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  • 1
    Electronic Resource
    Electronic Resource
    Control of gaseous nitrogen losses from urea applied to flooded rice soils (1988)
    Springer
    Nutrient cycling in agroecosystems 18 (1988), S. 31-47 
    Details
    ISSN: 1573-0867
    Keywords: ammonia loss ; denitrification ; Oryza sativa L. ; algicides ; flooded soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This paper reports field experiments designed to determine whether the two main processes responsible for nitrogen (N) loss from flooded rice (ammonia volatilization and denitrification) are independent or interdependent, and glasshouse studies which investigated the effect of soil characteristics on gaseous nitrogen loss. In the first field experiment ammonia (NH3) loss from the floodwater was controlled using algicides, biocides, frequent pH adjustment, shade or cetyl alcohol, and the effect of these treatments on total N loss and denitrification was determined. Most treatments reduced NH3 loss through their effects on algal growth and floodwater pH. Total gaseous N loss (54% to 35%) and NH3 loss (20% to 1.2%) were affected similarly by individual treatments, indicating that the amount lost by denitrification was not substantially changed by any of the treatments. In a subsequent field experiment NH3 and total N loss were again affected similarly by the treatments, but denitrification losses were very low. In control treatments with different rates of urea application, NH3 and total N loss were each a constant proportion of the urea applied (NH3 loss was 17% and total N loss was 24%). These results indicate that techniques which reduce NH3 loss can be expected to reduce total gaseous N loss. The glasshouse experiment showed that gaseous N losses could be reduced by draining off the floodwater, and incorporating the urea into the 0–0.05 m soil layer before reflooding. Even with this method, losses varied widely (6–27%); losses were least from a cracking clay and greatest from a coarse sand which allowed the greatest mobility of the applied N. Incorporation of applied urea can therefore be expected to prevent losses more successfully from clay soils with high ammonium retention capacity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01064176
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  • 2
    Electronic Resource
    Electronic Resource
    Emission of nitrogen oxides (NO x ) from a flooded soil fertilized with urea: Relation to other nitrogen loss processes (1987)
    Springer
    Journal of atmospheric chemistry 5 (1987), S. 343-365 
    Details
    ISSN: 1573-0662
    Keywords: Nitrogen oxides ; nitric oxide ; biological production ; surface fluxes ; emission ; uptake ; rice paddy ; nitrogen fertilizer ; urea ; ammonia ; nitrification ; denitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Emissions of nitric oxide and other odd nitrogen oxides (NO x ) from a flooded rice field were studied after urea had been broadcast into the floodwater. The NO x flux from the fertilized area was very low (0.2×10-9 g N m-2 s-1) for the first few days after application of urea and was high (0.95×10-9 g N m-2 s-1) in the subsequent period when significant nitrite and nitrate were present in the floodwater. At night, little if any NO x was exhaled but ambient NO2 was absorbed by the floodwater. An uptake velocity for NO2 of 3×10-4 m s-1 was measured during one night. Maximum NO x losses were observed near 1300 h when temperature and solar ultraviolet light were maximum. While the amounts of nitrogen oxides emitted are of little agronomic importance (∼2×10-3 per cent of the fertilizer nitrogen was lost as NO x during the 10-day study period), they may well be of significance as a source for some gas reactions in the atmosphere and for the global nitrogen cycle. Of the fertilizer nitrogen applied (as urea) approximately 30% was lost to the atmosphere by NH3 volatilization, 15% by denitrification, presumably as N2, and the remainder, less minor losses of NO and N2O, remained in the plant/soil/water system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00114111
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  • 3
    Electronic Resource
    Electronic Resource
    Loss of ammonia after application of urea at different times to dry-seeded, irrigated rice (1988)
    Springer
    Nutrient cycling in agroecosystems 16 (1988), S. 47-57 
    Details
    ISSN: 1573-0867
