1. Phosphorus Microbiology in Organic Farming System
Dipankar Dey, Satadeep Singha Roy And Niharendu Saha*
Directorate of Research, Bidhan Chandra Krishi Viswavidyalaya,
Kalyani – , West Bengal, India. E- mail:
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
EC(ds/m)
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 a
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.