@article{buol_2009, title={SOILS AND AGRICULTURE IN CENTRAL-WEST AND NORTH BRAZIL}, volume={66}, ISSN={["0103-9016"]}, DOI={10.1590/S0103-90162009000500016}, abstractNote={Modern soil science, spearheaded by research in Brazil has facilitated the utilization of vast areas of previously uncultivated soil long considered unsuitable for human food production into highly productive agricultural land. Naturally acid soils with high contents of aluminum and iron oxides and low CEC values and organic matter contents long considered insurmountable obstacles to crop production in tropical latitudes could be extremely productive. With continued development of the infrastructure needed by commercial agriculture Brazil has the potential to lead the world in its quest to provide food for growing human populations.}, number={5}, journal={SCIENTIA AGRICOLA}, author={Buol, Stanley W.}, year={2009}, pages={697–707} }
 @article{sanchez_palm_buol_2003, title={Fertility capability soil classification: a tool to help assess soil quality in the tropics}, volume={114}, ISSN={["1872-6259"]}, DOI={10.1016/S0016-7061(03)00040-5}, abstractNote={The soil quality paradigm was originally developed in the temperate region with the overarching objective of approaching air quality and water quality standards. Although holistic and systems-oriented, soil quality focused principally on issues arising from large nutrient and energy inputs to agricultural lands. Soil quality in the tropics, however, focuses on three overarching concerns: food insecurity, rural poverty and ecosystem degradation. Soil science in the tropics relies heavily on quantitative attributes of soils that can be measured. The emotional, value-laden and “measure everything” approach proposed by some proponents of the soil quality paradigm has no place in the tropics. Soil quality in the tropics must be considered a component of an integrated natural resource management framework (INRM). Based on quantitative topsoil attributes and soil taxonomy, the fertility capability soil classification (FCC) system is probably a good starting point to approach soil quality for the tropics and is widely used. FCC does not deal with soil attributes that can change in less than 1 year, but those that are either dynamic at time scales of years or decades with management, as well as inherent ones that do not change in less than a century. FCC attributes can be positive or negative depending on the land use as well as the temporal and spatial scales in question. Version 4 is introduced in this paper. The main changes are to include the former h condition modifier (acid, but not Al-toxic) with “no major chemical limitations” because field experience has shown little difference between the two and to introduce a new condition modifier m that denotes organic carbon saturation deficit. Additional modifiers are needed for nutrient depletion, compaction, surface sealing and other soil biological attributes, but there is no sufficient evidence to propose robust, quantitative threshold values at this time. The authors call on those actively involved in linking these attributes with plant growth and ecosystem functions to provide additional suggestions that would enhance FCC. The use of diffuse reflectance spectroscopy (DRS) shows great potential on a wide range of tropical soils. The evolution of soil science from a qualitative art into a quantitative science has progressed well in the tropics. Regressing to qualitative and vaguely defined soil quality attributes would be a step backwards.}, number={3-4}, journal={GEODERMA}, author={Sanchez, PA and Palm, CA and Buol, SW}, year={2003}, month={Jun}, pages={157–185} }
 @book{soil genesis and classification (5th ed.)_2003, ISBN={0813828732}, publisher={Ames: Iowa State Press}, year={2003} }
