Soil dissolved organic carbon: Influences of water-filled pore space and red clover addition and relationships with microbial biomass carbon

Abstract

. 2004. Soil dissolved organic carbon: Influences of water-filled pore space and red clover addition and relationships with microbial biomass carbon. Can. J. Soil Sci. 84: 151-158. Soil dissolved organic carbon (SDOC) plays an important role in organic C cycling and translocation of nutrients and pollutants in the soil profile. Soil microbial biomass C (MBC) has been used as an indicator of soil quality. Both SDOC and MBC may be affected by management practices and indigenous soil properties, which however are not fully understood. Using a laboratory incubation technique, we determined the effects of red clover (Trifolium pratense L.) addition and soil water saturation as expressed in water-filled pore space (WFPS, 20-95%) on soil SDOC and MBC in three soils from Ontario. The levels of SDOC were the greatest at 20% WFPS, and decreased with increases in WFPS up to 95%. In comparison with the control, addition of red clover increased SDOC by up to 72% at 20% WFPS, but the effect was minimal or insignificant at WFPS above 50%. Reduction of SDOC with increases of WFPS both with and without red clover was attributed to the increased mineralization of labile organic C, as indicated by CO 2 production. Regardless of the legume amendment, soil available N (e.g., mineral N), labile organic C (e.g. initial level of SDOC) or the variable derived from these two measurements, available C:N ratio, were the factors predominately affecting dynamics of SDOC at WPFS from 20 to 50% after 1-mo incubation and at WFPS from 20 to 65% with extended incubation to 3-mo. Soil factors affecting SDOC at WFPS above 85% were total N and pH without red clover, but changed to organic C and soil labile organic C with red clover. High levels of MBC were found to occur mostly with the high WFPS, and were enhanced by red clover addition only in the Perth silt loam. Soil dissolved organic C was significantly related to MBC with WFPS from 20 to 65% without red clover. No relationships between SDOC and MBC were found at WFPS above 65% without red clover and at WFPS from 20 to 95% with red clover. Soil factors affecting SDOC and the availability of SDOC to microbial activity are WFPS dependent and related to soil legume amendment. Le carbone organique dissous dans le sol (CODS) joue un rôle important dans le cycle du carbone (C) organique et dans la translocation des éléments nutritifs et des polluants dans le sol. On se sert parfois du carbone de la biomasse microbienne (CBM) pour déterminer la qualité du sol. Cependant, le CODS et le CBM peuvent subir l'influence des pratiques culturales et des propriétés naturelles du sol, qu'on comprend mal. Les auteurs ont recouru à une technique d'incubation afin de préciser l'incidence du trèfle rouge (Trifolium pratense L.) et de la saturation d'eau, exprimée d'après la proportion de pores remplis d'eau (PRE, de 20 à 95 %), sur le CODS et le CBM dans trois sols de l'Ontario. La concentration la plus élevée de CODS a été observée à 20 % de PRE. Ensuite, elle diminue à mesure que la proportion de PRE s'approche d...

Impacts of Wet-Dry Cycles and a Range of Constant Water Contents on Carbon Mineralization in Soils under Three Cropping Treatments

“…Although some have found only weak relationships between mineralization rate and WFPS, or no relationship at all (Drewitt et al, 2002;Frank et al, 2002;Ruser et al, 2006), others observed relationships consistent with ours. For example, Zhang et al (2004b) and Rey et al (2005) found that CO2 emissions increased with soil water content until about 85% WFPS which was similar to the maximum observed at 90% WFPS in this study, then decreasing emissions with higher soil water content. Linn and Doran (1984) found that the highest soil respiration rates occurred between 40 and 70% WFPS with lower rates above and below this range.…”

“…Generally, CO2 emissions increase with soil water content until about 85% water-filled pore space (WFPS) and then decrease with higher soil water content (Zhang et al, 2004b;Rey et al, 2005).…”

The use of red clover (Trifolium pratense) in soil fertility-building: A Review

“…Agriculture both provides and relies upon ecosystem services (Zhang et al, 2004). RC is known to contribute multiple ecosystem services, which can enhance the sustainability of the overall system.…”

Effect of different types of organic fertilizers on the chemical properties and enzymatic activities of an Oxisol under intensive cultivation of vegetables for 4 years

“…Microbial biomass measurements have been used to give an early indication of the changes in the organic matter content of a soil as a result of variation in soil management (Garcia-Gil et al 2000;Hargreaves et al 2003;Insam et al 1989;de Vries et al 2007;Zhang et al 2004). Leita et al (1999) reported that the soil microbial biomass, which represents approximately 1-4% of total soil organic C, is a more sensitive indicator of changing soil conditions than direct analysis of the organic C content.…”