Boron phosphates (BPO4) as a seedling-safe boron fertilizer source
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Background and aims
Soluble boron (B) sources pose a risk of B toxicity to seedlings just after planting and leaching losses after application and before plant uptake. Boron phosphate (BPO4) has low water solubility and slowly releases B, and hence could be safe for seedlings. Therefore, we investigated the toxicity of several B sources co-granulated with mono-ammonium phosphate (MAP) or co-compacted with potassium chloride referred to as muriate of potash (MOP) on canola seedlings.
Ulexite, borax, colemanite and BPO4 compounds synthesized at 500 or 800 °C for 1 h were co-granulated with MAP or co-compacted with MOP at inclusion rates of 0.5, 1.0 and 2.0 % B. The seedling toxicity of these products was evaluated by placing a fertilizer granule in the centre of a soil-filled Petri dish in which canola was seeded. The area of the non-vegetated zone around the granule application site was evaluated after 7 and 12 days of growth.
Application of ulexite, borax and colemanite co-granulated with MAP resulted in toxicity symptoms at the lowest concentration of 0.5 % B, and the area of the affected zone increased with increasing concentrations of B in the granule, whereas no toxicity symptoms were observed with the application of co-granulated BPO4 products even at 2.0 % B content. Similar results were observed for the MOP fertilizers, except for colemanite which showed no toxicity when combined with MOP. Hot water-soluble B concentrations were measured in concentric sections around the granule application site and were in agreement with the toxicity results, with concentration in the toxic range close to the granule for the most soluble B sources.
BPO4 is potentially a seedling-safe B fertilizer source.
KeywordsBoron phosphate Slow-release fertilizer Toxicity
The first author thanks the University of Adelaide for the scholarship to enable her to pursue her PhD and the Sarawak State Government for a study leave. The authors also thank Bogumila Tomczak, Deepika Setia, Colin Rivers, Ashleigh Broadbent and the staff of CSIRO Land and Water for their advice and technical support.
- Abat M, Degryse F, Baird R, McLaughlin MJ (2014b) Responses of canola to the application of slow-release boron fertilizers and their residual effect. doi: 10.2136/sssaj2014.07.0280
- Bingham FT (1982) Boron. In: Page AL, Miller RH, Keeney DR (eds) In methods of soil analysis part 2 - chemical and microbiological properties, 2nd edn. Soil Science Society of America, Madison, pp 431–448Google Scholar
- Broschat TK (2008) Release rates of soluble and controlled-release boron fertilizers. Hort Techn 18:471–474Google Scholar
- Cayton MTC (1985) Boron toxicity in rice. pp 1–11. International Rice Research InstituteGoogle Scholar
- Gupta UC (1979) Boron nutrition of crops. Adv Agron 31:273–307Google Scholar
- Hughes-Games G (1991) Boron for field crops. Soil factsheet order no. 631.021-1. Ministry of Agriculture and Food British Columbia, Abbotsford, pp 1–3Google Scholar
- Keren R, Bingham FT (1985) Boron in water, soil and plants. Adv Soil Sci 1:229–276Google Scholar
- Marschner H (1986) Mineral nutrition in higher plants. Academic, LondonGoogle Scholar
- Ray LF (1972) Boron phosphate as boron source for plant life. Ed. U S Patent. pp 1–4, United StatesGoogle Scholar
- Sims JT, Johnson GV (1991) Micronutrient soil tests. In: Mortvedt JJ, Cox FR, Shuman LM, Welch RM (eds) Micronutrients in agriculture, 2nd edn. Soil Science Society of America, MadisonGoogle Scholar