Saturday, 15 July 2006

Soil Enzyme Activity as Affected by the Integrated Use of P Sources with Vermicompost and Phosphobacteria in Cotton (Gossypium Hirsutum) Pulse (Vigna Ungigulata) MIX in an Inceptisol.

Subramanium Thiyageshwari and Duraisamy Selvi. Tamil Nadu Agricultural Univ, Lawley Rd, Coimbatore District, Coimbatore, India

Phosphorus is one of the major nutrients which is required in large quantities by crops, but nearly 98 per cent of Indian soils have inadequate P supply. The effective use of rock phosphates for the soils other than the acidic soils is also proved and its efficiency can be improved with the conjoint application of Vermicompost (V) and Phosphobacteria (PB). As little information is available regarding the use of rock phosphate with vermicompost and phosphobacteria in calcareous soils on its enzyme activities in cotton-pulse mix, a field experiment was conducted in black calcareous soil of Inceptisol (vertic Ustropept) at a farmers' holding in Coimbatore with a pH of 8.5,Electrical conductivity of 0.3dSm-1 and Olsen's-P of 10.82 kgha-1 with cotton (Gossypium hirsutum) var.LRA 5166 and blackgram (Vigna ungiculata) var.CO5. The treatment comprised of two sources of Phosphorus fertilizers namely Single Super Phosphate (SSP) and Gafsa /Tunisia rock phosphate (TRP) @ 0,50,75 and 100 per cent with 0 and 2tha-1 of Vermicompost and 0 and 2kgha-1 of Phosphobacteria (Bacillus megaterium var.phosphaticum). The post harvest soil samples were analysed for the urease, dehydrogenase and phosphatase activities and the data were statistically scrutinized. Application of TRP (100%) +V+PB recorded maximum urease activity in cotton and blackgram. The increase in inorganic P level was found to decrease the urease activity, while 75% of TRP with V and PB recorded the maximum dehydrogenase activity. With respect to phosphatase, the activity decreased with increasing P levels, while the application of PB and V increased its activity.

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