 @article{buol_eswaran_2000, title={Oxisols}, volume={68}, DOI={10.1016/s0065-2113(08)60845-7}, abstractNote={Soils now known in Soil Taxonomy as Oxisols have been historically identified as Laterites, Latosols, and various Lateritic soils. Other soil classification systems identify them as Ferrisols, Kaolisols, and Ferrasols. The geographic distribution of Oxisols is primarily related to geologic materials and stable geomorphic surfaces in intertropical regions. Some oxisols form from in situ rock weathering or easily weathered basic rock, but many form in polycyclic sediments that have undergone weathering prior to deposition. Oxisols are present in all soil moisture regimes, but most occur in perudic, udic, or ustic soil moisture regimes. Chemical properties are dictated by an abundance of low charge clays and sesquioxides. Sand and silt fractions contain few weatherable minerals. All Oxisols have relatively low cation exchange values and some have a net positive charge in the subsoil. Most have low-base saturation but some, formed from basic parent materials, are highly base saturated. Physical characteristics include low bulk density, high permeability, friable consistence, and low plant available water-holding capacity. There is little micromorphological evidence of clay translocation, and particle-size distribution is nearly uniform with depth in most pedons. Pedogenic scenarios are varied but relate to a relative loss of silica and concentration of iron and aluminum oxides. Many areas of Oxisols remain in natural vegetation. In areas devoid of modern agronomic technology, “slash and burn” agronomic practices provide meager subsistence for sparse human populations. Where modern agronomic infrastructure provides access to markets, natural limitations of acidity and low nutrient content have been overcome economically with lime and fertilizer applications. Robust agronomic production is now a reality on Oxisols.}, number={2000}, journal={Advances in Agronomy}, author={Buol, S. W. and Eswaran, H.}, year={2000}, pages={151–195} }
 @article{buol_amoozegar_vepraskas_2000, title={Physical, chemical and morphological properties of some Regoliths in North Carolina}, volume={39}, number={3/4}, journal={Southeastern Geology}, author={Buol, S. and Amoozegar, A. and Vepraskas, M. J.}, year={2000}, pages={151} }
 @article{beck_robarge_buol_1999, title={Phosphorus retention and release of anions and organic carbon by two Andisols}, volume={50}, ISSN={["1365-2389"]}, DOI={10.1046/j.1365-2389.1999.00213.x}, abstractNote={Summary}, number={1}, journal={EUROPEAN JOURNAL OF SOIL SCIENCE}, author={Beck, MA and Robarge, WP and Buol, SW}, year={1999}, month={Mar}, pages={157–164} }
 @misc{buol_kamprath_1998, title={A comparison of the contributions of clay, silt, and organic matter to the effective CEC of soils in sub-Saharan Africa}, volume={163}, ISSN={["0038-075X"]}, DOI={10.1097/00010694-199806000-00009}, number={6}, journal={SOIL SCIENCE}, author={Buol, S and Kamprath, EJ}, year={1998}, month={Jun}, pages={508–508} }
 @article{pittillo_hatcher_buol_1998, title={Introduction to the environment and vegetation of the southern Blue Ridge province}, volume={63}, number={3}, journal={Castanea}, author={Pittillo, J. D. and Hatcher, R. D. and Buol, S. W.}, year={1998}, pages={202–216} }
 @inbook{buol_cook_1998, title={Red and lateritic soils of the world: Concept, potential, constraints, and challenges}, booktitle={Red & lateritic soils}, publisher={Rotterdam: Brookfield}, author={Buol, S. W. and Cook, M. G.}, editor={J. Sehgal, W. E. Blum and K. S. Gajbhiye, K. S.Editors}, year={1998}, pages={49–56} }
 @article{osher_buol_1998, title={Relationship of soil properties to parent material and landscape position in eastern Madre de Dios, Peru}, volume={83}, ISSN={["0016-7061"]}, DOI={10.1016/S0016-7061(97)00133-X}, abstractNote={Properties of soils in the eastern part of Madre de Dios, Peru, were characterized and related to landscape position and parent material texture. Level uplands, dissected side slopes and recent flood plains dominate the topography in this region. Soil textures vary from clayey to sandy, depending on the texture of sedimentary materials from which each pedon formed. Parent material textural variation is a result of differences in the energy of the meandering rivers that deposited the ancient alluvium. Fourteen soil profiles were described and sampled in the field and analyzed in the laboratory. Data for eight soil profiles representative of the region are presented here. The profiles include soils formed in both sandy and fine-textured parent materials and soils with moisture status ranging from well drained to poorly drained. Soil moisture conditions vary with position on the landscape, such that as distance from streams increases, average depth to the fluctuating water table decreases. Redoximorphic features are present in all mineral soils. The average depth to redoximorphic features is least in locations furthest from streams. Soils in landscape positions that are poorly or somewhat poorly drained contain significant amounts of plinthite. In all