EFFECT OF POTASSIUM APPLICATION RATES AND VARIETIES ON GROWTH AND SEED YIELD OF ONION Department of Horticulture, Sindh Agriculture University, Tandojam, Pakistan

Abstract

Although, potassium is one of the essential macronutrients for plants; majority of our onion growers in Sindh province prefer to apply only nitrogen and phosphorus and avoid applying potassium fertilizers in their onion fields; which not only stunts crop growth, but it deteriorates the quality of onion seed; mainly used by farmers for cultivation of next season crop. In order to investigate the effect of potassium application rates on growth and seed quality; we conducted a field experiment during the winter season of 2017-18, applied potassium fertilizer (SoP) @ K₁: 0, K₂ : 25, K₃ 50, K₄ : 75, K₅ 100 and K₆ 125 kg K₂O ha^-1 to three most common local onion varieties, viz., Phulkara, Nasarpuri and Thano Bolakhan. The study was conducted at Horticultural Garden, Sindh Agriculture University Tandojam, Hyderabad. The experiment was laid out in a Randomized Complete Block Design (RCBD) with three repeats. It was observed from the experiment that among the six potassium application rates included in the study; the potassium applied @ 100 kg K₂O ha^-1 (K₅) remained more positively effective for seed quality traits including days to 50% bolting, flowering and maturity, flower stalk height, number of seeds umbel^-1, seed index and per hectare seed yield. Averaging overall potassium application rate treatments we found that Phulkara variety took fewer days to 50% bolting, gave more seed yield (g umbel^-1) and displayed maximum seed index; whereas variety Nasarpuri took fewer days to both 50% flowering and 50% maturity, showed tallest flower stalk, gave more seeds umbel^-1 and produced higher per hectare seed yield as well.