Volatile losses of sulfur from intact plants

Abstract

Losses of volatile sulfur (S) compounds were measured from intact plants of 22 species including tropical and temperate crop and pasture species grown under glasshouse conditions. All species released substantial amounts of S during a 22‐hour collection period. The amounts lost ranged from 0.13 μg S g dry weight of shoot^‐1 22 hours^‐1 in barrel medic to 2.68 μg S g dry weight of shoot^‐1 22 hours^‐1 in rape. These losses represented 0.005% of the total S in the shoot in barrel medic and 0.92% in rape. There was no obvious division between temperate and tropical species in terms of the amounts of volatile sulfur compounds released, but the evidence suggested that tropical species released a different spectrum of volatile sulfur compounds from temperate species. Thus in tropical grasses and legumes, a higher proportion of the total volatiles was recovered in cold traps, whereas in temperate grasses and legumes, a higher proportion of the total volatiles was recovered in activated carbon traps located after the cold traps. When all 22 species were considered together, the amount of volatile S lost was not correlated with the S concentration in the shoot. Extrapolation of these short term observations in the glasshouse to longer term losses under field conditions suggests that losses of volatile S from fields of alfalfa, Rhodes grass, and wheat may be in the order of hundreds of grams of S ha^‐1 year^‐1, while losses from fields of cotton may be in the order of thousands of grams of S ha^‐1 year^‐1.

Key words:

• Sulfur
• volatile losses
• intact plants
• pasture legumes
• pasture grasses
• crop species
• temperate species
• tropical species