Biochar, a co-product of thermochemical conversion of lignocellulosic materials into advanced biofuels, may be used as a soil amendment to enhance the sustainability of biomass harvesting. We investigated the impact of biochar amendments (0, 5, 10, and 20 g-biochar kg− 1 soil) on the quality of a Clarion soil (Mesic Typic Hapludolls), collected (0-15 cm) in Boone County, Iowa. Repacked soil columns were incubated for 500 days at 25 °C and 80% relative humidity. On week 12, 5 g of dried and ground swine manure was incorporated into the upper 3 cm of soil for half of the columns. Once each week, all columns were leached with 200 mL of 0.001 M CaCl2. Soil bulk density increased with time for all columns and was significantly lower for biochar amended soils relative to the un-amended soils. The biochar amended soils retained more water at gravity drained equilibrium (up to 15%), had greater water retention at − 1 and −5 bars soil water matric potential, (13 and 10% greater, respectively), larger specific surface areas (up to 18%), higher cation exchange capacities (up to 20%), and pH values (up to 1 pH unit) relative to the un-amended controls. No effect of biochar on saturated hydraulic conductivity was detected. The biochar amendments significantly increased total N (up to 7%), organic C (up to 69%), and Mehlich III extractable P, K, Mg and Ca but had no effect on Mehlich III extractable S, Cu, and Zn. The results indicate that biochar amendments have the potential to substantially improve the quality and fertility status of Midwestern agricultural soils. RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. Biochar, a co-product of thermochemical conversion of lignocellulosic materials into advanced biofuels, may be used as a soil amendment to enhance the sustainability of biomass harvesting. We investigated the impact of biochar amendments (0, 5, 10, and 20 g-biochar kg − 1 soil) on the quality of a Clarion soil (Mesic Typic Hapludolls), collected (0-15 cm) in Boone County, Iowa. Repacked soil columns were incubated for 500 days at 25°C and 80% relative humidity. On week 12, 5 g of dried and ground swine manure was incorporated into the upper 3 cm of soil for half of the columns. Once each week, all columns were leached with 200 mL of 0.001 M CaCl 2 . Soil bulk density increased with time for all columns and was significantly lower for biochar amended soils relative to the un-amended soils. The biochar amended soils retained more water at gravity drained equilibrium (up to 15%), had greater water retention at − 1 and −5 bars soil water matric potential, (13 and 10% greater, respectively), larger specific surface areas (up to 18%), higher cation exchange capacities (up to 20%), and pH values (up to 1 pH unit) relative to the un-amended controls. No effect of biochar on saturated hydraulic conductivity was detected. The biochar amendments significantly increased total N (up to 7%), orga...
Sand-based turfgrass root zones have limited nutrient retention and water-holding capacity. Peat moss oft en is used to off set these defi ciencies, but peat moss decomposes. Biochar is a co-product of several biofuel production processes used to produce bio-oil. Biochar is stable and could have similar water and nutrient retention impacts as peat moss when mixed in sand-based turfgrass root zones. Th e objective of this research was to evaluate the effi cacy of biochar as a sand-based root zone amendment. Water retention, water infi ltration, creeping bentgrass (Agrostis stolonifera L.) rooting depth, and nutrient evaluation experiments were conducted on six sand and biochar root zone mixtures. At fi eld capacity, sand-based media containing 25% (v/v) biochar retained 260 and 370% more water compared to media containing 5% biochar and a pure sand control, respectively. Saturated hydraulic conductivity (K sat ) of the root zones decreased as biochar concentrations increased. Th e rooting depth of bentgrass was reduced up to 46% at biochar concentrations >10%. Extracted pore water electrical conductivity and dissolved total organic carbon increased as biochar concentrations increased. Nitrogen leaching was reduced as biochar concentrations increased. According to the results, biochar may improve water storage, reduce overall water use, and decrease N fertilizer applications in sand-based turfgrass ecosystems.
Diffusion‐based coupled soil heat and water transfer theory includes capability to describe transient behavior. Unfortunately, laboratory tests of theory typically include a single initial water content distribution with a single set of boundary conditions, rather than providing a set of experimental conditions with a range of measurements for comparison with predictions. Agreement between theory and measurements can result from calibration, but this provides an incomplete test of theory. The objective of this work was to test diffusion‐based coupled heat and water transfer theory by comparing theory‐based predictions with measured transient temperature and water content distributions. Data from a single boundary condition were used for calibration of each of two soils, silt loam and sand. Subsequent testing was performed at additional boundary and initial conditions using measurements from the same soil. Results indicate that the theory can be calibrated for a single boundary condition with adjustment of soil saturated hydraulic conductivity and/or the vapor enhancement factor, which adjust the liquid and vapor fluxes, respectively. For silt loam, calibration reduced Root Mean Square Error (RMSE) by 67 and 18% for water content and temperature distributions, respectively. For sand, RMSE was reduced by 14 and 46% for water content and temperature, respectively. Using this calibration, there was agreement between calculated and measured distributions for additional boundary and initial conditions with RMSE ≤ 0.03 m3m−3 and 1.28°C for water content and temperature distributions, respectively. However, when the boundary temperature gradient was instantly reversed, noticeable differences occurred between measured and calculated patterns of heat and moisture redistribution. The theory described observations well when boundary temperature conditions were changed gradually, but results suggested a need for further development of coupled heat and water transfer theory combined with testing under transient conditions to make improvements in the description of transfer mechanisms.
The soil water retention curve (SWRC) is a key tool for understanding the fundamental relationship between soil moisture content and its associated energy. The objective of this study was to measure soil water retention including hysteresis at the dry end of the SWRC and to examine the effect of wettability on the SWRCs of two wettable soils and their hydrophobized counterparts. Two conditions, wettable and hydrophobic, were measured for each soil. The method used to measure the SWRCs was vapor equilibration over salt solutions of known osmotic potentials. Free water in the form of individual droplets was found to be present at the surface of the unwashed hydrophobic soils due to decreases in the osmotic potential during the hydrophobizing process. Water droplets did not form on the hydrophilic and washed hydrophobic soils. Soil wettability was found to affect soil water retention in relatively dry soil. The hydrophilic soils used in this study exhibited significant hysteresis in the water potential range of −2.3 to −19.2 MPa. Soil wettability and hysteresis should be considered when studying water sorption and desorption in relatively dry soil.
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