Phosphorus Microbiology in Organic Farming System Dipankar Dey, Satadeep Singha Roy And Niharendu Saha* Directorate of Research, Bidhan Chandra Krishi Viswavidyalaya, Kalyani – 741 235, West Bengal, India. E- mail: nihar_bckv@rediffmail.com Introduction Results and Discussion Organic farming is one of the widely used methods, which is thought of as the best alternative to avoid the ill effects of chemical farming. Organic agriculture is now becoming a promising practice.The question of replenishment of phosphorus levels in organic agricultural systems is indeed as one of the main challenges for the long-term productivity of organic farms. Recycling of soil native phosphorus- microbiologically exploited P pool and external sources like composted-P, poultry droppings etc. are the better alternative sources to overcome the problem. Providing adequate levels of P for plant grow depends on both microbial activity to mineralize organic P forms and solubilization of insoluble inorganic P. Under this background soils of established and certified organic tea gardens were analysed to understand the character and dimension of some microbiologically exploited phosphorus pools contributing P nutrition of crop plants. Phosphate solubilising microbial load under organic and conventional tea gardens of Assam Site Bacteria (CFUX105) Fungi (CFUX103) Actinomycetes (CFUX104) Belseri 39.60a 10.36a 26.73bc Chardwar 29.67b 8.71ab 22.03c Irrangmara 28.13b 6.95bc 27.2bc Jalinga 32.30b 9.04ab 40.1a Kalachera 26.37b 9.21ab 22.53bc Rose Candy 19.04c 4.9c 23.3b Alkaline phosphatase, Acid Phosphatase and Phytase enzyme activity of different organic and conventionally managed tea gardens of Assam Results showed that acid phosphatase activity was significantly increased under organic tea husbandry over conventional tea gardens in all the locations irrespective of management practices adopted in tea gardens. The results indicates the effect of organic farming systems on higher enzyme activity. It was recorded that soils of organically managed tea gardens maintained significantly higher alkaline phosphate activities while comparing with conventional tea gardens irrespective of location and management practices followed. The highest alkaline phosphatase acivity was found in soils of Belseri and Kalachera tea gardens under Brahmaputra Valley and Barak Valley, respectively. Whereas, the lowest being recorded in Jalinga tea estate under Brahmaputra Valley and Barak Valley, respectively. In conventional tea gardens the activity was drastically reduced from their counterpart organic tea gardens. On an average, 1.5 to 75 % increased level of phytase activity was recorded under organic production systems over conventional one. Among the organic gardens under Brahmaputra Valley significantly highest phytase activity was recorded under Chardwar tea garden. This higher rate of phytase activity might be due to higher organic matter content of that garden. Objectives To enumerate phosphate solubilizing bacterial load under different organic production systems, To assess and understand the microbiological and biochemical processes leading to P-transformation in organic farming soils To explore microbiologically exploited potential P-pools in organic farming soils- their characterization and quantification. Phosphate solubilising microbial load under organic tea gardens was greater than conventional tea gardens. Hypothesis To address the above mentioned objectives following were the hypotheses put forward. Microbiologically driven P-transformations are vibrant under organic farming systems, Organic soils have biologically regulated strict p-pools. Mineralization rate, Mineralization Potential, Net Mineralization, Immobilization potential and MBP of different organic and conventionally managed tea gardens of Assam Site Mineralization Rate ( µg/ kg / day) Mineralization Potential (kg/ha) Net mineralization Immobilization potential MBP (μg /g) Belseri 0.049c 39.35 33.09 6.26 28.46d Chardwar 0.057b 45.77 38.54 7.23 32.88c Irrangmara 0.019e 15.26 11.49 3.77 17.14f Jalinga 0.04d 32.12 24.47 7.65 34.76b Kalachera 0.067a 53.80 46.88 6.92 31.46c Rose Candy 10.65 4.61 20.96e Materials and Methods Phosphate Solubilizing Power of different organic and conventionally managed tea gardens of Assam Soil : Different certified organic and conventional Tea Estates of Assam under two agro ecological zones of Brahmaputra Valley and Barak Valley. It was noticed that irrespective of location agro ecological zone, age of organic garden and management packages, organically managed gardens secured significantly higher insoluble inorganic phosphate solubilizing power of soils. Name of the Garden and company Jalinga Kalachera Belseri Chardwar Rose candy Irrongmara Name of the place/ district Dwarbund North Bank block Chaklabil Tejpur Name of the state Assam Agro-ecological Zone Barak Valley Barak Valley Brahmaputra valley Textural Class Sandy Loam Sandy Loam Sandy Clay Loam Sandy Clay Loam Sandy Clay Loam PH of soil 4.10-5.0 4.10-5.10 EC(ds/m) 0.5-0.8 0.6-0.8 0.3-0.5 0.4-0.5 Status Organic Conventional Accredited by LACON (India) LACON (India) Year of starting of organic gardening 2006 2007 Results demonstrated that organically managed tea gardens showed more than two to three times higher potentially mineralizable fraction of P over conventionally cultivated tea gardens. Poorest size of potentially mineralizable P fraction under conventional tea gardens Irrangmara and Rose Candy were in accordance with their lower organic carbon content. Organic production systems having higher microbial biomass phosphorus(MBP). Microbiologically exploited Phosphorus pools under different organic and conventionally managed tea gardens of Assam Percent of P solubilised in different organically and conventionally managed tea gardens of Assam Site Acetic Acid Soluble P2O5 (kg/ha) Citric Acid Soluble P2O5(kg/ha) Lactic Acid soluble P2O5(kg/ha) Ca-lactate+lactic acid+Acetic Acid soluble- P2O5(kg/ha) Double Lactate soluble P2O5 (kg/ha) 2 keto glutaric acid soluble P2O5(kg/ha) Belseri 8.61c 35.52de 16.83b 17.04ab 34.89f 115.65c Chardwar 8.49c 34.39e 25.50a 19.05a 40.28e 139.57b Irrangmara 5.63d 7.99g 26.42a 8.57d 29.25g 62.70e Jalinga 11.36a 75.98a 18.84b 11.86c 50.78b 148.69a Kalachera 8.50c 37.55d 25.97a 18.78a 47.57c 150.79a Rose Candy 5.40d 11.19f 28.48a 9.69d 34.12f 77.60d Acid phosphatase, alkaline phosphatase and phytase enzyme activity of different organic and conventionally managed tea gardens of Assam Site Acid Phosphatase Activity ( μg p-np/g/hr) Alkaline Phosphatase Activity Phytase Activity (µ mole Pi released/sec/g) Belseri 1080.56a 179.34a 26.23b Chardwar 749.69c 137.97c 30.86a Irrangmara 452.04f 124.42d 17.63d Jalinga 582.98e 126.64d Kalachera 800.66b 142.17c 22.23c Rose Candy 438.09f 101.48e 17.38d Parameters analysed Chemical attributes Biological attributes Soil pH Microbial biomass P Soil EC Mineralizable P Available N, P and K Acid and alkaline phosphatase activity Oxidisable organic C Phytase activity Organic acid extractable P Phosphate solubilising microorganism P solubilizing Power Citric acid, 2 keto glutaric acid and a cocktail of Lactic and Acetic acid may contribute P in organic farming soils. Conclusion Organically managed production systems are vibrant in regard to phosphorus transformation while comparing with conventional production systems. Microbiologically elaborated organic acid soluble P may be considered as potential P pools contributing in P nutrition to crop plants. Standard protocols for physio-chemical and chemical analyses were followed all through the study.