Salinity Tolerance of Kentucky Bluegrass as Affected by Nitrogen Fertilization

Abstract

In most semiarid and arid areas, fresh water shortage compels managers to use low quality water sources w ith high salinity to irrigate turf and landscape. Recent research has noticed that management of nitrogen fertilization can alleviate salinity effects on plants. This greenhouse sand culture experiment was conducted in order to investigate morphological an d physiological responses to salinity stress in Kentucky bluegrass ( Poa pratensis L.) grown using different nitrogen sources. Three salinity levels (0, 40 and 80 mM NaCl) and three NO 3 - /NH 4 + ratios (6/0.5, 6/1 and 6/2) were applied in nutrient solutions. U nder non saline conditions, higher ammonium concentration increased T urf Q uality (TQ), leaf NO 3 - , proline content, N itrate R eductase A ctivity (NRA), shoot and root growth. On the other hand, leaf potassium (K + ) sodium (Na + ) and M alon DiA ldehyde (MDA) conten t were not affected. During the first week , the 40 mM NaCl treatment showed that the positive effects of NH 4 + on salinity tolerance were stil l perceptible . However, the 80 mM NaCl treatment showed that the adverse effects of high salinities were more prono unced when turf received high ammonium rate nutrient solution, as manifested by the decrease of TQ, NO 3 - , NRA, K + /Na + ratio, shoot and root growth and by the increase of leaf MDA content . T his suggests that effects of NO 3 - /NH 4 + ratio on salt tolerance vari es with salinity levels. Keywords : M orphologi cal and physiological responses, NO 3 - /NH 4 + ratio, Salt tolerance.