Effects of cover crops, rotation, and biological control products on soil properties and productivity in organic vegetable production in the Northeastern U.S.

Authors: Larkin, Robert - Bob

Submitted to: Organic Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2019
Publication Date: 7/6/2019
Citation: Larkin, R.P. 2019. Effects of cover crops, rotation, and biological control products on soil properties and productivity in organic vegetable production in the Northeastern U.S. Organic Agriculture. 10:171-186. https://doi.org/10.1007/S13165-019-00257-3.
DOI: https://doi.org/10.1007/S13165-019-00257-3

Interpretive Summary: Successful sustainable organic vegetable farming faces many production challenges, from maintaining adequate soil health and fertility, and management of weeds, pests, and diseases, to balancing multiple different vegetable crops. The effective use of cover crops and rotations, which help build soil health and management of pests and diseases, are especially critical for developing productive sustainable organic vegetable production systems. In this research, the potential benefits different cover crops, biological control amendments, and vegetable rotation on soil chemical and biological properties, crop development and yield, and disease development in organic vegetable production, as represented by green snap bean, yellow summer squash, and sweet lunchbox pepper vegetable crops, were evaluated in a multi-year field trial in Maine. All cover crops, which included a combination of winter rye and hairy vetch, a mustard green manure, and a mixture of 8 different cover crops together, improved yield in beans and squash by 7-13%, but only the mixture increased yield for pepper (by 7-11%). Biological control amendments did not affect yield, but reduced powdery mildew disease on squash and a leaf spotting disease on beans by 10-28%. The vegetable rotation used was also important, with beans yielding 8% higher following squash vs. pepper, squash yielding 15% higher following beans vs. pepper, and pepper yielding 11% higher following beans vs. squash. These results help define specific management practices to improve organic vegetable production and provide useful information and options for growers.

Technical Abstract: The potential benefits of different cover crops, biological control amendments, and vegetable rotation on soil chemical and biological properties, crop development and yield, and disease development in organic vegetable production, as represented by legume (green bean), cucurbit (yellow squash), and solanaceous (sweet pepper) vegetable crops, were evaluated in a multi-year field trial in Maine, USA. Cover crops evaluated included winter rye/hairy vetch, mustard green manure, a multi-species mixture (8 different crops), and a fallow control. Overall, cover crops had only marginal effects on soil chemical properties, but all cover crops improved biological properties compared to fallow soil. The multi-species mixture and rye/vetch cover crops resulted in earlier emergence in beans and squash. All cover crops improved yield in beans and squash by 7-13%, but only the mixture increased yield for pepper (by 7-11%). Minimal crop diseases were observed throughout these studies, and biological control amendments, which included commercial formulations of Streptomyces, Trichoderma, and Bacillus sp., in general, did not positively affect yield, but reduced powdery mildew on squash and leaf necrosis on beans by 10-28%. The vegetable rotation also had significant effects, with beans yielding 8% higher following squash vs. pepper, squash yielding 15% higher following beans vs. pepper, and pepper yielding 11% higher following beans vs. squash. These results help define specific management practices to improve organic vegetable production and provide useful information and options for growers.