Abstract: Studies on the effect of different municipal sludges on seed germination and seedling growth of Ipomoea aquatica and Brassica parachinensis show that the original sludges from Shenzhen and Foshan and the original sludge and its compost from Guangzhou were observed to be inhibitory to the germination of , but ameliorative to that of B.parachinensis seed. The same sludges and compost were found to be inhibitory or even harmful to the seedling growth of both I.aquatica and B.parachinensis. Organic acids and aldehydes in the sludges and compost were the major compounds inhibitory to the seed germination and seedling growth. Digestion and composting could degrade these organic matters, and hence, attenuate or eliminate the inhibitory effect of original sludges, which can be used as a practical way of the safer agricultural application of sludges. Immediate dissemination of crop seeds to newly-sludge-fertilized land is not recommendable.

Key words: Municipal sludge, Seed germination, Seedling growth, Ipomoea aquatica, Brassica parachinensis, loessial soil, annual nitrogen fertilizer use efficiency, accumulated nitrogen fertilizer use efficiency, long-term fertilization, Loess Plateau