|Title||Influence of land application of dairy factory effluent on soil nutrient status and the size, activity, composition and catabolic capability of the soil microbial community|
|Publication Type||Journal Article|
|Year of Publication||2011|
|Authors||Liu Y.Y, Haynes R.J|
|Journal||Applied Soil Ecology|
|Keywords||Bacterial community structure, Catabolic function, Dairy factory effluent, microbial biomass, Pastoral soils, Soil nutrient status|
Recycling of water and nutrients in factory effluents back to the land is desirable although it can cause degradation of soil quality. For this reason, the effects of irrigation with dairy factory effluent (DFE) on soil chemical properties and its consequent effects on microbial properties of grazed pastoral soils were investigated in soils surrounding a dairy factory. Long-term DFE irrigation resulted in an increase in pH, electrical conductivity, exchangeable Na, K, exchangeable Na percentage and extractable P reflecting the use of phosphoric acid, NaOH and KOH as cleaning agents in the factory. Effluent P accumulated principally in the inorganic soil fraction and a P fractionation procedure revealed large increases in the NaHCO3-, NaOH(I)- and HCl-Pi fractions. Exchangeable Mg and aggregate stability, as measured by wet sieving, were both decreased by long-term DFE additions. Long-term DFE irrigation had no measureable effect on soil organic matter content (organic C, total N) but caused a decrease in the C/N ratio and substantial increases in microbial biomass C and N and basal respiration which were attributed to regular inputs of soluble organic C (e.g. lactose) present, as milk residues, in the effluent. There was no measureable increase in metabolic quotient caused by long-term DFE irrigation suggesting that it had not caused undue stress on the microbial community. Principal component analysis of soil properties from 11 fields surrounding the factory confirmed that DFE irrigation induced increases in pH, exchangeable Na and K, extractable P, EC, soluble N, microbial biomass C and N, and a narrowing of the C/N ratio. Effluent irrigation had no measureable effect on either catabolic capability of the soil microbial community, as measured using MicoResp™ or the structure and diversity of the bacterial community as measured by PCR-DGGE of 16S rDNA amplicons. It is suggested that this was because locality, soil type and plant cover were similar for all samples and these are the major factors influencing microbial community structure. It was concluded that although DFE irrigation caused substantial changes in soil chemical properties and increases the size and activity of the microbial biomass, community structure and catabolic capability were resilient to change.
|Short Title||Appl. Soil Ecol.|