Increasing plant density in spring wheat to ameliorate the effects of salinity on grain yield

Root-zone salinity reduces the grain yield of spring wheat mainly by preventing the initiation and growth of plant tillers. A counter practice might be to multiply the number of plants grown per unit area, thereby, increasing the number of more resistant mainstems. A spring wheat cultivar (Katepwa) was seeded in large greenhouse sand tanks and watered with hydroponic solutions containing Na and Ca solutes in treatments of 2, 4, 6, 9, 12, and 16 dS/m. Seeding densities equalled 100, 232 and 344 seeds/m2, the numbers necessary to achieve below, at, and above normal plant densities for dryland wheat production. The average number of plants harvested per m2 across all salinities equalled 97.6, 225.8, and 33l.3/m2, respectively, resulting in a mean correlation coefficient of 0.998. Grain yields averaged for all salinity levels except one increased significantly with all increasing seeding densities at p = 0.10, but were only significant between the below-to-normal seedings at p = 0.05. Progressively greater salinity significantly reduced biomass, grain yield, and spikes per m2, but not the number of plants/m2. The number of spikes and the grain yield per plant also decreased significantly, but not the grain per spike; the harvest index even grew slightly as salinity increased. The results showed that the increases above the normal Katepwa wheat population that would be necessary in order to offset reductions in grain yield caused by salinity could be logarithmically governed. Consequently, to be effective, plant densities would have to increase to such numbers that water requirements in non-irrigated, semiarid climates will still likely limit production during most years. Crowding multi-tillering Katepwa wheat plants appear to offer only limited hope for compensating grain losses caused by salinity.