Phosphorus Mobilization and Weed Suppression by Buckwheat.

Phosphorus Mobilization and Weed Suppression by Buckwheat.

Summary

In the Red River Valley of Minnesota/North Dakota all major crops have a serious disease or insect problem. The only alternative to high pesticide inputs for many farmers, especially organic farmers, is black fallow, which depletes both the weed seed bank and disease inoculum. Conversely, it also depletes soil organic matter and requires long hours on the tractor, with high fuel costs. We need summer cover crops that are suitable to the Red River Valley and that can substitute for the weed and disease control benefits of black fallow while simultaneously add some diversity to the farming system of the region.

Objectives: To assess the value of buckwheat and other summer cover crops as alternative to black fallow in the crop rotation of the Red River Valley, and to verify their value for:
1) Mobilizing soil phosphorus (P) and possibly other nutrients,
2) Suppressing weeds,
3) Conditioning soil,
4) Providing habitat to beneficial insects,
5) Suppressing diseases.

Farmers will plant one cover crop in each field, but will leave a weed fallow strip through each one as a control. Data will be analyzed using the statistical techniques of a paired plot comparison. Up to 10 farmers or 40 fields will be used, in the Crookston and Fargo/Moorhead areas. The farmers will decide collectively which specific cover crops to look at, and how they will be managed, collectively choosing up to five treatments. They will plant the same crop in the subsequent year in order to gauge P uptake and long-term weed suppression.

Measurements will include soil tests for pH, P, K, and organic matter, and for aggregate stability to asses soil quality. These will be measured prior to planting cover crops and again after plow-down and residue decay. Cover crop and weed populations, biomass, and P uptake data will be collected just prior to cover crop plow-down, and again in the subsequent cash crop: It is the data from the subsequent cash crop that will be of primary importance. Insect populations will be counted at one-week intervals for the duration of the growing season.

Results of this project will be shared with other farmers by means of summer field days in the plots, talks at winter meetings, newspaper articles, and radio and TV spots, as well as in an annual Extension Educator Research Report. Curt Petrich, a leader amongst local organic farmers, had been conducting a series of informational meetings in the winters. Daylong seminars for beginning organic farmers put on at the Southwest Experiment and Outreach Station in Lamberton, Minnesota, and Elizabeth Dyck’s SARE-funded Organic Conversion project are other venues for dissemination of results.