Book of Extended summaries ISDA

International Conference on Reimagining Rainfed Agro-ecosystems: Challenges & Opportunities
during 22-24, December 2022 at ICAR-CRIDA, Hyderabad
Methodology
The field experiment was conducted for four years during 2018-2021 at Hayathnagar research
farm of ICAR-CRIDA, Hyderabad. Each year, for the four years, vermicompost (VC) and fresh
gliricidia loppings (GL) were applied to soil at rates equivalent to 0, 2, 4 and 6 Mg C/ha
(treatments) and incorporated thoroughly into the soil. Pigeonpea and castor were grown in
rotation (pigeonpea in 2018 and 2020, castor in 2019 and 2021). Carbon input to soil by crops
through litter was quantified. Carbon input through roots was estimated using shoot:root ratios
(Srinivas et. al., 2017). Rhizodeposited C was estimated as 65% of root biomass (Bolinder et al.,
2007). Total C input to soil was obtained by adding C inputs through treatments and crop C
inputs. Soil bulk density and organic carbon from 0-20 cm and 20-40 cm depths were measured
before the start of the experiment and at the end of 4 years, and soil organic carbon stocks were
computed. Change in SOC stock up to 40 cm depth was computed as difference between stock
after 4 years and initial stock
Results
Total carbon input by crops (4 years) ranged from 5.22 Mg/ha in control plots (no external C
input) to 7.75 Mg/ha in plots that received 6 Mg C/ha every year through vermicompost taking
the total C input in this treatment to 31.75 Mg/ha (24 Mg/ha through applied vermicompost and
7.75 Mg/ha through crop). Soil organic carbon in the 0-20 cm depth, which was 3.14 g/kg before
the start of the experiment, decreased slightly to 2.85 g/kg in control and increased to a
maximum of 5.01 g/kg in the 6 Mg C/ha through vermicompost treatment. In the 20-40 cm
depth, initial SOC of 2.44 g/kg decreased to 2.38 g/kg in control and increased to a maximum of
2.92 g/kg in the 6 Mg C/ha through vermicompost treatment. Changes in bulk density were small
and statistically non-significant.The initial SOC stock up to 40 cm depth was 18.3 Mg/ha and it
decreased by 0.53 Mg/ha in the control plots, while in the plots that received external C inputs,
the carbon stocks increased. SOC stocks were significantly higher in the 0-20 cm depth over the
20-40 cm depth. The highest C stock of 25.7 Mg/ha was recorded in plots that received 6 Mg
C/ha through vermicompost. Increase in C stock as percentage of total C input (treatment C input
+ crop C input) ranged from 15.8% in 4 Mg C/ha through gliricidialoppings to 23.4% in 6 Mg
C/ha through vermicompost.
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