Predicting Mineral N Release during Decomposition of Organic Wastes in Soil by Use of the SOILNiNO 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 SOILNiNO 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 degree C for 8 weeks. Secondly, the calibrated model was tested by use of NO sub(3) super(-) 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 SOILNiNO model reproduced relatively well the NO sub(3) super(-) 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 NO sub(3) super(-) leaching. To achieve a satisfactory simulation of the NO sub(3) super(-) leaching, recalibration of the model had to be carried out. Thus, SOILNiNO 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.