SOIL BORON FRACTIONS AS INFLUENCED BY SELECTED SOIL PROPERTIES AND CROPPING SYSTEM IN BOKO BLOCK OF KAMRUP (RURAL) DISTRICT OF ASSAM
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Date
2021
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Abstract
The present study was conducted with the twin objective to assess the
influence of basic soil physico-chemical properties and cropping system (CS) on soil boron
fractions in Boko Block of Kamrup (Rural) District of Assam. A total of twenty- four (24)
geo-referenced surface soil samples (0-15 cm) were collected from across the blocks under
each cropping system viz., Rice-Rice, Rice- Fallow, Vegetable-Vegetable and Plantation
crops. The soil groups were found to vary in their physico-chemical properties irrespective
of cropping system practised. The studied soil samples showed wide variations in texture
varying from sandy clay loam (SCl) to clay loam (Cl). The ranges for pH, SOC (%), Av.
Nitrogen (kg ha-1), Available P2O5 (Kg ha-1), Available K2O (Kg ha-1), CEC [Cmol (p+)
kg-1], EC (dSm-1) ranged between very strongly acidic to strongly acidic (4.7-5.6), medium
to high (0.6-1.6 %), Low to Medium (175.6-326.4 kg ha -1), Low to High (5.93- 57.68 kg
ha -1), Medium (130.8-276.2 kg ha -1), Low (2.8-9.6 Cmol (p+) kg-1), Normal range (0.01-
0.03 ds m-1) respectively. The selected properties viz., CEC, pH and SOC were chosen
based on past research findings to analyze its effect on soil boron fractions. Each of the
three parameters were split in two groups: CEC (two groups-2.8-5.8 and 5.9-9.6 C mol(p+)
kg-1), pH (two groups- 4.7-5.0 and 5.1-5.6) and SOC (two groups- 0.6-1.0 and 1.1-1.6 %).
The data was analyzed using independent sample t-test. It was found that pH and CEC did
not significantly affect soil B fraction. However, SOC had a significant effect on soil boron
fraction viz., oxide bound and organic bound. In case of CS, majority of the soil properties
viz., pH, soil organic carbon, available nitrogen, available phosphorus, cation exchange
capacity, sand content (18.1- 49.5%) and silt content (24.1-48.4%) did not differ
significantly among the cropping system. However, soil properties like available K2O
content, EC, and clay (22.6-38.2%), was found to differ significantly between the cropping
system. Cropping system did not significantly affect the various boron fractions in the
present study. Significant positive correlation has been observed for soil organic carbon
with Oxide bound B (r= 0.834**), Organically bound B (r= 0.541**), Specifically adsorbed
B (r= 0.505*) and EC (r= 0.502*). A significant negative correlation has been observed in
between sand and silt (r= -0.905 **) as well in sand and clay (r= -0.587**) content among
the CS. The available boron (0.56 to 1.69 mg kg-1) and five boron fractions viz., Readily
Soluble Boron (0.04-2.41 mg kg-1), Specifically Adsorbed Boron (0.15-1.92 mg kg-1),
Oxide Bound Boron (5.18-17.41 mg kg-1), Organically Bound Boron (6.86-20.3 mg kg-1)
and Residual Boron (17.73- 36.57 mg kg-1) did not differ significantly between the
cropping systems. Results revealed that the relative proportion of various fraction of boron
in soils are in the following order i.e. readily soluble B< Specifically adsorbed B < Oxide
bound B< Organically bound B < Residual B. The Soil Quality Index for each CS were in
the order: Rice-Rice (16.752)> Rice-Fallow (14.645)> Veg-Veg (12.979) > Plantation
(12.742). None of the measured parameters were found to be significantly correlated with
the yield of crop under the studied cropping system. The study, therefore explores the
possibility of soil physico-chemical influence on soil boron fractions owing to cropping
system over long period of time. The study reveals the selected soil properties influence on
soil B fractions and cropping system being a non- determinant influencing any of the boron
fraction studied.