[Effects of maize and rice straw amendment on the pH, CO2, and exchangeable NH4+ of submerged soil].

A greenhouse incubation test was conducted to study the effects of amendment with different amounts of maize and rice straws on the soil pH,CO2,and exchangeable NH4+ under continuous flooded condition.The results showed that in a near-neutral soil,straw amendment could decrease soil pH,with a significant difference(P0.05) between the treatments of 4 g straws·kg-1 and control(CK),but no significant difference(P0.05) between the treatments of 1 g straws·kg-1 and CK.The CO2 content in soil solution increased with increasing rate of straw amendment,with the peak value being 35.9% and 31.9%(v/v) in the treatments of 1 g maize straw·kg-1 and 1 g rice straw·kg-1,respectively.These two treatments had significantly higher CO2 contents(P0.05) than CK,but no obvious difference between themselves(P0.05).In treatments 4 g maize straw·kg-1 and 4 g rice straw·kg-1,the peak value of CO2 content was 54.2% and 41.8%(v/v),respectively,being significantly higher than that of CK(P0.01),and significantly different between themselves(P0.05).Under non-N fertilization,soil NH4+-Nconcentrationdecreased after straw amendment,and the increase of the amendment rate caused a further decrease of soil NH4+-N concentration,with a significant difference(P0.05) between the doses of 1 and 4 g straw·kg-1.Under N fertilization,soil NH4+-N concentration increased after 1 g straw·kg-1amendment,but decreased after amendment with 4 g straw·kg-1.No significant differences were observed between maize straw and rice straw amendment regardless with or without N fertilization(P0.05).