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Isotopic Studies of Azolla and Nitrogen Fertilization of Rice : Report of an FAO/IAEA/SIDA Co-ordinated Research Programme on Isotopic Studies of Nitrogen Fixation and Nitrogen Cycling by Blue-Green Algae and Azolla - K.S. Kumarasinghe

Isotopic Studies of Azolla and Nitrogen Fertilization of Rice

Report of an FAO/IAEA/SIDA Co-ordinated Research Programme on Isotopic Studies of Nitrogen Fixation and Nitrogen Cycling by Blue-Green Algae and Azolla

By: K.S. Kumarasinghe (Editor), D.L. Eskew (Editor)

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Published: 31st March 1993
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Nitrogen is the most limiting element for crop production. Traditionally, expensive commercial fertilizers are used to correct soil N deficiencies. Indeed, 50% of the increase in rice yields after World War II can be attributed to increased fertilizer N use. Although an increased rate of fertilizer N application has been advocated to meet the growing demand for food, it is unrealistic to advise the farmers to apply fertilizers they could hardly afford, and whose prices are likely to escalate in the years ahead. In addition, when they are not applied judiciously there are problems of environmental pollution as plants are capable of taking up only a relatively small portion of the applied nitrogen, a substantial amount being lost through various chemical and biological processes. The exploitation of cheaper alternatives or supplements to fertilizers have therefore gained much interest in recent years.
Our increased interest in biological nitrogen fixation as a supplement or alternative to nitrogen fertilizers led to the convening of a consultants meeting on "The role of isotopes in studies on nitrogen fixation and nitrogen cycling by blue-green algae and the Azolla-Anabaena azollae association", in Vienna from 11-15 October 1982. S.K.A. Danso of the Soil Fertility, Irrigation and Crop Production Section acted as the Scientific Secretary of this meeting. The consultants group recommended that the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture embark on a Co-ordinated Research Programme in this field and that initial emphasis should be placed on Azolla-Anabaena symbiosis. As a result, a Co-ordinated Research Programme was initiated in 1984 which was concluded in 1989. The results and conclusions reported here are those that were generated during the five years of its operation.

Preface
Introductionp. 1
Assessment of nitrogen fixation in Azolla using the [superscript 15]N isotope dilution techniquep. 3
Comparison of the direct and indirect [superscript 15]N methods for evaluation of N uptake by rice from Azollap. 16
Use of [superscript 15]N-labelled ammonium sulphate and [superscript 15]N-labelled urea as a source for labelling Azolla with [superscript 15]Np. 23
Effects of urea and Azolla on N uptake and yield of ricep. 32
Co-ordinated field evaluation of Azolla N uptake and yield response of rice in Bangladesh, China, Indonesia, Pakistan, The Philippines, Sri Lanka and Thailandp. 42
Residual effects of Azolla N to a second crop of rice or wheatp. 55
A comparative study of the effects of Azolla species and strain on availability of N to ricep. 61
Comparison of the availability of N from fresh vs dried Azollap. 66
Effects of phosphorus fertilization on growth and N accumulation in Azollap. 71
Nitrogen balance studies in Azolla/rice cropping systemsp. 79
Increasing fertilizer use efficiency of urea using Azollap. 87
Summary and conclusionsp. 98
Referencesp. 103
List of participantsp. 109
Appendicesp. 113
Table of Contents provided by Blackwell. All Rights Reserved.

ISBN: 9780792322740
ISBN-10: 0792322746
Series: Cancer Treatment and Research
Audience: Professional
Format: Hardcover
Language: English
Number Of Pages: 148
Published: 31st March 1993
Publisher: SPRINGER VERLAG GMBH
Country of Publication: NL
Dimensions (cm): 24.18 x 16.56  x 1.78
Weight (kg): 0.43