Soil Salinity Has Species-Specific Effects on the Growth and Nutrient Quality of Four Texas Grasses
Introduction
Farmlands in xeric areas of the southwestern United States are often heavily irrigated. This surface irrigation can increase soil salinity and eventually make the soil unsuitable for some food and fiber crops (Isidoro and Grattan 2011). As a result, landowners may opt to implement alternative land management practices when soils become increasingly saline. If palatable grasses for forage can grow in high-salinity soils while maintaining their nutritive value, they would prove to be a valuable land management practice to repurpose saline land unusable for food and fiber agriculture (Masters et al. 2007).
Salinity stress alters plant processes. For instance, high soil salinity can alter cellular functioning, including nutrient uptake and concentration, protein synthesis, and osmotic activity (Hamilton III et al. 2001; Masters et al. 2007; Uddin and Juraimi 2013). For most plants not adapted to saline conditions, exposure to saline soil may cause reductions in cell turgor, which would reduce the amount of water that can be brought in by the plant from its surrounding environment and negatively affect its growth (Masters et al. 2007; Flowers and Colmer 2008). In addition, plants can face ion toxicity and nutrient imbalances if ion uptake and retention from the soil is too great (Uddin and Juraimi 2013). These effects act to reduce germination (Dai et al. 2009; Guo et al. 2010) and plant growth (Wang et al. 2002; Marcum and Pessarakli 2006; Dai et al. 2009).
Plant responses to environmental stressors can vary by species (Wang and Frei 2011). This is often the case for studies examining plant growth responses to salinity. For instance, the impact of salinity on germination (e.g., Bayuelo-Jiménez et al., 2002; Zhang et al. 2011; Janousek and Folger 2013; Dudley et al. 2014) and biomass (e.g., Marcum and Murdoch 1994; Marcum 1999; Hamilton III et al. 2001; Harris et al. 2010; Zhang et al. 2011; Defalco et al. 2017) can vary widely between species. Roots are also one of the most sensitive plant organs to salinity and will usually be the first to show signs of salt stress (Muscolo et al. 2003). However, the response of roots to salinity stress has also been shown to be species specific (e.g., Hamilton III et al. 2001; Dai et al. 2009).
Although many prior studies have been conducted to understand the effects of salt on warm-season grass germination and growth, few have examined the effects of soil salinity on indicators of plant nutritive value, such as leaf nitrogen content. Forage selection by grazers depends on tissue nutrient quality (Westoby 1974), and plants with high shoot nitrogen content are preferred by grazers (Pauler et al. 2020). Still, it is unclear how salinity might impact forage quality, as previous findings concerning the nutritive value of salt-tolerant plants show inconsistent results (Masters et al. 2007). It was also reported that the response of the content of crude proteins in forage grasses to increasing salinity were inconsistent, although nutritive value may generally increase with increasing salinity (Robinson et al. 2004). However, if high salinity interferes with a plant's ability to take up nitrogen (e.g., Hawkins and Lewis 1993), then introducing forage grasses to saline environments could compromise grazer nutrition.
Here, we tested the effects of soil salinity concentration on the germination, biomass, and nitrogen content of four perennial C4 grasses that are used for forage in West Texas (Texas A&M AgriLife Extension 2019). We hypothesized that increasing salinity would decrease germination, shoot and root biomass, and foliar nitrogen content due to impaired plant-water relations. While we expected these general patterns to hold across all species, our goal was to quantify species-specific responses to identify characteristics that could best inform land manager choice of species for growth as forage on saline lands. In the experiment, we chose species previously identified as salt tolerant (see “Methods” later). However, we expected the non-native bermudagrass to be more salt tolerant than the native species because of its previous use on saline lands and reported higher salinity tolerance than other turfgrasses (Marcum and Murdoch 1994; Uddin and Juraimi 2013). Within the native species, we expected little bluestem to be more salt tolerant than the Bouteloa species because of its wide native range.
