Abstract: Biosolids contains a wealth of nutrients and biologically active substances (BAS) and is useful for soil improvement and as fertilizer following appropriate treatment. The purpose of this research was to study the effects of sewage sludge obtained from Jiuxianqiao sewage treatment plant in Beijing and exogenous auxin on the growth and drought tolerance of kentucky bluegrass (Poa pratensis). A split plot trial design was used with main plot treatments being moisture availability (well-watered and drought stress). Subplots included treatments of sewage sludge, 2 μmol·L^-1 endogenous indole butyric acid (IBA) and a control. Three months after establishment watering in the drought stress plots was stopped until the soil water content fell to 25% of field capacity. Subsequently irrigation commenced again for a month, with held again until 25% field capacity and then fully irrigated for another month. The well-watered treatments were fully irrigated for the duration of the study. Turf quality, wilt rating, leaf relative water content, chlorophyll and carotenoids content, proline content, ABA content, IAA content and MDA (malondiadehyde) content of all treatments were measured at every beginning and end of drought stress. Sewage sludge and endogenous IBA improved turf quality and leaf chlorophyll content under well-watered conditions, and increased leaf IAA content (P<0.05); sewage sludge had a more lasting effect than IBA. Both sewage sludge and IBA enhanced the turf quality, leaf relative water content and chlorophyll content (P<0.05) under the drought stress. At the end of drought stress, the proline contents of control, sewage sludge and IBA treatments were respectively 433, 385 and 254 μg·g^-1, ABA content was 1.74, 0.68 and 0.70 μg·g^-1, respectively and MDA content 62.39, 40.08 and 25.38 nmol·g^-1, respectively. Proline, ABA and MDA contents of sewage sludge and IBA treatments were significantly lower than that of the control (P<0.05). The study indicated that both sewage sludge and IBA could promote the growth of Kentucky Bluegrass; sewage sludge raised drought resistance while IBA enhanced drought tolerance.

Key words: sewage sludge, Poa pratensis, indole butyric acid, drought