BORON-AMENDED WATER AND SOIL - RESPONSE

Well and drainage water with high B concentrations may be an alternati ve source of water for irrigated agriculture in the western USA. Irrig ation water with even moderate levels of B may, however, be toxic to p lants. Two greenhouse studies were conducted to evaluate the growth re sponses of kenaf (Hibiscus cannabinus L.) and cotton (Gossypium hirsut um L.) to B-amended irrigation water (Experiment I) and B-amended soil s (Experiment II) irrigated with B-free cater. In Experiment I, both k enaf 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 grow n at two different times in B-amended soils (approximate to 45 mg tota l B kg(-1) soil and 7 mg extractable B L(-1)). In Experiment I, dry ma tter (DM) yield of both species was significantly reduced by B-amended water (P < 0.05 level). Compared with plants irrigated with control w ater, total DM yields were 50 and 30% lower for kenaf and cotton, resp ectively. 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 Ex periment II, growing kenaf and cotton in B-amended soils reduced DM yi eld of kenaf and cotton 27 and 17%, respectively. Mean leaf tissue B c oncentrations 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.