Estimation of Optimum Available Phosphorous Extraction Methods for Reddish Brown Earth Soil

Abstract

Several extraction methods are used to determine plant available Phosphorus (P) that affect
for growth and yield of plants. This study was conducted to evaluate the different available P
extraction methods for reddish brown earth (RBE) soil in dry zone of Sri Lanka. The
experiment was conducted as a randomised complete block design (RCBD) with four
replicates at Kahatagasdigiliya in Anuradhapura district during Maha (2013/2014) season.
Seven extraction methods, i.e., Olsen‟s, Bray 1, Borax, Mehlich III, Modified Kelowna,
ammonium chloride and distilled water were tested. Soil samples were collected at the
tasseling stage of maize plants (Zea mays L.) treated with four fertiliser rates: 0 (T1), 20 (T2),
30 (T3) and 40 (T4) kg of P ha-1. Soil samples were analysed for pH, available P and total P
apart the initial chemical characterisation. The effect of extraction methods for soil available
P and the P recovery, interactions among the P levels with different extraction methods were
evaluated. Available P extraction and P recovery using Modified Kelowna method was
significantly greater than other methods (p<0.05). Olsen‟s, Bray 1, Borax, Mehlich III,
Ammonium Chloride extraction methods were not significantly different (p>0.05) in
available P determination. The extraction methods and fertiliser levels were significantly
different (p<0.05) with soil available P. The P extraction in T4 was comparatively higher than
other methods except distilled water extraction. Modified Kelowna method was most
appropriate in available P extraction under experimental conditions in RBE soil.

Keywords: Phosphorus, P extraction methods, P recovery, RBE