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Browsing by Author "Jacinthe, Pierre André"
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Item Evaluation of antibacterial and antifungal compounds for selective inhibition of denitrification in soils(RSC, 2016-12) Ladan, Shiva; Jacinthe, Pierre André; Department of Earth Sciences, School of ScienceNitrous oxide (N2O) is an atmospheric constituent implicated in climate warming and stratospheric ozone depletion. Both bacteria and fungi participate in N2O production, but information is lacking with regard to the relative contribution of bacterial and fungal denitrifiers to the denitrification process in agricultural soils. The selective inhibition (SI) technique is widely used to assess the contribution of different groups of microbes to soil processes, but success of the technique depends on the effectiveness of the inhibitors. In this study, laboratory experiments were conducted to assess the contribution of bacteria and fungi to denitrification using soils from a woodlot, agricultural fields under conventional plowing (PT), and no-till for either 50 years (long-term) or 11 years (medium-term). A selective inhibition (SI) technique was developed using two bactericides (streptomycin and bronopol) and two fungicides (cycloheximide and captan) applied at different rates (0–32 mg per g soil). Regardless of the application rate, streptomycin and cycloheximide were not effective inhibitors of denitrification, with a degree of inhibition only between 2 and 20% relative to controls. These results are significant given the wide use of these products in SI studies. However, the bactericide bronopol and the fungicide captan effectively inhibited denitrification, with the strongest inhibition observed at an application rate of 16 mg per g soil. The ratio of fungal to bacterial denitrification activity (F : B) was generally less than 1, indicating a dominance of bacteria in denitrification activity in the soils investigated. However, an increase in the F : B ratio from 0.24 in medium-term NT to 0.87 in long-term NT soils was noted, suggesting perhaps a progressive increase in the role of fungal denitrifiers with a longer duration of NT farming.Item Meta-Analysis of Phosphorus Loss from No-Till Soils(ACSESS, 2017) Daryanto, Stefani; Wang, Lixin; Jacinthe, Pierre André; Earth Sciences, School of ScienceAgriculture is a significant contributor to phosphorus (P) enrichment in aquatic ecosystems. No-till (NT) farming has been proposed as an alternative approach to conventional tillage (CT) in reducing soil P export, but published data have shown contrasting impacts, likely due to the interacting effects of different physical (climate region, rainfall variability, transport pathway, slope gradient) and management variables (NT duration, crop species). We conducted a meta-analysis to understand the extent to which each of these variables controls the concentration and load of different P fractions (dissolved P, particulate P) in agricultural runoff and leaching. In comparison with CT, particulate P loss was significantly lower with NT adoption (45 and 55% reduction in concentration and load, respectively), but an increase in dissolved P loss was observed. The extent of the reduction or increase, however, varied with different physical and management variables. In comparison with CT, for example, NT was not effective in reducing particulate P concentration during wet years and particulate P load on steep slopes (4–9%). Total P concentration was also similar with CT at sites under prolonged NT duration (∼10 yr) and at NT fields planted with soybean [Glycine max (L.) Merr.]. Our results underscore the need to consider the covarying physical and management factors when assessing the potential of NT farming in controlling P loss in the environment. The limited impact of NT on dissolved P loss remains a serious impediment toward harnessing the water quality benefits of this management practice.Item Soil organic carbon pools across paired no-till and plowed Alfisols of central Ohio(Wiley, 2016-12) Nakajima, Toru; Shrestha, Raj K.; Jacinthe, Pierre André; Lal, Rattan; Bilen, Serdar; Dick, Warren; Department of Earth Sciences, School of ScienceNo-till (NT) farming can restore the soil organic carbon (SOC) pool of agricultural soils, but the SOC pool size and retention rate can vary with soil type and duration of NT. Therefore, the objectives of this study were to determine the effects of NT and soil drainage characteristics on SOC accumulation across a series of NT fields on Alfisols in Ohio, USA. Sites under NT for 9 (NT9), 13 (NT13), 36 (NT36), 48 (NT48) and 49 (NT49) years were selected for the study. Soil was somewhat poorly drained at the NT48 site but moderately well drained at the other sites. The NT48 and NT49 on-station sites were under continuous corn (Zea mays), while the other sites were farmers' fields in a corn–soybean (Glycine max) rotation. At each location, the SOC pool (0–30 cm) in the NT field was compared to that of an adjacent plough-till (PT) and woodlot (WL). At the NT36, NT48 and NT49 sites, the retention rate of corn-derived C was determined using stable C isotope (13C) techniques. In the 0- to 10-cm soil layer, SOC concentration was significantly larger under NT than PT, but a tillage effect was rarely detected below that depth. Across sites, the SOC pool in that layer averaged 36.4, 20 and 40.8 Mg C/ha at the NT, PT and WL sites, respectively. For the 0- to 30-cm layer, the SOC pool for NT (83.4 Mg C/ha) was still 57% greater than under PT. However, there was no consistent trend in the SOC pool with NT duration probably due to the legacy of past management practices and SOC content differences that may have existed among the study sites prior to their conversion to NT. The retention rate of corn-derived C was 524, 263 and 203 kg C/ha/yr at the NT36, NT48 and NT49 sites. In contrast, the retention rate of corn-C under PT averaged 25 and 153 kg C/ha/yr at the NT49 (moderately well-drained) and NT48 (somewhat poorly drained) sites, respectively. The conversion from PT to NT resulted in greater retention of corn-derived C. Thus, adoption of NT would be beneficial to SOC sequestration in agricultural soils of the region.