Abstract:
Phosphorus (P) is an essential macro nutrient for plant growth and development.
Soil P exists in organic and inorganic forms. However, only a fraction of soil P is
readily available to plant. Plant available and total P concentrations in soils vary
among soil types due to the differences in soil mineralogy, structure, physical &
chemical properties, and fertilizer application. Therefore, this research was
conducted to estimate the concentrations of plant available and total P in major rice
growing soils (i.e. 18 soil types) in Sri Lanka, and to study their relationships with
grain P concentration. Total of 200 soil samples and grain samples were collected
representing paddy lands across the country using a stratified random sampling
approach. Available P (Olsen-P) and total P in soils, and grain P concentrations were
measured. Available P concentration in paddy soil samples ranged from 5.4-76.9 mg
kg−1. The highest available P concentration was recorded in Reddish Brown Earths
& Immature Brown Loams soil (RBE_IBL) (34 mg kg−1) and the lowest in Red-Yellow
Latosols soil (RYL) (12 mg kg−1). Soil total P concentration had a wide range of
values i.e., 142-5685 mg kg−1. The Red-Yellow Podzolic soils with soft or hard
laterite (RYP) had the highest soil total P concentration (2525 mg kg−1). Grumusol
soil and RYL soil reported the lowest total P, i.e., < 1000 mg kg-1. Grain P
concentration varied among soil types and it ranged between 0.6-1.8 mg g-1.
However, there was no correlation between the grain and soil P concentrations.
This information would be important for sustainable P-nutrient management in Sri
Lankan rice soils.
