Bhutan was traditionally an agrarian society with almost the entire population engaged in agricultural work. The Bhutanese farmers cultivated a wide range of crops including cereals, vegetables, fruits and fodder. They grew cereals such as paddy, maize, millet in the lower altitude, buchwheat, wheat and barley in the highlands. Mustard was grown for oil and they also grew fodder in some fields. They practised shifting cultivation to allow the soil to regenerate, and slash and burn for better yield. Traditional Bhutanese agricultural know-how includes techniques of soil management, irrigation systems, manure production, shared cropping culture and methods, rituals and processes of cultivation.