The field experiment entitled "Effect of soil and foliar application of silicon on soil nutrient availability, uptake, yield and quality of kharif onion” was conducted during kharif 2016 - 2017 at Post Graduate Institute research farm, Mahatma Phule Krishi Vidyapeeth, Rahuri with a view to study the effect of levels of silicon on growth, yield, and quality of kharif onion. The investigation was carried out in Randomized Block Design (RBD), fourteen treatments combinations comprised of soil application of three levels of calcium silicate (50, 100 and 150 kg Si ha−1) and three concentration of silicic acid (SA) 1, 2, and 3 ppm through foliar spray. Two treatments absolute control and GRDF were taken for comparison having 0 kg Si ha−1. The neck thickness, equatorial diameter, polar diameter and, total yield of bulbs and straw yield of onion were recorded. The chemical properties viz. pH, EC and OC showed significantly influenced due to application of silicon. In case of treatment T14 recorded significantly superior pH, EC and OC (8.35, 0.54 and 0.60% respectively). The treatment T14 recorded significantly highest polar diameter (5.55cm), equatorial diameter (5.94cm), neck thickness (0.88 cm) highest weight per bulb (83.50 g), bulb yield (37.50 t ha−1) and straw yield (2.40 q ha−1) respectively. It is concluded that treatment (T14) was found beneficial for maintaining soil fertility, for enhance crop growth and for increase yield and yield contributing character of onion on shallow soil.