5 research outputs found
Transport of Cryptosporidium parvum oocysts in soil columns following applications of raw and separated liquid slurry
No full textThe potential for transport of viable Cryptosporidium parvum oocysts through soil to land drains and groundwater was studied using simulated rainfall and intact soil columns which were applied raw slurry or separated liquid slurry. Following irrigation and weekly samplings over a four week period, C. parvum oocysts were detected from all soil columns regardless of slurry type and application method although recovery rates were low (<1%). Soil columns with injected liquid slurry leached 73% and 90% more oocysts compared with columns with injected and surface applied raw slurry, respectively. Among leachate samples containing oocysts, 44/72 samples yielded viable oocysts as determined by a dye permeability assay (DAPI/PI) with the majority (41%) of viable oocysts found in leachate from soil columns with added liquid slurry. The number of viable oocysts was positively correlated (r=0.63) with the total number of oocysts found. Destructively sampling of the soil columns showed that type of slurry and irrigation played a role in the vertical distribution of oocysts, with more oocysts recovered from soil columns added liquid slurry irrespectively of irrigation status. Further studies are needed to determine the effectiveness of different slurry separation technologies to remove oocysts and other pathogens, as well as whether application of separated liquid slurry to agricultural land may represent higher risks for ground water contamination as compared to application of raw slurry
Factors influencing the survival and leaching of tetracycline-resistant bacteria and <i>Escherichia coli</i> through structured agricultural fields
No full textPlant–water relations in subtropical maize fields under mulching and organic fertilization
No full textThe plant–water relationship of maize under conservation practices needs to be assessed to quantify the effectiveness of the practices in conserving soil water for crop production. This study evaluated in three trials how straw and plastic film mulching and organic manure application could potentially change water fluxes in the root zone and increase maize yield. A mathematical model HYDRUS-1D was calibrated against the observed soil water content and drainage data to predict the water fluxes in the root zone soil. The model simulated soil water dynamics in the root zone with satisfactory performance (RMSE of 0.6–2.3%, CD of 0.37–1.41, NSE of 0.18–0.88, and R2 of 0.62–0.91) during both the calibration and validation periods. The model predicted the observed drainage in a lysimeter with only a 5.5–11.7% bias and actual evapotranspiration (ETc) with a 2.6–6.7% bias for the control conditions in all three trials when the model was provided with measured plant growth, soil properties, and weather data. Both measurement and modeling confirmed that mulching augmented soil water storage by reducing ETc, i.e., 0.24–0.37 mm d-1 by straw mulching and 0.05–0.24 mm d-1 by plastic mulching during the trials. Manure application did not affect the ETc rate and resulted in the highest grain yield (6.8–8.3 Mg ha˗1) followed by plastic mulching (6.1–8.1 Mg ha˗1) and straw mulching (5.3–7.5 Mg ha˗1). Manure application increased the harvest index by optimally allocating biomass because of a steady supply of water and nutrients. The straw mulch, plastic mulch, and manure treatments increased grain yield by 13%, 24%, and 35%, respectively, compared to the control condition. Large-scale implementation of these practices would lessen blue water scarcity in agriculture
Irrigation and percolation management for reducing water footprint and nutrient leaching in rice-based ecosystems
No full textInefficient water management can lead to water and nutrient losses in rice cultivation, causing economic and environmental challenges. This study evaluated the effects of irrigation and percolation management on nutrient leaching, rice yield, and water footprint using field lysimeters during the Aman (wet) and Boro (dry) seasons in Mymensingh, Bangladesh. Irrigation treatments included zero ponding (saturated soil), 2-cm ponding, and 5-cm ponding, while percolation management involved uncontrolled percolation, reuse of percolated water, and no percolation. Leachate samples collected every 10 d were analyzed for mineral nitrogen and available phosphorus, with yield and water use measurements. The zero ponding treatment yielded lower water footprints in the Aman and Boro seasons (1 224 L/kg and 1 289 L/kg, respectively) than the 2-cm ponding (1 252 L/kg and 1 662 L/kg, respectively) and 5-cm ponding (1 360 L/kg and 1 953 L/kg, respectively) treatments, with comparable grain yields. The no-percolation treatment increased tiller count in the Aman season but had no significant effect in the Boro season. The uncontrolled percolation treatment resulted in total percolated water depths of 10–13 cm and 20–21 cm in the Aman and Boro seasons, respectively. The no-percolation treatment led to lower water footprints (1 224–1 289 L/kg) than the uncontrolled percolation (1 409–1 706 L/kg) and percolation-reuse (1 448–1 516 L/kg) treatments. Percolation reuse reduced phosphorus leaching in the Aman season, lowered NH4+-N leaching late in the Boro season, and decreased NO3−-N leaching in multiple events compared to uncontrolled percolation. These findings inform improved water and nutrient management strategies in rice ecosystems for enhanced sustainability
Simulating hydrological and nonpoint source pollution processes in a karst watershed: A variable source area hydrology model evaluation
No full textAbstractAn ecohydrological watershed model can be used to develop an efficient watershed management plan for improving water quality. However, karst geology poses unique challenges in accurately simulating management impacts to both surface and groundwater hydrology. Two versions of the Soil and Water Assessment Tool (SWAT), Regular-SWAT and Topo-SWAT (which incorporates variable source area hydrology), were assessed for their robustness in simulating hydrology of the karstic Spring Creek watershed of Centre County, Pennsylvania, USA. Appropriate representations of surface water – groundwater interactions and of spring recharge – discharge areas were critical for simulating this karst watershed. Both Regular-SWAT and Topo-SWAT described the watershed discharge adequately with daily Nash-Sutcliffe efficiencies (NSE) ranging from 0.77 to 0.79 for calibration and 0.68–0.73 for validation, respectively. Because Topo-SWAT more accurately represented measured daily streamflow, with statistically significant improvement of NSE over Regular-SWAT during validation (p-value=0.05) and, unlike Regular-SWAT, had the capability of spatially mapping recharge/infiltration and runoff generation areas within the watershed, Topo-SWAT was selected to predict nutrient and sediment loads. Total watershed load estimates (518t nitrogen/year, 45t phosphorus/year, and 13600t sediment/year) were within 10% of observed values (−9.2% percent bias for nitrogen, 6.6% for phosphorous, and 5.4% for sediment). Nutrient distributions among transport pathways, such as leaching and overland flow, corresponded with observed values. This study demonstrates that Topo-SWAT can be a valuable tool in future studies of agricultural land management change in karst regions
