The narrow-row production system for dry bean allows the use of seeding equipment designed for other crops. Bean crops seeded with airseeders or other solid-seeding implements emerge in rows 15 to 30 cm (6-12 in.) apart which do not allow between-row cultivation. The use of tramlines should be considered in narrow-row bean production to avoid wheel track damage to emerged bean plants. Damaged plants often mature later, complicating harvest timing.
Dry bean seedlings can display a condition called baldhead, where only cotyledons and seedling stem emerge, and no leaf development occurs. Baldhead is caused by mechanical injury to the seed during handling or seeding, especially when seed moisture content is below 14 per cent.
To reduce baldhead, the airseeder fan speed and ground speed should be reduced as much as possible while still maintaining proper seed distribution. Some airseeders can be modified with deflector pads within the seed delivery manifolds to reduce seed cracking. Belt conveyors are available on some new airseeders to reduce mechanical injury while loading.
Baldhead can also be reduced by using seed that is 14 per cent moisture or higher. Bean growers have learned to soak their seed before planting to slightly moisten the seed coat and reduce mechanical injury while seeding. This can be done by suspending a mini-bulk bag containing the seed and running water into the top of the bag until the excess water runs out the bottom of the bag. This process should be repeated after eight hours. After thoroughly wetting the seed, it should be allowed to temper for at least 24 hours before the seed is placed in the seed tank. Wetting the seed should be done before applying seed treatment fungicides or inoculant.
Extra care must be taken when handling bean seed.
Seed treatment fungicides can be applied to the seed to reduce the risk of seed-borne and soil-borne seed rot and seedling blight of dry bean.
In Saskatchewan, dry bean should be seeded between May 25 and June 5. Earlier planting increases the risk of seedling death due to late-spring frosts. Seeding later increases the risk of crop injury by early-fall frosts. Seeds germinate and develop slowly if the average soil temperature at depth of seeding is less than 12°C.
The recommended seeding depth for dry bean is 5-6 cm (2-2½ in.). Dry bean seed is comparatively large and absorbs moisture from the soil when it germinates and starts to develop. For this reason, the seedbed should be moist for proper growth. Shallow seeding increases the risk of the seedling drying out after germination, while seeding too deep weakens seedlings and increases the risk of soil-borne diseases.
Seeding rates for dry bean depend on the seed size (Table 1). The target plant population for narrow-row production of the crop is 45 plants per m2 (four plants per ft.2). Higher seeding rates are required for narrow-row production of varieties with determinate (Type I) growth habit. Varieties with an indeterminate growth habit (type II and III) require a lower seeding rate because the individual plants are larger and are able to close the crop canopy more rapidly. Higher seeding rates can increase the risk of foliar diseases, such as white mould, under high moisture conditions.
The following formula should be used to calculate the proper seeding rate.
Seeding rate (lb. /acre) = (population/ft2 x 1000 seed wt. g / % field emergence or survival) x 10
Example (for CDC Pintium variety beans 350 g/ 1000, assuming 90 percent of plants surviving):
(4 plants x 350 / 90) x 10 = 156 lb / acre or 175 kg / ha
Ensure that seeding equipment delivers seed uniformly at an even seeding depth. A common problem for first time growers is the occurrence of gaps in the seed row followed by dense numbers of seedlings due to uneven seed flow. The gaps allow weeds to become established, and the dense bean areas can increase the risk to plant diseases.
Land rolling of fields seeded to dry bean is done to level soil ridges and push any stones into the soil surface to ease harvest and reduce earth tag. Rolling should be done immediately after seeding or up to three days after seeding. Land rolling of dry bean should not be done after seed germination or emergence of the crop as this practice will most likely break the stems of seedlings. Unlike pea, lentil or chickpea, dry bean seedlings do not have the ability to re-grow from scale nodes if damage to the stem occurs.