长期施肥对稻田土壤可溶性有机氮和游离氨基酸剖面分异的影响

Effects of long-term fertilization on soil soluble organic nitrogen and free amino acid profile variations in paddy fields

为探讨长期不同施肥对稻田土壤可溶性有机氮(SON)和游离氨基酸(FAA)剖面分异的影响,阐明长期施肥稻田土壤SON和FAA的剖面迁移特性。以不施肥(CK)、单施氮磷钾化肥(NPK)、氮磷钾配施牛粪(NPKM)和氮磷钾结合秸秆还田(NPKS)4种处理的稻田长期(33年)施肥定位试验小区为研究对象,采用带总氮检测器的总有机碳分析仪(TOC-TN)、连续流动注射和氨基酸自动分析仪测定不同深度(0~20、20~40cm和40~60cm)土层SON、FAA及其组分的含量。结果表明:长期不同施肥水稻土SON含量剖面分异较明显,0~20、20~40cm和40~60cm土壤SON含量分别为24.14~49.80、11.30~13.86mg·kg-1和6.35~9.38mg·kg-1;不同处理0~20 cm土壤SON含量表现为NPKS>NPKM>NPK=CK,NPKS处理较NPK和CK分别提高67.1%和106.3%,NPKM处理较NPK和CK分别提高了28.5%和58.7%;不同土层SON与可溶性总氮(TSN)的比值为40.0%~69.3%。长期不同施肥水稻土FAA含量也存在较明显剖面差异,0~20、20~40cm和40~60cm土壤FAA含量分别为8.15~15.91、0.83~2.13mg·kg-1和0.69~0.99mg·kg^-1,FAA/SON比例的均值分别为35.3%、12.6%和11.2%;NPKM和NPKS处理0~20cm土壤均包含20种FAA,较CK和NPK处理增加了3种易分解的碱性氨基酸(鸟氨酸、赖氨酸和精氨酸);NPK、NPKM和NPKS处理20~40 cm土壤均包含10种FAA,较CK处理增加了3种中性氨基酸(缬氨酸、胱氨酸和苯丙氨酸),而40~60cm土壤则均包含7种FAA,较CK处理增加了2种中性氨基酸(异亮氨酸和胱氨酸);不同处理不同深度土壤FAA组成均以中性氨基酸占优势。研究表明:土壤SON、FAA含量与组分及其剖面分异和施肥模式密切相关,长期化肥配施牛粪和秸秆能增加0~20cm土壤SON、FAA含量且丰富FAA种类。

In order to investigate the effects of long-term fertilization on the profile differentiation of soluble organic nitrogen(SON)and free amino acid(FAA)in paddy soils,the leaching characteristics of SON and FAA in long-term fertilized paddy soils were determined.The SON contents,FAA amounts,and FAA types,in paddy field soil sampled at 0~20 cm,20~40 cm,and 40~60 cm depth,with a 33–year history of different fertilization,were analyzed.The fertilization regimes included control(CK),chemical fertilizer(NPK),cow manure combined with chemical fertilizer(NPKM),and rice straw combined with chemical fertilizer(NPKS).The results showed that the profile differentiation of SON contents varied greatly in the sampled soil layers.The SON contents in the 0~20 cm layer showed the following order after different treatments:NPKS>NPKM>NPK=CK.The soil SON in the 0~20 cm layer,under NPKM and NPKS treatments,included 20 types of FAA,and showed increases in three types of basic amino acids(ornithine,lysine,and arginine),compared with CK and NPK treatments.The soil SON in the 20~40 cm layer,under NPK,NPKM,and NPKS treatments,contained 10 types of FAA,and increased levels of three neutral amino acids(proline,cystine,and phenylalanine),compared with CK treatment.The soil SON in the 40~60 cm layer,under NPK,NPKM,and NPKS treatments,contained seven types of FAA,and increased levels of two types of neutral amino acids(isoleucine and cystine),compared with CK treatment.The FAA compositions in the paddy field under different treatments were dominated by neutral amino acids.Overall,profile differentiations of SON and FAA in the paddy fields were closely related to fertilization and SON contents,and both the amounts and types of FAA in the 0~20 cm layer of the paddy soil could be increased by long-term fertilizations with NPKS and NPKM.