Master of Science (MS)
Renewable Natural Resources
Agriculture and moist-soil management are important management techniques used on wildlife refuges to provide adequate energy for migrant and wintering waterbirds. However, in arid systems, the presence and accumulation of soluble salts throughout the soil profile can limit total biomass production of wetland plants and agronomic crops and thus jeopardize meeting waterbird energy needs. It is unknown how moist-soil management and traditional agriculture practices influence the accumulation and distribution of soluble salts of soil profiles. In this study of an arid wetland ecosystem, I determine: 1) the effect of long-term, distinct surface hydrologic regimes associated with moist-soil management and agricultural production on salt accumulation; and 2) the specific effects of rototillage and irrigation frequency on salinity concentrations and plant biomass in moist-soil impoundments. My study was conducted at Bosque del Apache National Wildlife Refuge near San Antonio, New Mexico. In May 2012, prior to the growing season, I collected one meter deep soil cores from both moist-soil impoundments and agricultural fields; cores were analyzed in 10 cm segments for soluble salt concentrations. I implemented a split-plot experiment to evaluate salinity concentrations in moist-soil impoundments between rototilled and no-till soils under a 9 and 14 day irrigation frequency. Soil salinity was measured in May and August of 2011 and 2012 and plant biomass in August. My findings suggest that agricultural fields contain significantly higher concentrations of soluble salts in deeper portions of the profile. This may be attributed to the lack of leaching afforded by summer agricultural irrigations as little connectivity to the groundwater and groundwater salinity was detected during groundwater monitoring. In contrast, periodic flooding in winter and summer flood irrigations in moist-soil impoundments may serve as leaching events and created a more dynamic groundwater hydrograph. This seasonal wetland hydroperiod may facilitate lower soil profile salinities but further research is needed to evaluate its successful use in agriculture fields to lower soil salinities. Few differences in soil salinity were detected between tillage and irrigation treatments within moist-soil impoundments. However plant above ground biomass of annual wetland grasses was greater in rototilled soils. This is most likely attributed to the effects of physical disturbance that stimulates germination rather than differences in soil salinity, however greater aboveground biomass does not necessarily equate to higher seed or tuber production.
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Fowler, Drew Nathan, "Evaluating abiotic influences on soil salinity of inland managed wetlands and agricultural fields in a semi-arid environment" (2013). LSU Master's Theses. 59.