Harold P. Collins

Biochar: A Synthesis of Its Agronomic Impact beyond Carbon Sequestration

Biochar has been heralded as an amendment to revitalize degraded soils, improve soil carbon sequestration, increase agronomic productivity, and enter into future carbon trading markets. However, scientific and economic technicalties may limit the ability of biochar to consistently deliver on these expectations. Past research has demonstrated that biochar is part of the black carbon continuum with variable properties due to the net result of production (e.g., feedstock and pyrolysis conditions) and postproduction factors (storage or activation). Therefore, biochar is not a single entity but rather spans a wide range of black carbon forms. Biochar is black carbon, but not all black carbon is biochar. Agronomic benefits arising from biochar additions to degraded soils have been emphasized, but negligible and negative agronomic effects have also been reported. Fifty percent of the reviewed studies reported yield increases after black carbon or biochar additions, with the remainder of the studies reporting alarming decreases to no significant differences. Hardwood biochar (black carbon) produced by traditional methods (kilns or soil pits) possessed the most consistent yield increases when added to soils. The universality of this conclusion requires further evaluation due to the highly skewed feedstock preferences within existing studies. With global population expanding while the amount of arable land remains limited, restoring soil quality to nonproductive soils could be key to meeting future global food production, food security, and energy supplies; biochar may play a role in this endeavor. Biochar economics are often marginally viable and are tightly tied to the assumed duration of agronomic benefits. Further research is needed to determine the conditions under which biochar can provide economic and agronomic benefits and to elucidate the fundamental mechanisms responsible for these benefits.

Dynamics of resistant soil carbon of Midwestern agricultural soils measured by naturally occurring 14C abundance

Information on the mean residence time (MRT) of soil organic carbon (SOC) on different soil types and management regimes is required for pedo-geological, agronomic, ecological and global change interpretations. This is best determined by carbon dating the total soil together with acid hydrolysis and carbon dating of the non-hydrolyzable residue (NHC). Midwestern US soils in a transect from Lamberton, MN to Kutztown, PA were found to contain from 33% to 65% of their SOC in the non-hydrolyzable fraction. Soils on lacustrine deposits had the most NHC; glacial till and shale soils, the least. The MRTs of the SOC of surface horizons of soil ranged from modern to 1100 years with an average of 560 years. The MRT increased to an average of 1700 years in the 25–50-cm depth increment and 2757 years at 50–100 cm. The NHC was 1340 years greater at the surface and 5584 years at depth. The MRTs of the total SOC were inversely correlated to sand and directly related to clay content. Silt did not have a significant effect on the MRT of total SOC, but was significantly correlated with the MRT of the NHC. A four-parameter model described the relationship between the SOC content and MRT. The complexity of this equation reflected the strong effect of depth, which greatly decreased SOC while increasing the MRT. The MRT of these soils, as determined with carbon dating of the naturally occurring 14C, was compared to that measured with the 13C signal produced by approximately 30 years of continuous corn (Zea mays L.) (C4) on soils with a known plant history of C3–C4 cropping. The equation of 14C MRT=176(13CMRT)0.54 with an R2 of 0.70 showed that although short-term 13C studies correlate well with the total MRT, they reflect the dynamics of the active and slow pools, not the total SOC.

Evolution of CO2 and soil carbon dynamics in biologically managed, row-crop agroecosystems

