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The total nitrogen content depends largely on the soil organic matter content, which in turn depends on texture, climate, vegetation, topography, age and soil management. [40] Soil nitrogen typically decreases by 0.2 to 0.3% for every temperature increase by 10 °C. Usually, grassland soils contain more soil nitrogen than forest soils, because ...
Nitrogen deficiency is a deficiency of nitrogen in plants. This can occur when organic matter with high carbon content, such as sawdust, is added to soil. [1] Soil organisms use any nitrogen available to break down carbon sources, making nitrogen unavailable to plants. [1] This is known as "robbing" the soil of nitrogen.
Nitrogen is plentiful in the Earth's atmosphere, and a number of commercially-important agricultural plants engage in nitrogen fixation (conversion of atmospheric nitrogen to a biologically useful form). However, plants mostly receive their nitrogen through the soil, where it is already converted in biological useful form.
Nitrogen directly affects soil respiration in several ways. Nitrogen must be taken in by roots to promote plant growth and life. Most available nitrogen is in the form of NO 3 −, which costs 0.4 units of CO 2 to enter the root because energy must be used to move it up a concentration gradient. Once inside the root the NO 3 − must be reduced ...
If the soil pH is too high, plants are not able to absorb many micronutrients, such as manganese and iron. When soil pH is too low, plants cannot uptake macronutrients, such as nitrogen or phosphorus.
Plants need nitrogen for protein synthesis, calcium for cell wall stiffening, phosphate for nucleic acid synthesis, and iron and magnesium for chlorophyll synthesis. The soil is often waterlogged, which favours the production of toxic ions such as ammonium, and its pH is an acidic 4 to 5. Ammonium can be used as a source of nitrogen by plants ...
The ability to fix nitrogen enables lichen to live in nutrient-poor environments. Lichen can also extract nitrogen from the rocks on which they grow. Nitrogen fixation, and hence the abundance of lichen and their host plants, may be decreased by application of nitrogen-based agricultural fertilizer and by atmospheric pollution.
In general, organic matter contacting soil has too little nitrogen to support the biosynthetic needs of the decomposing soil microbial population. If the C:N ratio of the decomposing organic matter is above circa 30:1 then the decomposing microbes may absorb nitrogen in mineral form as, e. g., ammonium or nitrates. This mineral nitrogen is said ...