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Loss of nitrogen from decomposing nodules and roots of the tropical legume Centrosema pubescens to soil


Chulan, Azizah and Waid, John S. (1981) Loss of nitrogen from decomposing nodules and roots of the tropical legume Centrosema pubescens to soil. In: Nitrogen Cycling in South-East Asian Wet Monsoonal Ecosystems, 5-10 Nov. 1979, Chiang Mai University, Thailand. (pp. 150-153).

Abstract / Synopsis

Samples (20 g) of an air-dry, sieved (<2mm) silty loam with or without (controls) the incorporation of 200 mg root portions of Centrosema pubescens, were moistened to 50% moisture holding capacity at 0.33 bar (33 kPa). The root portions were healthy, freshly harvested, clean samples of nodules, laterals or radicles; treatments Nod, Lat and Rad respectively. Soil samples were incubated aerobically at 30 C for 16 weeks. The radicles, laterals and nodules respectively contained 1.65, 3.46 and 6.91 mg N per sample and their C to N ratios were 16.5, 7.0 and 4.2. The root fragments disappeared rapidly and less than 40% and 10% of their initial dry weight remained after 1 and 16 weeks respectively; nodules decomposed more rapidly than laterals and laterals more quickly than radicles. At 16 weeks the total N contents of the controls had not changed but Rad, Lat and Nod soils respectively showed gains over the controls from week 1 onwards and by week 16, these amounted to 8.2, 17.1 and 31.8%. Concentrations of mineral N increased in all soils from week 4 onwards and by week 16, the amounts of mineral N that had accumulated in Nod, Lat and Rad were 1.62, 1.16 and 1.14 times greater than in the controls (201 ~ N g-l oven-dry soil). Under the conditions of this experiment, the legume root and nodule tissues discomposed rapidly and all of the legume root N (except an unaccounted for 5.6% of the nodule N) was transferred to the soil without any apparent net loss or gain of volatile N.

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Additional Metadata

Item Type: Conference or Workshop Item (Paper)
Divisions: Faculty of Science and Environmental Studies
Universiti Pertanian Malaysia
Publisher: Australian Academy of Science
Keywords: Centrosema pubescens; Forage; Pastures and feedstuffs; Forage legumes; Centrosema pubescens; Nitrogen transformation; Decomposition; Root system; Malaysia
Depositing User: Mohd Hafiz Che Mahasan
Date Deposited: 14 Apr 2015 10:47
Last Modified: 14 Apr 2015 10:49
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