SOIL STRUCTURE AND ORGANIC CARBON STABILITY OF RAINFED ALFISOLS UNDER LONG-TERM APPLICATION OF MANURE AND FERTILIZERS
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Date
2024-05-22
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Acharya N G Ranga Agricultural University
Abstract
The present study entitled “SOIL STRUCTURE AND ORGANIC
CARBON STABILITY OF RAINFED ALFISOLS UNDER LONG-TERM
APPLICATION OF MANURE AND FERTILIZERS” was carried out as
part of the long-term experiment during kharif, 2021 on red sandy loam
(Haplustalf) soils at Regional Agricultural Research Station, Acharya N.G
Ranga Agricultural University, Tirupati, Andhra Pradesh. The experiment was
laid out in randomized block design with eleven treatments and four
replications. The treatments includes T1: control (no manure and fertilizers), T2:
Farm yard manure @ 5 t ha-1 (once in 3 years), T3: 20 kg nitrogen (N) ha-1, T4:
10 kg phosphorus (P) ha-1, T5: 25 kg potassium (K) ha-1, T6: 250 kg gypsum
ha-1, T7: 20 kg N + 10 kg P ha-1, T8: 20 kg N + 10 kg P + 25 kg K ha-1, T9: 20 kg
N + 10 kg P + 25 kg K + 250 kg gypsum ha-1, T10: 20 kg N + 10 kg P + 25 kg K
+ 100 kg lime ha-1, T11: 20 kg N + 10 kg P + 25 kg K + 250 kg gypsum + 25 kg
ha-1 zinc sulphate (once in 3 years).
Soil samples were collected from each treatment at two depths viz., 0-15
and 15-30 cm after harvest of crop during kharif, 2021. The data was recorded
on soil physical, physio-chemical properties along with yield and yield
attributing characters.
The physical properties viz., bulk density, porosity, maximum water
holding capacity and structural indices viz., mean weight diameter, geometric
mean diameter, per cent water stable aggregates (>0.25 mm) and per cent
aggregate stability were improved by the long-term application of FYM @ 5 t
ha-1 (T2) once in three years for the past 41 years compared to other treatments.
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The treatmental combinations viz., NPK+gypsum+ZnSO4 (T11),
NPK+lime (T10), NPK+gypsum (T9) and NPK (T8) were showed improvement
in soil physical properties viz., bulk density, porosity, water holding capacity
and structural indices compared to the control, whereas long-term application
of K fertilizers alone showed deterioration in soil physical properties compared
to the control.
Long-term application of manure and fertilizers to groundnut showed a
slight decrease in soil pH compared to initial soil pH recorded during 1981.
Whereas the accumulation of salts was not observed over a period of 41 years
of experimentation in surface and sub-surface layers. However, soil organic
carbon (SOC) content was improved in all the treatments including control over
41 years of cropping and application of manure and fertilizers. However the
SOC was higher at surface layer than sub-surface layer in all the treatments.
Long-term application of FYM @ 5 t ha-1 (T2) once in three years was
recorded significantly highest SOC stocks, build-up (%) and carbon
sequestration rate at surface and sub-surface layers and which was comparable
with other treatmental combinations viz., NPK+gypsum+ZnSO4 (T11),
NPK+lime (T10), NPK+gypsum (T9) and NPK (T8). Whereas the application of
single nutrient fertilizers viz., N alone (T3), P alone (T4) and K alone (T5)
treated plot showed negative SOC stock build-up (%) compared to control in
both the soil layers.
Soil aggregate fractions under long-term application of FYM @ 5 t ha-1
(T2) and treatmental combinations viz., NPK+gypsum+ZnSO4 (T11), NPK+lime
(T10) and NPK+gypsum (T9) were showed significantly higher proportion of
large and small macro-aggregates fractions compared to control. Whereas,
single nutrient fertilizer treatments showed higher micro-aggregates fractions.
The aggregate associated-C was significantly higher in large macro aggregates compared to small macro and micro-aggregate fractions in both the
soil layers. However, aggregate associated-C was higher in surface layer
compared to sub-surface layer.
The significantly highest pod and haulm yields were recorded with FYM
alone (T2) and NPK+gypsum+ZnSO4 (T11), respectively compared to all other
treatments. However, comparable with other treatments viz., NPK+lime,
NPK+gypsum and NPK treated plots.
The treatments received with single nutrient fertilizers viz., N or P or K
alone were inferior interms of soil structure, organic carbon stability and pod
yield as compared to the combined application of nutrients. The study clearly
indicated that application of FYM and treatmental combinations viz.,
NPK+lime, NPK+gypsum+ZnSO4 and NPK+gypsum would be better for the
improvement of soil structure, organic carbon stability and groundnut pod yield
on sustainable basis.