Poultry-based amendments and cover crops enhance nutrient cycling and soil health in greenhouse conditions mimicking organic vegetable production

Authors: Freidenreich, Ariel; PELEGRINA, G - University Of Florida; VICTORES, S - University Of Florida; MALTAIS-LANDRY, G - University Of Florida

Submitted to: Journal of Soil Science and Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2024
Publication Date: 6/6/2024
Citation: Freidenreich, A.S., Pelegrina, G., Victores, S., Maltais-Landry, G. 2024. Poultry-based amendments and cover crops enhance nutrient cycling and soil health in greenhouse conditions mimicking organic vegetable production. Journal of Soil Science and Plant Nutrition. https://doi.org/10.3390/horticulturae10060594.
DOI: https://doi.org/10.3390/horticulturae10060594

Interpretive Summary: Organic produce and related products are becoming increasingly popular in the United States. In organic systems, fertilizer options are limited because they must be from naturally derived sources. Vegetable production systems require inputs like fertilizers and amendments to supply crops with necessary nutrients for optimal development. Besides fertilizers, farmers can grow cover crops (plants used to cover the soil during fallow) to help supply nutrients and improve soil health. It is unclear how organic amendments and cover crops work together to impact soil health and provide nutrients to crops. Therefore, we conducted an experiment to test four types of cover crop residues (millet, sorghum sudangrass, cowpea, and sunn hemp) and three fertilizer amendments (heat treated poultry manure, poultry manure biochar, and a processed fertilizer) on spinach growth and soil nutrient indicators. Overall, we found that cover crops had the greatest impact on improving soil health indicators and manure-based amendments had the greatest positive effects on spinach nutrient uptake and yield. Results from this study can be used by organic producers to inform their on-farm nutrient management strategies to improve crop yield and soil health.

Technical Abstract: Background and aims: Organic production relies on alternative management practices and amendments, but producers have few certified organic options to meet crop N demand. Poultry-based amendments, including manures and processed fertilizers from livestock waste (e.g., feather and blood meal), are commonly used in these systems, but synchronizing nutrient release with plant demand remains a challenge. As most organic systems use cover crops, cover crop residues may also interact with amendments to affect soil health and nutrient cycling. Methods: We conducted a greenhouse study to quantify the effects of four cover crop residues (millet, sorghum sudangrass, cowpea, and sunn hemp) and three fertilizer amendments (heat treated poultry manure, poultry manure biochar, and a processed fertilizer) on spinach. We measured spinach yield and nutrient uptake, in addition to soil inorganic N, total C and N, permanganate oxidizable C (POXC), and autoclaved-citrate extractable (ACE) protein. Results: The fertilizer and legumes released the greatest inorganic N throughout the growing season. All cover crop types increased ACE protein whereas manure-based products had higher ACE protein than the fertilizer. Grass cover crops increased POXC relative to sunn hemp, but POXC was not impacted by amendments. In contrast, soil total C was altered by amendments (highest with biochar) but not cover crops. Spinach yield and nutrient uptake was highest with biochar, whereas cover crops did not have a consistent effect on nutrient uptake (except for higher N uptake with cowpea). Conclusion: Cover crops had the greatest effect on POXC and ACE protein although manure-based amendments had the greatest positive effects on spinach nutrient uptake and yield. Keywords: spinach, nitrogen, phosphorus, potassium, permanganate oxidizable C, autoclaved-citrate extractable protein