Wheat emergence and seedling development concerns
Over the next month or two, wheat stands will hopefully become established over most of the state. Ideally, the wheat will take on a solid green color, form a secondary root system, and develop one or two tillers in addition to the main tiller. But sometimes there are problems. The most common problems are discoloration, stunting, loss of leaves, or dying of emerged seedlings.
Causes of chlorosis or poor growth
If wheat is yellow or stunted and not growing this fall, what are the possible causes? Is it something producers can correct? Will it hurt yields? Some of the most common causes of yellowing and/or stunting in the fall are:
* Nitrogen deficiency. Nitrogen deficiency causes an overall yellowing of the plant with the lower leaves yellowing and dying from the leaf tips inward. Nitrogen deficiency also results in reduced tillering, top growth, and root growth in the fall. The primary causes of nitrogen deficiency are insufficient nitrogen fertilizer rates, leaching from heavy rains, early-season denitrification or volatilization, and the presence of heavy amounts of crop residue, which can immobilize nitrogen. Topdressing the field during the winter can solve the problem, provided there is enough moisture to move the fertilizer into the root zone (and the ground isn’t frozen at the time of application).
* Poor root growth. Chlorosis and stunting can also be due to poor root development, which can often result in nitrogen deficiency. If the plants have been emerged for several weeks or more, can be pulled up easily, and have only a couple primary roots visible, then the plants are yellow or stunted because the root systems are not extensive enough to provide enough nutrients. This may be due to dry soils, waterlogging, or poor seedbed conditions at planting time. If conditions improve, plants should develop secondary roots and the color should improve. If conditions do not improve and root growth remains stunted, the plants may winterkill more easily or may not be strong enough next spring to reach their full yield potential.
* Aluminum toxicity (low-pH soils). Strongly acid soils may present several problems for wheat production. Aluminum toxicity is the most common problem associated with acid soils. Typical symptoms include thin stands and lack of vigor. High concentrations of aluminum will reduce development of the roots, giving them a short stubby appearance. The roots will often have a brownish color. In general terms aluminum toxicity will reduce yield potential when soil pH levels get below 5.5 and KCl-extractable (free) aluminum levels are greater than 25 parts per million. When soil pH levels are 5.0 or less, yields start dropping off rapidly in most cases. Selecting adequate varieties for low pH conditions is essential. In addition, liming to adequate pH levels following recommendations from a soil test can fix the problem long term.
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