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Author: search.filters.author.Jayasinghe, C.K.Subject: search.filters.subject.Nitrogen fertilizers

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    Effect of different levels of supplemental nitrogen on CO2 assimilation rates and productivity of Pueraria phaseoloides (Roxb) Benth and Desmodium ovalipolium (prain) wall. ex ridely grown in agalawatta series soil
    (Rubber Research Institute. Agalawatte, 1985) Nugawela, A.; Jayasinghe, C.K.; Aluthhewage, R.; Wettasinghe, S.
    Plant dry matter production is linked to CO2 assimilation rates, respiratory losses and total leaf area. Experiments were undertaken to determine the effect of different levels of supplimental nitrogen given to legume cover crops, on their CO2 assimilation rates and productivity. They were found to be highest for Pueraria phaseoloides and Desmodium ovaliforlium when given around 140 and 35 ppm of supplimental nitrogen. Reciprocal of specific leaf area and laef nitrogen content were also determined and they showed a positive linear relationship with supplemental nitrogen levels. How nitrogen could a influence the CO2 assimilation rates of cover crops studies are discussed.
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    Effect of combined nitrogen on nodule function of leguminous crops with special reference to tropical soils
    (Rubber Research Institute. Agalawatta, 1991) Jayasinghe, C.K.
    The effect of combined nitrogen on nitrogen fixation has been discussed by several investigators and from their findings it could be concluded that inorganic nitrogen may have either stimulatory, neutral of negative effect on nitrogen fixation depending on the type of legome and soil condition. It was reported in some instances that low levels of combined nitrogen especially when applied as a "Starter" fertilizer at germination, stimulates plant growth and enhances nodule mass and nitrogen fixation. On the other hand when most of the legumes are grown in soil high in available nitrogen, the nitrogen fixation rate is severely affected. This phenomenon may become more critical when legumes are grown as cover crops where non legume counterpart is fertilized with nitrogenous fertilizer. The degree of inhibition appears to vary with sevaral factors vis, concentration of combined nitrogen, host species, cultivar, strain of root nodule bacteria, rate of inculation, light intensity and temperature. However, the most critical factor is the concentration of combined nitrogen and it has been shown that very low concentrations such as 240 ppm N reduced