Assessment of polyhalite fertilization on nutrient uptake and  post-harvest soil nutrient balance in onion (<i>Allium cepa </i>L.) var Co (on) 6

The application of potassium and secondary nutrients through polyhalite significantly enhances the growth, yield of tomatoes and cluster beans etc. Polyhalite is a highly useful nutrient source for maintaining soil health, particularly in terms of soil fertility. In view of above facts, the present investigation was carried out on evaluation of polyhalite on nutrient uptake and post-harvest soil nutrient status in onion var Co (on) 6 at a farmer’s field in Maattiyampatti village Kaarimangalam taluk, Dharmapuri district, Tamil Nadu. The experimental soil was sandy loam in texture, with a pH of 7.56 and an EC of 0.24 dS m-1. The experiment was laid out in a randomized block design consisting of 12 treatments and 3 replications. The polyhalite and muriate of potash were used as a potassium source at different levels (10 to 50 kg K2O ha-1). The recommended doses of nitrogen (60 kg ha-1) and phosphorus (60 kg ha-1) were applied as urea and single super phosphate, respectively, in all treatments except the absolute control. The results of the study clearly showed that the application of polyhalite performed better than muriate of potash across all parameters. The highest plant and bulb nutrient uptake of N, P, K, S, Ca and Mg (96.5, 49.8, 97.1, 52.2, 22.3, 19.3 kg ha-1 in bulb respectively) at all growth stages and maximum soil available nutrient status in post-harvest soil were recorded under application of potassium through polyhalite as 40 kg K2O ha-1 recommended dose of nitrogen and phosphorus (T11). The minimum values were observed in the absolute control (T1).