低磷石灰性土壤施磷和小麦秸秆后土壤微生物量磷的变化

通过室内培养试验，向低磷的石灰性土壤加入磷(0、25、50、100 mg P·kg^-1，KH₂PO₄)和小麦秸秆(5 g C·kg^-1)，25 ℃下培养90 d，研究在施肥和秸秆还田条件下土壤微生物量磷及微生物含磷量的变化特点，及其与土壤有效磷之间的关系.结果表明：土壤微生物量磷、微生物含磷量随加入无机磷量的提高而增加，最高分别为71.37和105.34 mg·kg^-1；除非加入足够的无机磷(如100 mg·kg^-1)，否则同时加入秸秆会降低土壤微生物量磷和微生物含磷量，这种效果在培养初期更加明显.土壤微生物量磷和微生物含磷量与土壤有效磷之间存在显著的正相关关系（相关系数R²分别为0.26和0.40，n=49）.加入的无机磷可迅速转化为微生物量磷，表观贡献率最高可达71%，秸秆的加入可使表观贡献率进一步提高.

Effects of applying inorganic P and wheat straw on the microbial biomass P and microbial P concentration in a calcareous soil with low concentration available P .

In an incubation test, a calcareous soil with low concentration of ava ilable P was amended with KH2PO4 (0, 25, 50, and 100 mg P·kg-1) and g round wheat straw (5 g C·kg-1), and incubated at 25 ℃ for 90 days. The aim was to investigate the change patterns of soil microbial biomass P and microbial P concentration as well as their relationships with soil available P. The results showed that both soil microbial biomass P and microbial P concentration increased with increasing inorganic P addition, with the maximum being 7137 and 10534 mg·kg-1, respectively. The combine d application of inorganic P (except 100 mg P·kg-1) and wheat straw decre ased the soil microbial biomass P and microbial P concentration, being most obvi ous at early incubation period. Soil microbial biomass P and microbial P concent ration had significant positive correlations (P<005) with soil available P (R2=026 and 040, n=49, respectively). The applied P could rapidly transform into microbial biomass P. The maximum apparent contribution rate of applied P to microbial biomass P was 71%. The added wheat straw could further improve the appar ent contribution rate.