Edible Beans – Plan Before Planting

Excellent yields and strong prices in 2004 have increased interest in growing edible beans. Selecting the right field to grow edible beans is one of the most important considerations. Edible beans are a more delicate crop than soybeans, require more management, and are less tolerant of variable soil conditions. Factors such as soil type, drainage, stoniness, weed pressure, previous crop(s), soil structure, previous herbicides have a large impact on successful bean production.

Soil Compaction

Soil compaction can be a major problem in edible bean production. Some growers have reported yield reductions as high as 50% caused by soil compaction. The affects of tillage, planting, harvesting and other field operations on soil compaction should be carefully considered. Compaction takes time to alleviate and cannot always be overcome through tillage. Some soils recover from compaction as a result of freezing and thawing, or wetting and drying cycles. Deep compaction below the top few centimeters of soil can last for more than 6 years.. Avoid growing edible beans in fields in which compaction is a concern.

Soil Structure

Edible beans are one of the most responsive crops to good soil structure. Heavy soils that have poor drainage, crust, or are hard to till, increase the risk of uneven emergence and poor stands. Uneven emergence results in uneven ripening, delayed harvest and immature beans that increase the "pick" and lower grade and price at market time. The previous crop has a large influence on soil structure.

One good measure of soil structure is aggregate stability. A low index for water – stable aggregates means that soil aggregates will dissolve readily in water and form soil crusts. These soil crusts reduce seedling emergence, water and air penetration and lead to consolidated soils that restrict root growth. It is generally regarded that the field crops that promote aggregate stability are (in order of greatest to least): forage grasses > forage legumes > winter cereal (especially when plowdown red clover is also included) >spring cereals > corn > soybeans > edible beans. Is it any wonder some dairy and beef producers have some of the highest average edible bean yields? Of course, these producers also practice a long rotation of 4 years or more between bean crops.

Disease Control

Crop rotation is the most effective biological control method for controlling a number of soil borne diseases. Two important diseases of edible beans, white mould and root rot, attack several crops and crop rotation must take this into consideration.

White mold survives from year to year in overwintering structures in the soil called sclerotia. 2004 was an ideal year for white mold that provided a huge innoculum source of sclerotia for next year. White mold can affect edible beans, soybeans, sunflowers, mustard and canola. Some broadleaf weeds can also act as alternate hosts for white mould. Maintaining a minimum 3 – 4 year rotation between these crops reduces the risk. Tillage is not effective in reducing the inoculum level, because the overwinting structures can survive a long time in the soil. Reduced tillage has been credited with reduced survival of sclerotia because it favors the bacteria that breakdown these structures.

Root rot is more challenging to control through rotation because it has a wide host (crop) 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. Seed treatments can help to protect seedlings during emergence, but do not provide season long control. If you can provide an environment that gets beans off to a fast start, and keep them growing, root rot is often not much of an issue. Long rotations (4-5 years) reduce the severity of the disease. Plants beans only on well-drained soils or try to improve drainage.

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Weed Control

Options for controlling annual broadleaf and perennial weeds are more limited in edible beans, so they need to be controlled in the previous crop. Annual weeds, such as ragweed, can be a problem if beans follow winter wheat, and if there are weed escapes. Some perennial weeds like nightshade and pokeweed can cause staining of beans at harvest. Corn is often favoured as a previous crop because of the number of options for controlling problem weeds.

Insects

Seedcorn maggot and wireworm can sometimes be a pest problem of edible beans. The risk of these pests will be greater following a forage crop or plowdown.

Tillage

White and black beans have been the most easily adapted bean types to a no-till system. All edible beans respond to some tillage. This is often because of the less aggressive root system of edible beans. In a no-till system, within-row tillage is beneficial for white and black beans For most other bean types, conventional tillage is most suitable.

Previous Crop

When all these factors are taken into consideration, the previous crops that are often most suitable for edible beans are corn, followed by forages and cereals. A previous crop of corn, provides a good opportunity to control weeds, and an effective break in edible bean diseases. A cereal crop in which weed control was good would be preferred over a corn field, in which compaction might be an issue following a wet fall harvest. Forages provide the best soil structure, but soil insects and weed pressure could be an issue.

Manure

Some mention should also be made of the success some producers have in growing edible beans on a field in a good rotation that also received manure the previous year. Edible beans tend to respond more to residual fertility than applied fertility. Research is beginning to identify the value of manure in promoting a healthy soil microorganism profile, and in some instances, suppression of some crop pathogens.

Good soil structure and a long rotation are cornerstones in successful edible bean production. It is very likely that seed production issues and the increased interest in white beans may limit seed availability for the most popular white bean varieties in 2005.

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