The Effect of Alternate Wetting and Drying on the Ammonium and Nitrite Nitrogen Transformation in Soils

Investigations were carried out to study the effect of alternate wetting and drying cycles on the mineralization, nitrification, and denitrification of soil nitrogen in two soils, in the presence or absence of added ammonium and nitrite. Soils were analyzed at the end of each drying cycle for total inorganic nitrogen, ammonium, and nitrite nitrogen. Gaseous products, i.e., ammonia, and the oxides of nitrogen (NO and NO2) were collected in the course of drying for determination. The drying cycles accelerated the rate of nitrogen mineralization in both soils and further increased the oxidation of applied and available ammonium. The rate of ammonium transformation was faster in Yolo clay loam soil than in Miami silt loam. A faster rate of nitrification was also observed in Yolo clay loam. This may be because of a higher pH of the Yolo clay loam soil. The successive drying cycles had a pronounced effect on the nitrate formation in both soils. The extent of nitrite decomposition was inversely related to soil pH. The amount of nitrogen oxides (NO and NO2) evolved were inversely related to soil pH, but significant amounts of NO and N02 were evolved from even the slightly alkaline Yolo clay loam. The loss of nitrogen oxides increased with increased number of drying cycles and, further, the losses of nitrogen increased with increase in nitrite level. The majority of the nitrogen losses from these soils may be due to the direct decomposition of nitrite and possibly slight losses due to an interaction of nitrite and ammonium ions during the course of drying the soil. A considerable amount of nitrogen remained as undetected in treatments receiving either ammonium or nitrite or both. These losses of nitrogen apparently are other than by the release of NO, NO2, and NH3. The undetected nitrogen loss from the soil system may be either in the form of N2O or N2. No volatile losses of ammonia were recorded from the acid Miami silt loam soil. The greatest amount of applied ammonium nitrogen volatilized as ammonia in Yolo clay loam during the initial drying cycles. The rate of ammonia volatilization increased with increase in applied ammonium concentration

MODELING AND SIMULATION OF LOW VOLTAGE POWER SUPPLY FOR ACTIVE PHASED ARRAY RADAR

This paper deals with the modeling and simulation of low voltage power supply (LVPS) unit to the ACTIVE PHASED ARRAY RADAR, which is used for sensing different targets at a time. This RADAR system contains flat bank of small identical antennas and huge number of transmitting and receiving modules for electronic scanning. This radar antenna requires power in different levels for various electronic devices. The proposed design of LV power supply will have the ability to manage temperature variations with high efficiency under different loading condition. The closed loop control such as voltage mode control and current mode control are used to regulate the output voltage with high switching frequency of 400khz has been designed. Simulations are performed using MATLAB / SIMULINK software

Growth of Forage Legumes and Grasses in Acidic Soil Amended with Flue Gas Desulfurization Products

Large amounts of flue gas desulfurization products (FGDs) are produced when SO2 emissions are trapped in the coal burning process for generation of electricity. FGDs are normally discarded instead of being reused, and reuse on soils could be important in overall management of these products. Glasshouse experiments were conducted to determine effects of various levels of three FGDs (a FGD gypsum, an oxidized FGD + Mg, and a stabilized FGD) and the control compounds CaCO3, CaSO3, and CaSO4 on growth of alfalfa (Medicago sativa), white clover (Trifolium repens), orchardgrass (Dactylis glomerata), tall fescue (Festuca arundinacea), switchgrass (Panicum virgatum), and eastern gamagrass (Tripsacum dactyloides) in acidic (pH 4) soil (Typic Hapludult). The FGDs enhanced growth of each plant species, with alfalfa, white clover, and tall fescue receiving greater increases than the other species, especially when grown in soil amended with FGD + Mg. FGD gypsum did not often enhance growth unless high amounts were added. FGDs containing high B and low levels of CaSO3 were detrimental to growth. Overall, FGDs improved growth responses of these forage plants grown in an infertile low pH soil

Proceedings of the Workshop on Adaptation of Plants to Soil Stresses

Sustainable production of food and forage with a focus on plant adaptation to stress environments will be a continued priority for developing countries in the future. Since many areas of the world which support substantial human populations are drought prone, such as the subsaharan African zone and others, the primary focus has been on drought. However, one of the greatest restraints to sustainability of agriculture worldwide is the lack of sufficient soil nutrients for crop growth, or other soil constraints such as acidity or salinity which hinder crop production substantially. Optimizing soil fertility or amending acid and saline soils to achieve high production is difficult in areas of low economic stability since inputs are costly or quite often technically not feasible. The other obvious alternative to increase stability in stress areas is by genetic improvement of crops. Dr. Donald L. Plucknett, in a recent lecture on science and agricultural transformations, stated that while not all yield gains in the Green Revolutions can be attributed to plant breeding, it is doubtful such gains would have taken place without the new varieties or hybrids . Development and release of new and improved germplasm is probably the most economic method of technology transfer currently available. According to Dr. Plucknett, most studies indicate about half of yield gains can be attributed to genetic improvements. This statistic is undoubtedly argued in many circles, but regardless of the final figure, gains from genetic improvement are substantial

The impact of elevated CO2 and water deficit stress on growth and photosynthesis of juvenile cacao (Theobroma cacao L.).

Atmospheric CO2 concentration continues to rise and is predicted to reach approximately 700 ppm by 2100. Some predictions suggest that the dry season in West Africa could be extended with climate change. This study examines the effects of elevated CO2 concentration and water deficit on growth and photosynthesis of juvenile cacao. Light saturated photosynthesis (Pmax), quantum efficiency and intrinsic water use efficiency increased significantly in response to elevated CO2, as did a range of growth and development responses (e.g. leaf area and leaf number), but the magnitude of the increase was dependent on the water treatment. Stomatal index was significantly greater in the elevated CO2 treatment; an atypical response which may be a reflection of the environment in which cacao evolved. This study shows a positive effect of elevated CO2 on juvenile cacao which may help to alleviate some of the negative impacts of water deficit stress