N2 fixation and rhizosphere ecology of aspalathus linearis subsp. linearis(rooibos tea)

Master Thesis


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University of Cape Town

Aspalathus linearis subsp. linearis grows in acid sands of the Cedarberg with pH ranging from 3.8-5.5. Under these conditions:, some essential nutrients are likely to be limiting. In this study, the response of Aspalathus linearis subsp. linearis to N, P, Ca and B was investigated I under field and glasshouse conditions to determine whether provision of supplemental mineral nutrients promotes growth and N2 fixation for increased tea production, and whether this legume from low nutrient environment responds to fertilization. Interestingly, provision of N and P stimulated plant growth and symbiotic performance under field and glasshouse conditions. However, like most legumes, there was sensitivity to high levels of N which resulted in a decline in nodulation and N2 fixation. Unlike P and N nutrition, Ca supply led to a significant decrease in symbiotic performance of the legume under both glasshouse and field conditions. The amounts of N fixed ranged from 50 to 225 mg N/plant under glasshouse conditions and 3.8 to 7.1 g N/plant in the field. When inoculated with soils collected from different areas outside the Cedarberg, Aspalathus linearis subsp. linearis failed to nodulate, suggesting the possible absence of specific bradyrhizobia which nodulate this legume.

Summary in English.

Bibliography: pages 117-138.