Effect of proportional substitution of potassic fertilizer with biofertilizers in onion

A fundamental shift has taken place in agricultural research and world food production. Today, the drive for productivity is increasingly combined with a desire for sustainability. A field experiment was carried out in sandy loam soil during kharif 2016-17 with kharif onion cv. Agrifound Dark Red using Azolla and vermicompost for sustainable crop production. The experiment comprised of 8 treatments, T1 (no K application), T2 (50 per cent RDK), T3 (100 per cent RDK), T4 (50 per cent RDK + 50 per cent K by Azolla), T5 (50 per cent RDK + 50 per cent K by Vermicompost), T6 (50 per cent RDK + 25 per cent K by Azolla + 25 per cent K by Vermicompost), T7 (100 per cent K by Azolla) and T8 (100 per cent K by Vermicompost). Full dose of N and P were applied in all the treatments through urea and SSP, respectively. However, potassium was supplied through muriate of potash (MOP) having 60 per cent K2O, vermicompost (0.8 per cent potassium) and Azolla (2.62 per cent potassium on dry wt. basis). Results from field experiment showed that treatment T7 was found significantly superior over all other treatments to increase plant height of onion at 90 (45.59 cm) and 120 DAT (50.80 cm) and the lowest plant height was recorded in control (T1). Dry matter content (14.34 g plant-1) was found to be the highest with treatment T5 at 120 DAT. However, treatment T4 resulted highest dry matter 0.513, 1.52, 5.54 g plant-1 at 30, 60 and 90 DAT respectively. Equatorial (55.86 mm) and polar (47.59 mm) diameters of onion bulbs were found to be significantly higher with treatment T5. The highest bulb weight (45.17 g) and yield of onion (13.17 t ha-1) were recorded with treatment T5 which was 16.24 and 41.46 per cent higher bulb yield as compared to that recorded with T3 and T1 respectively. However, the lowest bulb weight (35.10 g) and bulb yield (9.31t ha-1) were recorded in the plots receiving no potassium. Calculation of cost of production and benefit obtained showed that the treatment T3 gave maximum benefit: cost ratio of 2.1. However, B: C ratio of T4 and T5 was 1.9 and 1.6, respectively.