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NPN can also be used to artificially raise crude protein values, which are measured based on nitrogen content, as protein is about 16% nitrogen and the only major component of most food that contains nitrogen is protein. The source of NPN is typically a chemical feed additive, or sometimes chicken waste, [7] [8] and cattle manure.
Excess nitrogen can disrupt mutualisms; for example, in the legumes-rhizobia resource mutualism nitrogen deposition results in the evolution of less-cooperative rhizobia. [22] Because of the increase in decomposition in the soil, its organic matter content will be depleted which results in lower overall soil health. [23]
In agriculture, the leaching out of nitrogen compounds from fertilized agricultural lands is a nonpoint source water pollution. [3] Nutrient runoff in storm water from "sheet flow" over an agricultural field or a forest are also examples of non-point source pollution.
Nutrient pollution, a form of water pollution, refers to contamination by excessive inputs of nutrients.It is a primary cause of eutrophication of surface waters (lakes, rivers and coastal waters), in which excess nutrients, usually nitrogen or phosphorus, stimulate algal growth. [1]
Human impact on the nitrogen cycle is diverse. Agricultural and industrial nitrogen (N) inputs to the environment currently exceed inputs from natural N fixation. [1] As a consequence of anthropogenic inputs, the global nitrogen cycle (Fig. 1) has been significantly altered over the past century.
Leached agricultural inputs, i.e. fertilizers and manures, accounts for 75% of the anthropogenic source of nitrogen. [4] The Food and Agriculture Organization of the United Nations (FAO) estimates world demand for nitrogen fertilizers will increase by 1.7% annually between 2011 and 2015. An increase of 7.5 million tonnes.
Agricultural waste are plant residues from agriculture. These waste streams originate from arable land and horticulture. Agricultural waste are all parts of crops that are not used for human or animal food. Crop residues consist mainly of stems, branches (in pruning), and leaves. [1]
Increasing levels of nitrogen deposition is shown to have several adverse effects on both terrestrial and aquatic ecosystems. [52] [53] Nitrogen gases and aerosols can be directly toxic to certain plant species, affecting the aboveground physiology and growth of plants near large point sources of nitrogen pollution. Changes to plant species may ...