Abstract:
Monoculture cropping system adopted for more than a hundred years in rubber (Hevea
brasiliensis) plantation with same agro-management practices has resulted in nutrient
imbalance due to either depletion or accumulation of nutrients in soils. Phosphorus (P) is
an essential macronutrient for rubber plantations. The main objective of this study was to
determine P behaviour in Boralu series soil in relation to soil pH, organic carbon,
available P, moisture content, cation exchange capacity, and bulk density. Forty-eight soil
samples representing Boralu series soil were evaluated for available P by NH4F/HCl and
organic carbon by the Walkley Black method. Descriptive statistical data were derived
and a regression analysis was also carried out to find a relationship between soil
parameters. Available P varied from 30.77mg kg-1
in manure circle and 23.20mg kg-1
outside the manure circle. Organic carbon content in both areas, in and out of the manure
circle, varied from 1.16 to 1.16%. Significant (p=0.03) differences were observed
between the inside and outside the manure circle for organic carbon content. Whereas no
significant differences between the inside and outside of manure circle were observed for
the moisture content (p=0.31), available P (p=0.37), and cation exchange
capacity(p=0.13). There was a positive correlation between organic carbon and available
phosphorus with R2=0.27 by the action of phosphorus solubilizing microbes. There was a
negative correlation between the organic carbon content and soil pH with R2=0.27as well
as available P and bulk density with R2=0.25. Results show that available P content
increase with organic matter.
Keywords: Available phosphorus, Boralu series, Bulk density, Organic carbon, pH
