INFLUENCE OF BIOCHAR ON SOIL PHYSICO-CHEMICAL PROPERTIES
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Date
2021
Authors
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Journal ISSN
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Publisher
AAU, Jorhat
Abstract
The study on „Influence of biochar on soil physico-chemical properties‟ was
conducted during 2019-2021 with the aim to characterize biochar obtained by pyrolysis of
different organic sources, viz., ipomoea, rice straw and rice husk; and to study the influence
of application of biochar on the physico-chemical properties of soils over a period of 90
days of incubation. Biochar was prepared by pyrolysis of organic sources under anaerobic
condition at a temperature ranging from 350 to 400oC using the biochar kiln. pH, EC,
CEC, available N, available P2O5, available K2O, water holding capacity (WHC) and bulk
density of biochars ranged from 7.34 to 9.69, 0.70 to 1.13 dS m-1, 17.3 to 18.4 cmol(p+)
kg-1, 0.0028 to 0.00504%, 0.0126% to 0.0258%, 0.17 to 0.34%, 101.58 to 255.36% and
0.267 to 0.465 Mg m-3 respectively. Soil samples of three different textural classes, viz.,
clay, clay loam and sandy were collected from the Titabor subdivision of Jorhat district for
the incubation study. Soil samples were incubated for 90 days at 60% FC with each type of
biochar (ipomoea, rice husk and rice straw) at 4 different levels (1, 2, 3 and 4%) in a
completely randomized design.
Biochar improved soil physical properties like hydraulic conductivity, soil water
retention at field capacity, soil water retention at permanent wilting point, soil available
water, increased sand and silt sized particles, while it decreased the clay sized particles
compared to the initial value of the soils. Rice husk and rice straw biochar significantly
decreased the percentage of clay sized particles (2.73%), by significantly increasing the
percentage of sand and silt sized particles. All three soils showed a proportionate increment
in sand and silt sized particles, while clay sized particles declined with the increase in the
rate of application of biochar from 1 to 4%. When applied at a rate of 4%, rice husk
biochar significantly increased the percentage of sand sized particles by its maximum value
(2.25%) and rice straw biochar significantly increased the percentage of silt sized particles
by its maximum value (2.42%). Application of rice husk biochar significantly improved
hydraulic conductivity of the soils to the highest value (7.73 mm hr-1). Application of
biochar derived from ipomoea led to significantly higher water retention at field capacity
(28.10%), water retention at permanent wilting point (10.94%) and soil available water
content (17.16%). Biochar showed corresponding increase in hydraulic conductivity till the
application rate of 3% for clay loam and sandy clay loam soil. At the application rate of
3% rice husk biochar resulted for the highest hydraulic conductivity of the soil (9.11 mm
hr-1). Soil water retention at field capacity and permanent wilting point increased
proportionately with increase in the rate of application of biochar from 1% to 4% for all
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soils except for sandy clay loam soil where soil water retention at field capacity
proportionately decreased. Application of biochar at the rate of 3% and 4% significantly
increased the soil available water content to the highest value (17.19%). Ipomoea at the
rate of 4% led highest water retention at field capacity (29.91%) and soil available water
(18.43%).
Biochar significantly altered the soil pH, EC, CEC, organic carbon, available
nitrogen, phosphorous and potassium content of the soils. Rice straw biochar led to
significantly higher pH (5.88), EC (0.093 dS m-1) and organic carbon content (1.11%).
Ipomoea biochar prompted significantly higher CEC [9.80 cmol(p+) kg-1], soil available
nitrogen (251.38 kg ha-1) and available potassium content (311.41 kg ha-1). Rice husk
biochar led to significantly higher available phosphorous content (72.69 kg ha-1). Soil
chemical properties such as pH, EC, organic carbon, CEC, available phosphorous and
potassium content was significantly increased with the increasing rate of application of
biochar from 1 to 4%. Application of 4% rice straw biochar increased the soil pH, EC and
soil organic carbon content to the highest level (6.39, 0.120 dS m-1 and 1.41%
respectively). Ipomoea biochar at the rate of 4% led to highest CEC and soil available
potassium content [11.07 cmol(p+) kg-1 and 358.59 kg ha-1 respectively]. Biochar made
from rice husk at the rate of 4% increased the soil available phosphorous content to the
highest level (96.06 kg ha-1). However, application of biochar till 2% resulted in increase
in available nitrogen content of the soils. Further increase in application rate resulted in
decrease in available nitrogen content of the soils. Ipomoea biochar at the rate of 2%
increased the soil available nitrogen content to the highest level (271.71 kg ha-1).