Absorption of spring applied nitrogen in satsuma mandarin orchard covered with rat's-tail fescue, Vulpia myuros
2006
Ishikawa, K.(Ehime-ken. Fruit Tree Experiment Station, Matsuyama (Japan)) | ; Kimura, H.
A sup(15)N-tracer method was used to study the absorption of nitrogen applied in the spring to satsuma mandarin trees and rat's-tail fescue, Vulpia myuros, in a mandarin orange orchard covered with rat's-tail fescue. The amount of nitrogen applied in the spring that was absorbed by mandarin orange trees in a plot covered with rat's-tail fescue was markedly smaller, about 47%, than that in a clean cultivated plot; the difference was particularly large in new leaves. The amount of nitrogen absorbed by rat's-tail fescue in a sod culture plot was about twice as large as that absorbed by the trees in the plot. Trees in the clean cultivated plot showed higher rates of sup(15)N occupied by supplied nitrogen in all organs than trees in the sod culture plot did; the difference was particularly large in newly developed organs. However, rat's-tail fescue in the sod culture plot showed a markedly higher rate of sup(15)N ocupied by supplied nitrogen than the trees showed. A comparison of the utilization rates of nitrogen applied in the spring to trees in two different plots demonstrated that the rate was 16.7% in the sod culture plot and 35.3% in the clean cultivated plot; the rate was markedly higher in the clean cultivated plot. However, the utilization rate including an absorbed amount by rat's-tail fescue was 51.6% in the sod culture plot, which was about 1.5 times as high as that in the clean cultivated plot.
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