Effect of ethephon [(2-chloroethyl) phosphonic acid] on onions grown under environmental conditions conducive and non-conducive to bulb formation

Abstract

The effects of ethephon [(2-Chloroethyl) Phosphonic Acid)] on onions grown under environmental conditions conducive and non-conducive to bulbing were investigated. Parameters studied and analyzed were plant height, leaf number, bulb index (bulbing), bulb weight, soluble solids, dry matter, marketable grade, multiple growing points, maturity and storage. Onion cultivars respond differently to ethephon in its influence on plant growth and development. Ethephon does not induce bulbing of onions grown under environmental conditions non-conducive to bulb formation, nor does it enhance bulbing when environmental conditions are conducive to bulbing. Ethephon does not substitute for the primary environmental conditions, e.g. day length and temperature, necessary to induce bulbing of onions. At concentrations of 2500 ppm or when applied multiple times at lower concentrations, plant height, leaf number and bulb weight are reduced by ethephon. The inhibitory effect on growth and development results in early fall of tops and consequently earlier maturity. The effects are more pronounced when ethephon is applied to onions at a mature stage of growth. Storage losses and bulb regrowth of onions harvested prior to full maturity are reduced by ethephon due to its effect on maturity and leaf growth. Onions developing during less than ideal environmental conditions produce a large amount of bulbs with multiple growing points. When planted during late summer, New Mexico Yellow Grano has the ability to produce fair yields of marketable size bulbs.