Enzyme activity, nitrogen uptake and corn growth as affected by ammonium concentration in soil solution

Abstract

Abstract Few studies have related the activity of enzymes responsible for nitrogen incorporation in the plant with ammonium concentration in the soil. The objective of this experiment was to relate the glutamine synthetase and glutamate dehydrogenase activities, nitrogen uptake and corn (Zea mays L.) growth with ammonium concentration in soil solution. Corn, cv. Beck 65X, was grown for 20 days after seeding in Raub silt loam (Aquic Argiudoll) in a climate controlled chamber. Rates of 0, 90, 180, 450, 900, 1800 and 4500 mg N.kg‐1 of soil provided six concentrations in fertilized soil equivalent to 90 mg N.kg‐1 of soil applied to 100, 50, 20, 10, 5 and 2% of the soil volume. The soil was previously leached to remove nitrate and an inhibitor of nitrification (Nitrapyrin) was used. High rates of nitrogen induced very high ammonium concentrations in soil solution and limited plant growth. While glutamine synthetase activity increased with ammonium concentration up to 3mM and then decreased, glutamate dehydroge...