জৈব ও অজৈব সার [Manures And Fertilizers]   Ø Syllabus: Manures and fertilizers: Role of manures and fertilizers in crop production, important manures and fertilizers: compost, farm yard manures, green manure, oil cake, ammonium sulphate, urea, calcium, ammonium nitrate, super phosphate, potassium sulphate, mixed fertilizers-their properties and uses সূচনা (Introduction): জমিতে ক্রমাগত চাষ,