| Biochar is a stable,carbon-rich coproduct of pyrolysis by organic materials such as crop straw,kitchen waste,etc.,through a certain process,in the case of no oxygen or limited oxygen,high temperature.At present,some studies have found that biochar amendment in field can not only improve soil environment and change soil microbial community,but also have a series of effects on crops,such as improving crop growth,improving root system structure,and even changing plant defence-related gene expression.Therefore,the agricultural use of biochar,by changing a series of characteristics of crops and their soil environment,will inevitably affect plant herbivores on crops indirectly.However,researches about these are rarely reported at present.Therefore,the purpose of this thesis is to explore the effects of biochar amendment in soil on herbivorous,so as to provide a theoretical basis for a more systematic evaluation of biochar and a theoretical basis for incorporating biochar into integrated pest management.The main results and conclusions are as follows.1.Effects of biochar amendment to soils on life history traitss of S.avenaeTo examine the effect of biochar types and application rates on life history characteristics of aphid Sitobion avenae,this study tested three types of biochar derived from feedstock of corn straw(CB),rice straw(RB)or wheat straw(WB),each at three amendment rates:0(the control),1.5%,3%and 5%.Following attribute are measured:pre-larviposition time,lifetime fertility and life span.Biochar application had no significant effects on pre-larviposition time and life span,while affected lifetime fertility.Compared to the control,the fertility reduced by 12.08%at 1.5%amendment of CB,20.23%at 5%of RB,and 17.24%at 5%of WB.2.Effects of biochar amendment on population growth of S.avenaeTo examine the effect of biochar amendment type and application rate on population growth of S.avenae,this study tested three types of biochar derived from corn straw(CB),rice straw(RB)or wheat straw(WB),each applied at four amendment rates:0,1.5%,3%and 5%.Following results were obtained.Compared to the control,application of CB,RB and WB at 5%decreased the number of aphids by 30.28%,25.90%and 26.38%,respectively.Young aphids accounted for a major part in a population under biochar amendment than under the control.The results suggest that biochar application can reduce aphid population size.3.Effects of biochar amendment on aphid population growth and natural enemy abundnaces in the fieldTo examine the effect of biochar amendment on wheat aphid and its natural enemy populations in the field,this study tested biochar derived from wheat straw in field experiments at two sites.At Suzhou site,biochar application at the rate 20 t/hm2 was randomly made to three of six 9 m2 plots with remaining three plots as the control.At Nanjing site,biochar was applied to one 1.5 hm2 plot at 20 t/hm2 and another similar sized plot was used as the control.The sampling of aphid populations showed that that aphid population size decreased over three years in biochar applied plots compared to the control at both sites.The decrease was 13.78%at Suzhou site and 44.66%at Nanjing site.Abundances of natural enemies of aphids did not vary between biochar applied plot and the control.The results suggest that biocharapplication increase the ratio of beneficial insects to pests in number,so increasing biological control effects.4.Effects of biochar amendment on feeding behaviors of S.avenaeTo examine the effect of biochar amendment in type and application rate on feeding behaviors of aphid S.avenae,this study tested three types of biochar derived from either corn straw(CB),rice straw(RB)or wheat straw materials(WB),each at four rates of amendment:0,1.5%,3%and 5%.The electrical penetration graph technology was used to record waveform duration and frequency of stylet penetration activities.Biochar amended in soil impaired feeding behavior of aphids by decreasing total duration of the waveforms corresponding to phloem-sucking activities and increasing the frequency of those corresponding to intracellular puncturing behaviors.The results suggest that biochar application decreases feeding efficiency of aphids on wheat.5.Effects of biochar amendment on nutrient chemicals in wheatTo examine the effect of biochar type and application rate on nutrient chemicals in wheat,this study tested three types of biochar derived from either corn straw(CB),rice straw(RB)or wheat straw(WB),each at four amendment rates:0,1.5%,3%and 5%.Biochar amendment decreased the contents of N,P,soluble sugars and free amino acid,which have the function of enhancing feeding activity,and increased Si and K,which are sucking inhibitors.These results suggest that biochar application can alter plant uptake of nutrient elements and chemicals associated with feeding activities.6.Effects of biochar amendment on plant defense-related gene expressionTo examine the effect of biochar amendment on plant defense-related gene expression,biochar derived from rice straw was amended to soils at four rates:0(the control),1.5%,3%and 5%.Four defense-related gene expression,involved in salicylic acid(SA)and jasmonic acid(JA)pathway,were analyzed with RT-PCR.Compared to the control,biochar application increased the expression of four defense-related genes(AOS,LOX,PAL and PR)in wheat plants with extension of feeding time by aphids.the results suggest that biochar application enhances herbivory-induced wheat defenses. |
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