Study On Soil Quality And Its Indicators Of Waterlogged Paddy Soil In South China

The waterlogged paddy soil in south China has large area,wide distribution and low production.Waterlogged paddy soil has a series of characteristic:poor physical properties,more organic matter,more reducing resistance,low soil temperature,deficiency effective nutrient,poor permeability.Investigation on the soil quality and selecting soil quality indicators is crucial to soil quality assessment of waterlogged paddy.Therefore,The present study investigated on soil physical-chemical and biological properties of waterlogged paddy and non-waterlogged paddy in south China.Meanwhile,We developed soil quality indicator system and established the minimum data set.The main conclusions were listed as follow:(1)The contents of soil organic matters(44.04±1.52 g/kg),total nitrogen(2.27±0.08 g/kg)and C/N(11.34±0.26)in waterlogged paddy were significantly higher than that in non-waterlogged paddy,of 26.2%,11.2%and 12.3%respectively.The contents of soil total phosphorus,available nitrogen and available potassium ware not significantly different between waterlogged paddy and non-waterlogged.The contents of soil available phosphorus(5.39±0.92 mg/kg)in waterlogged paddy were significantly lower than that in non-waterlogged paddy with 84.56%.The contents of soil moisture,available iron,available manganese,available zinc,Fe2+,Mn2+,total reducing agents in waterlogged paddy were significantly lower than that in non-waterlogged paddy.Their average value were respectively 45.13%,905.44 mg/kg,117.11 mg/kg,6.42 mg/kg,956.10 mg/kg,61.36 mg/kg,2.48cmol/kg.Compared with non-waterlogged paddy soil,they were 77.9%,91.5%,108.1%,17.0%,349.5%,143.1%,217.9%higher,respectively.(2)The contents of soil microbial biomass carbon(228.24±69.37 mg/kg)and phosphatase activities(95.31±11.62 mg/kg/h)in the waterlogged paddy were significantly lower than that in non-waterlogged paddy,with 43.81%and 25.16%respectively.The contents of soil catalase activities in the waterlogged paddy were significantly higher than that in non-waterlogged paddy,with 21.1%.The contents of invertase soil activities ware not significantly different between waterlogged paddy and non-waterlogged paddy.(3)The individual density of soil nematode in waterlogged paddy(301.95±78.53 individuals/100g dry soil)were significantly lower than that of non-waterlogged paddy(584.31±151.30 individuals/100g dry soil).Nematode community composition and structure of waterlogged paddy soil were generally similiar to that of non-waterlogged paddy soil:plant-parasites>bacterivores>fungivores>predators-omnivores.Filenchus,Hirschmanniella,Aphelenchoides and Cephalobus were the dominant and common genera which widely distributed in paddy of southern China.The Shannon index(H')and richness index(SR)in the waterlogged paddy soil were significantly higher than that in non-waterlogged paddy soil.(4)By paired sample T test and principal components analysis,the results showed that soil total nitrogen,available phosphorus,available manganese,Fe2+,pH and Margalef richness index(SR)were minimum data set(MDS)indicators for soil quality assessment of waterlogged paddy.Soil quality index of waterlogged paddy was significantly lower than that of non-waterlogged paddy.In summary,the content of soil nutrient in waterlogged paddy is not low,however the content of soil moisture and reducing substances are very high in waterlogged paddy.Therefore,drainage improvement is a top priority of waterlogged paddy soil improvement,while tillage improvement and fertilizer improvement are also important ways to improve production of waterlogged paddy.