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Soil organic matter (SOM) is of primary importance for maintaining inherently low SOC contents (typically below 1%, Hunt soil productivity, and agricultural management practices may signifiet al., 1982). Consequently, small changes in the SOM cantly influence SOM chemical properties. However, how SOM chemical characteristics change with agricultural practices is poorly under-content are significant to the agricultural production of stood. Therefore, in this study, we evaluated the impacts of tillage the region. An evaluation of tillage and crop residue (conventional vs. conservation) management on the structural and management practices to rebuild SOC levels has been compositional characteristics of SOM using cross-polarization magicconducted by Hunt et al. (1996). These researchers monangle-spinning (CPMAS) and total sideband suppression (TOSS) itored changes in SOC levels in numerous small tillage solid-state 13 C nuclear magnetic resonance (NMR) and diffuse reflecplots and found that after 9 yr of CnT, the SOC content tance Fourier transform infrared (DRIFT) spectroscopy. We characin the top few centimeters was significantly higher than terized both physically and chemically isolated SOM fractions from a the soil under CT management. Campbell et al. (1999) Norfolk soil (fine-loamy, siliceous, thermic Typic Kandiudults) under reported that over an 11-to 12-yr period, increases in long-term tillage management (20 yr). The solid-state 13 C NMR results C storage in the 0-to 15-cm soil depth, because of indicated that humic acid (HA) from conventional tillage (CT, 0-5 cm) was less aliphatic and more aromatic than HA from conservation adoption of no-tillage, were small (0-3 Mg ha Ϫ1). Most tillage (CnT). The aliphatic C content decreased with increasing depth of the differences were observed in the 0-to 7.5-cm soil (0-15 cm) for both CT and CnT treatments. The reverse trend was depth, with little change in the 7.5 to 15 cm. However, true for aromatic C content. Based on reactive/recalcitrant (O/R) the short and long-term influences of disturbance on C peak ratio comparisons, HA was more reactive in the top soil (0-5 mineralization are complex and may vary depending cm) under CnT than CT. Both soil organic C (SOC) and light fraction on types of soil and plant residues (Hu et al., 1995; (LF) material were higher in the 0-to 5-cm soil of CnT than CT Franzleubbers and Arshad, 1996; Alvarez et al., 1998). treatment. Our results show that long-term tillage management can The strong influence of soil management on the amount significantly change the characteristics of both physical and chemical and quality of SOM was also reported by others (Janzen fractions of SOM.

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In this study, we used a commercial pilot-scale pyrolysis reactor system to produce combustible gas and biochar at 620 °C from three sources (chicken litter, swine solids, mixture of swine solids with rye grass). Pyrolysis of swine solids produced gas with the greatest higher heating value (HHV) followed by the mixture of swine solids with rye grass and chicken litter. Relatively high S-containing gases were produced; dimethyl sulfide and methyl mercaptan concentrations were higher than the OSHA PEL limits. Biochar yield ranged from 43 to 49% based on dry weight with about 53% of carbon recovery. Whereas the HHV of the chicken litter biochar was slightly below that of low rank coals, swine-based biochars had HHVs between high and low rank coals. Approximately 50% of the feedstock energy was retained in biochar and 25% in produced gases. Manure biochars contained higher concentrations of P and K than that of original manure feedstocks. Consequently, these could be used as a low-grade fertilizer to improve soil fertility and crop yields. Extremely high energy (232.3 MJ/kg) was required to make 1 kg of biochar from wet swine manure with 97% MC. However, dewatering of the wet swine manure to 75% MC substantially reduced the external energy requirement by 19 folds. Mixing of dried biomass such as rye grass with the dewatered swine solids almost eliminated the need for external energy. If one can copyrolyze wet animal wastes with additional feedstock that are drier and more energy dense than rye grass such as waste plastic pellets, it may be possible to produce both valuable biochar and extra power.

