Sulfur supply effects on production and mineral nutrition of Tanzania guinea grass under barium levels in nutrient solution

Abstract

High barium (Ba) availability can occur in mining and waste disposal areas and cause phytotoxicity in plants. Nutrient supply, especially the sulfur (S), supply can mitigate Ba phytotoxicity. The present study was carried out to evaluate plant growth, visual symptoms, and nutritional status of Tanzania guinea grass (Panicum maximum Jacq.) grown with combinations of S and Ba levels in the nutrient solution under greenhouse conditions for two growth periods (29 and 51 days). The treatments consisted 13 combinations between S and Ba in the nutrient solution (0.1/0.0, 1.9/0.0, 3.7/0.0 – no Ba, 1.0/2.5, 2.8/2.5 – low Ba, 0.1/5.0, 1.9/5.0, 3.7/5.0 – medium Ba, 1.0/10.0, 2.8/10.0 – high Ba, 0.1/20.0, 1.9/20.0 and 3.7/20.0 – very high Ba, mmol L−1, of S/Ba, respectively). Combinations with 0.1 mmol L−1 S decreased the shoot dry matter production in 4.3-folds compared to the higher S levels, regardless of the Ba exposure. Barium levels did not affect the shoot dry matter production in the first harvest. However, Ba exposure caused high mortality of tillers. Plants grown with Ba also showed impaired leaf area production, even with above 1.9 mmol L−1 S. The combinations with high S and Ba levels resulted in a decrease of 1.7-fold in leaf area compared to combinations with high S without Ba. Combinations with higher S and Ba levels enhanced the accumulations of these elements, mainly in culms plus sheathes and roots. The results suggest that high S levels can alleviate the Ba stress through the precipitation of this element in roots, probably by barium sulfate formation.