The activity and kinetic parameters of oxidoreductases in phaeozem in response to long-term fertiliser management

This study describes the effects of balanced versus nutrient-deficient fertilisation on soil nutrient content and selected oxidoreductase activity and kinetic parameters in a long-term (28 years) field experiment conducted using a phaeozem type soil in the Jilin Province of northeast China. As compared to no or unbalanced fertilisation, balanced fertilisation improved the overall chemical fertility of the soil and sig- nificantly increased the activities and Vmax values of soil dehydrogenase and cata- lase. Compared with control (CK), unbalanced fertilisation (with the exception of P deficiency) significantly increased the total carbon content and soil dehydrogenase activity but had less of an effect on the Vmax of the enzyme, whereas the soil cata- lase activity and its Vmax were less affected under unbalanced fertilisation condi- tions. The Km value of soil dehydrogenase increased with the application of chemi- cal NPK combined with farmyard manure but decreased under the application of NPK, NP, and PK. The Km value of soil catalase decreased under the application of NK and showed little difference between CK and the other fertilisation treatments. The variations in the activities and kinetic parameters of the enzymes revealed the benefits of long-term balanced fertilisation, particularly the combined application of chemical and organic fertilisers, by improving the chemical and biological fertility of phaeozem. The results also indicated that unbalanced fertilisation with P deficiency (NK) could enhance phaeozem quality, but this effect was limited.