Cover Crops in Annual Systems

Annual cropping systems tend to have high management intensity – soil is frequently disturbed by tillage, soil between crop rows is left exposed to erosion, and little crop residue is returned to the system. This leads to depletion of soil carbon and reduction in soil health and system resiliency in the face of climate change.  

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, reduction in fertilizer need, building soil organic matter, improving soil health, improving soil structure, increasing water infiltration, breaking pest and disease cycles, and moderating soil temperature. 

Hear from one of our producers on why they wanted to participate in this activity:

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. 

Four different cover crops and two termination timings were established on farms by the producers as part of 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 either the spring or fall. Different termination timing could have an impact on soil carbon, winter weed pressures, and the amount of nitrogen 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 require a fine seedbed that could be challenging to achieve with fibrous cover crop residues in the spring. 

For this activity, each treatment strip was divided with one half being spring terminated and half being fall terminated.  All fall terminated cover crop treatments were terminated using herbicides. In the spring, red clover and the winter wheat control were terminated using herbicides. The oat/pea mixture and brown mustard will be spring terminated by allowing them to winter kill.  

All our BMPs are being monitored for carbon sequestration and GHG emissions. However, cover crops can have other impacts that are important in the decision-making process for farmers.  For our cover crop BMP, we are also monitoring the yield and health of the following cash crop. It is important to show that there is not a negative impact of the cover crop on the main crops of a rotation, as this can be a major barrier to adoption. We are also monitoring soil health, soil moisture, pest populations (such as nematodes), and cover crop biomass.  

One barrier to adoption for many farmers is knowing how to include cover crops in their farming system. There are many questions to answer, such as which cover crop to use, when to plant it, and how and when to terminate the cover crop. More information on the type of cover crop and termination strategies is needed to help growers choose the right combination to maximize the benefits of cover crops without adversely impeding cash crop production.  

Feedback from participating producers has been invaluable and has resulted in some changes over the life of the BMP thus far. For example, fall rye replaced the mustard treatment at one of the horticulture rotation sites to address concerns around brassica pests. 

Perennia is pleased to be working in partnership with several farms to develop, improve, and refine cover crop and termination treatments. Thank you to Winding River Farms, A&J Bent Farms, and Marsh Farms for co-developing and testing BMPs in field crop 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. Dr. David Burton’s lab and Dr. Derek Lynch’s lab at Dalhousie University, Faculty of Agriculture, is gratefully acknowledged for their role in analyzing the GHG samples and soil carbon samples, respectively.