长期不同施肥模式对大麦-双季稻田根际土壤有机氮组分的影响

根际土壤有机氮组分在土壤养分和作物氮素营养中具有重要作用。本研究依托长期（37年）定位施肥试验田，设置4个施肥处理：不施肥对照（CK）、单独施用化肥（CF）、秸秆还田+化肥（RF）和30%有机肥+70%化肥（OM），于晚稻成熟期测定大麦-双季稻田根际土壤基础理化性质、微生物量氮和有机氮组分（氨基酸态氮、氨基糖态氮、酸解氨态氮、酸解未知态氮、非酸解性氮）含量。研究表明：相对CK处理，RF和OM处理显著增加了稻田根际土壤有机碳、全氮、铵态氮和硝态氮的含量。RF和OM处理土壤微生物量氮含量分别比CK处理增加了19.8%和30.7%。酸解性氮作为根际土壤全氮的主体部分，占全氮的59.6%~72.1%；各处理根际土壤酸解性氮含量大小顺序表现为OM>RF>CF>CK。各施肥处理中，酸解有机氮中的氨基糖态氮、氨基酸态氮和酸解未知态氮含量均以OM处理最大，分别比CK处理增加139.3%、47.9%和110.0%；酸解氨态氮以RF处理最大，比CK处理增加69.9%。土壤有机碳、全氮、铵态氮、硝态氮与土壤氨基酸态氮、氨基糖态氮、酸解未知态氮以及微生物量氮均呈极显著（p<0.01）正相关。因此，秸秆、有机肥配施化肥均能有效提高大麦-双季稻田根际土壤的供氮能力，是改善稻田土壤肥力的有效手段。

Effects of long-term application of fertilizers on rhizosphere soil organic nitrogen fraction in barley-double cropping rice field

Rhizosphere soil organic nitrogen (N) fraction play an important role in soil nutrient and crop N nutrition. This study was based on a long-term (37 years) located fertilization experimental field, including four fertilization treatments: without fertilizer input as a control (CK), chemical fertilizer alone (CF), rice straw residue and chemical fertilizer (RF), and 30% organic manure and 70% chemical fertilizer (OM). At the maturity stage of late rice, the rhizosphere soil basic physical and chemical properties, microbial biomass N and organic N fractions, including amino acid N, amino sugar N, ammonia N, hydrolysable unknown N, non-hydrolysable N in barley-double cropping rice field were determined. The result indicated that RF and OM treatments significantly increased the content of soil organic carbon, total N, ammonium N and nitrate N in rhizosphere soil relative to the CK treatment. Soil microbial biomass N content was significantly increased by 19.8% and 30.7% with RF and OM treatments, respectively, compared to the CK treatment. Rhizosphere soil acid hydrolyzable N was the main component of soil total N, accounting for 59.6~72.1% of total N. The order of soil acid hydrolyzable N content in rhizosphere soil with all fertilizer treatments was showed OM>RF>CF>CK. Among the four fertilizer treatments, soil amino sugar N, amino acid N and hydrolysable unknown N contents were found to be significantly highest with OM treatment, increased by 139.3%, 47.9% and 110.1%, respectively, compared to CK treatment. Soil ammonia N content was significantly highest with RF treatment, with an increase of 69.9% over the CK treatment. Soil organic carbon, total N, ammonium N and nitrate N contents all showed a highly significantly positive correlation with soil amino acid N, amino sugar N, hydrolysable unknown N and microbial biomass N contents. Therefore, the application of rice straw or organic manure and chemical fertilizer is an effective practice for improving soil fertility, which can effectively increase the capacity of rhizosphere soil N supply in barley-double cropping rice field.