The yellow colour seen on the leaves of plants is called chlorosis. These usually occur when the leaves lack chlorophyll, which is the nutrient that the plant manufactures to feed itself and which is responsible for the colour of the plant.
The problem is that without enough chlorophyll, photosynthesis will not occur properly, so the leaf will dry out and fall. Leaves with chlorosis are more susceptible to pests. If the problem persists, then the plant could die.
Why your beans plant turned yellow
The possible reason your bean plants turn yellow is due to inadequate watering. Almost all the leaves of your plant have acquired a deep yellow colour; even over the entire surface, you are probably not watering your plant properly.
However, if you are sure about the quantity of water your plant deserves, then the yellow colour on the leaves of your plant may also mean that soil is not draining properly and muds are beginning to form.
The best way to resolve this is to touch the ground with your hands. If the soil is very wet, it does not move but is caked, forming mud, which means it does not have good drainage.
On the other hand, if the soil is dry and your plant is unevenly yellow, it may not be getting enough water. So the plant sheds the leaves to avoid sweat and save what little water it receives.
Another factor is lighting problems. For photosynthesis to take place, your bean plant requires sunlight. If it is too shady for its species, you will notice that the leaves in the darkest or shaded part turn a very pale yellow, almost white.
Now, excess light can also be detrimental to specific plants grown in the shade or semi-shade. Again, inadequate iron absorption may affect your beans which results in chlorosis, thereby making your leaves turn yellow.
Nitrogen which is the nutrient that your beans plant requires to produce the green colour of the leaves and contributes significantly to growth may be insufficient.
Diseases can also cause your bean plant to turn yellow. Ensure that you investigate the soil before planting to know if the soil has previously been affected. Also, make sure that you buy your seeds from reliable sources.
Fixing the yellow leaves of your bean plants
Check to be sure that irrigation is not the reason your bean plant is turning yellow. Find out if you should be watering more or less. If the problem is lighting, then check the ideal conditions for your type of plant.
In the case, that iron chlorosis is the cause of your leaves turning yellow, then finding a way to balance the PH of the soil may be effective.
You can buy iron chelate, a powder that you can add to the soil, or look for a specific fertilizer for the type of bean plants. If it is a lack of nitrogen, then a specific fertilizer or nitrogen tablet, which you have to bury in the soil before watering, will be enough to replace the nutrients in the substrate.
Taking required measures to avoid the continued spread of yellow leaves, you may need to ensure that your bean plants are healthy and the seeds are from verified sources. Plan crop rotation, especially if the field has suffered from infections in the past.
Make sure you don’t plant beans near alfalfa, clover, or other legumes or flowers like gladioli. Also, ensure to keep the field and also surroundings free from weeds. You may also need to keep your use of insecticide low to encourage the benefits of some insects. Use plastic or organic mulch to interrupt the life cycle of aphids.