Effects of Nitrogen Level, Calcium Level and Nitrogen Source upon the Growth and Composition of Pinus taeda L.

Seedlings of loblolly pine were grown in sand culture at two concentrations of nitrogen 110 and 75 ppm N) and calcium (0 and 200 ppm Cal for a four month period in order to determine which form of nitrogen was used most readily and to learn if there was an effect of calcium on nitrogen metabolism. Three sources of nitrogen were employed: nitrate. ammonium, and urea. A number of indicators of growth were followed, and chemical analyses were made of foliage and roots. The results are summarized as follows: 1.Urea, when supplied at 75 ppm of N, resulted in production of the greatest height. diameter, fresh weight. dry weight. and the lowest root/ shoot ratio of any of the treatments. 2.A number of seedlings died when ammoniinn nitrogen was supplied in the presence of calcium. but not in its absence. .3. Use of urea was associated with the highest total nitrogen content of foliage and nitrate with the least. Nitrogen source, however, did not have a major influence on the total nitrogen content of roots. 4.The soluble nitrogen content of foliage and roots was greatest with urea, and least with nitrate. when nitrogen was supplied at 75 ppm and calcium at 200 ppm. 5.Total and individual free amino acids, especially arginine, glutamine. asparagine. and praline. varied greatly with the nitrogen source. Seedlings supplied with ammonium had the largest amount of free amino acids. while those receiving nitrate had the smallest reserves. Nitrogen deficiency symptoms were produced in all 10 ppm nitrogen treatments. There was very little difference in the appearance of the plants in any of the 10 ppm series. 7. Calcium deficiency symptoms were not produced at 0 ppm calcium. However. 200 ppm calcium in the nutrient solution resulted in slight increases in almost all indices of growth that were used. 8. The foliage total nitrogen content in most treatment sequences was influenced positively by the presence of calcium in the nutrient solution, whereas the root nitrogen content was generally influenced negatively when calcium was supplied. O. The calcium content of the foliage was influenced not only by calcium level, but also by the nitrogen source. Nitrate was associated with the greatest foliage calcium content at each level of nitrogen supplied. [ABSTRACT FROM AUTHOR]