Type and rate of fertilizer influence the level of organic carbon and total nitrogen in the
soil markedly, but the effect on different pools is open to question. Soil samples were
taken from a sandy Cambisol at Darmstadt, Germany, after 27 years of different
fertilization treatments. The six treatments were: straw incorporation plus application
of mineral fertilizer (MSI) and application of farmyard manure (FYM) each at high (140
– 150 kg N ha-1 year-1), medium (100 kg N ha-1 year-1) and low (50 – 60 kg N ha-1
year-1) rates. After 266 days of incubation (10°C, 50% water-filled pore space)
mineralization of C (1130 – 1820 kg ha-1) and N (90 – 125 kg ha-1) depended on the
rate and not on the type of fertilizer. Very labile and labile pools were obtained by
fitting a two-pool model on the mineralization data. The very labile pool (turnover: 17
days, C/N ratio: 23) was unaffected by treatments. Storage of C (1.8 – 3.2 t ha-1) in the
labile pool (turnover 462 days, C/N ratio: 22) increased significantly with the rate of
fertilizer. The size of the intermediate pool was significantly higher in FYM (15 -18 t
ha-1) than in MSI treatments (12- 14 t ha-1). A passive pool, obtained by oxidation with
Na2S2O8, was independent of treatments. Our study shows that labile and
intermediate pools were affected differently by fertilization
