Nitrogen addition can improve seedling establishment of N‐sensitive species in degraded saline soils

Abstract

Salinization is an important cause of land degradation globally, and these soils are usually nutrient deficient, which inhibits plant establishment and growth. Medicago sativa and Leymus chinensis are important legume and grass forage species, respectively, in China and are frequently used in pasture establishment. We aimed to test whether nitrogen (N) addition can increase the salt tolerance of these two glycophytes and whether the two species inhibit each other at the germination and seedling emergence stages. M. sativa and L. chinensis seeds were germinated separately or together in 0‐, 100‐, and 200‐mM NaCl solutions with supplemental 0‐, 20‐, or 40‐mM N solutions. N addition increased germination percentage and rate, shoot length, and seedling N concentration under moderate NaCl conditions for L. chinensis but had no effect on Na⁺ concentrations. Conversely, N addition stimulated Na⁺ uptake in M. sativa, but it had little effect on germination parameters, with salt suppressing N uptake. The presence of M. sativa stimulated L. chinensis germination percentage in mixed treatments. Our results suggest that proper N application may aid establishment of N‐sensitive species L. chinensis in grass–legume mixtures in degraded saline soils, through both direct influence as a nutritional and/or osmotic resource and indirect effect by increasing salt sequestration by M. sativa. N application had little effect on establishment of the N‐fixing species M. sativa.