As a pulse crop, dry bean has the ability to fix a portion of its required nitrogen from air in the soil through a symbiotic relationship with soil bacteria called Rhizobium. Successful inoculation of dry bean requires the correct species of bacteria called Rhizobium phaseoli.
When properly inoculated, the bean plant will form nodules on its roots where the bacteria convert nitrogen to a form that plants can use.
Generally, dry bean is poor at fixing nitrogen in comparison to pea, lentil, faba bean, and chickpea. Research completed on inoculated dry bean by the University of Saskatchewan and Agriculture and Agri-Food Canada (AAFC), Morden Research Station, indicated a positive yield response to the application of starter nitrogen at actual nitrogen rates of 25-75 kg/ha (22-67 lb /acre) when applied in conjunction with an effective rhizobial inoculant. This on-going research also indicates a difference between bean varieties with respect to their ability to fix nitrogen. For these reasons, the current recommendation for non-irrigated dry bean production in Saskatchewan is to inoculate the crop and use 55 kg / ha (50 lb /acre) starter nitrogen, broadcast or side-banded.
The use of some seed treatments can negatively affect nitrogen-fixing inoculants. Generally, seed treatments should be applied to the seed first, allowed to dry, and then the inoculant applied just prior to seeding. The use of an in-furrow granular inoculant can minimize contact with treated seed. For more information consult the inoculant label or see Inoculation of Pulse Crops.
Dry bean grows best in fertile soils, so soil samples should be taken and analyzed to provide an accurate assessment of the crop's fertility needs. Bean is very sensitive to seed-placed fertilizer, so all nitrogen, potassium and sulphur fertilizer must be placed away from the seed.
Sidebanding fertilizer is recommended. The maximum phosphate level placed with the seed is 17 kg / ha (15 lb /acre) P2O5, based on 15-17 cm (6-7 in.) row spacing and under good to excellent seedbed moisture conditions.
As mentioned, the current recommendation for non-irrigated dry bean production in Saskatchewan is to inoculate the seed and use 55 kg/ha (50 lb /ac) starter nitrogen, broadcast or side-banded.
In research carried out at the University of Saskatchewan, inoculated bean had a yield response to the addition of nitrogen fertilizer, even when properly inoculated with a rhizobial inoculant. This research also indicated that different bean varieties have varying responses to the addition of starter nitrogen fertilizer. Excessive nitrogen applications may cause increased vegetative growth, delayed maturity and an increased risk to foliar disease.
Phosphorus is extremely important for optimum nodule, flower and seed formation and advancing crop maturity. If phosphorus levels fall below 28 kg/ha (25 lb /acre), an additional 17 kg/ha (15 lb /acre) may be added. Seed placement of phosphate in excess of 17 kg/ha (15 lb /acre) can reduce plant stands.
For higher rates of phosphate, dry seedbed conditions or wider row spacing, sidebanding phosphate fertilizer is recommended. The use of Jumpstart® inoculant is an alternative or supplement to adding phosphate fertilizer and is used to increase the availability of phosphorus to the plant. Check the Jumpstart label for more information.
Most soils in Saskatchewan have high levels of available potassium, and thus the addition of potassium fertilizer is often not required. Potassium levels may be low on sandy soils and may require potassium fertilizer. If potassium fertilizer is required, consider blending it with nitrogen and sideband it away from the seed.
If a soil test indicates sulphur deficiencies, plant-available forms of sulphur fertilizer can be side-banded. Sulphur fertilizer can be added to the crop preceding dry bean as a management option.
Zinc deficiencies can occur in dry bean. However, research in Saskatchewan has not yet identified widespread zinc deficiency problems. Navy bean tends to be more susceptible to a zinc deficiency than coloured bean, and recent research indicates that zinc deficiency may be variety specific.
Zinc deficiencies are expected to occur first under irrigation and on sandy soil, and will most likely be seen in isolated patches within the field. Symptoms include yellowing of the newest leaves and the area between the leaf veins, while the veins remain green. Bean plants tend to be stunted due to shortening of the internodes. Bronzing of the older lower leaves, crinkled appearance of the leaves that curl downward and poor pod set are also symptoms of zinc deficiency.
Tissue and soil samples of unaffected and suspect areas in the field should be taken and analyzed to confirm a zinc deficiency. Zinc can be applied with the fertilizer blend and side-banded at seeding time or foliar applied as needed. Use the plant-available forms of zinc fertilizer.
Low soil temperatures or wet soils in the spring may lead to iron or zinc deficiency symptoms in dry bean that should become less evident in a few days when the soil warms and excess moisture is gone.