Effect of nursery bulb size and planting density on thrips population,plant height and yield of onion (Phulkara variety) in Bahawalpur,Pakistan

There is dearth of knowledge to improve the sustainable productivity of onion crop. present study investigates the effect of transplanting time,nursery bulb size and plant spacing on thrips population,plant height and onion yield under agro-climatic conditions of bahawalpur,pakistan. experiment was laid out in a randomized complete block design with split plot arrangement with planting density as main factor and bulb size as sub-factor. there were three replications for the experiment. in general,results showed that thrips population,plant heights and final yield of onion bulb were greater due to medium planting density when plants were spaced at 6 inches as compared to less or more planting density (4 or 9 inches distance between plants). effect of age of nursery bulb (bulb size) at transplanting showed that thrips population,plant heights and final yield was significantly more due to large bulb size (45-60mm) followed by medium bulb size (30-45mm); and least number of thrips,plant heights and onion yield was due to small bulb size (15-20mm) (p < 0.05). interactive studies showed that the large bulb size and medium planting density resulted in more population of thrips i.e. 11.83/plant and 5.88/plant in plots in early and late transplanting,respectively. however,in second transplanting,more thrips population was 13.81/plant due to large bulb size and least planting density. similarly,more plant heights were resulted due to large bulb size and medium planting density. in early and mid-transplanting highest yield was recorded in plots with medium planting density and large bulb size i.e. 19470.52 and 6976.52 kg ha-1,respectively. in general correlation between thrips population and plant height and between plant height and yield was positive however there was generally a negative correlation found between thrips population and yield. finally,these results show that onion seedlings transplanted with large bulb size and planted at medium distance in the field resulted in more height of plants,more thrip population and also more yield of onion.