The Effect of N Source. N Rate and a Vesicular-arbuscular Mysorrhizal Fungus on Nitrogen Leaching and Elemental Composition in Bermudagrass Tur'

Tavares, James William
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A glasshouse experiment was conducted to determine the effect of two sources and three rates of N and a mycorrhizal fungus on nitrogen leaching through common bermudagrass (Cynodon dactylon (L.) Pers.) grown on crushed basalt. Growth parameters were also measured to determine responses of common bermudagrass to N source, N rate and mycorrhizal infection. More NO3-N was leached from calcium nitrate than from ammonium sulphate. N lost as nitrate was 23%, 23% and 35% of N applied for the 24.4, 48.8 and 73.2 kg N/ha rates respectively of calcium nitrate. N lost as nitrate from ammonium sulphate was 21%, 12% and 10% of the N applied for the 24.4, 48.8 and 73.2 kg N/ha rates respectively. There was no effect of raycorrhiza on leaching loss of nitrogen. Root dry weights of mycorrhizal plants averaged 18854 kg/ha while non-mycorrhizal plants averaged 9819 kg /ha. Root dry weights were greater when ammonium sulphate was the source of N than with calcium nitrate. With increasing levels of N, there were increasing concentrations of N, K and Mg in the clippings. Ca concentration of clippings decreased with increasing ammonium sulphate levels. Silicon uptake was enhanced by mycorrhizal fungi. Higher concentrations were found in both roots and shoots of mycorrhizal plants. VAM infection levels decreased with increasing levels of anunonium sulphate and remained the same with increasing levels of calcium nitrate. VAM infection levels also decreased with increasing depths. Higher average VAM infection levels with ammonium sulphate indicates a possible preference by the fungus for ammonium over nitrate.
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