Interaction of soil boron application with leaf B concentration, root length density, and canopy size of citrus affected by Huanglongbing

Abstract

Good and balanced citrus nutrition is important for high fruit yields and improved tree performance. A study was conducted for 2 years to investigate the effect of soil application of boron (B) on leaf nutrient content, canopy size, and root length density (RLD). The study was conducted on 10-year-old Candidatus Liberibacter asiaticus (CLas)-infected Vernia sweet orange on Rough Lemon rootstock in a commercial grove east of St. Cloud, FL planted at 375 trees ha⁻¹ on a traditional soluble dry nutrition and spray programs. Treatments were supplied with various ground-applied controlled-release fertilizer treatments containing B. Boron was applied at 0×, 2×, and 4× current University of Florida recommendation where 1× = 1.12 kg ha⁻¹. Data collected included leaf B nutrient content, soil B concentration, trunk diameters, canopy volumes, soil electrical conductivity, and soil pH. The 0×, 2×, and 4× application rates corresponded with leaf nutrient contents ranging from 56 mg kg⁻¹ and 88 mg kg⁻¹ in March 2017, 162 mg kg⁻¹ and 288 mg kg⁻¹ in September 2017, and 122 mg kg⁻¹ and 320 mg kg⁻¹ in May 2018. Temporary, RLD decreased with time from March to September 2017 by 13, 30, and 37% at the 0, 2.24, and 4.48 kg B ha⁻¹ and increased by 309, 258, and 306% at the 0, 2.24, and 4.48 kg B ha⁻¹, respectively, from September 2017 to May 2018. No consistent pattern was established between soil B application with canopy size.

Keywords:

• Candidatus Liberibacter asiaticus (CLas)
• Citrus sinensis
• Huanglongbing
• micronutrients
• soil B application

Acknowledgements

The author is grateful to William Pihilla, Tanyaradzwa Chinyukwi, and Qudus Uthman for help with data collection. The author is also grateful to Dr. Jude Grosser for establishing the treatments and Orie Lee Groves for providing the grove for the experiment. The author would also like to thank Frank Rogers for assistance with controlled-release fertilizer (CRF) applications. Many thanks go to Jack Zorn (TigerSul^®) and Matt Shook (Harrell’s^®) for the donation of CRF products used in the trial.

Additional information

Funding

The USDA NIFA Project FLA-CRC-005593 is acknowledged for funding the publication and field research operations.