Cover Crops

Cover crops are being used in annual systems to help build soil carbon through carbon sequestration and reduce greenhouse gas emissions. Annual systems undergo higher management intensity which causes more soil disturbance and low return of residue into the soil. High management intensity is caused by farming practices like tillage, which can disrupt soil structure and increase surface runoff over time, leading to accelerated rates of soil erosion and loss of soil carbon. Fortunately, cover crops can be used to slow the processes of erosion and help build soil carbon. 

Cover crops are crops that are grown with the primary purpose of protecting soil and improving soil quality. Cover crops can be grown between cash crops, between rows of perennial crops, or within a crop. 

Cover crops provide many benefits to cropping systems. These benefits include reducing the rate of soil erosion, improving nutrient cycling which can reduce the amount of fertilizer needed because nutrients are staying on the field, building soil organic matter, improving soil health, improving soil structure which can increase water infiltration reducing the need for frequent irrigation, breaking pest and disease cycles, moderating soil temperature etc.

Cover crops will be planted in winter wheat systems because it is a common crop that’s included in horticulture and field crop rotations. Winter wheat is typically harvested in August and leaves the soil bare and exposed because plant residue that would typically be left behind is used for animal bedding.

While cover crops have many benefits, incorporating them into annual cropping systems can be a challenge for many farmers in Nova Scotia. The living lab activity aims to tackle this barrier to adoption by carrying out on-farm innovation and research activities that will develop practices using different cover crops and termination timings in a winter wheat system. The main goal is to reduce greenhouse gas emissions and improve carbon sequestration in agricultural soils. Therefore, both greenhouse gas levels and soil carbon will be measured throughout the duration of the activity to monitor how levels have changed as the activity progresses. In addition, other co-benefits such as pest management, increased yield, and improved soil structure will be monitored. 

Four different cover crops and two termination timings were established on farms by the producers as part of the Living Lab – Nova Scotia. These treatments were established in strips 20 ft wide and 200 ft long. The five cover crop treatments included:

Cover crops are typically terminated in the spring or fall. Different termination timing could have an impact on soil carbon, winter weed pressures, and the amount of nitrogen recovered from the soil from the previous crop or fixed by the cover crop and available to the subsequent crop. Depending on the lifecycle and winter-hardiness of the cover crop, they may either winter kill or need to be terminated with herbicides. Termination timing impacts the breakdown of cover crop residues which is important for tillage and seed-bed preparation in the spring, particularly for horticulture crops which typically require a fine seedbed that could be challenging to achieve with fibrous cover crop residues in the spring.

For this activity, each 200ft treatment strip was divided in half, each with a different termination timing: spring and fall.  All cover crop treatments were terminated in the fall using herbicides. The spring, red clover and the winter wheat control were terminated using herbicides. The oat/pea mixture and brown mustard will be terminated by allowing them to winter kill. 

Perennia is pleased to be working in partnership with several farms to develop, improve and refine cover crop and termination treatments. Farmers are taking an active part in developing and testing these practices on their farms by seeding cover crop treatments, applying herbicides for cover crop termination, and helping to decide on alternative treatments or methodology to ensure that the project is reflective of what can be implemented on-farm. One example of this was substituting a fall rye cover crop for the mustard treatment in a rotation that contained other brassica crops because of potential disease risks. 

Thank you to Winding River Farms, A&J Bent Farms, and Marsh Farms for co-developing and testing beneficial management practices (BMPs) in field crops rotations, and to Spurr Brothers Farms, Bragg Lumber, and Melvin Farms for co-developing and testing BMPs in horticulture rotations. We look forward to collaborating with more growers over the life of the project!

Since the beginning of the activity, Perennia Specialists, farmers, and industry have developed treatments that would be tested based on common crop rotations and discussed the challenges that could be faced when implementing cover cropping practices. In addition to being involved with the establishment of the cover crop and termination timing treatments, the Perennia team is collecting data from each of the sites. Field activities and data collection include biomass sampling, cash crop stands and yields in the growing season following the cover crops, greenhouse gas sampling, soil health and nematode sampling, and more. Dr. David Burton’s lab at Dalhousie University, Faculty of Agriculture is gratefully acknowledged for their role in analyzing the greenhouse gas samples.

The period after cereal harvest is a great time to plant a cover crop. Once the cereal comes off in August, there is plenty of time to establish a cover crop such as an oat/pea mix, or brown mustard as included in the project. Drilling would be the preferred planting method to ensure that there is good seed to soil contact for germination, but broadcasting and lightly harrowing in smaller seeds like mustard or oats would work as well. Larger seeds like peas do not do well being broadcast as it does not provide sufficient seed to soil contact, especially in the late August period when soil conditions are often dry. The cover crops included in this project could all be planted with confidence until about mid-September in most parts of the province. After that point, temperatures often turn cooler which could have a negative impact on stand establishment. Other cover crop mixes can work in this post-cereal harvest period as well, depending on the goals for the cover crop. 

Red clover is a great option for frost seeding into winter wheat in the early spring period. When the weather is conducive to maple syrup production (warm days, but temperatures going down below freezing over night), it is the perfect time to broadcast clover. The freeze-thaw action during this period will help to pull the small clover seed into the soil where it will germinate underneath the winter wheat. At this point in the winter wheat development, the establishment of clover should not impact the cereal yield. The clover grows slowly underneath the cereal canopy until harvest, at which point it has the potential to put on a lot of growth. 

The following seeding rates were used for the cover crops in this project. It is important to note that the oat/pea and mustard treatments were drilled, so the same treatments would require higher seeding rates if they were being broadcast to account for poorer seed to soil contact and establishment.