Fertility Requirements

AMOUNT REQUIRED

• Understanding the fertilizer requirements of dry bean is critical to reaching optimum yields. The crop will respond to added fertilizer nutrients when soil test levels are low to medium. It is always best to soil test as an aid in developing a sound fertilizer management program.

Nitrogen (N)

• While dry beans do fix a portion of their required nitrogen, in general it is recommended that beans receive between 80-100 lb/ac nitrogen total for row crop and as high as 100 to120 lb/ac when growing in solid seeded systems.
• In Manitoba, provincial guidelines based on residual nitrogen in the soil profile exist for both wide-row and narrow-row production in relation to the target yield. The recommendations are consistent with the Alberta recommendations.
• Wide-row production often has some tillage associated with weed control, which can increase mineralization rates of organic matter, contributing more nitrogen to the crop during the growing season, which is why nitrogen rates are slightly lower on wider row production.
• Mid-season N applications are normally not recommended. An exception would be under conditions of failed inoculation and obvious N deficiency.

Phosphorus (P2O5)

• Phosphorus is a nutrient required in relatively large amounts.
• A soil test is recommended to determine optimum phosphate fertilizer rates.
• Phosphorous is important for dry bean nodule formation, flowering, seed formation, and to help speed up maturity.
• Dry beans respond best to soils that are high in residual phosphorous more so than to phosphorus applied the year of planting.
• Proper planning in rotation can help ensure dry beans have a good supply of phosphorous available the year they are planted.
• If soil test levels are low (less than 28 kg/ha or 25 lb/ac), an additional 17 kg/ha (15 lb/ac) can be applied safely with the seed if solid seeded on 15 to 17 cm (6 to 7 in) rows, in good moisture.
• If higher rates are required, or if beans are grown on wider rows, then phosphorous should either be side banded or broadcast prior to seeding.
• Research has also shown that although phosphorus is a limiting factor in many Alberta soils, build-up of soil phosphorus tends to raise available soil phosphorus levels and phosphorus fertilizer responses are often not dramatic.
• Even if seed yield increases are not achieved every year, a dry bean crop may benefit from improved stress tolerance as a result of phosphorus application.
• Phosphate fertilizer cannot be safely applied with the seed, so apply either by banding prior to seeding or side band at planting time.

Potassium

(K2O)

• Levels of potassium in soil are usually adequate in most bean growing areas, so potassium fertilizer is not normally required.
• However, if soil test potassium levels are less than 200 lb./ac., then follow the analysis report recommendation for potassium.
• Many Alberta soils are medium to high in exchangeable potassium, often ranging from 400 to 1000 lb. of potassium/acre in the 0 inch to 6 inch depth of soil.
• Potassium deficiencies are most likely to occur on sandy soils that are intensively cropped or on Grey-Black transition soils and Grey Wooded soils.

Sulphur (S)

• Sulphur is required for optimum yield, but is normally not limited in most irrigated soil as irrigation water contains substantial amounts of sulfate-sulfur (amounts in the water vary over time) – approximately 30 lb./ac. of sulfate/sulphur is added to the soil with 12 inches of irrigation water.
• Some soils are deficient in plant-available sulphur in the topsoil but have enough sulphur in the subsoil to meet crop requirements.
• In wetter, cooler conditions, plants may suffer from a lack of sulphur before plant roots grow down into the subsoil containing sulphur.
• Sulphur deficiencies are frequently a problem in the Black and Grey Wooded soil areas of Alberta and occasionally a problem in the Brown and Dark Brown soil areas.
• Test soil to a depth of 24 inches to determine if sulphur fertilizer is required – if analysis levels are less than 20 lb./ac., follow recommendations of the analysis report.

Micronutrients

• Micronutrient deficiencies are not widespread across Alberta and it is not typically an issue in dry bean production.
• Dry bean requires a supply of all the essential micronutrients: namely boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo) and zinc (Zc).
• Zinc deficiency in bean plants may occur if soil pH is higher than 7.5, if soil has had high phosphate fertilizer or manure application, or if spring and early summer weather is cool and damp.
• Zinc deficiencies can be corrected with a pre-plant application of banded granular zinc sulfate at a rate of 2-5 lb./ac. – a foliar application of 0.5 per cent zinc sulfate should be applied if deficiency symptoms appear after emergence.
• Zinc deficiency is most evident following sugar beets in the rotation.

IMPACT OF MICRONUTRIENTS ON OTHER CROPS 

• Note that dry bean is not grown continuously on the same land – other rotation crops such as flax, wheat, canola and barley may respond optimally to the topped up levels of these minerals:
  • The three remaining micro-nutrients – iron, manganese and molybdenum – have a much more critical effect.
  • Most Alberta soils are adequate for iron but high pH soils or alkaline soils may lock up manganese availability so that a foliar application of this micronutrient may be necessary.
  • Molybdenum becomes much less available in acidic soils (below pH 6.5) especially at pH 5.5 or less.
  • Molybdenum is absolutely essential in the nitrogen fixation process in legumes – without it, no nitrogen can be fixed (in Europe, producers may apply 200 to 300 grams of actual molybdenum to the seed crop or soil every few years or lime the soil to bring up the pH and release more molybdenum).
• Based on soil test results, micro-nutrient fertilizer should be applied in test strips the first year. Sandy, low organic matter may show best response
• For more information, recommended soil micronutrient levels are included in the fact sheet: Minerals for Plants, Animals and Man, Agdex 531-3 and Micronutrient Requirements of Crops, Agdex 531-1.