Effects of Soil Temperature, pH, and Nitrogen Nutrition on the Development of Poa pratensis

A study was made of the effects of variation in soil temperature, pH, nitrogen nutrition, and clipping height on the development of Poa pratensis plants grown in sand cultures under greenhouse conditions. 2. Plants grown at temperatures of 15⚬ , 25⚬ , and 35⚬ C. produced at 15⚬ C. a tall, succulent, bushy top growth with many leaves and at 35⚬ C. an erect, non-succulent, short top growth with few leaves. Root systems of low temperature plants were large, white, succulent, and coarsely branched, while roots of high temperature plants were small in diameter, light brown, and densely tufted. 3. Plants grown with ammonium nutrition at varied pH showed best leaf, rhizome, and root development at pH 6.5, whereas nitrate plants showed little difference within a pH range of 4.5 to 6.5. 4. Nitrate plants were superior in leaf, rhizome, and root development to ammonium-supplied plants under the conditions of temperature and pH of the experiment. 5. Plants supplied with nitrate and ammonium nutrition at constant temperature and pH and clipped weekly at 1 and 2 inch heights showed greater yields with nitrate nutrition than with ammonium nutrition. Yields over a period of eleven weeks were greatest with clipping heights of 2 inches.