Development of phosphorus saturation indices for some selected soils of India
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Date
11-10-13
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University of Agricultural Sciences, Bengaluru
Abstract
The degree of P saturation (DPS) approach includes quantity and intensity
parameter and thus plays an important role in estimating the potential capacity of soils to
release P into environment. The investigation on “Development of phosphorus saturation
indices for some selected soils of India” was carried out using Jabalpur, Delhi, Bangalore
and Trivandrum soils with an objective of developing DPS indices using different
extractants namely Olsen, Bray1 and 2, Mehlich3, AB-DTPA and Ammonium Oxalate to
understand P movement and loss from agricultural soil. The four selected soils were
incubated at 0, 25, 50, 100, 150, 200, 400 and 800 % of P sorption maxima and used for
developing DPS indices with different extractants, column and pot study using maize as
test crop. The experiment was undertaken during 2011-12 with complete randomized
design including eight treatments and replicated thrice.
The critical threshold DPS Ol-1, DPS M3-3, DPSA.O.-1 for Jabalpur and Delhi soil was
52.67 37.52, 19.9 % and 29.09, 15.57, 8.60 % resulting in reactive P (RP) concentration
of 0.55 and 0.3 μg ml-1. Similarly, DPS By 1-1 DPS M3-2, DPSA.O.-1 for Bangalore and
Trivandrum was 33, 128, 11.2 % and 45.92, 169.12, 10.21 % resulting in RP
concentration of 0.12 and 0.14 μg ml-1. The environmental STP like WEP and CaCl2-P
showed better correlation with RP concentration in leachate as compared to agronomic
STP (Olsen, Bray, M3P, ABDTPA).
The threshold value of DPS Ol-1, DPSA.O.-1 and DPS M3-3 for crop yield in Jabalpur
and Delhi soils were 20.47, 11.7 and16.01 percent and 3.1, 1.22 and 2.51 per cent
respectively. In case of Bangalore and Trivandrum soils threshold DPS M3P-2, DPS By1-1
and DPS A.O.-1 for yield was 4.94, 6.8 and 4 percent and 10.3, 16.18 and 6.66 per cent
respectively.
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Keywords
extraction, concentrates, organic acid salts, yields, irrigation, inorganic acid salts, leaching, planting, fertilizers, crops