Comparison of microbial C, N-flush and ATP, and certain enzyme activities of different textured soils subject to gradual drying

Abstract

A clay loam, a silt loam and a sand soil were gradually dried from field moisture content to air-dryness at 25�C in the laboratory. Microbial C measured by substrate-induced respiration (SIR), fumigation-incubation (FI) and fumigation-extraction (FE), microbial N-flush measured by FI and FE, microbial ATP content, and soil phosphatase and sulfatase activities were monitored throughout a drying period of approx. 60 h achieved over 16 days. All the microbial and enzyme variables declined as the gravimetric soil water content ( W) decreased to air-dryness. In general, the relationship between microbial C or N-flush and W was linear, but was exponential between ATP or phosphatase and W. Soil texture appeared to affect the rates of decline and also the amounts of the microbial and enzyme variables remaining in air-dry soil; e.g., the lowest rate of microbial C decline and the largest amount remaining at air-dryness occurred in the clay loam soil. Sulfatase activity was not significantly affected by soil drying. Agreement between the SIR and FE estimates of microbial C was good (r = 0.92***). These two methods were applicable over a wide range of water contents. Microbial N-flush, estimated by the FE method, also showed a consistent trend and correlated highly with microbial C estimated by SIR or FE. In contrast, microbial C and N-flush estimated by the FI method were not significantly correlated with W or any of the other variables. ATP and phosphatase activity appeared to relate more closely to microbial activity (CO2 respiration/microbial C) than microbial mass. The reliability of the methods to measure the biomass and the influence of soil texture, water and carbon contents on microbial survival are discussed.

Restoration of Mine Spoil in a Dry Tropical Region: A Review

“…Van Veen et al (1984) argued that the composition of clay in soil influenc exits microbial preservation capacity. Similarly, West et al (1988) also found that clay loam soil had maximum levels of microbial C and N-flush compared to the sandy soils.…”

Elevated CO2 effects on carbon and nitrogen cycling in grass/clover turves of a Psammaquent soil

“…Under laboratory conditions, air-drying can markedly lower microbial C and N values, particularly in a sandy soil (West et al, 1988). In our environmental rooms, plant growth continued, although to a much reduced extent, during the slow 'summer' drying.…”

How air-drying and rewetting modify soil organic matter characteristics: An assessment to improve data interpretation and inference

“…Number of soil types and type of land use Clay (%) SOC (g kg À1 ) Experimental conditions: Duration of air drying method used to determine microbial biomass Changes in microbial biomass C due to air drying: field moist vs. air dried samples Sparling et al, 1986 16; pasture Not given 17e88 10 days Chloroform fumigationeincubation method (Jenkinson and Powlson, 1976; K c factor: 0.45) Substrate-induced respiration technique (Anderson and Domsch, 1978;West and Sparling, 1986) 1e75% decrease (12 soils) 4e98% increase (4 soils) 3e69% decrease West et al, 1988aWest et al, , 1988b 6; pasture 4e55 53e91 16e17 days Chloroform fumigationeincubation method (Jenkinson and Powlson, 1976; K c factor: 0.45) Substrate-induced respiration technique (Anderson and Domsch, 1978;West and Sparling, 1986) Fumigationeextraction moist soil samples. These authors used the carbohydrate signatures of the released hydrophilic substances to demonstrate a strong contribution of microbial derived compounds to WEOM.…”