Effects of H/sub 2/S on crop and forest plants

Continuous fumigation of alfalfa, grapes, lettuce, sugar beets, California buckeye, ponderosa pine, and Douglas fir with 3000 parts per billion (ppb) H/sub 2/S caused leaf lesions, defoliation, reduced growth, and death of sensitive species. Three hundred ppb caused lesser but similar effects. Sulfur accumulated in leaves depending upon dosage. Lower levels of H/sub 2/S, 30 ppb and sometimes 100 ppb, caused significant stimulation in growth of lettuce, sugar beets, and alfalfa. The stimulation occurred at certain times of year. Addition of 50 parts per million (ppm) of CO/sub 2/ to the fumigation atmospheres overcame growth reduction caused by 300 ppb H/sub 2/S in lettuce and sugar beets. Two varieties of grapes and one variety each of pears and walnuts were fumigated with the highest ambient levels of H/sub 2/S found near The Geysers, treble ambient H/sub 2/S and amounts of SO/sub 2/ equivalent to the treble levels of H/sub 2/S. No deleterious growth or fruiting symptoms were observed which could be ascribed to the treatments.