Paper No. 10
Presentation Time: 10:50 AM
AGRICULTURAL LAND USE CONTROLS ON CRITICAL ZONE INTERACTIONS IN SOIL AND WATER IN UNGLACIATED EAST CENTRAL OHIO
Agricultural practices such as application of lime, chemical fertilizers, and manure have dramatically affected the critical zone. Yields of base cations and alkalinity have increased in response to application of acid-forming fertilizers and dissolution of applied lime. Conversion of landscapes from forest to agriculture, or from one crop to another also alters hydrologic flowpaths. Yet, little work has examined how land use associated hydrology and soil chemistry profiles relate to the release of base cations and alkalinity. A comparison of 2003–2009 storm and base flow yields from conventional agricultural (corn, mixed-use fields, and grazed pasture), a no-till corn site, and a forest site in the unglaciated, low cation exchange capacity soils of the North Appalachian Experimental Watershed, Coshocton, Ohio suggested that sites with greater baseflow in streams yield more Ca+Mg. In fact, the forest site had total Ca+Mg yields that were 20% higher than any agricultural site. Molar Ca+Mg:alkalinity ratios from 2008–2009 samples reveal that losses of alkalinity from conventional agricultural sites (1:1) likely occur during storm events but not from forested sites (1:2). Soil chemistry also exhibits distinctions between landuse types despite similar parental lithology. Ca+Mg:Ti molar ratios in surface soils (<25cm) were >2.3 in the agricultural sites, and below 1.6 in the forest site. Thus, agricultural activities have greatly increased Ca+Mg concentrations in agricultural surface soils. All sites had elevated N:Ti in surface soils, but the forest site (1.5) and the no-till corn (1.3) had the greatest. Watershed response to agricultural amendements is multifaceted, with agricultural streams underlain by younger, more reactive soils, contributing more to the increases in Ca+Mg observed in these basins. In older soils, sites with greater baseflow, including forested areas, may contribute more to the Ca+Mg flux in streams.