Service crops (SCs) are widely used in low input systems as a source for nitrogen (N), and in intensive cropping systems for reducing N leaching by taking up residual soil N after the harvest of the main crop. This chapter discusses benefits of SCs, which are defined here as crops grown for providing ecosystem services and not grown for harvest, and include cover and catch crops. The chapter includes a discussion on SCs grown in the period between two main crops, or intercropped with the main crop and also focuses on the benefits regarding reduction in N leaching losses and transfer of N from the SCs to the main crop, including the fertiliser replacement value of SCs.