Nitrogen as a Nutrient

A critical load for nitrogen as a nutrient (CLn) should be determined as ... 

In a second experiment, we attempted to determine which nutrient elements gave the same quantitative response as the complete mineral nutrient solution. Results of this experiment demonstrated that nitrogen (NO3), phosphorus, and calcium, the elements applied in the field study, were the ones needed to produce a growth response quantitatively the same as the complete mineral nutrient solution. The need for repetitive application of these elements suggests that one or more may have a dual role, first as a nutrient and second as a soil conditioner that might exchange or complex with an Inhibitory molecule deposited in the soil by the herbaceous weeds. 

Figure 6.3. Block diagram of energy flows (calm-3 da-1) in the trophic pyramid of the Arctic Basin ecosystem. This is realized as block MEF. The boxes with elements denote the generalized trophic levels of the Arctic ecosystem. All of the elements are described by means of averaged parameters for the biological community of the northern seas. It is supposed that this trophic pyramid takes place in each of the Arctic Basin seas. The trophic relations between the elements of the model are described on the basis of the energy principle (Nitu et al., 2000b). Biomasses, rates of production and exchange (respiration), and food rations are expressed in energy units. Total nitrogen serves as a nutrient salts prototype in the model.

Nitrate (NOj) Nitrate is readily soluble in water and highly mobile in soils. Together with ammonium, it is the nitrogen form used by plants, microbes, and other biota as a nutrient. 

Defined as non-nutrients produced by one organism that affect the behavior, health or ecoiogical welfare of another, allelochemics includes a large array of chemicals. The allelochemic effect is both concentration-dependent and situation-dependent (see Reese, 1979). A chemical classified as a nutrient for one species may act as an alleiochemic in some situations, and a chemical such as L-canavanine which is highly toxic to many herbivores may be utilized as a source of dietary nitrogen by adapted specialists (Rosenthal et al., 1977 1982). Thus, the distinction between a nutrient and an allelochemic is not always clear-cut (see also Bernays and Woodhead, 1982). 

Oxidation-reduction processes are very important in the nitrogen cycle. The initial product of the biodegradation of nitrogen-containing biomass (protein) and the form normally applied to farm lands as fertilizer is ammonium ion, NH4. To be assimilated as a nutrient by algae or in field crops, it normally requires microbial oxidation to NOj ... 

Nitrogen is of paramount importance to all forms of life. Yet plants and animals cannot make use of elemental nitrogen and rely on certain bacteria and algae to fix nitrogen in a combined form to use as a nutrient. Nitrogen assimilation, which takes place in the presence of an enzyme, is not yet fully understood, but coordinate bonding of N2 to... 

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