ISSN:
1432-0789
Keywords:
Biological N2 fixation
;
Sesbania speciosa
;
Sesbania rostrata
;
Green manure
;
N transfer
;
Wetland rice
;
15N isotopic techniques
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Geosciences
,
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Summary We used 15N technology to investigate N2 fixation by Sesbania speciosa and Sesbania rostrata and its transfer to a lowland rice crop after incorporation of the Sesbania spp. into soil as green manure. During the first 50 days after establishment in November–December 1989, S. speciosa and S. rostrata produced 1126 and 923 kg dry matter ha-1 respectively. They gathered 31 and 23 kg N ha-1 respectively, of which 62%±5% and 55%±3% respectively, came from N2 fixation. Both these species produced a greater biomass during September–October 1989, with S. rostrata producing more than S. speciosa. These results reflected differential responses by the plants to different day lengths at different times of the year. Furthermore, the dry matter yield and %N of 15N-labelled S. speciosa were smaller than those of the unlabelled plants, possibly due to inhibition of N2 fixation in root nodules by the chemical N fertilizers added during labelling. These differences were not so pronounced in the stem-nodulated S. rostrata. The increased grain yield of rice fertilized with N in the form of chemical fertilizer or green manure was a result of an increased number of panicles per hill. The rice crop manured with S. speciosa produced a lower grain yield, with a lower grain weight than that manured with S. rostrata. This was due to a low uptake of soil N by rice manured with S. speciosa. Recovery of N from the green manure in rice straw with S. speciosa was significantly higher than from rice manured with S. rostrata, because of the higher applied N uptake by rice manured with the former.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00336300
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