Soil Salinity Has Species-Specific Effects on the Growth and Nutrient Quality of Four Texas Grasses

Irrigation of farmlands in xeric areas can increase soil salinity, reducing their suitability for food and fiber crops. One way to repurpose these lands is to convert them for use in grazing. To choose the best forage species, it is important to understand the impact of soil salinity on the growth and nutritional quality of potential forage grasses. Here, we grew four perennial C₄ grasses: blue grama (Bouteloua gracilis), sideoats grama (Bouteloua curtipendula), little bluestem (Schizachyrium scoparium), and bermudagrass (Cynodon dactylon) in soil treated with four different concentrations (0, 8, 16, and 24 dS/m) of sodium chloride salt (NaCl). We then determined the effects of soil salinity on germination, biomass production, and plant tissue nitrogen content (an indicator of nutritional quality). We found a high degree of variability in salinity responses among species. S. scoparium performed poorly relative to the other species across all metrics. C. dactylon showed high biomass and low sensitivity to soil salinity for each index but had the lowest shoot nitrogen concentration of all species tested. This indicated a tradeoff of tissue quality for quantity. On the other hand, the two Bouteloua species showed opposite results, falling on the shoot quality end of the quantity-quality spectrum and even showing increased nitrogen concentration with increasing soil salinity. Given their complimentary traits, C. dactylon and Bouteloua spp. may be good candidates for interseeding on saline lands. These results indicate that species choice can help mitigate negative impacts of soil salinity on forage production and quality and should be carefully considered by land managers.