Boron-amended water and soil - Response

Well and drainage water with high B concentrations may be an alternative source of water for irrigated agriculture in the western USA. Irrigation water with even moderate levels of B may, however, be toxic to plants. Two greenhouse studies were conducted to evaluate the growth responses of kenaf (Hibiscus cannabinus L.) and cotton (Gossypium hirsutum L.) to B-amended irrigation water (Experiment I) and B-amended soils (Experiment II) irrigated with B-free cater. In Experiment I, both kenaf and cotton were irrigated with water amended with 7.5 mg B L(-1) as boric acid or with water containing <0.25 mg B L(-1). In Experiment II, B uptake and B tolerance were evaluated for kenaf and cotton grown at two different times in B-amended soils (approximate to 45 mg total B kg(-1) soil and 7 mg extractable B L(-1)). In Experiment I, dry matter (DM) yield of both species was significantly reduced by B-amended water (P < 0.05 level). Compared with plants irrigated with control water, total DM yields were 50 and 30% lower for kenaf and cotton, respectively. Leaf tissue B concentrations ranged from 500 to 1400 mg B kg(-1) DM for kenaf and from 300 to 800 mg B kg(-1) DM for cotton. In Experiment II, growing kenaf and cotton in B-amended soils reduced DM yield of kenaf and cotton 27 and 17%, respectively. Mean leaf tissue B concentrations were 422 mg B kg(-1) DM in kenaf and 222 mg B kg(-1) DM in cotton. Results show that high soil B in greenhouse pot conditions decrease DM production of kenaf and cotton.