Chickpea rhizobium populations: Survey of influence of season,soil depth and cropping pattern |
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| Institution: | 1. Odum School of Ecology, University of Georgia, 140 E Green St, Athens, GA 30602, USA;2. Joseph W. Jones Ecological Research Center, 3988 Jones Center Drive, Newton, GA 39870, USA;3. Warnell School of Forestry and Natural Resources, University of Georgia, 180 E Green St, Athens, GA 30602, USA;1. CIRAD, UMR AGAP, Montpellier F-34398, France;2. ICRISAT WCA, BP 320, Bamako, Mali;3. ULPC, BP 18, Dioïla, Mali;4. CIRAD, UPR Green, Montpellier F-34398, France;5. CIRAD, UPR AÏDA, Montpellier F-34398, France;1. International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Hyderabad, AP, 502324 India;2. Centre for Crop Systems Analysis (CCSA), Wageningen University and Research, Wageningen, The Netherlands;3. School of Land and Food, Tasmanian Institute of Agriculture, University of Tasmania, Hobart, Australia;1. International Livestock Research Institute, c/o ICRISAT, Patancheru 502324, India;2. International Crops Research Institute for the Semi-Arid Tropic (ICRISAT), Patancheru 502324, India |
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| Abstract: | Chickpea Rhizobium populations in soil samples from research stations and farmers' fields in different geographic regions of India ranged from <10 to > 104 rhizobia g−1 soil. Fields on research stations with a known history of chickpea cropping had more rhizobia (calc. 103 to 105 rhizobia g1̄ soil) than the majority of farmers' fields (calc. < 10 to 103 rhizobia g−1 soil). In the absence of chickpea in the cropping pattern, soils generally had < 102 rhizobia g1̄ and crops in such fields nodulated poorly. However, poor nodulation was also observed when populations of rhizobia were high, indicating that other factors were also important for nodulation. There was no obvious consistent correlation of Rhizobium population with pH, electrical conductivity and nitrate-nitrogen status of the soil.Rhizobium populations declined with soil depth and were highest (about 104 rhizobia g−1 soil) in the top 30 cm of the profile and lowest, but still present (calc. 103–103 rhizobia g'1 soil), at 90–120 cm—a depth where no nodules are found. Populations fluctuated most in the top 5 cm, being reduced during periods of high soil temperature in summer and recovering after rains. Rhizobium populations were at a maximum after chickpea but survived well under pigeonpea, groundnut and maize. When rice followed an inoculated chickpea crop, there was about a 100-fold decrease in the Rhizobium population. |
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