Onion (Allium cepa L.) is a perennial (often biennial) monocotyledonous bulbous belonging to the Amaryllidaceae family and one of the most important crops of vegetables and spices grown under a wide range of climatic conditions worldwide. It is also called as "Kitchen Queen." Applied nutrients are subjected to losses like leaching and volatilization, resulting in an economic loss to the farmer. To maximize yield and profit, different crops require balanced fertilization. There is meagre information on the balanced use of NPK fertilizers with organic sources (Biomix and Humic Acid) for the onion crop. So, in the last few years, a greater concern regarding the use of organic sources as alternative / supplement / compliments to NPK fertilization has been derived to reduce the leaching and volatilization losses with high cost that inorganic fertilizers represent in Horticultural production. The research work on the effect of organic sources (Biomix and humic acid) on onion crops in world is scanty. No systematic guidelines have been generated scientifically till now. Therefore, keeping all these points in view, the present book is very useful.