a b s t r a c tAn exploratory study of CO 2 concentrations and fluxes was conducted during 2013, at a site 12 km North of Harare, Zimbabwe. CO 2 measurements were made over four adjacent fields of differing surface vegetation. The data illustrate the role of atmospheric intermittency as a mechanism for transferring CO 2 between the surface and the atmosphere. At night, limited atmospheric mixing permits CO 2 concentrations to increase to levels well above those conventionally reported (exceeding a spatial average of 450 ppm on some nights), but these high levels are moderated by a periodic intermittency that appears similar to that observed elsewhere and often associated with the presence of strong, synoptic-scale winds aloft (especially low-level jets). The availability of CO 2 data with adequate time resolution facilitates investigation of the general behavior, which is suspected to be a common although rarely observed feature of the lower terrestrial atmosphere. If true, this means that the nocturnal vertical transfer of momentum, heat and mass is not solely through a constrained spectral continuum of turbulence as much as by intermittent bursts, propagating from above and penetrating the surface boundary layer.
Global food demand requires that soils be used intensively for agriculture, but how these soils are managed greatly impacts soil fluxes of carbon dioxide (CO 2). Soil management practices can cause carbon to be either sequestered or emitted, with corresponding uncertain influence on atmospheric CO 2 concentrations. The situation is further complicated by the lack of CO 2 flux measurements for African subsistence farms. For widespread application in remote areas, a simple experimental methodology is desired. As a first step, the present study investigated the use of Bowen Ratio Energy Balance (BREB) instrumentation to measure the energy balance and CO 2 fluxes of two contrasting crop management systems, till and no-till, in the lowlands within the mountains of Lesotho. Two BREB micrometeorological systems were established on 100-m by 100-m sites, both planted with maize (Zea mays) but under either conventional (plow, disk-disk) or no-till soil management systems. The results demonstrate that with careful maintenance of the instruments by appropriately trained local personnel, the BREB approach offers substantial benefits in measuring real time changes in agroecosystem CO 2 flux. The periods where the two treatments could be compared indicated greater CO 2 sequestration over the no-till treatments during both the growing
While the literature is clear about excessive tillage decreasing soil carbon (C) content, there are few experimental studies that document the comparative effects of soil and crop management on C sequestration. Using micrometeorology we measured CO 2 flux from a maize crop grown on both no-till and tilled soils in north-central Ohio. We used Bowen Ratio Energy Balance (BREB) systems to quantify the flux between the atmosphere and either the soil surface (at crop planting) or 0.2 m above the canopy once the crop was established and growing. The no-till plot sequestered 263 g CO 2 m -2 (90% confidence interval -432.1 to -99.9) while the tilled plot emitted 146 g CO 2 m -2 (90% confidence interval -53.3 to 332.2) during 104 days of the 2015 growing season; a net difference of 410 g CO 2 m -2 . The difference is statistically significant at the 90% confidence level (based on a bootstrap analysis). The results indicate that no-tillage practices can sequester C, maintain soil productivity, and ensure landscape sustainability.
Industrial biotechnology waste as a soil amendment approximates farmer practice yields. Applying waste amendments significantly increased soil organic C compared with farmer practice. Using waste nutrients for agriculture and soil organic matter improves sustainability. Reuse of industrial biotechnology by‐products has become an important component of circular bio‐economies whereby nutrient‐rich wastes are returned to agricultural land to improve soil fertility and crop productivity. Heat‐inactivated spent microbial biomass (SMB) from the production of 1,3‐propanediol is an industrial fermentation by‐product with nutrients that could replace or supplement conventional fertilizers. Our objectives were to determine if SMB utilization as a soil amendment in agriculture could generate environmental benefits while meeting farmer yield expectations and assess the impact of SMB application on CO2 emissions. This study examined the replacement of typical farmer fertilizer practices with the application of SMB. In addition to yellow dent maize (Zea mays L. var. indentata) grain yield and aboveground biomass, soil organic carbon (SOC) was measured. The eddy covariance (EC) micrometeorological method was used to measure CO2 flux. Overall maize yields were positively correlated with increasing application rates of SMB. After two SMB applications, SOC increased by 45% on the SMB plot as compared with an increase of 11% on the farmer practice plot. The SMB‐treated plot also emitted more CO2 (794 g CO2 m−2 yr−1) compared with the farmer practice treatment (274 g CO2 m−2 yr−1). Results from this study provide information on the efficacy of waste product nutrient cycling in the soil–plant ecosystem that could improve productivity and sustainability.
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