The utilization of Azolla as a source of nitrogen forrice production in Ghana
1996
Nyalemegbe, K., University of Ghana Agricultural Research Station, Kpong, Ghana | Oteng, J.W., University of Ghana Agricultural Research Station, Kpong, Ghana | Ahiabu, R.K., University of Ghana Agricultural Research Station, Kpong, Ghana
The performance of the local strain of Azolla. Azolla pinnata var. africana, as a green manure for rice was compared with inorganic nitrogen alone and a combination of Azolla and inorganic nitrogen. The Azolla was incorporatedunder the rice crop (cv. GRUG 7) grown under irrigation on the vertisol. Within a period of 4 weeks and a doubling time of 5 days, a total biomass of 18 t1ha of Azolla, equivalent to 25 kg N/ha was produced. This is 28 per cent of the optimum recommended nitrogen rate (90 kg N/ha) for rice cultivation on the vertisols of the Accra Plains. Azolla, in combination with 40 kg N/ha ammonium sulphate fertilizer, gave significantly higher grain yields than Azolla only, 60 kg N/ha ammonium sulphate fertilizer and the control plot. No significant grain yield differences were observed between the single and double Azolla incorporations,but the double incorporation of Azolla only gavea yield equivalent to that obtained under 60 kg N/ha ammonium sulphate while a lower yield was observed forthe single incorporation. The grain yields were 4.8, 3.5,2.7 and 1.8 t1ha for the Azolla plus N-fertilizer, 60 kg N/ha, Azolla only and the control plot respeectively.
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