| In the content of world population growth, increased demand for bio-energy, climate change and the deterioration of ecological environment, growing problems of food security is becoming more and more serious. Huanghuaihai-Farming Region (HFR) which is the most important grain-producing areas in China plays an important role in essuring food production. Narrowing the gap between actual farmers’yield and potential yield of crops is an important way to increase grain production. The research foucus on the yield gap of winter wheat and summer maize that are the main planting crops in HFR, using DSSAT model, and combining farmers’survey and field experiment, to quantify the room for increasing farmers’ yield in HFR, to analyse the temporal and spatial distribution of yield gap1, and to explore the constraints for narrowing the yield gap. The purpose of the study is to provide theoretical and technical support for narronwing the yild gap of winter wheat and summer maize in HFR.1.There are obvious spatial distribution characteristics of potential yield of winter wheat and summer maize in Huanghuaihai-Farming-Region, the potential yield in the east of HFR is higher than the potential yield in the west. The potential yield of winter wheat and summer mazie show significant decrease over1961to2012. What affect the potential yield of winter wheat and summer maize in spatial scale are daily solar radiation and daily maximum temperature.The potential yield of winter wheat and summer maize showed a decrease trend during the period from1961to2012. The main constraint of potential yield of winter wheat in temporal scale is the decrease in radiation, and the reason for the decrease of the potential yield of summer maize are decrease in radiation and increase in temperature.2. There exists gap among farmers’actual yield, attainable yield, and potential yield, which can demonstrate that there’s room for the increase of crop production in HFR. The area weighted average winter wheat yield gap between potential yield and actual yield was4396kg/hm2at county level, while the area weighted average summer maize yield gap was5441kg/hm2. The area weighted average yield gap of winter wheat and summer maize that can be narrowed were2319and2627kg/hm2, respectively. The yield gap thant can be narrowed show significant difference ambng7sub-farming regions. The area weighted average farmers’yield can reached74.2%and74.7%of attainalbe yield for winter wheat and summer maize in HFR. The yield gap was determined by natural resources and econical input which were different in each sub-farming region. Increasing economical and technical input can decrease the difference among7sub-farming regions to narrow rational yield gap.3. Approriate nitrogen management can narrow the yield gap significantly, however, the effect of nitreogen application was determined by climate and cultivar. The farmers’ nitrogen application to winter wheat and summer maize were unreasonable. The farmers’application of nitrogen to winter wheat was excess than the optimal yield which was simulated and analysed by DSSAT model, while the farmers’application of nitrogen to summer maize was inadequate. When there’s no nitrogen application, the attainable winter wheat yield can be decreased by28%under severe water deficit years than that under light water deficit years. The N fertilisition can increase up to41.5%of winter wheat yield, and37.7%of summer maize yield compared to no N fertilisition. There’s up to33.5%of winter wheat yield gap and55.8%of summer maize yield gap that can be narrowed with the application of N fertilisition. Replacement of cultivars, improvement of soil quality and enhancement of management practice can narrow the yield gap which can’t be narrowed by nitrogen management. |
