水氮耦合对黑土稻田土壤呼吸与碳平衡的影响

为探明不同水氮耦合方式对东北黑土区稻田碳循环的影响,以黑龙江省黑土稻田为研究对象,于2018年进行大田试验,试验设置常规灌溉(F)与控制灌溉(C)两种灌水方式,全生育期施氮量设置0、85、110、135 kg/hm24个水平(N0、N1、N2、N3),测定了8种不同水氮耦合方式下水稻不同生育期平均土壤呼吸速率、微生物呼吸速率和根呼吸速率的变化以及水稻收获后各器官的固碳量。结果表明,水稻植株总固碳量为446.49~716.92 g/m2,各处理水稻收获后各器官固碳量从大到小依次为穗、茎、叶、根,分别占植株总固碳量的53.69%~59.44%、27.42%~30.12%、7.24%~8.96%、4.71%~8.35%。控制灌溉模式能提高水稻植株固碳量,其中CN2处理的总固碳量最大。相同施氮量、控制灌溉模式下,茎、叶、根固碳量均大于常规灌溉模式,除CN0处理穗固碳量低于FN0处理外,其余相同施氮量、控制灌溉模式下的穗固碳量均大于常规灌溉模式。不同水氮耦合方式下,水稻从返青期至乳熟期各生育期平均土壤呼吸速率、微生物呼吸速率、根呼吸速率均呈先升高、后降低的趋势,且均在分蘖期达到峰值。除返青期外,与不施肥处理相比,施肥后各生育期平均土壤呼吸速率、微生物呼吸速率和根呼吸速率均增大,且随着施氮量的增加而增大。控制灌溉模式下各施氮量处理水稻各生育期(除返青期外)平均土壤呼吸速率、微生物呼吸速率和根呼吸速率均高于常规灌溉模式下相同施氮量处理。8种不同水氮耦合方式下黑土稻田均表现为较强的碳“汇”,控制灌溉模式能够增加碳“汇”强度,其中CN2处理碳“汇”强度最大。本研究结果可为提高黑土稻田固碳减排潜力提供理论基础,为估算区域乃至全球碳平衡提供数据支撑。

Effects of Water and Nitrogen Coupling on Soil Respiration and Carbon Balance in Black Soil Paddy Field

In order to find out the effect of different water and nitrogen coupling methods on the carbon cycle of paddy fields in the black soil area of Northeast China,the field experiment was conducted in the black soil paddy field in Heilongjiang Province.Field irrigation experiments were conducted in 2018.The conventional irrigation(F)and controlled irrigation(C)were used as two irrigation methods.Four N application rates:N0(0 kg/hm2),N1(85 kg/hm2),N2(110 kg/hm2)and N3(135 kg/hm2)were set in the whole growth period.Average soil respiration,microbial respiration and root respiration rates of rice under eight different water-nitrogen coupling modes were measured during the period from re-greening stage to milky stage and carbon sequestration of rice organ were measured after harvesting.The results showed that the total carbon sequestration of rice plants was 446.49~716.92 g/m2,of which the total carbon sequestration of CN2 treatment was the largest.At the same time,the carbon sequestration of rice organs after harvest from large to small was in the order of panicle,stem,leaf and root.The average carbon sequestration of four organs accounted for 53.69%~59.44%,27.42%~30.12%,7.24%~8.96%and 4.71%~8.35%of the total carbon sequestration of rice plants,respectively.Controlled irrigation mode could increase carbon sequestration of rice.Under the same nitrogen application rate,carbon sequestration of stem,leaf and root organs under controlled irrigation mode was higher than that under conventional irrigation mode.Carbon sequestration of panicles under controlled irrigation was higher than that under conventional irrigation except that of CN0 treatment,which was lower than that of FN0 treatment.The average soil respiration rate,microbial respiration rate and root respiration rate of rice were increased first and then decreased under all water-nitrogen coupling modes,and reached the peak at tillering stage.Compared with non-fertilization,the average soil respiration,microbial respiration and root respiration were increased after applying fertilization,and increased with the increase of nitrogen application,except the period of seeding.The average soil respiration rate,microbial respiration rate and root respiration rate of rice under controlled irrigation mode were higher than those under conventional irrigation mode at all growth stages,except the period of seeding.The carbon sink intensity of black soil paddy field was stronger under different nitrogen application coupling modes,but the carbon sink intensity was different among different treatments,and the carbon sink intensity of CN2 treatment was the largest.The research results can provide the necessary theoretical basis for improving carbon sequestration and emission reduction potential of black soil paddy field,and provide data support for estimating regional and global carbon balance.