Leguminous service crops in cereal production at high latitudes : provision of ecosystem services and disservices from a novel intercropping system

Sammanfattning: Service crops, crops grown to provide services such as soil protection, weed control, or nutrient capture and provision, can reduce the need for mineral fertilisers and intensive weed control. However, high biomass production is necessary in order for these services to be provided. This can be difficult to achieve at high latitudes (e.g. Sweden), where growing conditions are poor after main crop harvest, when service crops are usually sown. The aim of this thesis was to increase the understanding of service crop species choice and management on service and disservice delivery. Leguminous service crops were sown into oats in spring/early summer for early establishment of the service crop, and terminated in the following spring in winter wheat. The results showed that species sown at the same time as oats, rather than one month later, and which survived oat harvest and cold temperatures in winter, were best at suppressing weeds and increasing winter wheat yields, although they often also reduced oat yield in the establishment year. Presence of a productive service crop (>0.2 t dry weight (DW) per ha) reduced the occurrence of competitive-stress tolerant weed species, in favour of ruderal species, in the oat row and in combination with oat biomass >8 t DW ha-1 the occurrence of competitive perennial species was reduced. Modelling the system using APSIM NG revealed that the service crops mainly provided positive effects on the cropping system, in terms of increased winter wheat yield, increased soil carbon input and reduced losses of nitrogen and water during most of the study period. Drawbacks were reduced oat yield and increased nitrogen losses from winter wheat and in the fallow period after winter wheat. I conclude that the studied intercropping system has potential to provide services and reduce disservices, but that the system needs improvement. These improvements are mainly to ensure even establishment and good termination of the service crops.