Field CO2 production was related to soil carbon pools and fluxes determined by laboratory incubation of soils from agroecosystems designed to test the possibility of substituting biological for chemical inputs. Treatments included: conventional and organic-based row crops, woody and herbaceous perennial crops and historically tilled and never tilled successional fields. The CO2 efflux in corn and soybeans was affected by crop residues from previous years and growing season temperatures but not soil moisture. Overwinter cover crops and perennials such as alfalfa and poplar, resulted in fairly uniform fluxes of approximately 20 kg CO2‐C ha ˇ1 day ˇ1 throughout the non-frozen period. Highest fluxes occurred in alfalfa, historically tilled successional and never tilled, grassland successional treatments, although, highest aboveground productivity occurred in the corn and poplar. Summed, field CO2 fluxes were similar to residue-C inputs. Measurement of CO2 mineralized in extended incubations in the laboratory made it possible to use soil enzyme activity to determine the size and dynamics of soil C pools. The residue of acid hydrolysis defined the size of the resistant pool Cr. Carbon dating determined its mean residence time (MRT). Curve analyses of CO2 evolution plotted on a per unit time basis gave the active (Ca) and slow (Cs) pool sizes and decomposition rate constants ka and ks. Temperature correction factors provided field MRTs. The active pool of this coarse textured soil represents 2% of the soil C with a MRT of 30‐66 days. The slow pool represents 40‐45% of the SOC with field MRTs of 9‐13 years. The poplar soil has the greatest MRT for both the active and slow pools. The system approach to land use sustainability (SALUS) model, which predicts CO2 evolution from decomposition in the field as part of a plant growth ‐ soil process model, was tested using the decomposition parameters determined by incubation and 14 C dating. The model satisfactorily predicted the intra and inter year differences in field CO2 but over predicted fluxes from residues in the fall. It does not yet adequately consider a lag period during which the residues lose their hydrophobicity, are comminuted and colonized. # 1999 Elsevier Science B.V.

Effects of irrigation and tillage practices on yield of potato under high production conditions in the Pacific Northwest

The soil and climate conditions prevalent in the Pacific Northwest region are favorable for production of high potato (Solanum tuberosum L.) yields. Much of this production occurs on coarse, low organic matter, sandy soils which can be subject to wind and water erosion, and excessive leaching of water and soluble agrichemicals below the root zone, particularly when irrigation is not managed adequately. Tuber production and quality are adversely impacted when potatoes are subject to water stress. Therefore, optimal irrigation scheduling is important to support high production of good quality tubers and to minimize potential adverse impacts on water quality. Effects of two irrigation regimes and three tillage practices on production of two potato varieties were studied under four years rotation with either corn (Zea mays L.) or wheat (Trilicum aestivum L.). In two out of three years, as compared to irrigation to replenish full evapotranspiration (ET), deficit irrigation (85% of ET) decreased total tuber yield by 8 to 11% and 10 to 17%, and U.S. No. 1 tuber yield by 5 to 17% and 16 to 25%, in Russet Burbank and Hilite Russet cultivars, respectively. Tillage treatments evaluated were (i) conventional including raised ridges with dammer-dike; (ii) optimal, i.e., lower depth of the tillage and shallow furrow; and (iii) reduced tillage, i.e., flat planting. During the first two years of the study, the effects of tillage treatments were non-significant on the total as well as U.S. No. 1 tuber yield in both cultivars. On the third year, the tuber yield was significantly lower in flat planting treatment as compared to that in the other tillage treatments. This study demonstrated that in coarse textured soils with adequate water infiltration, excessive tillage and/or dammer-diking may not benefit potato production.

Biochar produced from anaerobically digested fiber reduces phosphorus in dairy lagoons.

This study evaluated the use of biochar produced from anaerobic digester dairy fiber (ADF) to sequester phosphorus (P) from dairy lagoons. The ADF was collected from a plugged flow digester, air-dried to <8% water content, and pelletized. Biochar was produced by slow pyrolysis in a barrel retort. The potential of biochar to reduce P in the anaerobic digester effluent (ADE) was assessed in small-scale filter systems through which the effluent was circulated. Biochar sequestered an average of 381 mg L P from the ADE, and 4 g L ADF was captured as a coating on the biochar. There was an increase of total (1.9 g kg), Olsen (763 mg kg), and water-extractable P (914 mg kg) bound to the biochar after 15 d of filtration. This accounted for a recovery of 32% of the P in the ADE. The recovered P on the biochar was analyzed using P nuclear magnetic resonance for P speciation, which confirmed the recovery of inorganic orthophosphate after liquid extraction of the biochar and the presence of inextractable Ca-P in the solid state. The inorganic phosphate was sequestered on the biochar through physical and weak chemical bonding. Results indicate that biochar could be a beneficial component to P reduction in the dairy system.

Greenhouse gas fluxes from an irrigated sweet corn (Zea mays L.)-potato (Solanum tuberosum L.) rotation.

