Evaluation Of Agricultural And Environmental Performance Of Combination Of Organic Sources And Chemical Fertilizer On Cropping Systems

Agricultural organic material was an important resource. The combined application of organic materials and mineral fertilizer was considered as an important agricultural production practice in increasing productivity, reducing fertilizer consumption and protecting environment in the future. However, the potential of this practice in increasing crop yield, replacing chemical fertilizer and enhancing the sustainability of cropping system is yet to be tested. In the current study, according to the literature data from32long-term field experiments in China, the effect of different agricultural management systems (organic or chemical fertilizer alone, and a combination of both) on crop yield and soil organic matter (SOM) was studied, firstly. And then, based on long-term experiment of various organic materials (Compost, Manure, Straw, Biogas-residues and Black carbon) recycling in North China Plain, the net global warmer potential (Net-GWP) and greenhouse gas intensity (GHGI) of different systems (various organic materials or chemical fertilizer alone, and the combinations of various organic materials or chemical fertilizer), were lizer) were investigated by using LCA methods. The major results as following:1) According to the results from32long-term field experiments in China, combined application of organic and mineral fertilizers than CK increased the yield of wheat, maize and rice by53%,40%and8%, respectively. While combined fertilizer and organic increased significantly wheat, maize and rice yields over three crops by29and8%on average than either organics or fertilizers alone. Overall, higher responses in terms of increased yield relative to initial value (TR ratio) and control plots (TNMR ratio) were found with combined organics and fertilizers in the sequence wheat (52%)> maize (40%)> rice (8%). Thus, regardless of crop species, the results suggest that organics and fertilizers combined increased productivity and enhanced sustainability of cropping systems.2) Addition of organic materials was also needed to build up SOM. Compared with CK, chemical fertilizer only, organic alone, and combination of both could increase SOM on average by8,18and23%. The higher SOM contents and control ratios in combined organics and fertilizers than (for dry land), or similar to those of organics alone (for dry-flooded and flooded systems) emphasizes the long-term benefits of combined-applications in supporting higher productivity and sustainability of the systems.3) In the experiment of various organic materials recycling in North China Plain:N2O emission showed seasonal trends with more emission in summer maize than winter wheat. The accumulative emission after10days of major agricultural practices such as fertilization accounted for46%of total emission of whole rotation period. Combined various organic materials with chemical fertilizer showed diverse trends in N2O emission. Contrast to no changes for combinations of biogas-residue and black carbon (BgRopt and BCopt) and reduction for straw (Sopt), combinations of compost and manure with chemical fertilizer (Copt and Mopt) increased significantly N2O emission than chemical fertilizer only.4) Application of various organic materials only led to negative Net-GWP and with lower crop yield; Chemical fertilizer system (Fopt) alone could increase yield on average by95%for wheat and32%for maize, but Fopt led to positive Net-GWP which showed cropping system were a carbon source; While combined various organic materials with fertilizer could get similar or higher crop yield, and with lower Net-GWP and GHGI than Fopt.5) Differences in agronomic productivity and greenhouse gas emission between various organic materials recycling systems could be found. BgRopt and Copt led to higher crop yield than Fopt and with negative Net-GWP. Similar BCopt showed more negative Net-GWP than BgRopt and Copt, but the crop yield were similar to Fopt. Mopt and Sopt could get similar crop yield to BgRopt and Copt, but Net-GWPs were positive for both of them.6) Negative Net-GWP for Copt, BgRopt and BCopt were due to higher accumulation in soil organic carbon (SOC), which could offside CO2-eq emission derived from soil N2O emission, fertilizer manufacture and transport, and energy consumption of agricultural practices during crop production.