Landscape position and depth affect microbial abundance and community composition at three positions in an agricultural landscape

Non-Peer ReviewedStabilization/destabilization mechanisms of deep soil carbon are not well understood. A number of different controlling mechanisms are suggested; here we explore differences in microbial abundance and community structure as a controlling mechanism. Microbial abundance and community composition with depth was assessed at three different positions within an agricultural landscape. Microbial abundance was significantly affected by sampling depth, while differences in community structure could be attributed to depth, landscape position, and conditions found within the depositional position. Interestingly, substantial biomass existed at a depth of 81cm in a buried A horizon found in the depositional position

Quantitative changes in soil organic C over 37 years under conventional tillage - effect of crop rotations and fertilizers

Non-Peer Reviewe

Quantitative changes in soil C over 17 years under minimum tillage, well fertilized crop rotations in the Brown Soil Zone

Non-Peer Reviewe

Carbon pool ratios as scientific support to field morphology in the differentiation of dark subsurface soil horizons

In soil surveys, it is usual to find profiles with an uncommon disposition of horizons. Dark horizons in depth might be either the consequence of erosion and redeposition of soil materials from upslope or an indication of the podzolization process, which forms a spodic horizon. Few laboratory analyses are known to characterize dark subsurface horizons which could allow for the differentiation of spodic from buried A horizons. Some researchers propose C-humic and C-fulvic acid fraction ratios and forms of carbon to analyze characteristics of these horizons. Therefore, this research aimed to characterize dark subsurface horizons found in soils under a Eucalyptus minimum tillage system in the state of Rio Grande do Sul, Brazil, and to relate soil organic carbon to landscape features in toposequences. The characterization was performed by using the following ratios: humic acid and fulvic acid fractions (Cha/Cfa); pyrophosphate extractable-C and organic carbon (Cp/OC); fulvic acid fraction and pyrophosphate extractable-C (Cfa/Cp), and fulvic acid fraction and organic carbon (Cfa/OC). Soil organic carbon was related to slope gradient and Geomorphons in a Geographic Information System (GIS). None of the horizons analyzed met the criteria required for spodic horizon classification, where Cha/Cfa < 0.50, Cfa/OC < 0.30, and the ratio Cp/OC ≥ 0.50 simultaneously with Cfa/Cp ≥ 0.50. A relationship was found between landscape features and soil organic carbon content. The methodology proved to be satisfactory for providing scientific support to field morphology classification of dark subsurface horizons, specifically in the case where they could be misinterpreted as spodic horizons

The potential to regain organic carbon in degraded soils: A boundary line approach

There is a physical limit to the storage capacity of SOC that is dependent on fine particles in arable soils. Here it is demonstrated that a ceiling of SOC storage can be identified utilizing a boundary line approach relating SOC to the clay fraction of soils in Ontario. The method can determine the deficit of SOC in order to establish the potential to regain SOC and ameliorate eroded landscape positions.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author