Simulation on Nitrogen and Soil Organic Matter in Paddy Soils under Long-Term Application by WNMM.
KI-DO PARK1, Chang-Young Park2, Yong Li3, Deli Chen4, Jae-Saeng Lee2, Il-Soo Son2, Dong-Wook Lee2, Ui-Gum Kang2, and Sung-Tae Park2. (1) Yeongnam Agricultural Research Institute, NICS, RDA, 1085 Naeidong, Milyang, South Korea, (2) National Yeongnam Agricultural Research Institute, R.D.A, 1085 Naeidong, Milyang, South Korea, (3) The Univ of Melbourne, Royal Parade, Parkville, 3052, Australia, (4) The University of Melbourne, Royal Parade, Parkville, 3052, Australia
Rice yield, Soil Organic Matter (SOM), and crop Nitrogen (N) uptake on a fine, silt paddy soil were treated with nitrogen+phosphate+potassium (NPK) and NPK+compost (rice straw) and the same set was maintained as control (no treatment), in Milyang, South Korea (36o36'N, 128o45'E, elevation of 12m) from 1980 to 2003. The treatments were then simulated by a Water and Nitrogen Management Model (WNMM) and compared with field measurements. For N, P, and K fertilizers, or urea, triple super phosphate and potassium chloride were applied to the experimental fields at 150kg N per hectare per year, 100kg P per hectare per year, and 100kg P per hectare per year, respectively. Rice straw compost was applied at 10,000kg per hectare per year. The WNMM predictions for 23 years on rice yield, SOM, and N uptake were significantly different under each treatment. The rice yields and N uptake simulated by WNMM depended strongly on solar radiation in weather factor. SOM measured in the field varied as time went on; the reason for such was not clearly observed. R2 for the correlation between predicted and measured data for N uptake, rice yield, and SOM were 0.06. 0.12, and 0.04 in control; 0.15, 0.16, and 0.13 in NPK; and 0.41, 0.21, and 0.34 in NPK+compost, respectively. The WNMM predictions of rice yield, N uptake, and SOM in plot treated with NPK+compost showed the highest correlation with measured data. Keywords: simulation, rice, soil organic matter, compost, N uptake