Salinity Effects on Nitrogen Use by Wheat Cultivar Sonora 64 1

The importance of N nutrition to fulfilling the high production potential of some semidwarf wheat ( Triticum aestivum L.) cultivars under irrigation culture raises problems of balance between N and salinity. Inasmuch as growth may be limited in salt affected soils, thereby reducing total N requirement, the usual rates of fertilizer application may be excessive and thus contribute to the salinity problem. This study with ‘Sonora 64’ wheat was done to measure the effects of salinity and stand density on plant growth and grain yield, to estimate N uptake in relation to salinity and the stage of plant development, and to evaluate leaf‐N as a basis for diagnosing the N status of the plant. Plants were grown in sand cultures (pots) in the greenhouse and out of doors. Treatments were factorial combinations of salinity and N supply. Stand densities of 5, 10, and 15 plants/pot were compared. Some comparisons were made with an old line cultivar ‘Ramona 50’ grown simultaneously with the Sonora 64. Depression of grain yield by added chloride salts was caused primarily by reduced tillering, suggesting that significant compensation can be achieved by using higher seeding rates. Data on N concentrations in various plant tissues indicate that total N is not a useful index of N status. At flowering, factors other than N supply controlled tissue N concentrations and, at maturity, total N concentration increased with salinity. At flowering NO 3 ‐N in Y‐leaves correlated well with grain yield but did not reflect levels of N supply under saline conditions. Variations of apparent salinity tolerance associated with differences in plant density 1) indicates that this relationship needs to be included in salinity studies, and 2) raises doubts about the value of pot cultures for the purpose.