The most important factors in field selection include:
- disease history
- previous crop
- weed control and potential herbicide carry-over
- soil structure, slope and drainage
Soil Type and Structure
Fields planted to dry edible beans are susceptible to soil erosion due to late planting, slow growth and the relatively poor root systems of the crop. The crop canopy and crop residue only protect the soil for a relatively short period of the season. For beans in wide rows, the crop canopy may only fully cover the soil in August.
Dry edible beans are one of the most responsive crops to good soil structure and grow best on loamy, uncompacted soils. Heavy soils that are poorly drained, prone to crusting or hard to till risk uneven emergence and poor stands. Soil that remains saturated for 24 hours will cause severe seedling damage. Beans have relatively inefficient and poorly developed root systems that are susceptible to stress. Uneven emergence results in uneven ripening, delayed harvest and immature beans that increase the “pick” and result in lower grade and price when marketed.
Avoid growing dry edible beans in fields where compaction is a concern. Soil compaction is a serious dry bean production issue that restricts root growth, promotes root disease and increases risk of herbicide injury. Yield reductions from compaction and poor soil structure can be as high as 30%–50%. Compaction takes time to overcome and cannot be alleviated with tillage alone.
Disease History
A rotation where beans are grown only once in 3 years (or longer) is essential to avoid the build-up of diseases. The most common diseases encouraged by short rotations are root rots and white mould (Sclerotinia). Soybean, canola, potato and sunflower are poor rotation choices with beans since they are all susceptible to white mould. Root rots are challenging to control through rotation, because they have a wide crop-host range. The organisms that cause root rots are often invasive, infecting plants that are under stress. Soil compaction, poor drainage, frequent cropping to beans, and other factors cause plant stress that favours root rot. Dry edible beans are also hosts for soybean cyst nematode (SCN). Adzuki beans are particularly susceptible to SCN. For additional information about SCN and other dry edible bean diseases, see Chapter 16, Diseases of Field Crops.
Bean dealers and buyers may stipulate the crop protection products that are permitted to be used, based on the maximum residue limit (MRL) approval of importing countries. Producers need to check their production contract or guidelines and speak with their dealer for a list of approved products.
Weed Control
Options for controlling annual broadleaf and perennial weeds with herbicides are limited in dry edible beans, so weeds must be controlled in the previous crop. Weeds present at harvest may also create quality problems (i.e., seed staining) and reduce harvest efficiency. Nightshade and perennial pokeweed cause severe staining of beans at harvest. Corn is often favoured as a previous crop due to the number of options for controlling problem weeds. Cultivation between the rows can be used to control weeds. Refer to the Ontario Crop Protection Hub, for more information on cultural and chemical control options in dry edible beans. Note that not all dry edible bean classes are tested in herbicide-tolerance evaluations, and the classes may vary in their tolerance to certain herbicides.
Dry edible beans are very sensitive to certain herbicides that may be in the soil. To reduce carry-over injury from previous crops, select herbicides carefully the year prior to bean production.
Considering all the factors, the ultimate rotation crops for dry edible beans include corn, forages and cereals. A previous crop of corn or cereals provides a good opportunity to control weeds, and an effective break in edible bean diseases. The earlier harvest date of dry edible beans allows for timely planting of winter wheat. A cereal crop in which weed control was good would be preferred over a corn field where compaction following a wet harvest might be an issue. Forages promote the best soil structure, but soil insects and weed pressure can be an issue. For more information on appropriate crop rotations for dry edible beans and precautions under different tillage systems, please visit the Dry Bean Agronomy website.