Distribution and management of total and available sulfur under Durian orchard soils in the Eastern Thailand

Abstract

Sulfur is necessary plant nutrient but is rarely determined on a routine basis because of interpretive and analytical problems resulted in the lack of consistent identification of S sufficiency or deficiency in soils. Sulfur status of durian orchard soils in the Eastern Thailand was evaluated for plant availability. The result indicated that total S ranged from 315 to 1340 mg/kg (average 813 mg/kg) which 93-99% was in organic form and relatively the same comparison between topsoil and subsoil. Total S was significantly correlated with C (r = 0.41**), N (r = 0.36**), pH (r = -0.52**) and SOM (r = 0.51**). The C:S and N:S ratios varied from 7.8-54.8 and 0.74-4.67 respectively, indicating the dominance of the mineralization process toward sulfur nutrition. C:N:S was 20:2:1 due to heavy S fertilizer application. Extractable S (available S) was varied from high to very high ranged depending on soil standard, of which about 75% of soil samples were classified to be no response to S application. Out of the average available S of 24.2 mg/kg the topsoil (28.2 mg/kg) was higher than subsoil (25.6 mg/kg). Available S showed very closely correlation to total S (r = 0.72**), C (r = 0.61**), N (r = 0.57**), pH (r = -0.29**) and SOM (r = 0.61**). Stepwise multiple regression showed that approximately 73.0% variation in the extractable or available S could be explained in terms of several soil parameters