Blackwell Publishing Journal Backfiles 1879-2005
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
As French soils are naturally free of Bradyrhizobium japonicum, soya beans planted into new areas must be inoculated with this bacterium. Although, the B. japonicum inoculum can survive in soils for long periods of time even in the absence of a soya bean crop, re–inoculation may increase nodulation and grain yield. Thus, populations of B. japonicum can fall below optimum for plant growth. To identify the soil properties controlling survival of the inoculated bacteria samples of soil were collected from 52 sites from France that had previously grown soya beans. The samples were analysed for some physical and chemical characteristics and the B. japonicum population counted. The soil's CaCO3 content was the main factor affecting survival. The average B. japonicum numbers (per g soil) were 80 for calcareous soils and 15000 for non–calcareous soils. In the latter, silt and sand contents were correlated with the numbers of B. japonicum. The cropping frequency of soya bean and the time since the crop was last grown were other factors affecting Bradyrhizobium populations. Thus, there is a probability of enhancing economic benefit for farmers with re–inoculation of soya bean in calcareous and sandy soils.
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