Effects of different cover crops and soil amendments on soil and crop properties in organic vegetable production

Authors: Larkin, Robert - Bob

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2023
Publication Date: 1/23/2023
Citation: Larkin, R.P. 2023. Effects of different cover crops and soil amendments on soil and crop properties in organic vegetable production. Agronomy Journal. https://doi.org/10.1080/09064710.2023.2165963.
DOI: https://doi.org/10.1080/09064710.2023.2165963

Interpretive Summary: Sustainable organic vegetable farming faces many production challenges, including maintaining adequate soil health and fertility, management of pests and diseases, and balancing multiple different vegetable crops. The effective use of basic soil and crop management strategies such as the establishment and development of crop rotations, cover crops, and soil amendments are crucial for achieving sustainable vegetable production systems. In this research, the impacts of two different cover crop (CC) strategies, a mixture of multiple types of cover crops vs. a single cover crop species, as well as compost, silicon (Si), and biocontrol (BC) soil amendments were evaluated on soil chemical and biological properties, crop development and yield, and disease and pest issues in organic vegetable production, as represented by legume (green snap bean), cucurbit (green zucchini squash), and solanaceous (sweet pepper) vegetable crops, in a three-year field trial in Maine. Compost amendments improved soil pH, organic matter, and nutrient concentrations, as well as yield of all three crops compared to a non-compost treatment. Additions of silicon reduced powdery mildew disease of squash, but biocontrol treatments had no overall effects. These results emphasized the importance of compost and additions of organic matter for improving soil quality and supplying the soil properties, nutrition, and microbiology needed for enhanced crop performance and yield in organic vegetable production. These results help define specific management practices to improve organic vegetable production and provide useful information and options for growers.

Technical Abstract: The impacts of two different cover crop (CC) strategies, as well as compost, silicon (Si), and biocontrol (BC) soil amendments were evaluated on soil chemical and biological properties, crop development and yield, and disease and pest issues in organic vegetable production, as represented by legume (green snap bean), cucurbit (green zucchini squash), and solanaceous (sweet pepper) vegetable crops, in a three-year field trial in Maine. A multi-species CC mixture (6 crops, including legumes, grasses, and brassicas) was compared with a standard winter rye CC for potential benefits on soil fertility and biomass production. Soil amendments included a commercial organic fertilizer alone, composted dairy manure, compost plus BC (commercial formulations of Trichoderma and Streptomyces spp.), and compost plus Wollastonite, a natural source of Si. Poor stand establishment of some components of the multi-species CC mixture resulted in lower biomass and ground cover relative to winter rye, but no effect on crop development or yield. Compost amendments increased soil pH, organic matter, and nutrient contents, as well as yields of bean, zucchini, and peppers relative to a fertilizer-only treatment. Additions of Si increased Si content in plant leaves and reduced powdery mildew on squash and leaf necrosis of beans. In the absence of substantial soilborne disease, BC provided only marginal reductions in powdery mildew and leaf necrosis and no effects on yield. These results help define specific management practices to improve organic vegetable production and provide useful information and options for growers.