Book of Extended summaries ISDA

International Conference on Reimagining Rainfed Agro-ecosystems: Challenges &
Opportunities during 22-24, December 2022 at ICAR-CRIDA, Hyderabad
T5-28P-1333
Assessing Impact of Dry Spells on Sorghum Productivity over Telangana
State
Santanu Kumar Bal*, N. Manikandan, A.V.M. Subba Rao, M.A. Sarath Chandran
and Fawaz Parapurath
ICAR-Central Research Institute for Dryland Agriculture, Hyderabad – 500059 India
* santanu.bal@icar.gov.in
Rainfed agriculture is practiced over India in 67% of net sown area. The livelihood of 40%
population of the country is supported and 44% of food grain production in India is met by this
ecosystem. Rainfall during southwest monsoon period is very crucial for kharif season crops
and the yearly rainfall variation during this season have profound impact on the rainfed crop
production. The yield of rainfed crops is mainly determined by the distribution of southwest
monsoon rainfall or occurrence of dry spells during the crop growing period. Sorghum is one
of the important rainfed food grain crops and cultivated over 1.19 lakhs ha. in Telangana state
(AAP, 2021). The dry spell is a period where the weather has been dry, for an abnormally long
time, shorter but not as severe as a drought (Wilhite and Glantz, 1985). The frequency of dry
spells is often used as a potential indicator of moisture stress conditions, in the management of
water resource systems, particularly for agriculture (Gocic and Trajkovic, 2013). In this
context, an attempt has been made to develop Dry Spell Index (DSI), to quantify the frequency
and duration of dry spells during kharif (June-Sep) season over Telangana state at district level.
Trend in DSI and effect of dry spell on sorghum productivity in different districts of Telangana
state was also carried out.
Methodology
The district level daily rainfall data for the period 1991-2020 was used in this study to compute
the DSI. The value of the dry spell was worked out as the number of dry days divided by 7. For
example, the weightage value of a dry spell with 7-days duration will be 1.0, 10-days will be
1.43, 14-days will be 2.0 and 21-days will be 3.0 and so on. Later, values of all dry spells during
SWM were cumulated and the Dry Spell Index (DSI) was arrived for that season (Bal et al.
2022). The value of DSI is directly proportional to the increase in the number and duration of
dry spells within the season. An algorithm in Fortran program was developed to work out the
DSI for each year for each district in the study area during the period 1991–2020.
The district-wise crop area and productivity of sorghum for the period 1997–2016 was
collected from web portal of Ministry of Agriculture and Farmers Welfare, Government of
India (http://www.aps.dac.gov.in). Major sorghum growing districts in Telangana state were
selected on the basis of average crop growing area of sorghum with ≥ 500 ha. The time series
yield data was de-trended using linear regression method (Gommes and Hoefsloot, 2006) for
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