How cover crop mixtures of different diversity and fertilization approaches affect organic vegetable production in Florida – Part 1: Cover crop biomass production and in-season vegetable growth

Authors: Freidenreich, Ariel; XU, NAN - Oregon State University; VINCENT, ISAAC - Morning Star Fields; BARRO-NETTO FERREIRA, JULIA - University Of Maine; ZHAO, XIN - University Of Florida; MALTAIS-LANDRY, GABRIEL - University Of Florida

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2025
Publication Date: 12/17/2025
Citation: Freidenreich, A.S., Xu, N., Vincent, I., Barro-Netto Ferreira, J., Zhao, X., Maltais-Landry, G. 2025. How cover crop mixtures of different diversity and fertilization approaches affect organic vegetable production in Florida – Part 1: Cover crop biomass production and in-season vegetable growth. HortScience. 61(1):118-119. https://doi.org/10.21273/HORTSCI19023-25.
DOI: https://doi.org/10.21273/HORTSCI19023-25

Interpretive Summary: Long and warm growing seasons in Florida are favorable to producing specialty vegetable crops. With Florida being a major supplier of fresh produce for the United States, optimizing nutrient management is critical to ensure stable yields, economic prosperity, and environmental sustainability. In organic systems, fertilizer options are limited, causing challenges for farmers to supply necessary nutrients to plants at the right time. Besides fertilizers, farmers can grow cover crops during the fallow season to prevent erosion and potentially add nutrients to the system. Optimizing the use of cover crops and organic fertilizers can provide nutrient management solutions for organic vegetable growers in subtropical climates. We conducted an experiment to test different cover crop and fertilizer combinations on growth of three vegetables crops – bok choy, zucchini, and bell pepper– with differing growing season lengths and nutrient requirements. To do this, we tested five summer cover crop mixes – sunn hemp monoculture (SH); bicultures of SH with brown-top millet or sorghum sudangrass; a mixture with SH, the two grasses, and cowpea; and a weedy fallow control – and two fertilization approaches: preplant fertilization and an integrated approach combining preplant fertilization and in-season liquid fertilizer. We measured cover crop biomass and cash crop plant growth variables. The SH monoculture and SH+SSG biculture grew the best, but these cover crops had a limited impact on vegetable plant indicators. Cover crops reduced weed abundance for the shorter season bok choy crop. Fertilization approaches had a clearer impact on crop growth where preplant improved zucchini and pepper plants when compared to integrated fertilization. Bok choy was not affected by fertilization and therefore, either preplant or integrated nutrient management could be used with similar outcomes. The results of this experiment showed that shorter growing season crops with lower nutrient demand like bok choy may benefit from cover crops and integrated nutrient management more than longer growing season crops like zucchini and bell pepper.

Technical Abstract: Certified organic producers are limited in the nutrient sources they can use to meet plant nitrogen requirements, because nitrogen is not immediately available in manures and processed fertilizers, making it challenging to synchronize supply from nutrient inputs with crop demand. Developing integrated systems that optimize nutrient management by combining cover crops (CC) and nutrient inputs could benefit vegetable production. We conducted a two-year study comparing five summer CC treatments – sunn hemp (Crotalaria juncea) monoculture (SH); bicultures of SH with brown-top millet (Brachiaria ramosa) or sorghum sudangrass (Sorghum bicolor L. Moench x Sorghum Sudanese); a mixture with SH, the two grasses, and cowpea (Vigna unguiculata); and a weedy fallow control – and two fertilization approaches: preplant fertilization and an integrated approach combining preplant fertilization and in-season liquid fertigation. Three vegetable crops – zucchini (Cucurbita pepo), bok choy (Brassica rapa var. chinensis), and bell pepper (Capsicum annuum) – with differing growing season lengths and nitrogen demand were studied. The SH monoculture and SH+SSG biculture produced the most CC biomass, but CCs had a limited impact on vegetable growth indicators. In contrast, CC reduced weed abundance during the summer and during the growing season for bok choy. Preplant fertilization significantly improved crop growth in zucchini and pepper relative to integrated management, whereas bok choy was not affected by fertilization. Differences between fertilization approaches were reduced during the second growing season after adjustments to fertigation. This study highlights how CCs and integrated nutrient management may have a greater impact on short-growing season crops with low nitrogen requirements.