Abroal I.P., Bronson K.F., Duxbury J.M., Gupta R.K. 2000. Long-term soil fertility experiments in rice–wheat cropping systems. In: Rice–wheat Consortium Paper Series No. 6. Rice–wheat Consortium for the Indo-Gangetic Plains. New Delhi, India.
Biswas T.D., Jain B.L., Mandal S.C. 1971. Cumulative effect of different levels of manures on the physical properties of soil. Journal of the Indian Society of Soil Science 19: 31–37.
Cary P.R., Weerts P.G.J. 1992. Growth and nutrient composition of
Azolla pinnata R. Brown and
Azolla filiculoides Lamarck as affected by water temperature, nitrogen and phosphorus supply, light intensity and pH
. Aquatic Botany 43(2): 163-180. http://
doi.org/10.1016/0304-3770(92)90041-G
Cherr C.M., Scholberg J.M.S., McSorley R. 2006. Green manure approaches to crop production: a synthesis.Agronomy Journal 98(2): 302-319. http://doi.org/10.2134/agronj2005.0035
Dinnes D.L., Karlen D.L., Jaynes D.B., Kaspar T.C., Hatfield J.L., Colvin T.S., Cambardella C.A. 2002. Nitrogen management strategies to reduce nitrate leaching in tile-drainded midwestern soil. Agronomy Journal 94(1): 153–171. http://doi:
10.2134/agronj2002.0153
Doran J.W., Smith M.S. 1987. Organic matter management and utilization of soil and fertilizer nutrients. In: Follett et al. (Eds.), Soil Fertility and Organic Matter as Critical Components of Production Systems. SSSA Spec. Pub. 9. SSSA, Madison, WI, pp. 53–72. http://
doi.org/10.2136/sssaspecpub19.c4
Drinkwater L.E., Wagoner P., Sarrantonio M. 1998. Legume-based cropping systems have reduced carbon and nitrogen losses. Nature 396: 262–265. http://doi:
10.1038/24376
Hallmann A. 1999. Enzymes in the extracellular matrix of Volvox: an inducible, calcium dependent phosphatase with a modular composition. Journal of Biological Chemistry 274(3): 1691–1697.
https://doi.org/10.1074/jbc.274.3.1691
Julie E.H., Simpson R.J., Richardson A.E. 2000. The growth and phosphorus utilization of plants in sterile media when supplied with inositol hexaphosphate glucose-1-phosphate or inorganic phosphate. Plant and Soil 220: 165–174. http://doi:
10.1023/A:1004782324030
Kiguli L.N. 2000. The utilisation of Azolla filiculoides Lam. as a biofertiliser under dryland conditions. M. S. Thesis, Rhodes University, 100 pp.
Lefebvre D.D., Duff S.M.G., Fife C.A., Julien-Inalsingh C., Plaxton W.C. 1990. Response to phosphate deprivation in
Brassica nigra suspension cells. Plant Physiology 93(2): 504–511.
https://doi.org/10.1104/pp.93.2.504
Lumpkin T.A. 1987a. Collection, maintenance and cultivation of Azolla. In: Elkan G. H. (ed) Symbiotic nitrogen fixation technology. Dekker, New York Basel, pp 55–94.
Lumpkin T.A. 1987b. Environmental requirements for successful Azolla growth. In Azolla Utilization. Proceeditigs of the Workshop on Azolla Use, Fuzhou, Fujian, China, 31 March-5 April 1985. International Rice Research Institute, PO Box 933, Manila, Philippines, pp. 89-97. Research Institute, Azolla utilization: Proceedings of the Workshop on Azolla Use.
MacRae R.J., Mehuys G.R. 1985. The effect of green manuring on the physical properties of temperate-area soils. Advances in Soil Science 3: 71–94.
Nambiar K.K.M. 1994. Soil Fertility and Crop Productivity Under Long-term Fertilizer Use in India. ICAR, New Delhi, India.
Passarinho J.A., Rodrigues M.L., Osorio M.L., Ricardo C.P.P., Chaves M.M. 2000. Physiological responses of
Lupinus mutabilis to phosphorus nutrition and season of growth. Journal
of
Plant Nutrition 23(4): 487–505. http://doi:
10.1080/01904160009382034
Power J.F. 1990. Use of green manures in the Great Plains. In: Havlin, J.L., Jacobsen, J.S. (Eds.), Proceedings of the Great Plains Soil Fertility Conference, Denver, CO. 6–7 March. Kansas State University, Manhattan, KS, pp. 1–18.
Prasad B., Singh R.P., Roy H.K., Sinha H. 1983. Effect of fertilizer, lime and manure on some physical and chemical properties of a red loam soil under multiple cropping. Journal of the Indian Society of Soil Science 31: 601–603.
Robertson G.P., Paul E.A., Harwood R.R. 2000. Greenhouse gases in intensive agriculture: Contributions of individual gases to the radiative forcing of the atmosphere. Science 289(5486): 1922-1925. http://doi:
10.1126/science.289.5486.1922
SAS Institute 2003. SAS/STAT. User’s Guide. Version 9.1. SAS Inst., Inc., Cary, NC.
Singh S.S., Mishra A.K., Upadhyay R.S. 2010. Potentiality of
Azolla as a suitable P-biofertilizer under salinity through acid phosphatase activity. Ecological Engineering 36(8): 1076–1082. http:// doi:
10.1016/J.ECOLENG.2010.04.022
Tadano T., Ozawa K., Saki H., Osaki M., Matsui H. 1993. Secretion of acid phosphatase by the roots of crop plants under phosphorus-deficient and some properties of the enzyme secreted by lupin roots. Plant and Soil 156: 95–98.
Tuan D.T., Thuyet R.Q. 1979. Use of Azolla in rice production in Vietnam. In International Rice Research Institute, nitrogen and rice, International Rice Research Institute, Los Banos, Philippines, pp. 395-405.
Watanabe I. 1982.
Azolla-Anabaena symbiosis-Its physiology and use in tropical agriculture. In Y. R. Dommergues and H. G. Diem (eds.), Microbiology of tropical soils and plant productivity. Martinus Nijhoff/W. Junk, The Hague, pp. 169-185.
https://doi.org/10.1007/978-94-009-7529-3_6
Yadav R.L., Dwivedi B.S., Pandey P.S. 2000. Rice–wheat cropping system: assessment of sustainability under green manuring and chemical fertilizer inputs. Field Crops Research 65(1): 15–30. http://doi:
10.1016/S0378-4290(99)00066-0