Intensive agriculture and increased N fertilizer use have contributed to elevated emissions of the greenhouse gases carbon dioxide (CO(2)), methane (CH(4)), and nitrous oxide (N(2)O). In this study, the exchange of CO(2), N(2)O, and CH(4) between a Quincy fine sand (mixed, mesic Xeric Torripsamments) soil and atmosphere was measured in a sweet corn (Zea mays L.)-sweet corn-potato (Solanum tuberosum L.) rotation during the 2005 and 2006 growing seasons under irrigation in eastern Washington. Gas samples were collected using static chambers installed in the second-year sweet corn and potato plots under conventional tillage or reduced tillage. Total emissions of CO(2)-C from sweet corn integrated over the season were 2071 and 1684 kg CO(2)-C ha(-1) for the 2005 and 2006 growing seasons, respectively. For the same period, CO(2) emissions from potato plots were 1571 and 1256 kg of CO(2)-C ha(-1). Cumulative CO(2) fluxes from sweet corn and potato fields were 17 and 13 times higher, respectively, than adjacent non-irrigated, native shrub steppe vegetation (NV). Nitrous oxide losses accounted for 0.5% (0.55 kg N ha(-1)) of the applied fertilizer (112 kg N ha(-1)) in corn and 0.3% (0.59 kg N ha(-1)) of the 224 kg N ha(-1) applied fertilizer. Sweet corn and potato plots, on average, absorbed 1.7 g CH(4)-C ha(-1) d(-1) and 2.3 g CH(4)-C ha(-1) d(-1), respectively. The global warming potential contributions from NV, corn, and potato fields were 459, 7843, and 6028 kg CO(2)-equivalents ha(-1), respectively, for the 2005 growing season and were 14% lower in 2006.

Soil biology for resilient, healthy soil

What is a resilient, healthy soil? A resilient soil is capable of recovering from or adapting to stress, and the health of the living/biological component of the soil is crucial for soil resiliency. Soil health is tightly coupled with the concept of soil quality (table 1), and the terms are frequently used interchangeably. The living component of soil or soil biota represents a small fraction (<0.05% dry weight), but it is essential to many soil functions and overall soil quality. Some of these key functions or services for production agriculture are (1) nutrient provision and cycling, (2) pest and pathogen protection, (3) production of growth factors, (4) water availability, and (5) formation of stable aggregates to reduce the risks of soil erosion and increase water infiltration (table 2). Soil resources and their inherent biological communities are the foundation for agricultural production systems that sustain the human population. The rapidly increasing human population is expanding the demand for food, fiber, feed, and fuel, which is stretching the capacity of the soil resource and contributing to soil degradation. Soil degradation decreases a soils production capacity to directly supply human demands and decreases a soils functional capacity to perform numerous critical services, which…

Carbon storage and nitrous oxide emissions of cropping systems in eastern Washington: A simulation study

Conservation tillage is an agricultural strategy to mitigate atmospheric greenhouse gas (GHG) emissions. In eastern Washington, we evaluated the long-term effects of conventional tillage (CT), reduced tillage (RT) and no-tillage (NT) on soil organic carbon (SOC) storage and nitrous oxide (N2O) emissions at three dryland and one irrigated location using the cropping systems simulation model CropSyst. Conversion of CT to NT produced the largest relative increase in SOC storage (ΔSOC, average yearly change relative to CT) in the top 30 cm (11.8 in) of soil where ΔSOC ranged from 0.29 to 0.53 Mg CO2e ha−1 y−1 (CO2e is carbon dioxide [CO2] equivalent of SOC; 0.13 to 0.24 tn CO2e ac−1 yr−1). The ΔSOC were less with lower annual precipitation, greater fallow frequency, and when changing from CT to RT. Overall, ΔSOC decreased from the first to the third decade after conversion from CT to NT or RT. Simulations of ΔSOC for the conversion of CT to NT based on a 0 to 15 cm (0 to 5.9 in) soil depth were greater than the ΔSOC based on a 0 to 30 cm depth, primarily due to differences among tillage regimes in the depth-distribution of carbon (C) inputs and the resultant SOC distribution with depth. Soil erosion rates under CT in the study region are high, posing deleterious effects on soil quality, productivity, and aquatic systems. However, an analysis that includes deposition, burial, and sedimentation on terrestrial and aquatic systems of eroded SOC indicates that the substantial erosion reduction obtained with RT and NT may result only in minor additional SOC oxidation as compared to CT. Simulated N2O emissions, expressed as CO2 equivalent, were not very different under CT, RT, and NT. However, N2O emissions were sufficiently high to offset gains in SOC from the conversion of CT to RT or NT. Thus, reducing tillage intensity can result in net C storage, but mitigation of GHG is limited unless it is coupled with nitrogen (N) fertilizer management to also reduce N2O emission.

