Fertilizer nitrogen in soil

The distribution of ammonium nitrogen and nitrate nitrogen in the soils of field trials was followed in two growing seasons. In these trials ammonium nitrate limestone and calcium nitrate were, at several rates, applied as surface dressing. It was found that not only the ammonium nitrogen but also the nitrate nitrogen applied to the surface of loam, silt, silt clay, and fine sand clay soils tended to remain in the top inch for a considerable period in the absence of heavy rainfalls or a longer wet period. The plants appeared rapidly to deplete the layers downwards from 1 inch, but even after six and eight weeks from the application of the fertilizers the ammonium nitrogen and nitrate nitrogen contents of the surface inch could be markedly higher in the treated plots than in the untreated ones. In the non-cropped soil, eight weeks after the application of the fertilizers, the mineral nitrogen content of the top inch corresponded to about 60 % of the nitrogen applied. On the basis of these results the working in or placement of nitrogen fertilizers seems to be profitable. Fixation of ammonium nitrogen in unexchangeable forms was observed in some of the trials. This, however, did not significantly impair the value of ammonium nitrate limestone as a nitrogen source in these trials.