Journal ArticleDOI
Evaluation of N2-fixation and nitrogen economy of a maize/cowpea intercrop system using15N dilution methods
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Good agreement was obtained between estimates of N2 fixation of sole or intercrop cowpea (1984/85 season) based on the15N natural abundance and15N fertilizer dilution techniques, both in the field and in a glasshouse pot study.Abstract:
Yields of above ground biomass and total N were determined in summer-grown maize and cowpea as sole crops or intercrops, with or without supplementary N fertilizer (25 kg N ha−1, urea) at an irrigated site in Waroona, Western Australia over the period 1982–1985. Good agreement was obtained between estimates of N2 fixation of sole or intercrop cowpea (1984/85 season) based on the15N natural abundance and15N fertilizer dilution techniques, both in the field and in a glasshouse pot study. Field-grown cowpea was estimated to have received 53–69% of its N supply from N2-fixation, with N2-fixation onlyslightly affected by intercropping or N fertilizer application. Proportional reliance on N2-fixation of cowpea in glasshouse culture was lower (36–66%) than in the field study and more affected by applied N. Budgets for N were drawn up for the field intercrops, based on above-ground seed yields, return of crop residues, inputs of fixed N and fertilizer N. No account was taken of possible losses of N through volatilization, denitrification and leaching or gains of N in the soil from root biomass. N2-fixation was estimated tobe 59 kg N ha−1 in the plots receiving no fertilizer N, and 73 kg N ha−1 in plots receiving 25 kg N ha−1 as urea. Comparable fixation by sole cowpea was higher (87 and 82 kg N ha−1 respectively) but this advantage was outweighed by greater land use efficiency by the intercrop than sole crops.read more
Citations
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Book ChapterDOI
Biological nitrogen fixation: investments, expectations and actual contributions to agriculture
Mark B. Peoples,E. T. Craswell +1 more
TL;DR: The actual levels of N2 fixation attained by legume and non-legume associations are reviewed and their role as a source of N in tropical and sub-tropical agriculture is assessed.
Journal ArticleDOI
Use of the 15N natural abundance technique to quantify biological nitrogen fixation by woody perennials
TL;DR: While the natural abundance technique appears to provide quantitative measures of BNF in tree plantation and agroforestry systems, particular difficulties may arise which can often limit its application in natural ecosystems.
Book ChapterDOI
Building Soil Nitrogen Capital in Africa
Ken E. Giller,Georg Cadisch,Costas Ehaliotis,Edward S. Adams,Webster D. Sakala,Paramu L. Mafongoya +5 more
Journal ArticleDOI
Biological nitrogen fixation in mixed legume-cereal cropping systems
TL;DR: Cereal/legume intercropping increases dry matter production and grain yield more than their monocultures and the distance between the cereal and legume root systems is important because N is transferred through the intermingling of root systems.
Book ChapterDOI
Nitrogen Fixation by Legumes in Tropical and Subtropical Agriculture
TL;DR: The merits of the different techniques that have been used to quantify N 2 fixation are discussed and the role of symbiotic N 1 fixation in the N economies of the many legume-based production systems of the tropics and subtropics is reviewed.
References
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Methods of seawater analysis
TL;DR: The Automatic Determination of Dissolved Organic Carbon (DOC) by Wet Chemical Oxidation is described in this paper, along with the results of HPLC analysis of photosynthetic pigments.
Journal ArticleDOI
The Concept of a ‘Land Equivalent Ratio’ and Advantages in Yields from Intercropping
R. Mead,R. W. Willey +1 more
TL;DR: In this paper, the Land Equivalent Ratio (LER) concept is considered for situations where inter-cropping must be compared with growing each crop sole, and a method of calculating an effective LER is proposed to evaluate situations where the yield proportions achieved in intercropping are different from those that might be required by a farmer.
Journal ArticleDOI
Influence of Inorganic Nitrogen on Nitrogen Fixation by Legumes as Revealed by N151
TL;DR: In this paper, the ratio of absorption of fixed vs. applied nitrogen by two legumes was determined to determine the degree of reduction in nitrogen fixation in Ladino clover and alfalfa.
Journal ArticleDOI
Estimating N2-fixation in the field using 15N-labelled fertilizer: Some problems and solutions
TL;DR: In this article, the 15 N-labelled fertilizer dilution technique provides a method of obtaining estimates of biological N 2 -fixation in the field over the growing season, which explains these errors and allows a more rational choice of non-fixing control.