Nitrogen deficiency

All plants require sufficient supplies of macronutrients for healthy growth, and nitrogen (N) is a nutrient that is commonly in limited supply. Nitrogen deficiency in plants can occur when organic matter with high carbon content, such as sawdust, is added to soil. Soil organisms use any nitrogen to break down carbon sources, making N unavailable to plants. This is known as "robbing" the soil of nitrogen. All vegetables apart from nitrogen fixing legumes are prone to this disorder.

Nitrogen deficiency can be prevented in the short term by using grass mowings as a mulch, or foliar feeding with manure, and in the longer term by building up levels of organic matter in the soil. Sowing green manure crops such as grazing rye to cover soil over the winter will help to prevent nitrogen leaching, while leguminous green manures such as winter tares will fix additional nitrogen from the atmosphere.

Some symptoms of nitrogen deficiency (in absence or low supply) are given below :

Plants look thin, pale and the condition is called general starvation.

Symptoms of nitrogen deficiencies in plants is general chlorosis of the leaves, which is when leaves turn pale green, and leaves cup upwards quite severely in deficient plants. Nitrogen deficiencies also cause leaves to remain small, and drop prematurely, resulting in less photosynthesis occurring in the plant, and fewer, smaller tubers can form for harvest. Research done by Yara International has shown that there is a direct correlation between tuber size and yield, and the amount of plant-available nitrogen in the soil. This makes it crucial that the fields have enough nitrogen in the soil to grow a prosperous crop. However, excess nitrogen in the soil can also be harmful to potato production, influencing how well the roots are able to develop, and delays can occur in tuber initiation during the tuberization stage of potato growth.

The visual symptoms of nitrogen deficiency mean that it can be relatively easy to detect in some plant species. Symptoms include poor plant growth, and leaves that are pale green or yellow because they are unable to make sufficient chlorophyll. Leaves in this state are said to be chlorotic. Lower leaves (older leaves) show symptoms first, since the plant will move nitrogen from older tissues to more important younger ones. Nevertheless, plants are reported to show nitrogen deficiency symptoms at different parts. For example, Nitrogen deficiency of tea is identified by retarded shoot growth and yellowing of younger leaves.

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Wikipedia