Effect of organic amendments on boron availability in calcareous soils under raya (Brassica juncea L.) and soybean (Glycine max.L.)
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Date
2019
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Punjab Agricultural University, Ludhiana
Abstract
A pot experiment was conducted during rabi (2016-2017) and kharif (2017) season to study the response
of raya (Brassica juncea L.) (cv. PBR 357) and soybean (Glycine max L.) (cv. SL 958) to different levels
of boron (B) and different organic manures in boron deficient calcareous soils of Punjab. Three different
soils with varying calcium carbonate content viz. 0.65 (soil I), 4.1 (soil II) and 5.4 per cent (soil III) were
collected from Ludhiana, Sudhar (Ludhiana) and Bathinda Districts for experimental study. The
treatments comprised six levels of boron for soil application viz. 0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 mg B kg-1
and two levels of farmyard manure viz. control and FYM @10 t ha-1. The experiment was laid out in
CRD factorial design with three replications. Yield and yield attributing characters at different crop
growth stages (grand growth and maturity stage) increased significantly at 1.5 mg B kg-1 with FYM
irrespective of the soils. The boron content and its uptake was higher in leaves followed by stem, grains
and root, respectively both in raya and soybean crop. Among calcareous soils, soil I with lowest calcium
carbonate was the best soil in respect of yield, yield components, boron content and its uptake in
comparison to soil with medium and high calcium carbonate content. Boron transformation in soil after
the harvesting of raya and soybean crop revealed that readily soluble was higher in soil I compared with
soil II and soil III. Specifically adsorbed, oxide bound, residual and total boron were more in soil III
however, oxide and organically bound fractions were higher in soil II. The coefficient of determinations
(R2) for Langmuir adsorption isotherm were lower compared with Freundlich adsorption isotherm which
proved that Freundlich adsorption isotherm to be more valid for adsorption studies. It indicated that B
adsorption data fits excellent to Freundlich adsorption isotherm. The highest value of adsorption maxima
(b) (45.0 mg kg-1) was recorded in silty clay. However, the highest bonding energy constant (k) (0.111 L
kg-1) value was recorded in sandy soil whereas; the (k) lowest value 0.047 mg L-1 was recorded in silty
clay. The Freundlich bonding energy constant increased with increase in soil clay content having
minimum value in sandy soil 1.405 mg kg-1 and maximum (2.29 mg kg-1) in silty clay soil. In incubation
study, the availability of boron in soil was studied with six varying levels of boron (0.0, 0.5, 1.0, 1.5, 2.0
and 2.5 mg B kg-1), five organic amendments (control, farmyard manure, press mud, poultry manure and
rice straw compost) with three levels of calcium carbonate content (0.64, 4.1 and 5.4 per cent) at 15, 30
and 60 days of intervals. The soil was incubated in a temperature controlled room at 25oC. Boron
availability increased as a function of time and treatment for different soils. The mean boron content was
highest in soil application of 2.5 mg B kg-1 with farmyard manure followed by press mud, poultry
manure, rice straw and control (no-amendment) in different types of soils. Availability of boron was
highest in soil with low calcium carbonate content and decreased with increasing levels of calcium
carbonate content over time period.