Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 25, 1999
Publication Date: N/A
Interpretive Summary: Forage production on the semiarid Northern Great Plains is strongly affected by available soil water supply. Knowledge of relationship among plant development stage, plant water use, and plant rooting depth is beneficial in understanding response of grasses to grazing. Objectives here were to compare plant water use, rooting activity, soil water extraction patterns, and water-use efficiency of diploid and tetraploid Russian wildrye grown at two water levels (50 and 150% of seasonal average rainfall) and two N fertilizer rates (10 and 134 kg N/ha) in a rain shelter at Mandan, ND. Cumulative evapotranspiration through seed soft dough stage was 138 and 141 mm for the diploid and tetraploid entries, respectively. Rooting activity progressed to 1.2 m soil depth at the rate of 0.148 and 0.163 m per Haun development stage for the diploid and tetraploid, respectively. Forage yields and water- use efficiency were greater for the tetraploid than the diploid entry. Overall the tetraploid entry exhibited a more favorable soil-plant water relations compared with the diploid, which will make it suitable for seeding pastures in Northern Great Plains.
Technical Abstract: Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski] is an important cool-season forage grass for the Northern Great Plains. A major difficulty with this species is poor seedling vigor. Tetraploid (2n=4x=28) plants have been shown to have improved seedling vigor over diploid (2n=2x=14) plants. Objectives of this research were to compare water-use efficiency (WUE), evapotranspiration (ET), rooting activity, and water extraction in relation to Haun development stage for diploid and tetraploid Russian wildrye. A diploid and tetraploid entry were grown at two water treatments (50 and 150% of the long-term monthly average precipitation for 1 April to 30 October monthly rainfall) and two fertilizer rates (10 and 134 kg N/ha) in a rain shelter at Mandan, ND. Cumulative ET averaged over both the 50 and 150% water treatment was 138 and 141 mm for the diploid and tetraploid, respectively. Rooting activity was linear with Haun stage to 1.2 m depth. The rate of root activity progression to 1.2 m depth ranged from 0.148 to 0.163 m per Haun stage for the diploid and tetraploid, respectively, at 50% water. Forage yield of the tetraploid was greater than the diploid at the 50%, but not at the 150% water treatment. Water-use efficiency was higher for the tetraploid (3.8 g/kg) than the diploid (3.1 g/kg) at the 50% water, and greater at the high N (3.3 g/kg) compared with the low N rate (2.5 g/kg). Differences between the two entries for WUE and associated soil water measurements were generally greater when soil water was at a deficit or at 50% water compared with the 150% water treatment. Overall, the tetraploid entry exhibited a more favorable WUE and other soil water relations than did the diploid entry.