises decreasing landscape and species diversity. Before fertilizers and pesticides became available,farmers depended on ecosystem services such as pest control provided by natural enemies to pests and complementary crops in mixes competing with weeds. Today, ecosystem services are threatened e.g. by declining pollinator abundance important for crop yield and quality as well as loss of habitats for natural arthropod predators supporting pest control. Combining a main crop e.g. cereals for food production, together with a supportive under-sown crop in an intercropping system enhance the resource usage efficiency. At the same time, the under sown crop support resilience of the cropping system itself as well as to surrounding ecosystems and thereby future food production. My aim was to evaluate the effects of under-sowing oats with a mixture of the annual clover species, Trifolium incarnatum, T. resupinatum and T. squarrosum, both during the intercropping phase and in the autumn when clovers continued to grow to prolong effects and the continuity of vegetation cover. The field study was located in the counties of Uppsala, Stockholm, Södermanland and Västmanland in Sweden. The intercropping effects on pollinator abundance, ground-dwelling arthropod predators, aphid predation, weed biomass and yield of both clover and oats were studied. The results showed a higher abundance of flower resources and higher pollinator abundance in intercrops compared to sole crops of oats, without reducing oats yield. No effect on natural predators, aphid predation or weeds could be found. Intercropping oats with a cover crop of annual Trifolium species helps to boost biodiversity, have no impact on cash crop yield quantity and keeps the soil covered.