1. Danish Institute of Agricultural Sciences Department of Agroecology N-management in grass-arable crop rotations Jørgen Eriksen 96 Tools for reducing N-losses

2. Build-up in grassland Years of grassland 1002000 0 0.2 0.1 % N Source: Johnston 1991

3. Loss after ploughing 12 8 6 4 0 10 2 5 1520250 N (t/ha) Years after ploughing Source: Whitmore et al. 1992

4. What effects nitrate leaching? Fertilizer application Feeding Use (grazing/ cutting) Composition (grass/clover) Duration Grazing time Animal density

5. Leaching from grassland

6. Why lower leaching from grass-clover? Explanation 1: Reduced N-fixation leading to lower input

7. Nitrate leaching from grassland Unfertilized grass-clover Fertilized grass-clover Fertilized grass Total N input Nitrate leaching 250 200 150 100 50 0 1001502002503000 kg N/ha/yr Source: Ledgard

8. Grassland yields Why less leaching from grass-clover? Explanation 1: Reduced N-fixation resulting in lower input Explanation 2: Lower yields resulting in less grazing

9. Utilizing N in urine spots Source: Cuttle and Bourne

10. Crop rotation Time of ploughing Fertilizer application History What effects nitrate leaching?

11. Nitrate leaching – crop rotation

13. Winter wheat -> catch crop Bare soil -> catch crop Nitrate leaching – crop rotation

14. Utilizing the residual effect ”Old” pastures on coarse sandy soil 3-yr-old grass-clover far from the farm 5-yr-old grass-clover close to the farm Cultivation followed by: Green barley – Ital. ryegrass Barley maturity – per. Ryegrass Barley maturity – bare soil

15. N-uptake – cereals after grassland

17. Leaching – cereals after grassland

18. Management in grass-arable rotations During grazing Fertilizer in grassland Time of grazing (day/year) Grazing/cutting Following cultivation Time of ploughing Choice of crop (incl. catch crop) Fertilizer application year 1 and 2 Crop rotation Grassland age at ploughing Grassland frequency in rotation

19. Thank you for your attention!