外源氮在中、低肥力红壤中的转化与去向研究

采用盆栽15N示踪技术,研究了外源化肥氮和有机氮在中、低肥力红壤中的转化过程及其在土壤团聚体中的分配特征。结果表明:无论是低肥力还是中等肥力红壤上,化肥与有机肥配施都能显著增加土壤硝态氮、微生物生物量碳、氮及酶活性,且显著提高氮肥在土壤中的残留率,减少氮肥损失。相同施氮条件下,小麦生育期内中等肥力红壤上微生物生物量碳、氮及硝态氮含量分别相当于低肥力土壤的1.8、1.3和2.0倍。中等肥力红壤上尿素的施入对小麦生育期土壤硝态氮无影响,而低肥力红壤上施用尿素使土壤硝态氮含量提高了5.7倍。施肥可以显著提高低肥力红壤上小麦的地上部吸氮量,相当于不施肥的2.1~3.3倍,但对于中等肥力红壤,不同施氮条件对小麦的地上部吸氮量无明显影响。施入有机肥可以显著增加土壤各粒级团聚体中外源氮的残留量,是单施化肥的2.1~5.0倍。与单施化肥氮相比,有机氮或与有机肥配施的化肥氮优先进入到大团聚体中,而外源氮在微团聚体和粉粘粒中的残留与分配并无明显差异。本研究说明有机肥或化肥与有机肥配施能有效降低氮肥的损失,提高氮肥在土壤中的保存,特别是对于中等肥力的土壤,有机肥的配合施用对于后季作物的生长具有重要意义。

Exogenous nitrogen transformation and fate characteristics under different fertility red soils

The exogenous organic and inorganic nitrogen transformation process and its distribution characteristics in soil aggregate were studied in a pot 15N labeling techniques under low and moderate fertility levels with different fertilizer in red soil.Results showed that soil nitrate nitrogen,microbial biomass carbon and nitrogen,and enzymatic activity were significantly increased with chemical and organic fertilizer combination,whatever improving nitrogen fertilizer residue and reducing the loss in low or moderate fertility red soil.The content of microbial biomass carbon,nitrogen and nitrate nitrogen in moderate fertility red soil was equivalent to 1.8,1.3,and 2.0 times of low fertility red soil in the whole growth period under the same nitrogen application treatment,respectively.Urea application had no significant effect on nitrate nitrogen content in moderate fertility red soil,but it was increased by 5.7 times in low fertility red soil.N fertilizer application could significantly improve aboveground nitrogen uptake of wheat in low fertility red soil,which were 2.1~3.3 times as control,but there were no significant differences among different nitrogen application treatments in moderate fertility red soil.Organic fertilizer could significantly increase exogenous nitrogen residue in soil aggregates,which was 2.1~5.0 times of single chemical fertilizer.Compared with single nitrogen fertilizer,organic nitrogen or inorganic nitrogen combined with manure was prior to entering into the macro aggregate,but the residue and distribution of exogenous nitrogen had no obvious difference in micro aggregate and silt and clay.This research indicates organic fertilizer or combined with inorganic fertilizer could effectively reduce nitrogen loss and improve the nitrogen preservation in soil,especially organic inorganic fertilizer combination could significantly promote the growth of follow crops for the moderate fertility soil.