Nitrogen
Although dry edible beans are legumes, they obtain less than half their nitrogen requirement through nitrogen fixation. Studies have not shown a benefit to inoculation with rhizobia. Ontario nitrogen research has demonstrated yield increases in some years, but has not shown an economic response to pre-plant incorporated or banded nitrogen. Nitrogen applied pre-flower does not increase yield. Other jurisdictions (Manitoba, Michigan, Wyoming, North Dakota) have shown an economic yield response to pre-plant nitrogen and suggest between 18–36 kg N/ha (40–80 lb N/acre). Where phosphate fertilizers are banded, a small amount of nitrogen (10 kg/ha or 9 lb/acre) may improve the availability of the phosphate.
It is important to consider cropping history, soil organic matter levels, and manure application history in making a decision on applying additional nitrogen fertilizer. Nitrogen may not be required where beans follow a crop that received a high amount of nitrogen, where manure is applied or where the previous crop was a legume.
Nitrogen stimulates plant and root growth. This can be helpful when bean growth is slow due to environmental stresses or root rot. Where edible bean yields have traditionally been low due to bronzing or root rots, apply up to 100 kg/ha (90 lb/acre) of nitrogen before planting. Under these conditions, nitrogen will increase yield but will not cure bronzing or root rots. Applying nitrogen can increase plant height, which is helpful in narrow-row bean harvest or for beans grown on heavy clay soils. Nitrogen can increase the risk and severity of white mould because of increased vegetation, but does not significantly delay maturity.
Phosphate and Potash
Phosphate and potash recommendations for dry edible beans are presented in Table 1., Phosphate guidelines for dry edible beans and Table 2., Potash recommendations for dry edible beans. For information on the use of this table, or if an OMAFRA-accredited soil test is unavailable, see Fertilizer Recommendations.
Where manure is applied, reduce the fertilizer application according to the amount and quality of manure according to Table 9–11,Typical amounts of available nitrogen, phosphate and potash from various types of organic nutrient sources.
Where soil fertility levels are adequate, dry edible beans show minimal response to starter phosphorous. Where potassium fertility is low, deficiency symptoms appear in white beans as yellowing of the lower leaves and necrosis on leaf margins, as seen in Photo 1. Dry edible bean seedlings are very sensitive to ammonia toxicity and salt damage from starter fertilizer. No fertilizer should be placed in direct contact with the seed. Band starter fertilizer 5 cm (2 in.) to the side and 5 cm (2in.) below the seed. Banding is a more efficient method of applying phosphorus or zinc when they are required. Fertilizer may be broadcast and plowed down, worked in before planting or applied through a planter that has a separate attachment for fertilizer.
Photo 1. Potash deficiency in white beans as seen by yellowing of lower leaves and necrosis of leaf margins.
Table 1. Phosphate guidelines for dry edible beans
Table 2. Potash guidelines for dry edible beans.
Plant Analysis
For dry edible beans, sampling the top fully developed leaf (three leaflets plus stem) at first flowering is preferred for plant nutrient analyses. Refer to Table 3, Interpretation of plant analysis for dry edible beans. Sample plants suspected of nutrient deficiency as soon as the problem appears. If sampling at times outside of the recommended timing, collect samples from both healthy and injured areas so comparisons can be made. Take a soil sample from the same area and at the same time as the plant sample. Values in Table 3 apply to the top fully developed leaf (three leaflets plus stem) at first flowering.
Table 3. Interpretation of plant analysis for dry edible beans.
Micronutrients
Manganese
Manganese deficiency in dry edible beans has been diagnosed occasionally in Ontario. This problem is more likely to occur on muck soils or very sandy soils. Plants with manganese deficiency have pale green-to-white upper leaves. The veins of affected leaves will remain green. The pattern can appear similar to iron deficiency, but manganese deficiency occurs more generally over the entire plant whereas iron deficiency appears on new growth. Correct the deficiency as soon as it is detected by spraying the foliage with 2 kg/ha (1.8 lb/acre) of actual manganese from manganese sulphate (8 kg/ha (7.1 lb/acre) of manganese sulphate) in 200 L (53 gal) of water. Use of a “spreader-sticker” is recommended. Use a spray grade manganese product to prevent nozzle plugging.
In good growing conditions, the affected leaves should green up in 4–5 days. Chelated manganese products are equally effective if applying the same amount of manganese, but the cost is significantly higher than manganese sulphate. Low rates of chelated manganese are not effective in correcting a deficiency.
In general, beans will give a profitable response to manganese in the parts of the field where manganese deficiency is obvious. There is no benefit to applying manganese to beans that are not showing deficiency symptoms.
Zinc
Low zinc conditions may occur on low organic matter, compacted, sandy, very high pH and/or eroded soils. Deficiency symptoms may also appear when early growing season conditions are cool and wet.
Zinc is not very mobile in plants, so deficiency generally appears on new growth. Leaves will appear pale green between veins with yellowing of the leaf tips and outer margin. In the early stages of deficiency, leaves can be crumpled or dwarfed. Later in the season the leaf tissue may look like sunscald with bronzing or browning of leaves, and deficiency can cause terminal pods to drop during flowering leading to a delay in maturity.
Dry edible beans do not often respond to zinc fertilizer until zinc levels in the soil are low (zinc index below 15). For zinc soil and foliar application options, refer to Publication 811, Chapter 9, Soil Fertility and Nutrient Use.
Boron
Beans are very sensitive to boron and should not be grown in a field where boron was applied to rutabagas, sugar beets or forages the year before.