Ureolytic nitrification activities in forest and tea (Camellia sinensis) plantation soils and evaluation of ureolytic nitrifier sensitivity to pesticides

An experiment was conducted in 1992 to compare ureolytic nitrification acti vities in soil under tea (Camellia sinensis (L) O Kuntze) cultivation and f orest land adjacent to the tea plantations. Recovery of nitrate from the so il samples of tea plantations following incubation with urea confirmed that the active nitrification occurred even in the pH range of 4.5-5.5. A sligh t increase in ureolytic nitrification activity in sections showing higher y ield of made tea was detectable in plantations using lower dosages of synth etic fertilisers. Such a relationship was not, detected in samples from pla ntations using a higher dose of chemical fertilisers. Likewise neither the age, nor the organic carbon (%) and pH were related to the differences in u reolytic- nitrification activity observed in the samples. Comparison of the ureolysis and nitrification rates between plantation samples and the corre sponding forest samples showed that this activity was lower in tea plantati ons in all cases. The ureolytic nitrifier strains isolated from tea plantat ions were. able to grow in culture plates incorporated with several structu rally different types of pesticides.