PLANT-SPECIES RESPONSE TO AMMONIUM-NITRATE CONCENTRATION RATIOS

Most plants can use either nitrate (NO3) or ammonium (NH4) as a source of nitrogen. However, the degree of effectiveness of these two forms on plant growth and nutrient uptake is dependent on plant species and NH4:NCO3 ratio. The 77:77 ppm NH4:NO3-N concentration ratio in solution caused the most growth reduction for cabbage, melon, and corn with corn being least affected. Bean seems to be well adapted to the use of NH4, and was unaffected by equal concentrations of NH4:NO3-N. The presence of 28 ppm NH4-N in the mixture reduced only cabbage growth, whereas growth of melon, bean and corn was not affected.All of the species studied responded to the NH4 concentration increase by an increase in anion content in their leaf tissues. The K content in melon and corn leaf was increased with NH4-N up to 28 ppm. The K content in tomato and cabbage tissue was reduced at 28 ppm NH4. The K content in all the species tested was reduced with 77:77 ppm NH4:NO3-N concentration treatment. Calcium composition reduction in all the plant species was affected at 28 ppm NH4-N with reduction to 50% that of all NO3 nutrition at 77 ppm NH4-N. Magnesium composition of corn tissue was most scverely reduced by the 77:77 ppm NH4:NCO3-N nutrition. Bean Mg composition was not affected by the NH4-N concentration in the 14 to 77 ppm range. Magnesium was reduced in cabbage, melon, and corn by NH4-N concentrations above 28 ppm. © 1990, Taylor & Francis Group, LLC. All rights reserved.