soils, kaolinite is the dominant mineral in the <0.2 μm fraction, while quartz is the dominant mineral in very fine and fine sand fractions. All soils have low cation exchange capacity (CEC), low base saturation, and acid pH. Coarse-textured spodic soils with well developed zones of iron and organic matter translocation are formed in recent sand deposits of flood plains of 2nd-order streams. Organic soils are found in the wetlands associated with flood plains of some 3rd-order streams. Most properties of these soils appear to be controlled by the textures of their sedimentary parent materials and by their position on the landscape. The soils classify as Paleustults, Plinthaquults, Kandiustults, Placaquods and Troposaprists according to Soil Taxonomy. New subgroups of Paleustult are proposed.}, number={1-2}, journal={GEODERMA}, author={Osher, LJ and Buol, SW}, year={1998}, month={Apr}, pages={143–166} }
 @inproceedings{buol_1997, title={Overview of Kandi and other taxonomic changes in North Carolina}, booktitle={Soil Science Society of North Carolina proceedings, 40th}, publisher={Raleigh, N.C.: Soil Science Society of North Carolina}, author={Buol, S. W.}, year={1997} }
 @book{buol_hole_mccracken_southard_1997, title={Soil genesis and classification (4th ed.)}, ISBN={081381460X}, publisher={Ames: Iowa State University Press}, author={Buol, S. W. and Hole, F. D. and McCracken, R. J. and Southard, R. J.}, year={1997} }
 @article{schmidt_buol_kamprath_1997, title={Soil phosphorus dynamics during 17 years of continuous cultivation: A method to estimate long-term P availability}, volume={78}, ISSN={["0016-7061"]}, DOI={10.1016/S0016-7061(97)00011-6}, abstractNote={The ability to predict long-term plant-availability of soil P provides an additional management tool for sustainable agriculture. Our objective is to present a methodology using P fractionation data for predicting long-term plant-availability of soil P. Soil samples were collected (0–30 cm) in 1975, 1985, and 1992 from two continually cropped field trials. Soils were a Norfolk loamy sand and a Davidson clay loam, two Ultisols from North Carolina, USA. Four rates of P were applied from 1975 to 1986, and subsequently discontinued. The relationships between the resin and inorganic NaHCO3 fractions, and between the inorganic NaHCO3 and NaOH fractions, indicated that some level of equilibrium appeared to exist between these three fractions of soil P. Given this equilibrium condition, removal of resin P, as the most plant-available fraction, would subsequently reduce the levels of P in the inorganic NaHCO3 and NaOH fractions. Conversely, adding P as fertilizer would increase P in the resin fraction with a subsequent increase in the inorganic NaHCO3 and NaOH fractions. Although P applied as fertilizer was not completely accounted for in crop removal or net change in soil P, estimated numbers of crops based on our model for predicting available P reflected trends in yields at these two field sites. Sixteen and five crops were estimated for the Norfolk and Davidson soils, respectively. Both corn and soybean yields continued to be high on the Norfolk soil through 1992, while corn yields had declined after 1985 on the Davidson soil. Quantifying the long-term availability of soil P provides some measure of potential return on a capital investment of P fertilization in low-input agriculture.}, number={1-2}, journal={GEODERMA}, author={Schmidt, JP and Buol, SW and Kamprath, EJ}, year={1997}, month={Jul}, pages={59–70} }
 @inproceedings{buol_stokes_1997, title={Soil profile alteration under long-term, high-input agriculture}, booktitle={Replenishing soil fertility in Africa. Proceedings of an international symposium cosponsored by Divisions A-6 (International Agronomy) and S-4 (Soil Fertility and Plant Nutrition), and the International Center for Research in Agroforestry, held at the 88th Annual Meetings of the American Society of Agronomy and the Soil Science Society of America, Indianapolis, Indiana, 6 November 1996. Ed. by Roland J. Buresh, Pedro A. Sanchez, and Frank Calhoun. Madison, WI.: Soil Science Society of America, 1997}, author={Buol, S. W. and Stokes, M. L.}, year={1997}, pages={97–109} }
 @article{li_amoozegar_robarge_buol_1997, title={Water movement and solute transport through saprolite}, volume={61}, ISSN={["1435-0661"]}, DOI={10.2136/sssaj1997.03615995006100060027x}, abstractNote={Abstract}, number={6}, journal={SOIL SCIENCE SOCIETY OF AMERICA JOURNAL}, author={Li, K and Amoozegar, A and Robarge, WP and Buol, SW}, year={1997}, pages={1738–1745} }
