NITROGEN

Form taken up by plant:        NH4+, NO3-

Mobility in soil:         NH4+: no;  NO3-: yes:

                        NO3- water soluble, not influenced by soil colloids

Mobility in plant:        Yes

Deficiency symptoms:        Chlorosis in older leaves, under severe deficiency lower leaves are brown, beginning at the leaf tip and proceeding along the midrib.       

Soil pH where deficiency will occur:        None due to nitrate's mobility

Role of nutrient in plant growth:        N assimilation into amino acids for protein and amino acid synthesis, component of chlorophyll, vegetative growth       

Enzymes that require N:        Nitrate reductase, nitrite reductase, nitrogenase       

Role of nutrient in microbial growth:        Necessary for the synthesis of amino acids

Concentration in plants:        Wheat  1.7 - 3.0%

                                        Grain  2.0%

                                Forage 3.0 %

                                Straw

                        Corn  2.7 - 3.5%

                        Soybeans  4.2 - 5.5%

                        Grain sorghum 3.3 - 4.0%

                        Peanuts 3.5 - 4.5%

                        Alfalfa 4.5 - 5.0%

                        Bermudagrass 2.5 - 3.0%       

Effect of pH on availability:

            Precipitated forms (low pH):            none

            Precipitated forms (high pH):            none

at pH>8, no nitrification;  at pH>7, NO2- accumulates

Interactions with other nutrients:        Si: enhances leaf erectness, thus neutralizing the negative effects of high nitrogen supply on light interception (leaf erectness usually decreases with increasing nitrogen supply); P: symbiotic legume fixation needs adequate P or a N deficiency can result; Mo: component of nitrogenase therefore could have Mo induced N deficiency in N₂ fixing legumes (especially under acid soils conditions); Fe: necessary for nitrogenase and ferredoxin (electron carrier), legume hemoglobin, deficiency reduces nodule mass, and nitrogenase;        

Fertilizer sources:        ammonium sulfate, anhydrous ammonia, ammonium chloride, ammonium nitrate, ammonium nitrate-sulfate, ammonium nitrate with lime, ammoniated ordinary superphosphate, monoammonium phosphate, diammonium phosphate, ammonium phosphate-sulfate, ammonium polyphosphate solution, ammonium thiophosphate solution, calcium nitrate, potassium nitrate, sodium nitrate, urea, urea-sulfate, urea-ammonium nitrate, urea-ammonium phosphate, urea phosphate.       

References:

Burford, J.R., and J.M. Bremner.  1975.  Relationships between the denitrification capacities of soils and total, water-soluble and readily decomposable soil organic matter.  Soil Biochem. 7:389-394.

Marschner, Horst.  1995.  Mineral Nutrition in Higher Plants.  Academic Press, London.

Tisdale, S.L., W.L. Nelson, J.D. Beaton, and J.L. Havlin.  1993.  Soil Fertility and Fertilizers.  MacMillan Publishing Co., New York, N.Y.

Authors: Heather Lees, Shannon Taylor, Joanne LaRuffa and Wade Thomason