Evaluating the Validity and Sensitivity of the DNDC Model for Shimajiri Dark Red Soil

Abstract

The validities of the DeNitrification-DeComposition (DNDC) model and the simulation parameters were examined by using the experimental data obtained at Miyako Branch of Okinawa Prefectural Agricultural Research Center. The obtained simulation results were compared with the observed values and it was concluded that the simulation with the measured parameters could produce better simulation results than the simulation with the model provided default parameters. The model seemed to be able to predict the total amounts of leached water and nitrate and N 2 O emissions reasonably well, but the modifications in the model seemed to be still needed for capturing precise seasonal leaching and emission patterns. The sensitivity of the model was analyzed by either increasing or decreasing one of the crop and soil parameters by 25% while holding all other parameters and inputs constant. The changes in water filled porosity at field capacity were found to have the largest effects on the amount of leached water and N 2 O emissions. The amount of leached nitrate was affected by the changes in water filled porosity at field capacity only slightly, but it was reduced significantly by an increase in soil pH.

Field Validation of DNDC and SWAP Models for Temperature and Water Content of Loamy and Sandy Loam Spodosols

“…Nevertheless, in 2006 the DNDC model predictions showed a better match of the simulated soil temperatures to the measured data compared to those obtained by the SWAP model. As shown by Nakagawa et al (2008), the DNDC model demonstrated high sensitivity to air temperatures as well as a satisfactory efficiency in predicting soil temperatures at the depths of 15 and 35 cm.…”

“…However, the results of Jiang et al (2011) showed that the SWAP model could overestimate the soil water content at the depth of 15 cm and predict it efficiently at the depths of 35, 65, and 95 cm. Nakagawa et al (2008) reported that the DNDC model overestimated the soil water content but produced a better efficiency if the measured input parameters were used instead of default ones. The Nash-Sutcliffe efficiency (E) coefficients supported the results of the statistical analysis of the RMSE values.…”

Examination of the Effectiveness of Controlled Release Fertilizer to Balance Sugarcane Yield and Reduce Nitrate Leaching to Groundwater

“…According to the study conducted by Nakagawa et al [28], a total amount of 63.6 kg N/ha was leached as nitrate-N from their sugarcane-cultivated lysimeter unit, and they observed large increases in leached nitrate amounts during periods of typhoons and heavy rains [28]. In addition, Shuhei [29] reported that the trend in the concentration of nitrate-N at the springs on Miyako Island was only matched with that of N emission from chemical fertilizer and inferred that GW was predominantly affected by chemical fertilizers.…”