Variety Trails for Cover Crops in Vegetables
Field Day Recap | October 2024
Field vegetable growers in the Lower Mainland implement cover cropping as a practice to support soil and nutrient management objectives, but have outstanding questions about the performance of specific varieties against their goals. As supportive research for the BC Living Lab, Delta Farmland and Wildlife Trust conducted a fall variety trial to assess the characteristics of 20 cover species in Lower Mainland growing conditions. At the trial site in Ladner, growers compared varieties that had been monitored for height, plant cover, and weediness as candidates for winter cover cropping.
Finding the Right Fit
Cover crops in annual vegetable cropping systems are generally managed to be present in abundance overwinter and to be reduced or absent by the time crop seeding begins in the spring. Beyond these basics, growers discussed the characteristics they select for that can address farm conditions – in the Lower Mainland, weed suppression, nitrate retention, reducing erosion, and building organic matter were commonly cited priorities. In this trial, researchers were also considering:
- Plant height. In this trial, grains like oats, barley, and triticale were tallest, brassicas like turnip, tillage radish, and legumes like faba beans were mid-height, while peas and clovers were shortest.
- Susceptibility to winterkill: Cover crops that die back overwinter can be preferential as they require less cultivation to make for spring seeding.
- Risks of pests and diseases: Brassica varieties are biofumigants that can repel some insect pests, but can also host challenging pathogens like clubroot.
In-Field Insights
Most growers noted that they use barley as their primary winter cover crop, and some discussed how its affordability had made them less likely to consider other varieties. Seeing 20 varieties side-by-side created a lot of interest and excitement in alternatives to barley – most growers left with a handful of varieties they were interested in trialing on their farm. The cover crops were lush and vigorous in late October, but researchers are interested to see how comparisons of characteristics may change over the winter. For the BC Living Lab, these observations also look at how they’re supporting climate goals, by storing soil organic matter and holding nitrate overwinter.
What’s Up Next?
The BC Living Lab’s collaborative approach emphasizes the value of trialing, observing, and adapting practices to fit each farm’s goals and conditions. While working with growers to trial feasibility on active farms, researchers are continuing to assess how a winter cover crop mix performs in potatoes for weed suppression, plant coverage and nutrient management, and will adjust varieties as needed. Compost application and split nitrogen application in potatoes are also being trialed to see how they measure up for climate, productivity, and economic goals.
This field day was held on the shared, traditional, ancestral, and unceded territories of the Tsawwassen and Musqueam.
