Effect of sewage sludge compound fertilizer on soil enzyme activity and growth of Poa annua Linn.

To enhance the utilization of detoxified city sewage sludge, the effect of sewage sludge compound fertilizer on the growth of Poa annua Linn. and activity of soil enzyme were studied in a pot experiment. Results indicate dramatic enhancement of the activities of soil urease, protein enzyme and invertase with increasing rates of sewage sludge in compound fertilizer under consistent N, P, K amounts. At the same time, there is observable improvement in the color of grass, while the grass-cuttings and tillering number increase. And especially in the middle to late growth stages, grass color improves by two grades, weight of grass-cuttings increases by 10 ～ 15 g·pot^-1, tillering increases by 30 ～ 50 tillers per pot, while permeability of cell membrane reduces by 40%. However, if sewage sludge N nutrient goes above 60%, the sewage sludge fertilizer has very little effect on grass. Therefore, in using compound sewage sludge fertilizers, N nutrient should be kept within 60%.