Darbhanga: Wheat is the main food grain crop of India. It is cultivated on a large scale during the cold season. The most important thing in this is that its productivity largely depends on the initial growth stages. The first irrigation, given about 18–21 days after sowing, called the crown root initiation (CRI) stage, is a very sensitive stage for wheat. At the same time, it is observed by many farmers that after a few days of irrigation, the leaves of the plants turn from light green to yellow. In such a situation, farmers need to take special care of it.
Disease caused by moisture
Professor SK Singh, Head of Department, Post Graduate Department of Plant Pathology, explains that this phenomenon, despite being common, is scientifically important because it is directly linked to the physical-biological processes of the plant and the soil-nutrient-water balance. In its scientific analysis, there is a breakdown of water-air balance in the soil; in dry or moderately moist soil, a micro environment of about 50% air and 50% water vapor is present between the particles. Respiration of roots, activity of micro-organisms and dissolution-absorption of nutrients depend on this. Many times the soil gets completely filled with water after the first irrigation, due to which this balance gets broken. Water stress and root shock on the root system Sudden excessive moisture after the first irrigation reduces the efficiency of the roots for 48–72 hours. This is called water stress or root shock.
transient nitrogen deficiency
Nitrogen is the most important nutrient for wheat, which directly contributes to chlorophyll formation and protein synthesis. After the first irrigation, nitrogen in the soil leaches into the underlying surfaces with water, or becomes temporarily unavailable to plants.
sudden drop in soil temperature
The first irrigation is often given in winter. When very cold water reaches the soil, the soil temperature can drop by 3–6°C. Low temperatures slow root enzyme activity, reduce nutrient absorption and reduce photosynthesis rates.
temporary deficiency of micronutrients
Due to excessive moisture the pH and chemical balance of the soil gets affected. Elements like iron (Fe) and sulfur (S) get converted from soluble form to insoluble form and are not absorbed by plants.
Soil composition and effect of heavy soil
Black, heavy or loamy soils have more water holding capacity. After the first irrigation, drainage is slow, gas exchange is less, and the root zone remains anaerobic for much of the time.
fertilizer management errors
If farmers apply all the nitrogen at the time of sowing, top dressing is not done on time, or organic carbon is low, then after the first irrigation the nitrogen goes down rapidly and is not immediately available to the plant.
scientific suggestions
Light irrigation- Do not allow water logging in the field.
First top dressing- Give nitrogen 3–4 days after irrigation.
Drainage- Drain system is mandatory.
Zinc/sulphur/iron spray- If yellowness persists even after 7–10 days. Increase organic carbon.
