| Exploring a low carbon production technology for wheat and maize rotation system in North China Plain is urgent to reduce the negative effects of agricultural production on the ecological environment and to close yield gap.In this study,a three-years field experiment was conducted to evaluate the effect on increasing crop yield and efficacy of various technologies mix,i.e.straw returning,different tillage mode,irrigation technology and nutrient management.Finally,the greenhouse gas mitigation associated with different technologies mix was evaluated by Life Cycle Analysis?LCA?method.The main results are as follows:1.The improved technologies mix can achieve annual yield of 19.38×103kg ha-1,which is 3027 kg ha-1 higher than farmers' traditional practices.Optimized tillage practice contributed a yield increase of 1262 kg ha-1,optimized irrigation could increase 344 kg ha-1 and optimized nitrogen fertilizer management practice increased 5211 kg ha-1.And the yield increase mainly resulted from improved root density and root length in 0-20cm soil profile,and also improved the micro structure of wheat root which helped to boost a higher leaf area index,increased photosynthetic rate and the grain filling rate.Secondly,the optimized irrigation and nitrogen rate not only well matched crop demand,but also accelerated dry matter redistribution,such as wheat filling rate was maintained at a high level?2.37 mg grain-1 d-1?in 25 days after flowering,16.2%higher than farmers' practices.2.Optimized technology system can greatly increase the nitrogen fertilizer use efficiency,maintain higher soil productivity and reduce nutrient loss.In this study,optimized irrigation and nitrogen management practices could improved nitrogen production efficiency from 28.32 kg kg-1 to 38.76 kg kg-1 and soil nitrate nitrogen content in 0?20cm and 20?40cm has increased by 12.15%and 23.70%respectively even when total nitrogen fertilizer input was reduced by 30%.The increased nitrogen in root zoon helps to reduce basal fertilizer for next season's crop.Secondly,optimized irrigation and nitrogen management could reduce nitrate leaching by 43.25%and is beneficial to establish an effective source-sink relationship of crop by regulating the vegetative growth and reproductive growth of crops.3.The optimized technologies can achieve better function on regulating soil water conversation and increase the water use efficiency and reduce the amount of irrigation.In North China plain,the annual water gap for wheat-maize rotation system is as high as 110-230mm.The improved technologies mix,for example no tillage in winter wheat combined with tillage in maize season can increase soil water storage by 64.32?95.70 mm in 0-150cm soil profile,andreduced 2-3 times irrigation for winter wheat.The irrigation water use efficiency reached 10.18 kg m-3,which is 2.15 times higher than farmers traditional practices.4.The integrated management practices can reduce greenhouse gas emissions by 1925 kg CO2 eq ha-1 y-1.Total GHG mitigation from reducing field tillage,associated with the saving agriculture inputs?electricity for irrigation,fuel for machine and nitrogen fertilizer?could be 434 kg CO2 eq ha-1 y-1.The other GHG mitigation from crop field were contributed by optimized tillage(314 kg CO2 eq ha-1 y-1),optimized irrigation(165 kg CO2 eq ha-1 y-1)and optimized nitrogen fertilizer(576 kg CO2 eq ha-1 y-1).In summary,the three-years field experiment revealed the mechanism of the integrated technologies mix and interaction of various technologies?nitrogen fertilizer,tillage and irrigation?on enhancing soil water andnitrogen transport and crop uptake under the specific climatic conditions in North China plain.In addition,we evaluated the effectiveness of these improved technologies on increasing yield,water and nutrient use efficiency and reducing greenhouse gas emissions and help to achieve a new balance between regional natural resource and crop production.. |
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