Labelling technique for 15N-rice straw
1986
Wittaya Masayna | Thongpan Nonrucha | Duangsamorn Taja (Khon Kaen Univ. (Thailand). Faculty of Agriculture. Dept. of Soil Science)
Rice cultivation in Thailand during the past 10 years covered on yearly average 58 and 3.5 million Rai for major and the second rice, respectively. Part of rice straw left over in the field became feeds for ruminants while the remaining larger portion of straw were eliminated through burning which caused a loss of N between 1-8 kg N/Rai/year, depending on kind and amount of straw, and the completeness of burning. It is expected that annual loss of N in this manner would amount to several thousand Baht. Research on straw-N transformations and its subsequent availability to succeeding rice, was very meager in Thailand. So far the use of 15N-tagged straw, which normally yields more reliable results, has not yet been employed for this purpose. Rice straw was labelled with 15N in culture solution containing complete nutrients in a 4-liter plastic container. 15N from (15NH4)2SO4 was supplied as N source for the rice plants in culture solution. The nutrient solution was maintained at pH 5.0 while its strength varied as 1/3 and 1/2 of normal strength for the first and second week, respectively and, thereafter, the normal concentration was employed until the end of experiment at 115 days with a change of fresh nutrient solution at 7 day interval. Rice straw so obtained was oven-dried at 70 deg C for 72 hrs ground and analyzed for 15N. The tagged straw obtained contained 9.56 % atom 15N as a result of isotope exchange and the isotope dilution in the rice plants.
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