No abstract

Vegetated land surfaces play an important role in determining the fate of carbon in the global carbon cycle. However, our understanding of the terrestrial biosphere on a global scale is subject to considerable uncertainty, especially concerning the impacts of climatic variables on the carbon cycle. Soil is a source and also a sink of co 2 exchange and helps in carbon sequestration. Agricultural management practices influence soil water dynamics, as well as carbon cycling by changing soil CO 2 emission and uptake rates. the rate of soil co 2 emission varies for different crops and different organic amendments. the major goal of this study was to assess the impacts of the type and rate of organic amendment on soil co 2 emission in a collard greens crop grown in the southeast texas environment. thirty-six plots were developed to grow collard greens on prairie View A&M University's Research farm. three types of organic amendments (chicken manure, Dairy manure, and Milorganite), at four levels of application (0, 168, 336, and 672 kg N/ha) were used and replicated three times. Each organic amendment type was applied to nine randomly selected plots. three random plots were used as a control in each row. We measured daily soil co 2 emission for the first two weeks and every other day in a week during the experiment. We evaluated the effects of organic amendments and the application rates on soil co 2 emission for collard greens during two growing seasons. the results showed higher the application rates for each organic amendment, higher the co 2 emissions from the soil. the results also showed higher cumulative co 2 emissions for the soils amended with chicken manure and milorganite, but lowest for the soils amended with dairy manure. This field experiment and analyses help better understand the temporal and spatial variations of soil co 2 emission, and also help to develop best management practices to maximize carbon sequestration and to minimize soil co 2 emissions during the growth periods of collard greens under changing temperatures using different organic amendments, and application rates. Vegetated land surfaces play a significant role in controlling the carbon dynamics in the global carbon cycle; however, knowledge about the comprehensive role of the terrestrial biosphere on regional to global scale under changing climate is still limited 1. Greenhouse gases, including CO 2 emissions, are rapidly increasing because Earth's climate is continuously warming 2-4. The physiological processes of vegetation leaves and photosynthetic capacity, which influence carbon emission and carbon uptake, rely on daily and seasonal variations of weather parameters, and hydrologic and climatic variables (e.g., solar energy, soil and air temperatures, humidity deficits, soil moisture) 5-10. Hence, CO 2 fluxes over agricultural lands are expected to vary on daily and seasonal time scales. During the growing season, vegetation coverage reduces bare soil areas to the environment. For example, in the beginning, the soil surface used to be...

Reliable and accurate monitoring of soil water content (q) across the landscape is indispensable for many water resources applications. Capacitance-based in situ soil water content measuring devices are extensively used despite their sensitivity to soil properties besides water content, e.g., temperature and organic matter content. The main goals of this study were to: (i) examine the effects of temperature, hysteresis of the temperature response, and probe-to-probe variability on the performance of three (5TE, EC-5, and EC-TM) single capacitance sensors (SCS) in a Hawaiian Oxisol; and (ii) develop empirical calibration equations to correct for temperature and improve measurement accuracy. The SCS raw output and thermocouple temperature measurements were recorded at 1-min intervals during heating and cooling cycles between 1 and 45°C. The three SCS and thermocouples were inserted in uniformly packed soils with q varying from 0 to 0.55 m 3 m −3 . We used three probes for each SCS, and the entire experiment was replicated with two heating and cooling cycles. Temperature, hysteresis, and the probe-to-probe variability effects were highly significant (p < 0.05) for all three SCS. Estimated q using soil-specific calibrations at 25°C significantly increased with increasing temperature for all SCS. The 5TE sensor showed increasing temperature sensitivity with increasing water content. However, the EC-5 and EC-TM sensors exhibited a bidirectional response to temperature, with the highest sensitivity at ?0.10 m 3 m −3 water content. An empirically derived temperature-dependent calibration equation substantially reduced the variability (>90% reduction in interquartile range) in measured water content due to changing soil temperature. Applying differing temperature corrections for heating and cooling did not improve the calibration any further.Abbreviations: SCS, single capacitance sensors.

The objective of this investigation is to study the impacts of the global response to COVID-19 on air pollution and air quality changes in major cities across the globe over the past few months. Air quality data (NO2, CO, PM2.5, and O3) were downloaded from the World Air Quality Index project for the January 2019–April 2020 period. Results show a significant reduction in the levels of 2020 NO2, CO, and PM2.5 compared to their levels in 2019. These reductions were as high as 63% (Wuhan, China), 61% (Lima, Peru), and 61% (Berlin, Germany), in NO2, CO, and PM2.5 levels, respectively. In contrast, 2020 O3 levels increased substantially, as high as 86% (Milan, Italy), in an apparent response to the decrease in titration by nitrogen monoxide and its derivatives. Significant differences in the weather conditions across the globe do not seem to impact this air quality improvement trend. Will this trend in the reduction in most air pollutants to unprecedented levels continue in the next few weeks or even months? The response to this and other questions will depend on the future global economic and environmental policies.

Small-scale vegetable and fruit crop producers in the USA use locally available commercial organic fertilizers and soil amendments recycled from municipal and agricultural wastes. Organic soil amendments provide crops with their nutrient needs and maintain soil health by modifying its physical, chemical, and biological properties. However, organic soil amendments might add unwanted elements such as toxic heavy metals or salts, which might inhibit crop growth and reduce yield. Therefore, the objective of this study was to evaluate phytotoxicity of three commercial organic amendments, chicken manure, milorganite, and dairy manure, to collard greens using the seed germination bioassay and chemical analysis of the organic amendments. The seed germination bioassay was conducted by incubating collard greens seeds to germinate in 1:10 ( w / v ) organic amendment aqueous extracts. Results of this work identified phytotoxic effects of chicken manure and milorganite, but not dairy manure, to collard greens. Potentially phytotoxic chemicals such as copper, zinc, nickel, and salts were also higher in chicken manure and milorganite compared to dairy manure. In particular, nickel in chicken manure and milorganite aqueous extracts was 28-fold and 21-fold, respectively, higher than previously reported toxic levels to wheat seedlings. The results demonstrate the need for more research on phytotoxicity of commercial organic soil amendments to ensure their safe use in vegetable and fruit crop production systems.