Treatment of Growing Sugarbeets with Soil Injected Ethylene

Ethylene is an endogenous plant hormone which influences many aspects of plant growth and development, but its effect upon economic yield of crop plants is not understood well. Our objective was to evaluate the effect of ethylene treatment on sugarbeet (Beta vulguris L.) roots during the growing period on yield, sucrose content, and purity. Field studies were conducted in 1973, 1974, and 1975 in Colorado, Kansas, Nebraska, Wyoming, Mona tana, and Ohio. Ethylene was injected 20 cm into the soil between rows at the 11-leaf-stage of development. Tests showed that ethylene moves 24 m or more in the soil after injection and so ex eriments were designed to prevent cross-contamination of plots. Roots were analyzed for weight, sucrose percent, and clarified juice purity, immediately after harvest in September or October. The effect of ethylene on root and foliage growth was also evaluated in hydroponic studies. Ethylene increased green and dry weight yields of hydroponically grown sugarbeet roots 38.9 and 42.9%, respectively, over nontreated beets. Treated roots had a higher water content as well as a higher dry matter yield than non-treated beets. Ethylene also stimulated fibrous root formation in hydroponic solution. Ethylene injected at the rate of 0.25 liter/m of travel in field trials increased root yield 8.2% in 13 paired comparisons in 1973 and 1974, and 7.6% in six comparisons in 1975. The treatments, however, gave 3.3 and 1.5% reduction, respectively, in sucrose content in the respective tests so that the ethylene treatment resulted in no significant increase in sugar yield per hectare. Treatment at rates of 0.125 and 0.50 liter ethylene/m showed similar effects upon root yield and sucrose content but were not statistically significant. Hydroponic studies demonstrated that ethylene applied to the sugarbeet roots during the growing period can substantially increase dry matter yield. Economic yield increases — sucrose per hectare — were not, however, obtained with ethylene injection in field tests.