Long-term experiment

Abstract: Model runs with HERMES were performed over entire crop rotation cycles for two experimental sites on loamy and sandy soils in Germany with differently managed plots. The model was able to simulate soil water and nitrogen contents on the sandy plots of Muncheberg with an index of agreement (IA) >0.8 and >0.69. Crop growth and N-uptake was simulated well with IA values >0.89 and >0.75, respectively. For the loess site in Bad Lauchstadt model results for above-ground biomass, storage organ and N-uptake agreed well with observations over a 4-year rotation with IA values of 0.93, 0.94 and 0.71, respectively. Soil mineral nitrogen was significantly overestimated on the cropped plot (IA = 0.45) as well as on the black fallow plot (IA = 0.65) using the default initialization of the decomposable nitrogen pools from the organic matter content. Equilibration of the pools, using data from a neighbouring long term experiment, improved soil mineral nitrogen simulation to an IA of 0.72 for the cropped and 0.91 for the fallow plot. The long term model performance was investigated using data from 1903 to 2002 of four differently managed plots in Bad Lauchstadt. Soil organic carbon, derived from simulated nitrogen pools, showed acceptable results for the unfertilized plot, but a distinct underestimation on plots with farmyard manure application. Simulated historical winter wheat and potato yields were distinctly overestimated during the initial 50 years. Therefore, an adoption of crop parameters for older varieties is necessary. The index of agreement of 0.9 indicates that the annual weather impact on yield fluctuations was correctly reflected.

Abstract: The aim of the study is to analyze the effects of different fertilization of organic and inorganic fertilizers on soil organic carbon (SOC) sequestration and crop yields after a 22 years long-term field experiment. The crop yields and SOC were investigated from 1981 to 2003 in Dry-Land Farming Research Institute of Hebei Academy of Agricultural and Forestry Sciences, Hebei Province, China. The dominant cropping systems are winter wheat–summer corn rotation. There were totally sixteen treatments applied to both wheat and corn seasons: inorganic fertilizers as main plots and corn stalks as subplots and the main plots and subplots all have four levels. The results revealed: after 22 years, mixed application of inorganic fertilizers and crop residuals, the SOC and crop yields substantially increased. Higher fertilizer application rates resulted in greater crop yields improvement. In 2002–2003, wheat and corn for the highest fertilizer inputs had the highest yield level, 6400 kg ha−1 and 8600 kg ha−1, respectively. However, the SOC decreased as the excessive inorganic fertilizer input and increased with the rising application of corn stalks. The treatment of the second-highest inorganic fertilizer and the highest corn stalks had the highest SOC concentration (8.64 g C kg−1). Pearson correlation analysis shows that corn and winter wheat yields and the mineralization amount of SOC have significant correlation with SOC at p