Record ID No. |
4653 |
Author(s) |
Alain Atangana, Damase Khasa, Scott Chang, Ann Degrande , 2014 |
Affiliation |
Renewable Resources, University of Alberta, Edmonton, Alberta, Canada, Email: aatangan@ualberta.ca |
Title |
Biological Nitrogen Fixation and Mycorrhizal Associations in Agroforestry |
Source. Vol.(no):Page |
Tropical Agroforestry 173-202p. |
Categories |
Arbuscular Mycorrhiza |
Subjects |
Biological Interaction |
Sub-subjects |
Nodule forming nitrogen fixers |
Host |
Casuarina equisetifolia and C. junghuhnina, Leucaena leucocephala |
Organism |
Rhizobium, Arbuscular Mycorrhiza |
Country |
Canada, N. America |
Abstracts |
Biological nitrogen fixation is performed through both symbiotic and non-symbiotic means. Symbiotically, the most common association is that of roots and Rhizobium bacteria or filamentous actinomycete Frankia. Nearly all legumes used in alley cropping fix significant amounts of nitrogen in association with Rhizobium. Non-legume shrubs or trees such as Casuarinas and alders also fix significant amounts of nitrogen in association with Frankia. The amount of nitrogen fixed by legumes is variable. Leucaena leucocephala, which forms abundant nodulation, fixes between 100 and 550 kg of nitrogen per ha per year. The potential for nitrogen fixation by Acacia is also high, with up to 200 kg per ha per year. The contributions of fixed nitrogen to native as well as managed ecosystems by the actinorhizal symbioses (Frankia-non legume symbioses) are comparable to those of the more extensively studied Rhizobium-legume interactions. For instance, the roots of Casuarina equisetifolia and C. junghuhnina produce nodules where the bacteria fix atmospheric nitrogen (362 kg ha-1 year-1). The main selection criteria for provenances or species for introduction into an agroforestry system include the rate of nitrogen fixation. The species selected should have the highest possible rate for a range of climatic conditions, and must also be able to tolerate environmental constraints such as pests and low nitrogen levels in the soil. Agroforestry species form symbiotic associations with mycorrhiza, typically arbuscular mycorrhizas, to enhance nutrient and water uptake and plant growth. Possible topics of interest to researchers in agroforestry are the efficient use of ecologically adapted biofertilizers (nitrogen fixing and mycorrhizal inoculants) in relation to plant species and soil fertility (N and P availability), the quality assurance of commercial inoculants, as well as the response to inoculation (improvement of methods to estimate nitrogen fixation and P uptake). |