Dry beans can be planted from mid-May to early June in Manitoba. This later planting period protects seedlings from post-emergent frost damage, which can injure dry bean seedlings and reduce plant stand. Dry beans should be planted when soil temperatures are consistently above 15⁰C .
According to MASC data from 1989-2008, the second, third and fourth weeks in May produce the greatest navy bean yields in Manitoba.
Recent planting date research in North Dakota has shown that typical late May to early June planting dates for all dry bean market classes remain appropriate for optimum yield potential and reduced frost risk. From 2012 to 2015, pinto, black and navy bean beans yielded similarly between early (May 11-24), normal (May 22-June 5) and late (June 5-18) planting dates (Table 1). A trend toward higher yields for normal and late planting dates was observed, although this was not significant.
Like other large-seeded crops (i.e., field peas, soybeans), dry beans can withstand greater seed depth than small-seeded crops (i.e., canola, cereals) to ensure they have adequate seed to soil moisture contact. The recommended seeding depth range is 1.25 inches to 1.5 inches. Plant at a slower speed to minimize dry soil in the furrow and ensure adequate down pressure to achieve the desired depth.
Target Plant Stand and Seeding Rate
Target plant stands vary among dry bean market classes and row widths. Calculate seeding rates (seeds/ac) to establish the target plant stands (live plants/ac) listed in Table 2. Factor expected seed survival into seeding rate calculations. Also consider economic factors such as seed cost, expected grain price and yield.
Research led by Dr. Rob Gulden’s Weed Ecology & Management Lab at the University of Manitoba examining plant population and row spacing has shown that pinto and navy bean yields were relatively insensitive to changes in plant population in wet years (2015 and 2016) and responded positively to plant population in drier years (2017 and 2018). In 2017 and 2018, navy and pinto bean yields were most stable when grown on 7.5″ row widths targeting populations of 120 – 160,000 plants/acre. In the wetter years of 2015 and 2016, increasing plant population increased the severity of white mould disease pressure. In 2017 and 2018, white mould was not present in the experiments.
Recent research from Carrington, ND has found black bean yields were maximized by planting at 120 – 150,000 plants/acre, regardless of row width. Navy bean yields in their study were greatest when planting at populations greater than 115,000 plants/ac in 14″ rows.
Conduct a soak test to assess seed damage:
Place 200 seeds in water and calculate the percentage of seed coats that slough off. Factor this percentage into seeding rate calculations. Seeds that lose their seed coats may produce a “baldhead” seedling that has a damaged growing point and does not produce a viable plant (right). Watch this tutorial video from provincial pulse specialist, Dennis Lange on how to successfully conduct a soak test.
Baldheads are caused by mechanical injury to the seed. They will germinate and emerge and cotyledons may be attached or broken. These plants will die shortly after emergence, resulting in a lower plant population than desired.
Reduce mechanical damage by minimizing handling of the seed. Use seed that is at 14% moisture or greater. If using an airseeder, increase your seeding rate to account for more seed damage, and reduce fan speed and ground speed while maintaining proper seed distribution.
Dry beans have traditionally been planted in wide rows to promote airflow in the crop canopy to prevent disease development (e.g., white mould) and to facilitate inter-row cultivation to manage weeds. However, recent research conducted in Manitoba and Saskatchewan has pointed to yield benefits associated with planting at narrow rows. This is due to faster crop canopy closure that out-competes later flushes of weeds and captures sunlight more efficiently.
Results from Dr. Gulden’s research (U of M) have shown that yields of pinto and navy beans were greatest when planting at 7.5″ row widths and decreased as row spacing was widened to 15″ and 30″. Similar results have been reported by Jeff Ewen (Saskatchewan Ministry of Agriculture) who conducted field-scale research comparing narrow- vs. wide-row beans. Under dry conditions, narrower rows may also provide the added benefit of moisture conservation. However, farmers must also be aware of the increased risk of seed damage that can result from air seeders and seed handling.