MANAGEMENT OF ORGANISMS AND THEIR PROCESSES IN SOILS

Publisher Summary This chapter focuses on management of organisms and their processes in soils. Managing microorganisms can mean combating pathogenic or infectious organisms or promoting beneficial organisms or their products. Many of the agricultural, forestry, and rangeland practices used today actually have deleterious effects upon microorganisms and their processes. Practices including plowing, clear-cutting forests, and overgrazing of rangeland decrease organism populations and promote nutrient loss with an overall result of decreasing soil quality. Humans, as caretakers of the land, must reverse land degradation to increase soil quality and ecosystem health and to provide food and fiber for a growing world population. Forest management practices also contribute to the increase in soil quality and ecosystem health by increasing soil carbon. The conversion of marginal land and highly erodible land to forest increases soil carbon also provides an aboveground component of sequestered carbon to the ecosystem. The concepts related to changing soil organism populations and processes and the potential of managing microorganisms are elaborated along with a brief description of alternative agricultural management.

Response of Three Switchgrass (Panicum virgatum) Cultivars to Mesotrione, Quinclorac, and Pendimethalin

Abstract Annual grass weed control and switchgrass cultivar response to PRE-applied pendimethalin and POST-applied mesotrione and quinclorac was evaluated in 2005 and 2006 near Paterson, WA, in both newly seeded and 1-yr-old established switchgrass. Pendimethalin applied to newly planted switchgrass at 1.1 kg ai ha−1 at the one-leaf stage in 2005 or at 0.67 kg ha−1 PRE in 2006 severely injured and greatly reduced switchgrass stands. Mesotrione applied POST at 0.07 kg ai ha−1 injured newly planted switchgrass, reduced switchgrass height for several weeks after treatment, and reduced final switchgrass biomass by 54% both years. ‘Kanlow’ and ‘Cave-in-Rock’ cultivars were injured less by mesotrione than ‘Shawnee’ in 2005, whereas in 2006, Kanlow was injured less than Shawnee and Cave-in-Rock. Quinclorac applied POST at 0.56 kg ai ha−1 injured newly planted switchgrass less than mesotrione and pendimethalin but reduced final switchgrass biomass by 33% both years compared with treatment with atrazine alone. All three herbicide treatments controlled large crabgrass in the year of establishment. Green foxtail counts were reduced 93% or more by pendimethalin and quinclorac compared with nontreated controls, but mesotrione failed to control green foxtail. Pendimethalin applied PRE at 1.1 kg ha−1 did not injure 1-yr-old established switchgrass or reduce switchgrass biomass. Quinclorac applied POST at 0.56 kg ha−1 to established switchgrass reduced switchgrass biomass of the first harvest by 16% in 1 of 2 yr. Mesotrione applied POST at 0.07 kg ha−1 injured established switchgrass and reduced biomass of the first harvest by 33 and 17% in 2005 and 2006, respectively. Kanlow was injured the least by mesotrione in both years. Established switchgrass suppressed late-emerging annual grass weeds sufficiently to avoid the need for a grass-specific herbicide application. Nomenclature: Mesotrione; pendimethalin; quinclorac; green foxtail, Setaria viridis L. SETVI; large crabgrass, Digitaria sanguinalis L. Scop. DIGSA; switchgrass, Panicum virgatum L. ‘Cave-in-Rock’, ‘Kanlow’, ‘Shawnee’.