施用城市污泥对小叶黄杨光合特性和生长的影响

城市污泥作为有机肥料施用于园林植物已备受关注.本研究利用温室盆栽试验，分别设置不同用量城市污泥［低量（LC）、中量（MC）和高量（HC）］处理和无机肥（IF）处理，并以不施肥料和污泥为对照（CK），研究不同用量城市污泥对小叶黄杨幼苗光合特性和生长的影响.结果表明：施用城市污泥可以提高小叶黄杨幼苗叶片叶绿素和氮素含量，但随污泥施用量的增加，叶片净光合速率（P_n）呈下降趋势.在生长季的8月，与IF处理和CK相比，LC、MC处理的叶片P_n均提高，而HC处理却较IF和CK分别降低了25.9%和8.9%；至10月，LC、MC和HC处理的叶片P_n均低于IF处理，但LC处理的P_n仍高于CK，而MC、HC处理的P_n均低于CK，其中HC处理的P_n较IF处理和CK分别降低了48.4%和29.2%.IF处理小叶黄杨植株的株高、地径和根长最大，LC处理次之，且地上生物量最大；MC处理除了株高和地上生物量高于CK外，根长和地径均低于CK；而HC处理则严重抑制了根系的生长.小叶黄杨幼苗的城市污泥施用量应限制在30 t·hm^-2以内.

Effects of sewage sludge application on leaf photosynthesis and plant growth of Buxus microphylla

The application of urban sewage sludge as an organic fertilizer for garden plants has obtained an increasing attention. Taking Buxus microphylla seedlings as test objects, a greenhouse pot experiment was conducted to study theresponses of their photosynthetic characteristics and growth to the applicationof sewage sludge (SS). Five treatments were installed, i.e., low dosage SS (LC), medium dosage SS (MC), high dosage SS (HC), inorganic fertilizers (IF), and control (no application of sewage sludge and inorganic fertilizers, CK). The application of SS increased the chlorophyll and N contents in B. microphylla seedlings leaves, but with the increase of SS dosage, the net photosynthetic rate (P_n) decreased. In August, treatments LC and MC increased the P_n but HC decreased the P_n by 259% and 89%, respectively, compared with IF and CK. In October, treatments LC, MC and HC decreased the P_n, compared with IF, but the P_n in LC was still higher than that of CK. The P_n in treatments MC and HC was lower than that of CK, and the P_n in HC was 48.4% and 29.2% lower than that in IF and CK, respectively. The plant height, basal diameter, and root length were the greatest in treatment IF, followed by in LC. Treatment LC induced the greatest above ground biomass; MC increased the plant height and the above ground biomass, but decreased the basal diameter and root length, compared with CK; while HC seriously restrained the root growth. Our results indicated that the dosage of sewage sludge for B. microphylla seedlings should be lower than 30 t·hm^-2.