Predicting Mineral N Release during Decomposition of Organic Wastes in Soil by Use of the SOILN NO Model

In order to predict the mineral N release associated with the use of organic waste as fertilizer in agricultural plant production, the adequacy of the SOILN_NO model has been evaluated. The original thought was that the model calibrated to data from simple incubation experiments could predict the mineral N release from organic waste products used as N fertilizer on agricultural land. First, the model was calibrated to mineral N data achieved in a laboratory experiment where different organic wastes were added to soil and incubated at 15°C for 8 weeks. Secondly, the calibrated model was tested by use of NO3 − leaching data from soil columns with barley growing in 4 different soil types, added organic waste and exposed to natural climatic conditions during three growing seasons. The SOILN_NO model reproduced relatively well the NO3 − leaching from some of the soils included in the outdoor experiment, but failed to reproduce others. Use of the calibrated model often induced underestimation of the observed NO3 − leaching. To achieve a satisfactory simulation of the NO3 − leaching, recalibration of the model had to be carried out. Thus, SOILN_NO calibrated to data from simple incubation experiments in the laboratory could not directly be used as a tool to predict the N-leaching following organic waste application in more natural agronomic plant production systems. The results emphasised the need for site- and system-specific data for model calibration before using a model for predictive purposes related to fertilizer N value of organic wastes applied to agricultural land.