* Rains 24% less than normal in week to June 26 -IMD
* Rainfall deficit stands at 36% since June 1 -IMD
* Sowing of summer crops down 12.5% due to scanty rains -govt
* Monsoon revival needed in 2 weeks to save season -analyst (Adds details, analyst and farmer's quotes)
By Rajendra Jadhav
MUMBAI, June 27 (Reuters) - India's monsoon rains were below average for the fourth straight week, with rainfall scanty over central and western parts of the country in the week ended on Wednesday, raising concerns about major crop production and the impact on the nation's economy.
Monsoon rains are crucial for the country's farm output and economic growth. About 55% of India's arable land is rain-fed, and agriculture makes up about 15% of a $2.5 trillion economy that is Asia's third-biggest.
And India's economy, which grew at its slowest in more than four years over the January-March quarter, isn't in any condition to take a big hit from a poor monsoon.
If the rains don't improve over the next two to three weeks, India could be facing a crisis that hammers crop harvests and rural demand. Companies that sell everything from tractors to fertiliser to consumer goods to farmers would be vulnerable.
"Sowing has already been delayed by three weeks. If the monsoon doesn't revive in two, three weeks, then the entire season could be wiped out," said Harish Galipelli, head of commodities and currencies at Inditrade Derivatives & Commodities in Mumbai.
India received 24% less rainfall than the 50-year average in the week ended on June 26, data from the India Meteorological Department (IMD) shows. In some areas, such as the eastern part of Madhya Pradesh, known for growing soybean, the deficit was as high as 69 percent, the data shows.
The monsoon has so far delivered 36% less rainfall than normal since the start of the season on June 1 due to a delay in the onset of the seasonal rains.
The sowing of summer crops such as rice, soybeans and corn has been lagging as a result. Farmers had planted summer-sown crops on 9.1 million hectares as of June 21, down 12.5% compared with the same time last year, according to provisional data from India's Ministry of Agriculture.
WET MONSOON CRITICAL AFTER 2018 DROUGHT
India needs a good monsoon this year as in 2018 a drought ravaged crops, killed livestock, emptied reservoirs and drained water supplies to city dwellers and some industries.
Hardest hit were the western states of Maharashtra and Gujarat, along with Tamil Nadu, Karnataka, Andhra Pradesh and Telangana in the south, and Madhya Pradesh in central India.
Some municipalities like Chennai, Mumbai and Hyderabad were forced to cut water supplies to ensure their reserves lasted until monsoon rains replenished reservoirs.
The IMD has forecast average rainfall in 2019, while the country's only private forecaster, Skymet, has predicted below-normal rainfall.
A normal, or average, monsoon means rainfall between 96% and 104% of a 50-year average of 89 cm (35 inches) during the four-month monsoon season from June to September, according to the IMD's classification.
Farmers like Baburao Tadas from Wardha district in Maharashtra are praying for normal monsoon rains after their incomes were hit by erratic weather and lower crop prices over the past few years.
"I will plant cotton if we get rainfall in the next fortnight, otherwise I will switch to short duration crops such as corn or soybean," Tadas said.
(Reporting by Rajendra Jadhav; Editing by Martin Howell and Tom Hogue)