1. Scottish Government 2017 Economic Report on Scottish Agriculture 2017 Edition https://www2.gov.scot/Topics/Statistics/Browse/Agriculture-Fisheries/PubEconomicReport/2017docs
2. DEFRA (Department for Environment Food and Rural Affairs) 2017 The British Survey of Fertiliser Practice - Fertiliser use on farm for crop year 2017 https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/722598/fertiliseruse-report2017-5july2018a.pdf
3. Nitrogen Fixing Organisms
4. Cover crops and living mulches;Hartwig;Weed Sci.,2002
5. Reckling , M. Schläfke , N. Heckler , J.-M. Bachinger , J. Zander , P. 2013 Generation and evaluation of crop rotations .2 http://www.legumefutures.de/images/Legume_Futures_Report_4.3.pdf