Seed germination of selected crop and graminoid species in response to treatment with sodium chloride and oil-field brine solutions

Oil and gas development is often associated with the production of produced water or “brine”, which is a solution of dissolved salts (NaCl ≈ 90%) exhibiting electrical conductivity (EC) upwards of 200 dS m−1. Accidental releases of brine to soils inhibit seed germination through osmotic and ionic stressors. The final germination (FG; %) of four crop species, Hordeum vulgare L. (barley), Helianthus annuus L. (sunflower), Carthamus tinctorius L. (safflower), Beta vulgaris L. (sugar beet); and four graminoid species, Pascopyrum smithii (Rydb.) Barkworth & D.R. Dewey (western wheatgrass), Elymus hoffmannii K.B. Jensen & Asay (AC Saltlander), Leymus triticoides (Buckley) Pilg. (beardless wildrye), and Elymus trachycaulus (Link) Gould ex Shinners (slender wheatgrass), were determined using sodium chloride (NaCl) and brine solutions prepared at EC levels of 0, 4, 8, 16, 24, and 32 dS m−1. No differences (p > 0.05) in FG were found between NaCl and brine solutions across graminoid species or the crop species barley, sunflower, and sugar beet. AC Saltlander had the highest FG (81.9%) at the maximum EC level (32 dS m−1), compared with 47.2% and 0.8% for western wheatgrass and beardless wildrye, respectively. Within crop species, safflower exhibited the highest germination (10%–30%) across both solutions at 32 dS m−1. Barley (0%–2.9%), sugar beet (4.9%–7.7%), and sunflower (0%–1.4%) exhibited low germination at 32 dS m−1. The implications of this experiment are that previously established NaCl tolerance indices may be used to accurately determine the FG of plant species in brine-contaminated soils and that AC Saltlander, as well as western wheatgrass, have the highest FG at 32 dS m−1, indicating these species may have the greatest potential for successfully revegetating brine-contaminated soils.

Seed yield can be explained by altered yield components in field-grown western wheatgrass (Pascopyrum smithii Rydb.)

Western wheatgrass (Pascopyrum smithii Rydb.) is an important cool-season forage and turfgrass. However, due to seed dormancy and poor seedling vigor, it is difficult to develop high seed yield production systems, and assessing these components in response to seed yield. Based on multifactor orthogonally designed field experimental plots under various field management regimes, the effects of numbers of fertile tillers m−2 (Y1), spikelets/fertile tiller (Y2), florets/spikelet (Y3), seed numbers/spikelet (Y4), and seed weight (Y5) on seed yield (Z) were determined over three successive years. Correlation analysis indicated that fertile tillers (Y1) was the most important seed yield component. And the biggest contribution of those five yield component is fertile tillers (Y1), followed by seed numbers/spikelet (Y4), spikelets/fertile tiller (Y2), florets/spikelet (Y3) and seed weight (Y5), respectively. By using ridge regression analysis, we have developed an accurate model of seed yield with its five components. Finally, the results of synergism and antagonism among these yield components on seed yield showed that fertile tillers and seed numbers/spikelet had an antagonistic effect on seed yield. Therefore, selection for high seed yield by direct selection for large values of fertile tillers and seed numbers/spikelet would be the most effective breeding strategy for western wheatgrass.

Effect of Aminocyclopyrachlor on Seedling Grasses

When invasive weeds are removed with herbicides, revegetation of native species is often desirable. The extended soil activity of aminocyclopyrachlor is important for long-term weed control but could reduce recovery of native species as well. The effect of aminocyclopyrachlor applied alone or with chlorsulfuron on cool- and warm-season grass species commonly used for revegetation was evaluated. The cool-season grasses included green needlegrass, intermediate wheatgrass, and western wheatgrass, whereas the warm-season grasses were big bluestem, sideoats grama, and switchgrass. A separate experiment was conducted for each species. Aminocyclopyrachlor was applied at 91 to 329 g ha−1 alone or with chlorsulfuron from 42 to 133 g ha−1 approximately 30 d after emergence. Warm-season grasses generally were more tolerant of aminocyclopyrachlor than the cool-season grasses evaluated in this study. Switchgrass and big bluestem were the most tolerant of the warm-season species when aminocyclopyrachlor was applied at 168 g ha−1 and averaged 199 and 150% forage production, respectively, compared with the control. Green needlegrass was the most tolerant cool-season grass. Western wheatgrass was the least tolerant species evaluated because forage production only averaged 32% of the control the year after treatment and thus would not be suitable for seeding if aminocyclopyrachlor was applied. The effect of chlorsulfuron applied with aminocyclopyrachlor varied by grass species. For example, green needlegrass injury 8 wk after treatment (WAT) averaged 30 and 48% when aminocylopyrachlor was applied alone, respectively, but injury was reduced to less than 16% when aminocyclopyrachlor was applied with chlorsulfuron. However, injury on the less-tolerant intermediate wheatgrass ranged from 48 to 92% by 4 WAT when aminocyclopyrachlor was applied alone and from 60 to 86% when chlorsulfuron was included in the treatment.