Distribution of nitrogen pools in the soil profile of undisturbed and reseeded grasslands
2000
Bhogal, A. | Murphy, D.V. | Fortune, S. | Shepherd, M.A. | Hatch, D.J. | Jarvis, S.C. | Gaunt, J.L. | Goulding, K.W.T.
This study evaluated the effect of cultivation and reseeding on the distribution and fate of soil mineral N (SMN), soluble organic N (SON) and potentially mineralisable N (PMN) in the soil profile of two long-term grasslands in the UK. Cultivation and reseeding significantly increased the total soluble N concentration (SMN plus SON) of the soil profile (0-90 cm), with over 50 mg SON kg-1 observed. By contrast, the PMN pool was unaffected by cultivation and declined with increasing soil depth. The flush in SON and SMN observed in both soils disappeared within 1 year following cultivation. The fate of SON appeared to be dependent on soil type, with considerably more movement to deeper layers apparent in the profile of a silty clay loam (30% clay) than in a clay loam (49% clay). Mineralisation and/or mobilisation of SON in the topsoil probably accounted for the changes observed in the SON content of the clay loam. SON is an important N pool in grassland soils and cultivation has a significant impact on its release. Measurements of SON should therefore be included in studies of N cycling in agricultural cropping systems, so that full account may be taken of its potential as a source or sink of mobile N.
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