Crop 15N recovery course affected by spatial distribution of animal slurries in soils

Crop response to applied nitrogen in animal slurry as affected by distribution pattern and slurry type was examined in spring barley using two slurries enriched with isotopic nitrogen (¹⁵N). The slurries differing in immobilisation potential were either fully incorporated in the soil or injected in concentrated bands in two fields of low and high fertility caused by the preceding crop. Band-injection of slurry was combined with furrow type formed by different injector tines as well as the distance between the slurry band and seed row. Spring barley was sampled nine times during the season for determination of dry matter (DM) accumulation, total nitrogen (N) uptake and crop recovery of applied nitrogen (¹⁵N recovery). A sigmoid growth function was fitted to the recorded crop ¹⁵N recovery. A slurry band to crop row (SB-CR) distance of 4 cm clearly promoted crop ¹⁵N recovery by 6–12 days and increased total N-uptake and DM accumulation compared with a SB-CR distance of 12 cm. In contrast, the furrow type neither affected the crop ¹⁵N recovery course, total N-uptake, nor DM accumulation. An elevated immobilisation potential in the slurry slowed the ¹⁵N recovery course. In contrast, crop ¹⁵N crop recovery was unaffected by the residual effect of the preceding crop. The elevated immobilisation potential of the slurry also reduced the DM accumulation, but the mineralisation potential of the preceding crop clearly increased total N-uptake and DM accumulation. As the SB-CR distance had a significant effect, this should be taken into account in agroecological systems using application of animal slurry in bands by direct injection.