Answer : 4. "At the beginning of the South-West monsoon"
Explanation :

Kharif crops – The crops sown in June-July in the Indian subcontinent are called Kharif crops. These crops are harvested in October and November. These require high temperature and humidity at the time of sowing and dry environment at the time of ripening.

Main Kharif crops – Cotton, groundnut, paddy, millet, maize, sweet potato, urad, moong, moth cowpea (Chanwala), jowar, arhar, dhaincha, sugarcane, soybean, okra, sesame, guar, jute, flax etc.