Experiments on decomposition of residues of plants including various cereal crops,leguminous and aquatic green manure crops under field conditions were carried out on microplots of paddy soils and upland soils in Guangzhou (southern subtropics) and Wuzi (northern subtropics) respectively.The fraction of originally added plant C retafined in soil after the decomposition for 1 or 2 years was,as what has been previously found in the study at southern Jiangsu,correlated positively with the lignin content of plant residue regardless of different enc-ironments in which it decomposed,but it was related neither to its nitrogen content nor to its water-soluble substances content.For a given plant residue,the decomposition pattern in Guangzhou was very similar to that in Wuxi.Moreover,the decomposition rate of plant residue in Guangzhou was as fast as that in Wuxi,although the mean annual temperature and precipitation in Guangzhou were 6.4℃ and 550 mm higher than those in Wuxi respectively.Evidence obtained indicates that this is due to the lower pH value of soils in Guangzhou.It was found that in case of the same soil used for the decomposition experiments both in Guangzhou and Wuai,its decomposition rate in Guangzhou was significantly faster than thntin Wuri.