Enhancement of salinity tolerance in three crop species by potassium and nitrogen enrichment

Results of soil pot experiments in the Philippines indicate apparent ameliorative effects of varying KNO3 concentrations (0,60,600 ppm) on the growth and mineral nutrient uptake of rice and peanut irrigated with 3 levels of saline water (0.6, 5.6 and 10.6 mmhos/cm). Addition of K ions and NO3 ions depressed uptake of Na to the seventh power and Cl ions, respectively. Sixty (60) ppm KNO3 appears to be sufficient to counteract the growth depressing effect of water salinity level of 5.6 mmhos/cm. The morpho-physiological and biochemical responses of salt-sensitive IR-28 and salt-tolerant Nona Bokra rice varieties grown hydroponically in five NaCl levels (0, 25, 50, 75, 100 mM) and two N-sources (4mM each of NH4 and NO3) were studied in Israel under greenhouse condition. Significant interactions between variety, N-source and NaCl levels were generally observed on growth parameters, photosynthesis, transpiration, stomatal conductance, mineral nutrient (total N, K, Na, Cl) uptake and protein contents of shoot and root tissues. The presence of nitrate apparently enhanced salinity tolerance of both rice varieties. Sand-culture experiment was conducted in Israel to test five N-source application schemes for wheat cv. Barkai grown in non-saline and saline (60 mM NaCl) conditions. Significant interaction effects of N source-application schemes and NaCl salinity were noted on shoot and root fresh weights, photosynthesis, transpiration, stomatal conductance, water use efficiency, mineral nutrient uptake (N, K, Na, Cl) leaf protein content and grain yield parameters. The data generally indicate that a combination of ammonium and nitrate would be desirable to obtain higher grain yield in wheat even under salt-stressed condition. The over-all results revealed stimulatory effect of mild salinity on the different metabolic processes in three crop species studied especially in the presence of K or NO3. The current model to explain the possible ameliorative role of potassium and nitrate in enhancement of salinity tolerance is discussed in the light of the results obtained.