Soil Organic Matter Dynamics in Cropping Systems of Virginia's Valley Region

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dc.contributor.authorSequeira, Cleiton Henriqueen
dc.contributor.committeechairAlley, Marcus M.en
dc.contributor.committeememberThomason, Wade E.en
dc.contributor.committeememberMeisinger, John J.en
dc.contributor.committeememberShang, Chaoen
dc.contributor.departmentCrop and Soil Environmental Sciencesen
dc.date.accessioned2014-03-14T21:09:37Zen
dc.date.adate2011-03-17en
dc.date.available2014-03-14T21:09:37Zen
dc.date.issued2011-02-04en
dc.date.rdate2011-03-17en
dc.date.sdate2011-02-18en
dc.description.abstractSoil organic matter (SOM) is a well known indicator of soil quality due to its direct influence on soil properties such as structure, soil stability, water availability, cation exchange capacity, nutrient cycling, and pH buffering and amelioration. Study sites were selected in the Valley region of Virginia with the study objectives to: i) compare the efficiency of density solutions used in recovering free-light fraction (FLF) organic matter; ii) compare different soil organic fractions as sensitive indices of short-term changes in SOM due to management practices; iii) investigate on-farm effects of tillage management on soil organic carbon (SOC) and soil organic nitrogen (SON) stocks; and iv) evaluate the role of SOM in controlling soil available nitrogen (N) for corn uptake. The efficiency of the density solutions sodium iodide (NaI) and sodium polytungstate (SPT) in recovering FLF was the same at densities of 1.6 and 1.8 g cm⁻³, with both chemicals presenting less variability at 1.8 g cm⁻³. The sensitivity of SOM fractions in response to crop and soil management depended on the variable tested with particulate organic matter (POM) being the most sensitive when only tillage was tested, and FLF being the most sensitive when crop rotation and cover crop management were added. The on-farm investigation of tillage management on stocks of SOC and total soil N (TSN) indicated significant increases at 0–15 cm depth by increasing the duration (0 to 10 years) of no-tillage (NT) management (0.59 ± 0.14 Mg C ha⁻¹ yr⁻¹ and 0.05 ± 0.02 Mg N ha⁻¹ yr⁻¹). However, duration of NT had no significant effect on SOC and TSN stocks at 0–60 cm depth. Soil available N as controlled by SOM was modeled using corn (<i>Zea mays</i> L.) plant uptake as response and several soil N fractions as explanatory variables. The final model developed for 0–30 cm depth had 6 regressors representing the different SOM pools (active, intermediate, and stable) and a 𝑅² value of 65%. In summary, this study provides information about on-farm management affects on SOM levels; measurement of such effects in the short-term; and estimation of soil available N as related to different soil organic fractions.en
dc.description.degreePh. D.en
dc.identifier.otheretd-02182011-091927en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-02182011-091927/en
dc.identifier.urihttp://hdl.handle.net/10919/37381en
dc.publisherVirginia Techen
dc.relation.haspartSequeira_CH_D_2011.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectsoil nitrogen fractionsen
dc.subjectsoil carbon fractionsen
dc.subjectsoil qualityen
dc.subjectsoil organic matteren
dc.titleSoil Organic Matter Dynamics in Cropping Systems of Virginia's Valley Regionen
dc.typeDissertationen
thesis.degree.disciplineCrop and Soil Environmental Sciencesen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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