    Keywords: direct-seeding ; nitrogen fertilizer ; micrometeorology ; gas exchange ; irrigation ; volatilization ; denitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Ammonia loss from urea applied to dry-seeded rice, determined using a micrometeorological technique, varied considerably depending on the time of application. Ammonia volatilization was negligible, before and after flooding, when urea was applied to the dry soil surface two days before permanent flood. Before flooding, the urea prills remained undissolved and urea hydrolysis could not proceed. Thus there was no source of fertilizerderived ammonia for volatilization to occur. Upon flooding, the urea prills were washed into cracks in the soil which subsequently closed. Therefore the movement of soluble nitrogen into the floodwater was prevented, and again there was no ammonia source for the volatilization process. When urea was broadcast into the floodwater a few days after permanent flood, ammonia losses were high and varied from 11–21% of the nitrogen applied. These losses were associated with high floodwater pHs and high wind speeds near the water surface. However, when urea was applied into the floodwater at panicle initiation, ammonia losses were low (3–8% of the applied nitrogen). At this stage of growth the plant canopy shaded the floodwater, inhibiting algal photosynthesis and consequent pH elevation, thus resulting in low ammonia gas concentrations at the floodwater surface. In addition, the plant canopy restricted air movement at the water surface, thereby reducing ammonia transport away from the air-water interface. These findings provide basic information required for improving current fertilizer management practices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01053314
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of water depth on ammonia loss from lowland rice (1988)
    Springer
    Nutrient cycling in agroecosystems 16 (1988), S. 97-107 
    Details
    ISSN: 1573-0867
    Keywords: nitrogen loss ; volatilization ; micrometeorology ; denitrification ; gas exchange ; lowland rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This paper reports a study on the effects of water depth in modifying rates of ammonia emission and total nitrogen loss from flooded rice fields after fertilization with urea. Ammonia loss was determined by the mass balance micrometeorological method and total nitrogen loss by15N balance. Initially ammonia was lost at a faster rate from the shallow (0.05 m) than from the deep (0.14 m) floodwater; this was due to higher ammoniacal nitrogen concentrations and higher temperatures in the shallow water. Emission rates were more nearly comparable later in the experiment, but overall, 26% of the applied nitrogen was lost as ammonia from the shallow pond and only 18% from the deep pond. Even though changes in water depth markedly affected ammonia emission rates and the amounts of ammonia lost, they did not significantly affect total nitrogen loss. The results suggest that management practices based only on changes in water depth may not result in increased efficiency of fertilizer nitrogen for flooded rice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01049767
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  • 5
    Electronic Resource
    Electronic Resource
    Processes of nitrogen loss from fertilizers applied to flooded rice fields on a calcareous soil in north-central China (1988)
    Springer
    Nutrient cycling in agroecosystems 18 (1988), S. 101-115 
    Details
    ISSN: 1573-0867
    Keywords: Ammonia loss ; denitrification ; nitrogen balance ; algal growth ; transfer processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Losses of nitrogen were investigated after applications of ammonium bicarbonate and urea to flooded rice at transplanting. Ammonia (NH3) volatilization was determined by direct micrometeorological methods, and total loss of fertilizer nitrogen (N) was measured by15N balance. All the loss appeared to be in gaseous forms, since there was no evidence of leaching and runoff was prevented. The difference between N loss and NH3 loss was thus assumed to be denitrification loss. Both NH3 volatilization and denitrification losses were large, being 39% and 33%, respectively, of the ammonium bicarbonate N, and 30% and 33%, respectively, of the urea N applied by farmers' methods. Ammonia fluxes from the field fertilized with ammonium bicarbonate were very high for two days, and then declined rapidly as the NH3 source in the floodwater diminished. Moderate fluxes from the field fertilized with urea continued over 6 days, but calculations showed that NH3 transfer from floodwater to atmosphere was retarded during the middle period of the experiment, particularly on day 2 when a thick algal scum appeared on the water surface. The results indicate that this algal mass obstructed the transport of NH3 across the water-air interface until the scum was dispersed by wind action. Nevertheless, the prolonged NH3 losses on the urea treatment were due primarily to high floodwater pH values promoted by the strong algal growth during the daylight hours. Nitrogen-15 balance studies showed that incorporation of fertilizer into drained soil substantially increased recoveries of fertilizer N in rice plants and soil compared with incorporation of fertilizer in the presence of standing floodwater. Ammonia loss measurements on these treatments when urea was applied suggested that the improvement in fertilizer N efficiency was due mainly to reductions in NH3 loss.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01049507
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