Using processed fertilizers or composted poultry manure results in similar yields but contrasting nutrient budgets in organic cabbage production

Abstract

Certified organic farmers who grow mixed vegetables often rely on composted manure as their primary nutrient source to build soil organic matter and long-term fertility, but this can result in excessive phosphorus inputs relative to processed organic fertilizers. We established a two-year experiment to compare two certified organic fertilizers − 13-0-0 (derived from hydrolyzed feather meal, meat meal, and blood meal) and 10-2-8 (same components as 13-0-0 in addition to bone meal and sulfate of potash) – and composted chicken manure added to provide 112 kg plant-available N ha⁻¹ in organic cabbage production of Northern Florida. Crown diameter was highest with processed fertilizers in both years, whereas SPAD readings were highest with 13-0-0 in 2020. In both years, sap nitrate measured during the growing season was generally higher with processed fertilizers relative to the composted manure treatment. Marketable yield was highest with processed fertilizers for both years and nutrient concentrations at harvest were similar among treatments, except for nitrogen concentrations that were highest with 10-2-8 in 2021. Nutrient export generally followed differences in yields and was comparable for processed fertilizers and composted manure. Using composted manure resulted in large nutrient surpluses, as opposed to smaller surpluses for 10-2-8 and deficits of phosphorus and potassium for 13-0-0. Our results confirm that poultry manure composted directly onsite can result in comparable organic cabbage yields relative to processed fertilizers, although this resulted in important phosphorus surpluses when applied to meet crop N demand.

Keywords:

• Florida
• nitrogen
• nutrient management philosophy
• phosphorus
• potassium

Acknowledgements

We thank the UF/IFAS College of Agricultural and Life Sciences Field and Fork Program for logistical support, including interns and volunteers that helped with field maintenance. Additional support for field and lab work was provided by John Allar, Kayci Anderson, Angelique Bochnak, and students enrolled in SWS 4116/5115 – Environmental Nutrient Management in Spring 2020 and 2021 semesters. We thank a local organic farm for donating the composted poultry manure used in this experiment.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Programmatic funding from the University of Florida to the UF/IFAS College of Agricultural and Life Sciences Field and Fork Program supported farming infrastructure and land management used in this experiment, and course fees for students enrolled in SWS 4116/5115 – Environmental Nutrient Management paid for supplies (seeds, fertilizers) and laboratory analyses.