氮肥减量配施生物炭对黄壤稻田土壤有机碳活性组分和矿化的影响

Effects of chemical N fertilizer reduction combined with biochar application on soil organic carbon active components and mineralization in paddy fields of yellow soil

化肥减施增效有助于农业的可持续发展。本研究用等氮量生物炭替代化肥氮,设置0、10%、20%、30%、40%(CK,T1~T4)5个替代比例,在水稻收获后采集土壤样品进行室内分析,研究氮肥减量配施生物炭对黄壤稻田土壤有机碳活性组分和矿化的影响。结果表明:氮肥减量配施生物炭均可显著提高土壤有机碳(SOC)含量,且与生物炭配施量呈正比。氮肥减施20%条件下,土壤微生物生物量碳(MBC)和易氧化碳(ROC)含量均最高,分别为293.68和250.00 mg·kg-1,土壤可溶性碳(DOC)含量最低。SOC矿化速率在培养的第3天达到最高,前期(第3~6天)迅速下降,中期(第6~18天)缓慢下降,后期(第18~30天)趋于稳定,矿化速率随时间的动态变化符合对数函数;SOC累积矿化量和累积矿化率分别为0.66~0.86 g·kg-1和2.9%~4.0%,均以T2处理最低。稻谷产量随氮肥减施比例的增加呈先增加后下降趋势,T2处理最高,比CK显著增加了13.4%。本试验条件下,化学氮肥减量20%配施适量生物炭(5 t·hm-2)可有效提高SOC、MBC、ROC含量和水稻产量,降低SOC累积矿化量和累积矿化率,增强土壤固碳能力,是贵州黄壤稻田土壤固碳培肥的较好选择。

Reducing the application of chemical fertilizer and increasing fertilizer efficiency can contribute to the sustainable development of agriculture.To evaluate the impacts of N fertilizer reduction and biochar application on soil organic carbon active components and mineralization in yellow soil,an experiment was carried out with five different substitution rates of chemical N fertilizer by biochar under the same rate of N input,i.e.,0,10%,20%,30%,40%(CK,T1-T4).The results showed that chemical N fertilizer reduction combined with biochar application could significantly improve soil organic carbon(SOC),the magnitude of which was proportional to the amount of biochar application.Under the condition of 20%substitution rate(T2),soil microbial biomass carbon(MBC)and readily oxidized carbon(ROC)were the highest with 293.68 mg·kg-1 and 250.00 mg·kg-1,respectively,but the concentration of soil dissolved organic carbon(DOC)was the lowest.SOC mineralization rate reached the highest on the third day of incubation.Then,it decreased rapidly in the early period(day 3 of incubation to day 6),decreased slowly in the middle period(day 6 of incubation to day 18),and stabilized in the later period(day 18 of incubation to day 30).There was a logarithmic relationship between mineralization rate of soil organic carbon and incubation time.SOC cumulative mineralization amount and cumulative mineralization rate were the lowest in the T2 treatment with 0.66-0.86 g·kg-1 and 2.9%-4.0%,respectively.As the substitution rate of chemical N fertilizer by biochar increased,rice yield increased firstly and then decreased.Rice yield in the T2 treatment was the highest,which increased by 13.4%compared with the CK.The substitution of 20%chemical N fertilizer with biochar(5 t·hm-2)could effectively improve the contents of SOC,MBC,ROC,and rice yield,reduce the cumulative mineralization amount of organic carbon and cumulative mineralization rate,and enhance the capacity of soil carbon sequestration.Hence,it could be the most effective fertilizer practice for improving soil fertility and rice yield in paddy field of yellow soil in Guizhou Province.