Biochar and organic substitution improved net ecosystem economic benefit in intensive vegetable production

Biochar amendment and substituting chemical fertilizers with organic manure(organic substitution)have been widely reported to increase crop production and decrease reactive nitrogen(Nr)loss including nitrous oxide(N_(2)O),nitric oxide(NO),and ammonia(NH3)emissions,and N runoff and leaching.However,few comprehensive evalua-tions have been performed on the environmental and economic aspects of biochar amendment or organic sub-stitution.Here,we studied the comprehensive effects of biochar amendment,organic substitution,and biochar amendment combined with organic substitution on crop production,Nr loss,and net ecosystem economic benefit(NEEB)in intensive vegetable production by integrating life-cycle assessment for Nr footprints,empirical models for NH3 volatilization and N runoff and leaching derived from peer-reviewed publications and validated by the current measurements and direct field measurement for N_(2)O and NO emissions during 5 consecutive years of vegetable crop rotations.Five fertilization treatments were applied(SN:synthetic fertilizer application;SNB:SN plus 20 t ha^(−1)biochar amendment;SNM:substituting 50%of chemical N fertilizer with organic manure;SNMB:SNM plus 20 t ha^(−1)biochar amendment;and CK:no fertilizer or biochar addition).Compared with the SN,the SNB increased vegetable yield(28.4%,p<0.05;interannually varying from−10 to 74.9%)and nitrogen use efficiency(29.2%,interannually varying from−39.7 to 150.4%),and decreased field Nr loss(45.4%,p<0.01;interannually varying from−40.3 to 78.4%),and thus improved NEEB by 7.1%;meanwhile,the SNM increased vegetable yield(11.6%,interannually varying from−5.4 to 27.1%)and nitrogen use efficiency(45.7%,p<0.05;interannually varying from 2.3 to 154%),reduced field Nr loss(34.9%,p<0.01;interannually varying from 8.4-39.0%),and thus improved NEEB by 17.8%(p<0.05)compared to the SN,being 56.0×10^(3)Chinese Yuan(CNY)ha^(−1)crop^(−1).Due to the high foreground Nr loss during organic manure production and high input costs of biochar production,the SNMB decreased the NEEB by 8.0%as compared to the SN.Moreover,the SNB and SNM improved vegetable qualities by increasing protein,soluble sugar,and vitamin C contents while decreasing nitrate content(p<0.05).Therefore,single application of biochar amendment or organic substitution would achieve better NEEB and product quality in vegetable production.

Methane and nitrous oxide emissions in rice-crab culture systems of northeast China

Rice-crab integrated ecosystem has been confirmed to improve the ecological environment and brought greater economic benefits.In order to know greenhouse gases methane(CH_(4))and nitrous oxide(N_(2)O)emissions in ricecrab system,they were quantified from a flooding rice field in northeast China,as affected by integrated ricecrab cultivation.Three treatments with three replications each were given:(1)RC1-rice with crab(megalopa),(2)RC2-rice with crab(juvenile),(3)RM-rice only.Seasonal CH_(4) and N_(2)O fluxes were measured by closed chamber method.Compared with RM treatment,RC1 and RC2 treatments greatly enhanced the cumulative seasonal CH_(4) emissions(by 36.8%and 29.2%,respectively),and reduced the cumulative seasonal N_(2)O emissions(by 28.2%and 19.7%,respectively).Across treatments,CH_(4) represented over 97%of total global warming potential(GWP)and as a result,RC1 and RC2 treatments significantly increased the GWP than RM treatment.Although the GWP was highest in RC1 treatment,it provided highest rice yield(8780 kg/ha)and net ecosystem economic budget(NEEB,23,159 Yuan/ha)over RM(7668 kg/ha,15,130 Yuan/ha)and RC2(8042 kg/ha,18,713 Yuan/ha)treatments.To summarize,cultivation of megalopa in rice field is a better strategy to optimize the economic and environmental benefits in northeast China.