添加秸秆对土壤矿质氮量、微生物氮量和氮总矿化速率的影响

采用室内恒温培养法,研究了在乌沙土上添加15N标记秸秆后,秸秆15N在矿质氮、微生物氮和土壤不同组分中的分配情况,并应用氮同位素库稀释法测定了秸秆在乌沙土上的氮总矿化速率。结果表明:将秸秆添加到土壤后,微生物氮量显著增加,而土壤矿质氮量在14天时迅速下降。随着秸秆的分解,秸秆15N进入矿质氮库和微生物氮库,矿质15N在第7 d时最高,占到添加秸秆15N的6.7%,微生物15N在第14 d最高,占到添加秸秆15N的18.1%,随后矿质15N和微生物15N量都下降。56 d时,仍有50.8%的秸秆氮没有分解掉,5.4%的秸秆15N进入土壤53μm~2 mm组分,15.5%进入2~53μm组分,14.6%进入小于2μm组分,有13.6%的秸秆氮损失掉。在培养开始时,乌沙土的氮总矿化速率为2.81 mg kg-1d-1,秸秆在乌沙土上的氮总矿化速率分别为2.50 mg kg-1d-1。

Nitrogen Mineralization of 15N Labeled Straw Added into the Paddy Soils in Tai-hu Region

An incubation experiment was conducted to study the distribution of 15N in mineral nitrogen,microbial biomass nitrogen and different soil fractions after 15N labeled rice straw was added into the wusha soil.Gross nitrogen mineralization rates of rice straw in the soil were also measured using 15N isotopic pool dilution technique.Results showed that soil mineral nitrogen decreased after 14 days of straw addition.Microbial biomass nitrogen increased.Mineral 15N was the highest at 7 days and accounted for 6.7% of added straw 15N.Microbial biomass 15N was the highest at 14 days and accounted for 18.1%of added straw 15N.Mineral 15N and microbial biomass 15N decreased between 14 days and 28 days after straw addition,which suggested that straw nitrogen was possibly lost at this time.At 56 days after straw addition,5.4% of added straw 15N existed in soil 53 μm-2 mm fraction,15.5% was in soil 2-53 μm fraction,and 14.6% was in < 2 μm fraction.50.8% of added straw 15N was present in straw and 13.6% was lost at 56 days.Gross nitrogen mineralization rate of the wusha soil was 2.81 mg kg-1 d-1 at 0.5 days after straw addition,respectively.Gross nitrogen mineralization rate of rice straw in the wusha soil was 2.50 mg kg-1 d-1 at 0.5 days after straw addition,respectively.