Weed Supression with Winter Annual Cover Crops in Potato

2011 Annual Report for GNC10-123

Project Type: Graduate Student
Funds awarded in 2010: $9,950.00
Projected End Date: 12/31/2012
Region: North Central
State: North Dakota
Graduate Student:

Weed Supression with Winter Annual Cover Crops in Potato


Field experiments were conducted at Carrington in both irrigation and dryland to determine 1) if cover crops could be used in a mechanical weed management system in irrigated potato and 2) if cover crops affect potato yield. More specifically, the field trials evaluated the influence of cover crop and cover crop termination method on weed control, potato yield, and potato quality. Since potato production is a tillage intense system and the field trials consisted of a reduced tillage system, all difficulties with field operations were reported.

In general, cover crops presented a difficult situation during almost all phases of potato production. Cover crops terminated with herbicide were planted into a no-till field without customized no-till machinery. Lack of rigorous tillage before planting and the presence of cover crop residue made hill formation difficult throughout the season. Problems indicative of poor potato hill structure such as high rate of potato sun scald were prevalent. Hairy vetch was the cover crop considered most difficult to plant potatoes into due to its high biomass, slow dry down of vegetative tissue, and vine growth form.

Irrigated. When a cover crop was present, average weed control was not improved above the no cover crop treatments at Carrington. All cover crop and termination treatments provided at least 90% average weed control averaged over all three evaluations periods. Evaluating each treatment combination separately showed minimal weed pressure, with most treatment combinations averaging 0-11 plants/m2 and 0-15 g/m2 weed fresh weight. The checks did not have greater average weed density or weed fresh weight than any other combination of treatments. Cover crops did not have an effect on yield at Carrington. Treatments in this experiment lowered stand counts an average of 20%.

Dryland. Cover crops provided similar average weed control 12 and 28 DAP to the no cover crop treatment at Carrington in 2011. At 47 DAP, cover crop treatments averaged 5% greater average weed control than the no cover crop treatment. Roller-crimp had the lowest season-long weed control compared to disk-till and herbicide. Weed pressure was low with most treatment combinations averaging less than one weed/m2 and weed fresh weights less than 10 g/m2. Cover crops had a detrimental effect on yield at Carrington. The no cover crop treatment had 35% greater average marketable yield than cover crop treatments. The cover crop and termination treatment conditions in this experiment lowered stand counts.

Objectives/Performance Targets

Short-Term Outcomes: The cover crop weed suppression project in potatoes has the ability to greatly impact the weed control knowledge of growers currently producing organic potatoes in North Dakota and Minnesota. Grower’s knowledge of this research will expand the interest in organic potato production and show others new technology and science that should improve their operations. This project will be the initial step taken to resolve the issue of weed control, the major obstacle in organic potato production for this region. The awareness of cover crop benefits should increase the interest of adopting cover crops in other production systems.

Intermediate-Term Outcomes: This project will demonstrate the ability of cover crops to bring the nitrogen towards the soil surface for plant use and to reduce weed establishment. It will provide a new method of weed control for organic potato producers in this region and most likely increase yield and quality without increasing external inputs. It is anticipated that we will be able to build on the success of this project to show other producers the benefits of cover crops to the soil and thereby increase profitability and sustainability in their production system.

Long-Term Outcomes: The ultimate goal of the cover crop for weed suppression project is a positive effect to the whole system of organic agriculture. Not only would potato growers in North Dakota and Minnesota be impacted by the research, but growers throughout pertinent potato growing regions in the United States and other countries as well. Systemic changes could be achievable with the success of this research. The organic potato industry would have greater success with higher yields using cover crops for weed control as well as increasing soil quality and sustainable production practices. In organic agriculture, pests and nutrient deficiencies of all sorts have the potential to decrease yields and create major production problems for growers. Cover crops are the link which could serve multiple purposes in organic agriculture. A great aspect of this potential research is its ability to add knowledge to an integrated cover crop system for growers that have been content with conventional production practices, paving the way for more sustainable practices and the future of organic agriculture.


The second field season of this research began August, 2010 and was completed October, 2011. The study is being replicated in 2011 with both the dry land and irrigated sites at Carrington, ND. The results from 2011 were much different that 2010. The difficult task of growing potatoes in high residue, sometimes no-till field conditions was even more difficult with the addition of hairy vetch to the treatment list. Soil type in Carrington made hilling much more successful than 2012.

Impacts and Contributions/Outcomes

The second year’s research, summer 2011, was presented at the Weed Science Society of America annual meeting at Waikoloa, Hawaii on February 7th, 2012.

The 2012 field season will now be compiled with 2011 to gather a complete picture of cover crops in potato production in North Dakota.


Grant Mehring

graduate student
GSOrganization GSDept GSAddress1 GSAddress2 GSCity GSState GSZIP North Dakota State University Department of Plant Sciences
NDSU Dept. #7670 Box 6050
Fargo, ND 58108-6050
Office Phone: 7013717076