_a ~. ": "J ELSEVIER Agriculture, Ecosystemand Environment 57 (1996) 49-55 Agriculture Ecosystems & Enwronment Alleviation of injurious effects of sulphur dioxide on soybean by modifying NPK nutrients Manju Verma, Madhoolika Agrawal * Department of Botany, BanarasHindu University, Varanasi- 221 005, India Accepted 28 September 1995 Abstract Soybean (Glycine max L. JS-72-44) plants were grown at three mineral nutrient levels: NPK recommended dose, double NPK recommended dose and without nutrient application. The effects of sulphur dioxide and fertiliser singly as well as in combination on soybean plants were studied by exposing 30-day-old plants to 0.15 p.p.m. SO 2 for 4 h day -1, 5 days week- 1 for 6 weeks. Photosynthetic pigments, ascorbic acid and protein contents, biomass and productivity were quantified prior to fumigation and at 15 day intervals until the plants were 75 days of age. Following SO 2 exposure, all parameters decreased, the maximum reduction being in plants grown without nutrient application. The study suggests that plants receiving recommended amounts of fertiliser are not as severely injured by SO 2 as an unfertilised crop, but an increase in fertilisation above the recommended level did not provide further protection. Keywords: Sulphur dioxide; Soybean; Nutrients 1. Introduction Although there have been many investigations on the effects of air pollutants on agricultural crops, studies on its joint action with other environmental factors, particularly under field conditions, are mea- gre. SO 2 is a major atmospheric pollutant due to its potential hazard for vegetation as well as its wide distribution. Many workers have reported the adverse effects of SO 2 on photosynthetic pigments, metabo- lites, growth and yield of many leguminous plants (e.g. Sprugel et al., 1980; Kress et al., 1986; Maas et al., 1987; Agrawal et al., 1987). * Corresponding author: Tel. (19) 542 313799; Fax (91) 542 312059. As a result of India's increasing dependence on coal as an energy source, SO 2 concentration is in- creasing rapidly (Rajgopal, 1991). Concentrations of SO 2 around a thermal power plant in the range 65.1-156.6 I~g m -3 (annual average) with peaks reaching 300 txg m -3 (4 h average) have been reported (Rao et al., 1990). Soybean is an important legume crop and its requirement for NPK has been determined (Yiying et al., 1992). Recently, soybean has been introduced into eastern India, where nutri- ent deficiencies are often encountered. Rao et al. (1990) reported significant reductions in crop yield around thermal power plants. The long-term impact of chronic levels of air pollutants on the soybean crop has not been studied in field conditions in a tropical environment. Reports from temperate envi- ronments showed significant reductions in soybean 0167-8809/96/$15.00 © 1996 Elsevier Science B.V. All rights reserved SSDI 0167-8809(95)01000-9