Research On Climate-Smart Water And Nitrogen Management Measures For Staple Crops In Beijing-Tianjin-Hebei Region Based On APSIM Model

The Beijing-Tianjin-Hebei region is an important wheat and maize production base in China.At the same time,the water-food-environment contradictions in this area are also sharp.Optimizing a climate-smart water and nitrogen management measure with less water consumption,high yield and low greenhouse gas emission will improve the abilities of agricultural production to cope with climate change in this area and provide a scientific basis for ensuring national food security.In this paper,the main grain crops in the Beijing-Tianjin-Hebei region were taken as the research object,and three planting patterns,four irrigation treatments and four fertilizer treatments were set.The model simulation,cluster analysis,mathematical statistics and other technical methods were used in this study.The APSIM crop model was optimized based on meteorological,soil and crop observation data from 1981 to 2020,and the applicability of APSIM model in the Beijing-Tianjin-Hebei region was studied.Then,the temporal and spatial variations of crop yield,evapotranspiration and water use efficiency under different irrigation treatments were analyzed.Soil organic carbon,nitrous oxide,greenhouse gas emission,yield and greenhouse gas emission intensity under different fertilization treatments were quantitatively evaluated,and the differences of crop yield,water use efficiency and greenhouse gas emission under different irrigation and fertilizer management measures were discussed.Finally,the optimal climate-smart irrigation and fertilizer management measure for staple crops in the Beijing-Tianjin-Hebei region were optimized based on the k-means cluster analysis to select.The main conclusions were as follows:（1）Under the three planting patterns,the irrigation measures with the highest annual average water use efficiency and yield in the Beijing-Tianjin-Hebei region from1981 to 2020 were W3 treatment and W4 treatment.Under W3 irrigation,the average annual water use efficiency in the Beijing-Tianjin-Hebei region was the highest,the maximum was 13.9 kg·ha^-1·mm^-1.The average annual yield under W4 irrigation was24579.2kg·ha^-1.However,the average annual evapotranspiration under W1 irrigation treatment was the lowest,with the value of 1549.5mm.Under W3 irrigation,the WUE in the northern Beijing-Tianjin-Hebei region was lower,while the WUE distribution in other regions was more uniform.Under W4 irrigation,the yield in the northern part of Beijing-Tianjin-Hebei region was lower,while the yield distribution in other regions was more uniform.The high-value evapotranspiration area under W1 irrigation was distributed in the southeastern part of Beijing-Tianjin-Hebei and Shijiazhuang region,while the low-value area was distributed in the northern part of Beijing-Tianjin-Hebei region.（2）Under the three planting patterns,the fertilization measures with the minimum annual average greenhouse gas emissions and the highest yield in the Beijing-Tianjin-Hebei region from 1981 to 2020 were F2 treatment and F4 treatment.Under F2fertilization treatment,the average annual greenhouse gas emission intensity in the Beijing-Tianjin-Hebei region was the lowest,with the value of 0.06 kg·CO_2-eq·kg^-1.The maximum average annual yield under F4 fertilization treatment was 25887.63 kg·ha^-1,and the average annual greenhouse gas emission of soil under F1 fertilization treatment was the smallest,with the value of 0.36 Mg·CO_2-eq·ha^-1.The low values of greenhouse gas emission intensity under F2 fertilization treatment were mostly distributed in the northern,western and eastern parts of the Beijing-Tianjin-Hebei region.The low-value areas of yield under F4 fertilization treatment were distributed in the northern part of the Beijing-Tianjin-Hebei region,while the high-value areas were mostly distributed in the southern and central parts of the Beijing-Tianjin-Hebei region.Soil greenhouse gas emissions under F1 fertilization treatment were generally higher in the southern region of Beijing,Tianjin and Hebei,followed by the central region and lower in the northern region.（3）Based on the comprehensive evaluation of water use efficiency,yield and greenhouse gas emissions,the F3 fertilization treatment and W3 irrigation treatment were considered the best irrigation and nitrogen management measures in the Beijing-Tianjin-Hebei region.The overall variation ranges of yield under these measures were9031.85kg·ha^-1～27226.01kg·ha^-1.