A debate is currently underway on the extent to which variability in the South-West monsoon (SWM) rainfall will affect farm output due to the unusual rainfall pattern experienced in 2023. Though it is commonly believed that a reduction in SWM rainfall will hit agricultural production, some argue that the impact has come down over time due to a massive increase in irrigation. Is agriculture’s dependency on monsoon rainfall declining in India?

India receives an annual rainfall of about 118 centimetres (cm) which varies across the four major rainfall zones — north-western, north-eastern, central and southern peninsula — classified by the India Meteorological Department.

Of the total annual rainfall, SWM rainfall alone accounts for about 75 per cent or 87 cm. Therefore, any sharp deviation in SWM rainfall from the normal (defined as percentage departure of realised rainfall is within ± 10 per cent of the Long Period Average) is expected to make a heavy dent in the agricultural sector’s performance.

An analysis of monsoon rainfall’s impact on agriculture covering data from 1990 to 2021 shows that India received below normal rainfall 17 times out of 32 years. he district-level analysis reveals that about 30 per cent of the Indian districts received less-than-normal SWM rainfall less than normal in 20 out of 32 years.

As far as the year-on-year rainfall deviation is concerned, the SWM rainfall deviated negatively more than 10 per cent from its normal in six years and in four years, it deviated in the range of -5 to -10 per cent. SWM rainfall had positively deviated from its normal only in 12 out of 32 years, meaning that most of the time there was deficit rainfall.

Surprisingly, the SWM rainfall was below normal continuously for five years from 2014 to 2018. Are these changes in rainfall affecting the agricultural sector?

Rainfall vs irrigated area

While the deficient rainfall generally impacts the entire agricultural sector, its effects are more visible in three parameters — irrigated area, cultivated area and crop output. There is a close relationship between the rainfall level and the area irrigated through surface sources (canals, tanks and other small water bodies).

Though minor deviation in the rainfall will not impact the irrigated area, a large deficient rainfall (over 10 per cent from normal) is expected to have a considerable reduction in the surface irrigated area by reducing the water flows into water bodies including large dams. The analysis of the 1990 to 2021 period shows a considerable reduction in surface irrigated area in all those years where rainfall deficient was more than 10 per cent (see, Graph 1).

For instance, when the deficit of SWM rainfall was more than 10 per cent in 2000, 2002, 2009, 2014 and 2015, the surface irrigated area also declined considerably.

Deficient rainfall also impacts the cropped area. Since close to 50 per cent of cropped area is still under rainfed cultivation, a large deficit in SWM rainfall will have a considerable impact on the net and gross cropped area.

Most nutri-cereal crops (jowar, bajra, ragi, maize, etc), pulses, oilseeds and cotton are still predominantly under rainfed areas, where the monsoon rainfall plays a key role in deciding the area under cultivation.

An analysis of the percentage of districts having deficient rainfall with the area under cultivation of kharif crops shows that the area under nutri-cereals, pulses, oilseeds and cotton declined considerably when a large number of districts received deficient rainfall during the 1990 to 2021 period.

When the SWM rainfall deficit was about 22 per cent in 2002, the area under paddy declined to 3.72 million hectares (mha) over its previous period, and the decline was 1.96 mha in pulses, 1.15 mha in oilseeds and 2.46 mha in cotton.

A similar decline in area under cultivation was also observed in 2009 when there was a 21.4 per cent rainfall deficit. If anyone says that agriculture’s dependency on monsoon rainfall has declined, then the area under these crops should not have declined to this extent!

Impact on output

Besides reducing the area under cultivation, deficient rainfall will also reduce the productivity of crops because of reduced moisture availability and poor adoption of yield-increasing inputs, which in turn will lead to decline in output. Is this happening in India?

The analysis of data from 1990 to 2021 proves that the kharif production of major crops declines substantially when the SWM rainfall sharply deviates from its normal (see Graph 2). Interestingly, the reduction in kharif crop production increases wherever the rainfall deviation increases.

For instance, when the rainfall deviation is above 10 per cent, the average year-on-year growth in production declines by 8.63 per cent in foodgrains, 7.77 per cent in rice, 10.40 per cent in nutri-cereals, 10.58 per cent in pulses and 15.25 per cent in oilseeds (Table 1).

It is also observed that the average decline in production is relatively high among those crops that are predominantly cultivated under rainfed condition (nutri-cereals, pulses and oilseeds). It appears that the adverse consequence of deficient rainfall on irrigated area, cropped area and production of crops has not come down appreciably over time. Given the close relationship between irrigated area and the level of rainfall, expanded irrigation infrastructure is unlikely to reduce the adverse impact of rainfall.

Due to climate change, increased variability in rainfall is going to be the new normal. Therefore, mitigation strategies need to be worked out to reduce the negative shock of rainfall on crop production.

While promoting crops that consume less water, an increased adoption of modern irrigation technology (drip and sprinkler) that can save water and increase the productivity of crops may help reduce the rainfall shock on agriculture. Efforts are also needed to increase the overall water use efficiency in canal irrigation which is pathetically poor (around 35 per cent) in India.

The writer is former full-time Member (Official), Commission for Agricultural Costs and Prices, New Delhi