 @misc{buol_1995, title={SUSTAINABILITY OF SOIL USE}, volume={26}, ISSN={["0066-4162"]}, DOI={10.1146/annurev.es.26.110195.000325}, abstractNote={The finite quantities of essential elements contained in soil determine its sustainable use for food production. Various soils differ substantially in their ability to provide essential elements. Methods of managing soil to facilitate production of food crops differ depending upon the type of crop grown and the characteristics of the soil. Historical evidence reveals that low rates of food crop production are possible for 100 or more years on some soils, while only one or two crops are obtainable on others. High rates of food production can be achieved only if the concentrations of essential elements in the soil are enhanced. When dedicated to food crop production, soil properties are altered by management practices to favor the requirements of the crop plant and discourage the growth of other vegetation. No soil can sustain the constant depletion of critical elements contained in the plant parts used as food products and transported to another location for consumption. This elemental depletion must be compensated for use to be sustainable.}, journal={ANNUAL REVIEW OF ECOLOGY AND SYSTEMATICS}, author={BUOL, SW}, year={1995}, pages={25–44} }
 @article{buol_weed_1991, title={SAPROLITE SOIL TRANSFORMATIONS IN THE PIEDMONT AND MOUNTAINS OF NORTH-CAROLINA}, volume={51}, ISSN={["1872-6259"]}, DOI={10.1016/0016-7061(91)90064-Z}, abstractNote={In the Piedmont and Mountain Provinces of North Carolina average annual precipitation exceeds evapotranspiration. Soil solum thickness is usually 1 to 2 m. Saprolite thickness is variable but related to rock type and geomorphic position. Slow hydraulic conductivity in the zone between the soil and the saprolite appears to restrict vertical percolation of water, thus slowing saprolite weathering on convex slopes. In saprolite zones immediately above granitic gneiss, often about 5 m below the surface, halloysite, gibbsite and X-ray amorphous aluminosilicate clay are the initial secondary minerals formed. Halloysite contents increase upward in the saprolite, apparently from resilication of gibbsite and the amorphous aluminosilicates. In the upper zones of the saprolite the halloysite is recrystallized into kaolinite which is the predominant clay-sized mineral in the soil. Over gabbro and metagabbro rocks, the lower zones of the saprolite contain appreciable quantities of smectite, vermiculite, and where chlorite is present, regularly interstratified chlorite-smectite. Although these smectite minerals become partially interlayered with hydroxy aluminum in the overlying soil, they p persist as a substantial component of the clay-sized fraction. Saprolite thickness is less than over the granitic rocks. Increased run-off and lateral through-flow produced by low hydraulic conductives of smectite-rich argillic horizons and convex hill slopes are believed to be responsible for the thin saprolite above mafic bedrock. Soils and saprolites from biotitic gneiss on upper sideslopes in the Mountain physiographic province have mineralogical trends with depth similar to those found over the granitic gneisses of the Piedmont. Gibbsite often constitutes as much as 30% of the clay, and contents tend to increase in the deeper saprolite zones. Biotite sand, which is common throughout the soil and saprolite, alters to kaolinite sand under the acidic conditions of the saprolite. Sand-sized mica appears resistant to weathering except where there is evidence of physical transport.}, number={1-4}, journal={GEODERMA}, author={BUOL, SW and WEED, SB}, year={1991}, month={Nov}, pages={15–28} }
 @book{buol_hole_mccracken_1989, title={Soil genesis and classification (3rd ed.)}, ISBN={0813814626}, publisher={Ames: Iowa State University Press}, author={Buol, S. W. and Hole, F. D. and McCracken, R. J.}, year={1989} }
 @book{buol_hole_mccracken_1980, title={Soil genesis and classification (2nd ed.)}, ISBN={081381460X}, publisher={Ames: Iowa State University Press}, author={Buol, S. W. and Hole, F. D. and McCracken, R. J.}, year={1980} }
 @book{buol_hole_mccracken_1973, title={Soil genesis and classification (1st ed.)}, ISBN={081381460X}, publisher={Ames: Iowa State University Press}, author={Buol, S. W. and Hole, F. D. and McCracken, R. J.}, year={1973} }