Section snippets
Species Selection
The species selected consisted of three native species: little bluestem (Schizachyrium scoparium [Michx.] Nash), blue grama (Bouteloua gracilis [Willd. Ex Kunth] Lag. Ex Griffiths), and sideoats grama (Bouteloua curtipendula [Michx.] Torr.) and one non-native species, bermuda grass (Cynodon dactylon [L.] Pers.) (USDA NRCS 2020). These grasses are referenced to be fair forage for livestock (Texas A&M AgriLife Extension 2019) and good turfgrasses for erosion control (USDA NRCS 2020). Seeds of
Germination
A significant interaction between species and salinity treatment (P < 0.05; Table 1; Fig. 1) indicated that response of germination to salinity was species specific. Post-hoc analyses indicated that B. gracilis showed a significant (i.e., nonzero) reduction in germination probability with increasing salinity (P < 0.05; Table 2; see Fig. 1). However, the slope of the response was not significantly different from 0 for B. curtipendula, C. dactylon, and S. scoparium (P > 0.05 in all cases; see
Discussion
Saline soils can be detrimental to the growth and palatability of forage grasses (Hawkins and Lewis 1993; Wang et al. 2002; Marcum and Pessarakli 2006; Dai et al. 2009; Pauler et al. 2020). Here, we confirmed our hypothesis that sensitivity to saline soil varies by species, even within a group of salt-tolerant grasses. This confirms the results of previous studies (e.g., Marcum and Murdoch 1994; Marcum 1999; Hamilton III et al. 2001; Bayuelo-Jiménez et al., 2002; Harris et al. 2010; Wang and
Implications
Overall, our results indicate that saline soil can impact growth and nutritional quality of forage grasses but species responses vary widely, even within salt-tolerant grasses. This implies that species choice can be used to improve the suitability of saline lands for grazing. S. scoparium possessed neither high biomass nor high salinity tolerance; these traits, combined with a lack of positive response of tissue quality to soil salinity, likely make this species a poor choice for forage on
Data Availability
All data can be accessed via a GitHub repository at https://github.com/DogtoothTrail/texas_saltygrass (doi: 10.5281/zenodo.3923044).
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
The authors thank Risa McNellis, Evan Perkowski, Morgan Long, and Dr. Dylan Schwilk for their help with data collection and for their input on aspects of earlier versions of the manuscript.
References (47)
- et al.
Effect of feeding Atriplex browse to lactating ewes on milk yield and growth rate of their lambs
Small Ruminant Research
(2006) Halophytes and salt-tolerant plants as potential forage for ruminants in the Near East region
Small Ruminant Research
(2010)- et al.
Inter-specific variation in salinity effects on germination in Pacific Northwest tidal wetland plants
Aquatic Botany
(2013) - et al.
Buffel grass (Cenchrus ciliaris) as an invader and threat to biodiversity in arid environments: a review
Journal of Arid Environments
(2012) - et al.
Biosaline agriculture for forage and livestock production
Agriculture, Ecosystems and Environment
(2007) - et al.
Forage production and quality of a mixed-grass rangeland interseeded with Medicago sativa ssp. falcata
Rangeland Ecology & Management
(2005) - et al.
Effects of salinity on growth, carbohydrate metabolism and nutritive properties of kikuyu grass (Pennisetum clandestinum Hochst)
Plant Science
(2003) - et al.
Biomass accumulation and potential nutritive value of some forages irrigated with saline-sodic drainage water
Animal Feed Science and Technology
(2004) - et al.
Crop quality under rising atmospheric CO2
Current Opinion in Plant Biology
(2018) - et al.
Biophysical properties and biomass production of elephant grass under saline conditions
Journal of Arid Environments
(2002)
Stressed food—the impact of abiotic environmental stresses on crop quality
Agriculture, Ecosystems & Environment
Mycorrhizal dependence of Andropogon gerardii and Schizachyrium scoparium in two prairie soils
The American Midland Naturalist
The impact of 3 exotic, invasive grasses in the southeastern United States on wildlife
Wildlife Society Bulletin
Fitting linear mixed-effects models using lme4
Journal of Statistical Software
Salinity tolerance of Phaseolus species during germination and early seedling growth
Crop Science
Salinity effects on seed germination and vegetative growth of greens-type Poa annua relative to other cool-season turfgrass species
Crop Science
The role of salinity tolerance and competition in the distribution of an endangered desert salt marsh endemic
Plant Ecology
A nutritional explanation for body-size patterns of ruminant and nonruminant herbivores
American Naturalist
Roadway deicer effects on the germination of native grasses and forbs
Water, Air, & Soil Pollution
Diffusive and metabolic limitations to photosynthesis under drought and salinity in C3 plants
Plant Biology
Salinity tolerance in halophytes
New Phytologist
An {R} companion to applied regression
Forage quality and aggregation by large herbivores
American Naturalist
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Sodium ions removal by sulfuric acid-modified biochars
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This work was funded by grants from Texas Tech University Honors College, Beta Beta Beta Biological Honors Society, and Sigma Xi to AB. NGS acknowledges additional support from Texas Tech University.