Water/Nitrogen Utilization And Nitrogen Translocation Of Cereal-legume Multi-cropping Systems In The North China Plain

The agriculture of the North China Plain is facing the problems of water resources shortage,land degradation,farmland ecology environment deterioration and agricultural ecological cost increase.Exploring the resource utilization of different planting patterns on the level of cropping systems is of great significance to achieve sustainable agricultural development.Based on the field,micro-plot and pot experiments,using 15N labeling technique,the presented study researched the crop growth,yield and water/nitrogen utilization in wheat-peanut double cropping system,explored the effects of the decomposition and nutrients release of peanut straw and utilization,transfer of nitrogen in multi-cropping system,clarified the transfer and distribution of rhizodeposition nitrogen and peanut straw nutrients in crop-soil-subsequent crop.On these basis,through the analysis of the current situation of straw resources and water resources utilization,the regional ecological adaptability evaluation was carried out on the wheat-peanut double cropping system to explore the efficient,ecological and sustainable cropping patterns suitable for the North China Plain.The main results are as follows:（1）Different peanut straw returning methods all increased the yield of cereal-legume multi-cropping system.Compared with no plant returning（NPR）,mean yields of wheat in two seasons under plant returning whole（PRW）,plant returning aboveground（PRA）and plant returning root（PRR）treatments were increased by 620.7 kg hm 2,531.8 kg hm^-2 and 262.2 kg hm^-2 respectively;peanut yields of the second season were increased by 566.5 kg hm^-2,284.1 kg hm^-2 and 203.1 kg hm 2,respectively;indicating that the yield of wheat-peanut double cropping system was promoted by peanut straw returning.（2）By identifying the different soil water active layer of 0-200 cm below the ground,the depth of soil water active layer under plant returning whole（PRW）and plant returning aboveground（PRA）treatments of wheat season were both 120cm and significantly deeper than no plant retuming（NPR）.There was no significant difference in peanut and wheat crop water use efficiency（WUE）in the first season;while after two successive peanut straw returning,WUE of wheat under different peanut straw returning methods in the second season were all significantly higher than no plant returning（NPR）,increased by 5.2%,3.8%and 1.0%for PRA,PRR and PRW,respectively.（3）Both pot and field experiments indicated that the treatment’s yield of peanut straw combined with reduced chemical nitrogen fertilizer（S+EN）was higher than treatments of conventional level of fertilization（CK）and straw returning with conventional level of fertilization（S+CK）;compared to CK and S+CK,the yield of S+EN increased by 139.6 kg hm^-2 and 186.6 kg hm 2,respectively in potted trials,223.7 kg hm^-2 and 82.6 kg hm^-2,respectively in field trials.Despite the fact that the above difference was not significant,it suggested that peanut straw returning under reduced nitrogen input had no negative effect on the yield of succession crop.（4）The micro-plot experiment revealed that ratio of rhizosphere deposited nitrogen to total nitrogen was higher in peanut than in wheat,which was 17.68%and 9.13%,respectively.The amount of nitrogen accumulated in peanut straw was 80.7 kg hm 2,and the amount of rhizosphere deposited nitrogen was 35.7 kg hm^-2;the results of nitrogen transferred from peanut to subsequent wheat showed that the highest amount of nitrogen absorption was 4.3 kg hm^-2（PRW）,in which the nitrogen derived from the peanut rhizosphere deposition was 1.9 kg hm^-2,and from the peanut straw residue was 2.4 kg hm^-2;for PRA and PRR the nitrogen derived from peanut straw residue were 1.7 kg ha-1 and 0.9 kg hm^-2,respectively.（5）Results of regional groundwater footprint showed that if replacing the traditional summer maize with summer peanut.The groundwater footprint of wheat-peanut double cropping system was 7.54×10-7 km2 per m2,which was 4%lower than that of the existing winter wheat-summer maize double cropping pattern.On the basis of winter wheat-summer maize production area of the North China Plain,which was 3.5×106 km2 in 2014,if all replaced by winter wheat-summer peanut,the annual water footprint can be reduced by 1015.3 km2.（6）Peanut straw returning can improve the crop yield of wheat-peanut double cropping system,reduce nitrogen fertilizer and water resources consumption,and improve soil fertility in the North China Plain.Therefore,wheat-peanut double cropping could be a potential pattern in cropping systems adjustment of the North China Plain,and be of profound and lasting significance to the sustainable agriculture development.