Spatio-Temporal Of Crop Evapotranspiration And Yield Based On NDVI In North China Plain From 1981 To 2001

The North China Plain(NCP) is one of the most important food production regions in China. Water is the most important limiting factor for crop production due to the uneven distribution of precipitation and irrigation is :he main method to maintain and enhance agriculture production in the area. On the other hand, many problems occurred because of the excessive exploitation of irrigation. So studying on the temporal and spatial changes of regional evapotranspiration and production in NCP is very important for reasonable management of water recourse and implementing water-saving agriculture.Combined the process-based Vegtation Interface Processes (VIP) model and Light Use Efficiency-Yield (LUE-Y) model, the regional evapotranspiration and production of the main crop in the area from 1981 to 2001 was simulated. The distribution of dryland and irrigated land were detected by the NDVI in e arly May when the differences of crop growth between the two type lands were great. A digital elevation model was used to correct meteorological variables for altitude, and the inverse distance square method was adopted for spatial interpolation of precipitation over the basin.The values of precipitation during winter wheat season and summer maize season were averaged 231.8 mm and 42,8 mm respectively in NCP. The spatial distribution of precipitation in the two seasons was different.The regional evapotranspiration of winter wheat increased from south to north with lower annual changes and averaged 359 mm with the values of 403 mm and 217 mm for irrigated and dry lands respectively. The accumulated NDVI and biomass increased during 1980s and reached a stable value, while the grain y eld showed a obvious increase in the 21 years with a minimum value of 1892 kg/hm" in 1981 and a maximum value of 5820 kg/hm2 The validation was carried by comparing the simulated yield with the statistic yield, and a significant correlation between them was found.The averaged regional evapotranspiration for summer maize was 389 mm and the values of irrigated and dry lands were 335 mm and 413 mm due to the high rainfall during the growth season. The averages of accu nulated NDVI and biomass changed not obviously during the 21 years with the values of 4.8 and 13076 kg/hm2 respectively, while the averaged regional grain yields increased markedly from 3031 kg/hm2 in 1981 to 6189 kg/hm2 in 2001 due to the enhanced Harvest Index (HI). The comparison between simulated yield and statistic yield showed a significant correlation between them (P less 0.001).The increases in evapotranspiration and yield of winter wheat and summer maize were found in the low land along Hai River, which was caused by the improved irrigation conditions and integration management carried in this area through the recent years.