Effects Of Fertilization On Yield Sustainability And Greenhouse Gas Emissions Under Wheat-soybean Rotation System

Wheat-soybean rotation system is an important food system.Meanwhile,global wheat and soybean production is projected to increase by 40%and 80%,respectively,in 2050 to meet the growing demand.Therefore,sustainable improvement in the productivity of this rotation system is critical for global food security.Increased anthropogenic greenhouse gas?GHG?emission is the main driver of global warming.And agriculture accounts for 19%-29%of global anthropogenic GHGs.Thus,mitigating GHG emissions from croplands is of great significance.Fertilization for improving and stabilizing crop yield,significantly affects GHG emissions from croplands.Thus,understanding the effects of fertilization regimes on crop yield sustainability and GHG emissions are important to ensure food security and mitigate climate change.Though several studies have reported the effects of fertilization on crop yield and greenhouse gas emissions,less have been studied on wheat-soybean rotation system and the residual effects of fertilization in this system.Additionally,there is also a lack of relevant studies on the net greenhouse effects.Using two thirty year long-term fertilization experiments in Xiao County and Mengcheng County,a study was conducted to investigate the effects of different fertilizer application?i.e.sole organic fertilizer,balanced chemical NPK fertilizer and chemical NPK plus different organic materials?on yield sustainability and GHG emissions in a wheat-soybean rotation system.The objective was to provide a theoretical basis for the implementation of fertilization regimes for higher yield while lowering carbon emissions in the rotation system in Huang-Huai-Hai area,China.The main results were as follows:?1?The yield and sustainability under treatment of NPK combined with manure were better compared to the other treatments.NPK combined with organic materials recorded higher yield and yield sustainability than that of sole NPK fertilizer and sole organic fertilizer.The yield under treatment of NPK combined with manure was highest among all the treatments.Compared with NPK treatment,treatment of NPK plus manure increased wheat and soybean yield by 3.0%and 8.5%,respectively,under equal nitrogen input condition.The increase rate was 18.9%and 35.0%,respectively,under higher nitrogen input condition.?2?Partial replacement of chemical nitrogen fertilizer with organic fertilizer improved nitrogen use efficiency of the crops.In comparision with NPK treatment,NPK combined with organic materials increased the annual nitrogen use efficiency under equal nitrogen input condition,while NPK combined with organic materials decreased nitrogen use efficiency under higher nitrogen input condition.?3?The application of organic materials especially manure during the wheat cropping season significantly stimulated the soil GHG emissions.Compared with NPK treatment,the cumulative emissions of CO₂ and N₂O increased by 28.1%-35.9%and 17.1%-64.3%,respectively,with the application of manure alone or NPK combined with manure.?4?Fertilization during the wheat season had significant residual effects on emissions of CO₂,N₂O and CH₄ in the succeeding soybean season when no fertilizer was applied.of Organic materials application especially manure stimulated soil CO₂ and N₂O emissions during soybean season.The cumulative emissions of CO₂ and N₂O were increased by 10.7%-59.5%and 41.2%-115%,respectively,during application of manure alone or NPK combined with manure,compared with NPK treatment.?5?Application of organic materials improved soil carbon sequestration and reduced net greenhouse effects.In comparison with the NPK treatment,application of organic materials enhanced soil carbon sequestration,reduced the net global warming potential,greenhouse gas intensity and the greenhouse gas emissions per unit of soil fertility improvement in wheat-soybean system.Among these treatments,NPK plus cattle manure recorded the lowest net greenhouse effects.In conclusion,NPK combined with cattle manure significantly improved and sustained wheat and soybean yield while enhancing soil carbon sequestration and mitigating the net greenhouse effects.This makes it a more reasonable choice of fertilizer management under wheat-soybean rotation system.