Asar 15 or National Paddy Day holds great significance for the farmers of Nepal as it marks the beginning of paddy plantation shortly after the arrival of monsoon in the country. On this day, people plant rice saplings in the fields while singing traditional folk songs and splashing muddy water at each other. Also, the day is incomplete without eating dahi chiura (curd and beaten rice), which is why it is also known as Dahi Chiura Khane Din
So Rice is a popular cereal grain of Nepal. Ropain in Nepali means rice planting. Therefore,

The “Ropain Festival” of Nepal is one of the country’s most important monsoon season festival tha

symbolizes the first planting of the crop (rice-plant). It is celebrated mostly by farmers of Nepal to mark the day they plant new seedlings of rice crop of the year in their paddies. It is known as Ashar 15 or the fifteenth of Ashar – the day when the crop planting season officially begins. The month of Ashar (June-July) grips a great significance for every Nepali as it is the time of the year when farmers plant new seedlings of rice crops in their paddies wishing to grow Quintana of rice from kilos.
Farmers from all over Nepal get to their muddy wet fields with a new and positive enthusiasm. It is a time for rice plantation ceremony and celebrating, dancing, splashing muddy water along with the friends and relatives singing Ashare Jhyaure Geet / Nepali Asare geet or Khathe Geet (monsoon song) reciting the joys and sorrows of farmers.
Happy Asar 15th all my friends