Storage Effects on Biochemical Properties of Air-Dried Soil Samples from Southeastern Spain

Abstract

Soil biochemical properties are susceptible to change under sample storage, and as a consequence, these properties have usually been determined in fresh samples, kept cold or frozen for brief periods of time. However, air-dried soil would facilitate routine soil testing procedures in soils from semi-arid Mediterranean areas, which have soil water deficit most of the year. This research aims at assessing the effects of medium-term soil storage (6–9 months) at room temperature on air-dried soil samples from two Mediterranean forest locations for the measurement of various microbiological and biochemical properties (microbial biomass carbon, basal respiration, metabolic quotient, acid phosphatase activity, urease activiy, β-glucosidase activity, and soluble carbon). Storage of air-dried soil samples for 6 months had no significant effects on the studied properties in any location. With regard to samples stored for 9 months, we only found differences at the location with higher mean rainfall in the values of basal respiration, the metabolic quotient and β-glucosidase, and urease activities. Our results show that biochemical properties from Mediterranean semi-arid soils, are medium-term stable in stored air-dried soil samples. Thus, these findings would encourage the selection of biochemical properties on a practical basis, as there is no strict requirement to determine these properties immediately after sampling, as they remain valid for several months.

Keywords:

• enzyme activities
• mediterranean forest soils
• microbial activity
• microbial biomass
• soil storage

Notes

∗M: Sierra del Maigmó; O: Sierra de Orihuela.

†Fractions in the following order: sand (2–0.02 mm), silt (0.02–0.002 mm), clay (<0.002 mm).

‡EC: electrical conductivity; WHC: water-holding capacity (water content by weight); SOC: soil organic carbon; N _k : total Kjeldahl nitrogen.

∗MBC: microbial biomass carbon; BSR: basal soil respiration; qCO₂: BSR/MBC; SC: soluble carbon.

†0: measured immediately after sampling (August 2003); 6: measured after 6 months of storage.

‡t is calculated by paired-sample t-test. ∗, ∗∗, and ∗∗∗ indicate significant differences at P < 0.05, P < 0.01 and P < 0.001, respectively. ns: nonsignificant.

§PNP: p-nitrophenol. Values are mean ± standard deviation (n = 8).

∗MBC: microbial biomass carbon; BSR: basal soil respiration; qCO₂: BSR/MBC; SC: soluble carbon.

†0: measured immediately after sampling (May 2003); 9: measured after 9 months of storage.

‡t is calculated by paired-sample t-test. ∗, ∗∗, and ∗∗∗ indicate significant differences at P < 0.05, P < 0.01 and P < 0.001, respectively. ns: nonsignificant.

§PNP: p-nitrophenol.