长期秸秆还田对水稻土团聚体及氮磷钾分配的影响

Effects of long-term straw returning on distribution of aggregates and nitrogen,phosphorus,and potassium in paddy

为了探究秸秆还田配施化肥条件下水稻土团聚体组成及其稳定性,以及土壤团聚体氮、磷、钾养分特征,本研究进行了34年定位试验,设置无肥(CK)、化肥(NPK)、秸秆还田+化肥(NPKS)3个处理。采用湿筛法测定0~20、20~40 cm土层水稳性团聚体组成,量化分析氮、磷、钾养分分配特征、贡献率和活化度。结果表明:水稻土水稳性团聚体以>2 mm和0.25~1 mm粒级为主,<0.053 mm粒级含量最低。与CK相比,在0~20 cm和20~40 cm土层,NPKS处理增加了>2 mm和1~2 mm团聚体含量,降低了0.053~0.25 mm和<0.053 mm团聚体含量;NPK处理在0~20 cm土层也表现出与NPKS类似的规律。NPKS较NPK处理0~20 cm和20~40 cm土层团聚体平均重量直径(MWD)提高3.9%~15.5%,几何平均直径(GMD)提高6.3%~41.7%,不稳定团粒指数(E_(LT))降低5.7%~28.7%。NPKS处理显著提高了团聚体全氮、有效磷和速效钾含量,尤其是直径>0.25 mm部分,但对碱解氮和全钾的提升效果与NPK处理差异不显著。水稻土团聚体养分贡献率受到其团聚体组成的影响,NPKS处理明显增大了>1 mm团聚体氮、磷、钾养分贡献率。秸秆还田配施化肥可提高0~20 cm和20~40 cm土层团聚体稳定性,并增加团聚体氮、磷、钾养分含量,尤其是大团聚体(>1 mm)。该研究结果为调节土壤碳氮比来保障稻田土壤质量和资源可持续发展提供了科学依据。

In order to understand the composition and stability of soil aggregate in paddy filed,as well as the changes of soil aggregate-associated nitrogen(N),phosphorus(P)and potassium(K)after straw addition combined with chemical fertilization,soil samples were collected from a 34-year positioning experiment with three treatments,including no chemical fertilizer(CK),chemical fertilizer only(NPK),and straw addition plus chemical fertilizer(NPKS).The composition of water-stable aggregates at the soil layers of 0-20 cm and 20-40 cm were analyzed with the wet sieving method,as well as the distribution characteristics,contribution rate and activation rate of soil aggregate-associated N,P,and K.Results showed that the fractions of>2 mm and 0.25-1 mm aggregates dominated the soil water-stable aggregates in paddy field,while the contribution of<0.053 mm aggregates was lowest.Compared with CK,NPKS treatment increased the contents of>2 mm and 1-2 mm aggregates at the layers of 0-20 and 20-40 cm,and reduced the contents of 0.053-0.25 mm and<0.053 mm.Similar result in NPK treatment was observed at the layer of 0-20 cm.Compared with tat under the NPK treatment,mean weight diameter(MWD)and geometric mean diameter(GMD)increased by 3.9%-15.5%and 6.3%-41.7%in NPKS treatment,respectively.However,the unstable aggregate index(E_(LT))reduced by 5.7%-28.7%in the NPKS treatment.NPKS significantly increased the contents of total N(TN),available P(AP),and available K(AK)in soil aggregates,especially in the>0.25 mm aggregates.There were no significant diffe-rences about alkali-hydrolysable N(AN)and total K(TK)between NPK and NPKS treatments.The nutrient contribution of soil aggregates in paddy field was affected by aggregate composition.NPKS significantly increased the contribution of AN,AP,and AK within>1 mm aggregates.In all,straw addition combined with chemical fertilizer could increase the stability of soil aggregates at the layers of 0-20 cm and 20-40 cm,and increase the contents of soil aggregate-associated N,P and K,especially for the>1 mm aggregates.Our results provided insights into ensuring soil quality and sustainable development of resources in paddy field by adjusting the ratio of soil C to N.