The fate of clover-derived nitrogen (15N) during decomposition under field conditions: Effects of soil type

Seven soils were collected from different field sites in Southern Finland and placed into microplots confined in PVC-cylinders (30 cm i.d. × 50 cm). Subterranean clover material labelled with¹⁵N, contained in mesh bags, was buried into the microplots in October, and the plots were sown with barley the following May. The mesh bags were removed and soil samples taken immediately after the barley harvest. The crop, mesh bags and soil were then analysed for¹⁵N content. The soil type affected release of clover N from the mesh bags and its retention in soil only slightly; at the end of the experiment the mesh bags contained 30–38% and the soil (0–45 cm) 28–37% of the clover N input. The uptake of clover N by the barley crop varied from 11 to 20% and correlated best with the soil electrical conductivity (r=0.820^*). The total recovery of clover-derived N varied from 72 to 92%.