Soybean a miracle crop of the world and declared as golden bean, a meat that grows on earth. It is enriched with minerals, vitamins, oil, lipid, and carbohydrate components, along with the minor element’s iron (Fe), phytic acid and isoflavones.
In Asia soybean widely used to produce traditionally food items e.g. soymilk, soy sauce, tofu, soy paste, tempeh and miso. Moreover, soy protein, concentrates, and isolates are used as value added food ingredients in infant recipes, meat and baked goods.
More than half of soybean produced oil is used in cooking and salad oil while rest of in baking, frying, other industrial uses and for biodiesel production. Soybean is value able crop for oil, protein and for food.
Although it contains a significance amount of nutrition but unfortunately due to some reasons it shows iron deficiency. Fe is the main constituent for plant as well as for soybean consumer. Iron (Fe) is classified as a micronutrient which means it is required by plants in low quantities.
Iron is essential for several enzymes, pigments and assists in energy production within the soybean plant (Iron homeostasis). Iron is not used in the synthesis of chlorophyll but it is essential for its development that is why iron deficiency shows chlorosis in young leaves of soybean.
Out of all the micronutrients required by plant, iron is needed in the utmost quantity and its availability is dependent on the pH of the soil.
Iron Deficiency Chlorosis (IDC)
Iron deficiency chlorosis” (IDC) is a nutrient shortage condition. The plant expresses general symptoms of Interveinal chlorosis on the leaves and stunting of the plant growth due to iron shortage.
IDC symptoms begin to appear a few weeks after soybean emergence, as interveinal chlorosis on the first trifoliate leaves occurs and if symptoms retains up to 5th to 6th trifoliate leaves stage.
Because iron cannot translocate in the plant itself, plant at early stage will be most affected if the absence of iron persists, leaves will turn yellow with gloomy green veins and plants may remain undersized.
If there is severe iron deficiency plant leaf edges become necrotic and the necrosis will develop until entire plants are dead. The IDC symptoms show up in erratic patterns distributed across a field because of soil heterogeneity.
Alkaline and calcareous soils are major problem of Pakistan’s agriculture and its location in arid to semi-arid regions also hit very badly to this problem. In Pakistan 6.30 million hectares of land are salt affected and hence rendered unfit for cultivation.
Other natural reason for alkaline and calcareous soils is soil’s parent material, which is already high in salts and basic which provides alkaline nature to soil. A large part of saline area is created by human activities i.e. Irrigation with brackish and untreated sewage water.
Unchecked application of synthetic fertilizers, insecticides, herbicides which result in contaminating soil hence making soil unfit for agriculture. All above mention activities combined upsurge the levels carbonates, salts and also increase pH (>7.8) making iron uptake challenging for soybean plant.
How to manage IDC in soybean
Following practices should be adopted to tackle IDC;
- IDC tolerant varieties should be used for cultivation for soils having high pH.
- Intercropping of oats with soybean will remove excess of water and acidification of rhizosphere will occur which will help in mobilization sparingly soluble iron.
Soybeans in closely seeded fields will have less IDC symptoms as compared with the normal plant to plant distance because dense roots will release iron reducing agents in high concentration at once and Fe3⁺ in soil will be reduced into Fe²⁺ and readily available to plants.
Application of fertilizers which are rich in iron should be practiced i.e. Ferrous sulfate (FeSO4.7H2O), ferrous ammonium sulfate (NH4)2Fe(SO4)2·6H2O.
Application of iron chelate products has encouraging role in enhancing iron uptake. It can be used as Seed treatment or it can be applied as foliar spray at early stages of soybean plant growth.
Iron deficiency chlorosis (IDC) is one of major problems in the soybean production in Pakistan. Government should establish well equipped facilities according to modern trends in soybean production.
So we can understand more about iron uptake mechanism under high pH soil conditions. Government should provide iron-based fertilizer to farmer on low price to tackle the iron deficiency chlorosis (IDC) problem.
Authors: Muhammad Abrar, Muhammad Asad, Haroon Zaman Khan, Muhammad Atif Shabir, Syed Ali Zafar, Ahmad Mukhtar, Samee ullah, Muhammad Amjid and Areena Kiran.