Study On Reduction Of Soil Nitrogen Loss By Biodiesel Co-products

With the gradual depletion of fossil fuels,the constant outbreak of energy crisis and constant occurrence of extreme weather caused by climate change,the need for new,renewable and clean energy sources has become extremely urgent.Biodiesel as an alternative fuel to fossil fuels is getting more and more attention in recent years,the biodiesel industry has become one of the most rapidly growing industries,but the huge amount of biodiesel production has also produced a large amount of biodiesel co-products(BCP).Find a way to deal with BCP more economically and efficiently has become a serious issue.Some researchers tried to add BCP as an additive to the soil and found that it could greatly reduce the content of nitrate in soil.In order to take further step to study the influence of BCP brings into soil nitogen.This research has conducted three major expriments to study how the BCP application affects soil nitrogen,soil microorganisms and plants,trying to find out the feasibility of applying it to practical agriculture production applications.The main results are as follows:(1)After the BCP application,both microbial biomass and microbial activity have rapidly increased in a very short time.We assume it was caused by rapid assimilation of BCP by microorganisms,it can be seen that BCP is probably a high-quality carbon source for microorganisms.At the same time,the content of NO3-in the soil was greatly reduced,at 1500 ?g BCP g-1 soil level,each treatment in the three soils reduced the NO3-concentration by about 98%,a strong nitrate immobilization was produced by BCP,but the concentration of NH4+ did not change significantly.At the same time,by comparing the amount of NO3 reduction and CO2 increase in the soil,the C/N ratio between them was found to be close to 24,shows that microorganisms maybe use NO3-as a nitrogen source in soil.(2)By comparing the effectiveness of microorganism assimilating glycerin and BCP,little difference was found between glycerol and BCP,when exogenous nitrogen was added,the difference between them was amplified and glycerol was a relatively better carbon source.Microorganisms need to use inorganic nitrogen as one of the nitrogen source in the soil while using BCP for metabolism and reproduction,during this process,a large amount of soil mineral nitrogen was converted to organic nitrogen and stored in microbial cells,this process created the decrease of soil nitrate,we assume this is the mechanism of how BCP decreases soil nitrate content.In the later period,we speculated due to insufficient soil nutrients to maintain this huge part of this extra microorganism,then caused a large number of deaths,organic nitrogen was released by the cell body remineralization,and this part of nitrogen will turn into inorganic nitrogen and returned back into the soil,it can may explain why soil inorganic nitrogen inceased a little during this period.Ryegrass experiments show that plants maybe could use this part of the nitrogen.(3)Application of BCP can reduce the loss of dissolved organic nitrogen,the effect is similar to that of BCP on nitrate fixation,this is may be attributed to the fact that large numbers of soil microorganisms' reproduction after BCP application,and this part of microorganisms consumed a lot of small molecules of organic nitrogen.The addition of BCP itself would hardly be leached from topsoil,only 0.018%of BCP is lost to the leachate as DOC.BCP has negative effect to the growth conditions of the wheat,it reduces the nitrogen utilization rate of 13%compared with the control,maybe it was caused by the strong nitrogen fixation effect in the early stage of wheat growth after BCP addition.This research shows that application of BCP can be used as an efficient measurement to reduce the loss of soil nitrogen in agricultural production in the future.