Effects of Simulated Nitrogen Deposition on Soil Net Nitrogen Mineralization in the Meadow Steppe of Inner Mongolia, China.

Effects of simulated nitrogen (N) deposition on soil net nitrogen mineralization (NNM) were examined in situ during two growing seasons, using the resin-core technique in the semiarid meadow steppe in Inner Mongolia, China. The aim of this study is to clarify the effect of N levels (0, 10, and 20 kg N ha-1yr-1) and forms (NH4+ and NO3-) on soil mineral N and NNM. Our results showed that N levels had no significant differences on soil mineral N and NNM.

[LAI-based regional winter wheat yield estimation by remote sensing].

By using retrieved LAI from remotely-sensed imagery, this paper studied the regional winter wheat yield estimation in Huanghuaihai Plain of North China. In order to improve the quality of remotely sensed data for winter wheat yield estimation, a Savitzky-Golay filter was used to smooth the MODIS-NDVI time series data to reduce the cloud contamination and remove the abnormal data. Then, a Gaussian model was used to simulate the daily crop LAI which was corrected by interpolating the measured LAI to get the average LAI values for each phenological stage.

[Prediction of winter wheat yield based on crop biomass estimation at regional scale].

Based on the 2004 in situ data of crop yield, remote sensing inversed photosynthetically active radiation (PAR), fraction of photosynthetically active radiation (f(PAR)), climate, and soil moisture in 83 typical winter wheat sampling field of 45 counties in Shijiazhuang, Hengshui, and Xingtai of Hebei Province, a simplified model for calculating the light use efficiency (epsilon) of winter wheat in Huanghuaihai Plain was established. According to the crop accumulated biomass from March to May and corrected by harvest index, the quantitative relationship between crop biomass and crop yield for winter wheat was set up, and applied in the 235 counties in Huanghuaihai Plain region of Hebei Province and Shandong Province and validated by the official crop statistical data at county level in 2004. The results showed that the root mean square error (RMSE) of predicted winter wheat yield in study area was 238.