Untersuchungen an philippinischen Reisböden
Übersicht: Hintergrund | Abstract | Download
Die Arbeit mit dem Titel "Nitrogen mineralisation and enzyme activities in Philippine paddy soils" entstand im Sommer/Herbst 2000 als Abschlußarbeit zur Erlangung des M.Sc.-Abschlusses in "Mangement of Soil Fertility" am Department of Soil Science der Univeristy of Reading, England.
Den Hintergrund der Arbeit bildet eine Forschungskooperation zwischen Dr. Martin Wood (University of Reading) und Dr. Roland Buresh (International Rice Research Institute, IRRI), die zum Ziel hatte, Enzymaktivitäten und N-Mineralisation in Reisböden unter verschiedenen Nutzungsformen zu bestimmen.
Rice soils are known to be of comparatively low fertility, with N supply being the major constraint for rice growth. To examine aspects related to that topic, the International Rice Research Institute (IRRI, Los Baños, Philippines) established a long-term continuous cropping experiment (LTCCE) in 1963, with four different rates of N fertiliser as the mainplots. In order to examine possible differences in processes linked to the nutrient cycling, three methods of examination were applied to the LTCCE soils during this study:
microplate fluorometric assay to examine the activities of acid phosphatase, ß-glucosidase, glucosaminidase, cellobiohydrolase and leucine-peptidase
15N isotope dilution technique to estimate gross N mineralisation
anaerobic incubation for 1 week at 40°C to determine mineralisation under waterlogged conditions
Activities of glucosidase, glucosaminidase and leucine-peptidase were found to increase with increasing rates of fertiliser application, whereas phosphatase and cellobiohydrolase showed no significant differences between the four rates of N amendment. Gross mineralisation rates were around 6 µg N g-1 d-1 for all samples examined. Negative mineralisation values were obtained from the anaerobic incubation, most probably due to N losses via denitrification and NH3 volatilisation.
Correlation analyses showed that all enzyme activities were significantly correlated with each other and - except for cellobiohydrolase - with organic matter content estimated by loss on ignition. No correlation between enzyme activities and gross mineralisation rates was found.
It is concluded that the fluorometric enzyme assay has the potential of a fast and useful predictive tool for nutrient cycling in paddy soils,
especially if future studies should reveal correlations between enzyme activities and the results obtained by applying the version of anaerobic
mineralisation which has been modified by IRRI for waterlogged soils.