Regional yield estimation for winter wheat based on net primary production model

The timely and accurate crop yield data have always been useful to government. Winter wheat is one of the most important crops in China. So, the authors select a widely-used net primary production (NPP) model to estimate the yield of winter wheat in the Huanghuaihai Plain in China. The authors selected the data which come from the critical growth stage which is significant to the final yield of winter wheat. The parameter of photosynthetically active radiation (PAR, 400～700 nm) was calculated using the ultraviolet (UV) reflectance data at 370 nm which come from the Total Ozone Mapping Spectrometer(TOMS). And the fraction of the photosynthetically active radiation (fPAR) can be retrieved from MODIS Normalized Difference Vegetation Index (NDVI) image using the linear regression between the fPAR and NDVI (fPAR＝aNDVI+b). And biological efficiency of PAR conversion to dry matter (ε) is supposed to be a constant in this paper through referring to local experiments in field and published literature. Then the authors used the equation NPP=ε×fPAR×PAR to calculate the winter wheat net primary production. Finally, estimation yield data through converting the calculated NPP to dry matter and multiplying the dry matter by the Harvest Indices (HI) for specific winter wheat varieties were obtained. The authors also analyzed the accuracy of the prediction of NPP. And the accuracy of final yield estimation versus the field yield data was also analyzed. The relative error between the winter wheat biomass calculated from NPP and the actual biomass was -4.30% and relative error between the predicted yield of winter wheat and the actual yield was -4.41%. So the results are satisfactory and using the NPP parameter to estimate winter wheat yield is practical and reliable.