Beans require proper nutrition for normal growth and yields. Deficiencies or excesses of nutrients can cause disease-like conditions.
Symptoms and Signs
Symptoms vary depending on the nutrient involved, the bean variety, and environmental conditions.
Comments on the Disorder
The most common nutrient deficiencies occur with nitrogen, phosphorus, and potassium. Other possible deficiencies include boron, sulfur, and zinc. Excess boron may cause toxicity.
Soil pH plays an important role in availability of nutrients, with high or low pH affecting uptake of nutrients as described in the table below. Soil or plant tissue tests may be needed to precisely determine nutrient problems.
| Nutrient | Deficiency | When it Occurs |
|---|---|---|
| Nitrogen (N) | Older leaves are pale green to yellow; stunted plants with few flowers and poorly filled pods. | Occurs in all soils, but especially in sandy soils or soils with low organic matter; can be induced by heavy rains or irrigation that cause leaching of nitrates. If soil pH is outside 6.0–8.0 range, N availability may be restricted. |
| Phosphorus (P) | Slow growth; small dark green leaves in upper part of plant; older leaves yellow then turn brown and senesce. Stunted plants with thin stems and short internodes. Flowers abort. | Occurs in soils with low pH or that have leached nutrients. P availability is very reduced in soils with pH below 6.2. |
| Potassium (K) | Symptoms mainly in young plants. Marginal chlorosis of older leaves which turns to yellow brown scorch in between the veins (sometimes resembling common bacterial blight, but without water-soaked appearance); leaf may curl downward while scorched margins curl upward; plants can be stunted with poor root systems, leading to collapse. | Occurs in soils with low fertility but high calcium and magnesium, especially sandy soils. K is less available in soils with pH below 6.0. |
| Boron (B) | Terminal buds and apical meristems die; witches' broom; thick, deformed primary leaves; interveinal chlorosis; swollen stems near nodes. | Rare in beans—occurs in soils with coarse textures, low organic matter, and high aluminum and iron hydroxide. It can also occur in alluvial soils with high pH, or in dry, neutral to alkaline soils under intense light. |
| Sulfur (S) | Uniform yellow chlorosis of leaves, similar to N deficiency. | Rare in beans—can occur in soils with pH below 6.0. |
| Zinc (Zn) | Deformed, pale green younger leaves with yellow tips and margins, interveinal chlorosis, and development of necrotic areas with time; blossoms and pods may abort; dwarfed plants. | Occurs in soils with high pH (or acidic soils that have been 'over-limed' or have too much P). Can be worse under conditions of soil compaction, low organic matter, or too much manure or crop residue. The increased absorption of other nutrients can cause Zn deficiency, especially Fe. |
| Nutrient | Toxicity | When it Occurs |
|---|---|---|
| Boron (B) | Stunting, yellowing, necrosis. | Occurs with non-uniform applications of fertilizer or bands of fertilizer too close to seed, especially in dry weather; can also occur if beans follow a crop heavily fertilized with B, such as turnips. Boron toxicity is likely if dry beans are grown in the high-boron soils on the west side of the San Joaquin Valley, part of Yolo County, and several other areas in California.
Boron tolerance (ppm)
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Note: Excess soil salinity can also cause stunting, yellowing, and necrosis. Threshold soil salinity (EC or electrical conductivity of the saturated soil extract in dS/m):
- Common beans: 1.0
- Lima beans: 1.5
- Blackeyes: 4.9
Management
Know the pH, nutritional properties, and history of the fields in which beans are to be planted and follow recommended practices for cultivation of beans. Soil testing is recommended for determining nutrient levels in your field. To ensure a healthy crop, adjust nutrient levels when needed.