Understanding the movement of phosphorus (P) in soils receiving heavy animal waste application is important for nonpoint‐source pollution control. We investigated both P accumulation in soil and movement to ground water after 10 yr of intensive swine manure application (at atypical high rates) to a Coastal Plain spray field. Mehlich 3 phosphorus (M3P) was measured in soil cores collected in 1991 (following 4 yr of manure application) and 1997 (after 10 yr of application). Additionally, dissolved phosphorus (DP) was measured in ground water wells installed around the spray field. In both 1991 and 1997, the soil cores (0 to 15 cm) contained high contents of M3P (376–435 mg P kg−1) indicating substantial P accumulation. After 10 yr of manure application, soil cores at a depth of 107 cm were also high in soil M3P contents (151 mg P kg−1). Control soils were very low in M3P (<10 mg P kg−1) throughout the soil profile. Ground water DP concentrations were initially (1992–1995) very low (<40 µg P L−1), but by late 1996, DP concentrations in a few wells had increased substantially (40–480 µg P L−1). In contrast, ground water control wells (1994–1998) were very low in DP (<40 µg P L−1). Thus, the studied field, which received atypical high loading rates, had detectable leaching to shallow ground water as well as substantial P accumulation.

Integrating thermochemical conversion (TCC) technologies with current animal waste treatment practices can treat and reduce quantities of manure from consolidated animal feeding operations. Additionally, TCC technologies can produce value-added, renewable energy products. These products can meet heating and power needs or be catalytically converted into liquid fuels. The primary objectives of this study were to assess opportunities and obstacles in the treatment and energy conversion using currently available TCC processes. Both dry and wet livestock manures were assessed. Dry wastes like poultry litter and feedlot manures can be processed directly via pyrolysis and air/steam gasification technology. The solids in the aqueous waste streams from dairy and swine operations can undergo wet gasification or direct liquefaction processes. Alternatively, these solids can be separated and dried before conversion. Due to high ash and sulfur contents, pretreatment of manure is necessary to prevent catalyst poisoning and promote effective unit operation. While the energy input requirements for a conceptual wet gasification manure treatment system of a model swine farm is larger than a traditional anaerobic digestion operation, there are many significant advantages in implementing TCC technology including the following:  compact design; faster treatment times; reduction of odors, BOD, and pharmaceutically activated compounds; and elimination of sludge.

To meet future demands, alternative energy sources will be needed because long-term energy problems have not been solved. Crop residue may provide a readily available on-farm bioenergy source, but effects of removing residue on soil fertility, water conservation, and crop production need further investigation. A 4-yr field experiment was conducted on a Norfolk sandy loam (Typic Paleudults) to determine the effects of removing crop residues on soil pH, extractable nutrient concentrations, and yield of corn (Zea mays L.). Four stover management treatments evaluated between 1979 and 1982 included conventional tillage with stover incorporated, and con!iervation tillage with 0, 66, or 90% of the stover removed. Treatments were split and evaluated with and without supplemental irrigation. Extractable nutrient concentrations were evaluated by comparing values obtained from an initial soil sampling with those of samples collected each fall thereafter. Ear leaf analyses were used to monitor treatment effects on plant nutrient status. Annual corn stover yields of 3 to 7 Mg ha-1 provided 5 to 11 X 10' kJ ha-1 of potential bioenergy without reducing winter surface cover below 80%. Harvesting corn residues increased annual N, P, and K removal by 26 to 57, 6 to 14, and 49 to 124 kg hal, respectively. Soil extractable and plant nutrient concentrations indicated fertilization rates were adequate to compensate for nutrients removed with crop residues. Annual soil analyses showed that surface-applied lime and fertilizer were rapidly leached through low exchange capacity surface horizons, but accumulated in subsoil horizons even when conservation tillage practices were utilized. Irrigation, tillage, and residue management treatments resulted in few significant differences indicating that in this physiographic region, some crop residues could be utilized for bioenergy production. However, j>lant nutrients contained in those residues would have to be rpplaced by increased fertilization.