Fig 1. Field experimental setup.

Barley, faba bean and turnip rape, as first crops, were grown in one block in the first year. In the second year, second crops were sown in randomized complete block designs with four replicates in each block of First crops. The whole plots of caraway and white lupin were incorporated into the soil at flowering stage, and the residues of the whole plots of barley were incorporated after harvest. Half plots of buckwheat, faba bean and hemp were incorporated into the soil at flowering stage and the residues of the other half were incorporated after harvest. In the third year, all the plots were sown with barley. The first year of site II coincided with the second year of site I.