Proper between‐row and within‐row spacing is essential for optimizing alfalfa seed yields and stand longevity. Using three alfalfa (Medicago sativa L.) cultivars (WL232HQ, Derby, and Algonquin), we conducted a field study from 2004 to 2007 to evaluate the effects of three between‐row spacing treatments (60, 80, and 100 cm) and four within‐row spacing treatments (15, 30, 45, and 60 cm) on seed yield, seed yield components, plant height, basal stem diameter, and lodging. Our hypothesis was that the intermediate between‐row and within‐row spacing would gradually improve seed yields in later years. The highest seed yields were obtained with 60‐cm between‐row spacing and 15‐cm within‐row spacing in 2004, but with 80‐cm between‐row spacing and 30‐cm within‐row spacing in 2006 and 2007. The significant year × between‐row spacing and year × within‐row spacing interactions for seed yield indicated that 80‐cm between‐row spacing and 30‐cm within‐row spacing produced the best seed yields as years advanced, and our results confirmed this. With the increase of within‐row spacing, stems per square meter decreased, while racemes per stem increased significantly. The effects of between‐row and within‐row spacing on seeds per pod, however, were not significant in four years. The results suggest that 80‐cm between‐row spacing and 30‐cm within‐row spacing can decrease the risk of lodging and optimize seed yields in the third and fourth harvest years.

Highlight: iVa tive grass species show differences in leaf and root growth response to soil water potential. Soil water potential developed by blue grama at the time of leaf growth stoppage ranged from <-80.0 bars at 5 cm depths to-8.4 bars at 35 cm depths, while corresponding values for little bluestem were-24.3 and-3.0 bars, and-30.0 and-15.3 bars for western wheatgrass. Soil water potentials at the time of root growth cessation were somewhat lower with a minimum of-16.6 bars at the S cm depth of blue grama and a maximum of-5.0 bars at the 25 cm and 35 cm depths of little bluestem. The R2 values indicate a lower level of correlation between soil water potential and root growth than between soil water potential and leaf growth. In ranking the three mixed prairie grass species as to their growth tolerance to decreasing soil water potential, blue grama ranks the highest followed by western wheatgrass and little bluestem, respectively.

The use of plant growth regulators (PGRs) has opened new prospects for increased seed production in grasses and legumes, but little information is available on the effects of PGRs on alfalfa (Medicago sativa L.) seed production. This study was conducted to evaluate the effects of applying chlormequat chloride (CCC) (2‐chloroethyl‐trimethyl‐ammonium chloride) in combination with five PGRs {naphthylacetic acid [1‐naphthylacetic acid], sodium nitrophenolate, gibberellic acid 3 [2,4a,7‐trihydroxy‐1‐methyl‐8‐methylenegibb‐3‐ene‐1,10‐carboxylic acid‐1, 4a‐lactone], triacontanol [1‐triacontanol], and brassinolide [(22R,23R,24R)‐2α,3α,22,23‐tetrahydroxy‐ β‐homo‐7‐oxa‐5α‐ergostan‐6‐one]} on seed yield, aboveground biomass, harvest index, plant height, basal stem diameter, lodging, yield components, and seed quality. Chlormequat chloride was applied annually at the stooling stage while five PGRs were applied twice each year at the stages of flower bud formation and peak flowering. We hypothesized that CCC would decrease plant height, while the five PGRs would increase flowering and seed set. In theory the combined application of CCC with a PGR would be more efficient in improving seed yield. All the PGRs increased the mean 3‐yr seed yield and harvest index by 10%, but did not affect aboveground biomass. Chlormequat chloride reduced plant height and lodging, but reduced mean seed yield. The effects of CCC on seed yield depended on climatic conditions. No interactions between CCC and PGR on seed yield were noted. Neither the PGRs nor the CCC affected seed quality. Our results suggest that these PGRs could be used in alfalfa breeding to increase seed yield while maintaining high seed quality.

Basin wildrye is a native, cool-season, perennial bunchgrass adapted to deep, well-drained soils of the prairies and foothills of the western USA and Canada. In zones of lesser precipitation, basin wildrye is found in run-in areas or along gullies and intermittent water courses. This grass is broadly adapted to elevations from 600 to 2750 m, and where average annual precipitation ranges from 200 to 500 mm. It is very winterhardy and drought tolerant, and has good tolerance to acidity, alkalinity, and salinity (6). Stems are typically erect, stiff, and stout and 100 to 200 tall, but can reach heights of 300 croon good sites. Leaves of this species are firm and fiat, up to 2 cm wide and 50 to 76 cm in length. The seed heads (spikes) are 10 to 25 cm long and erect, with three to six spikelets per node and persistent awnlike glumes. Trailhead originated from line M-27, which was mass-selected from vigorous, indigenous basin wildrye plants near Roundup, MT, in 1959. This silty range site is at 1100 m elevation, and receives 250 to 355 mm of precipitation annually. Seed from more than 200 plants was bulked to form line M-27. From 1960 through 1990, USDA-NRCS established 172 basin wildrye field accessions in unreplicated observation trials (field plantings) under dryland conditions at the Bridger Plant Materials Center. These accessions were collected in Montana, Wyoming, Colorado, Alberta, and Saskatchewan. These lines were evaluated visually for establishment, vigor, and production potential. Based on superior performance, a seed-increase field of line M-27 was established at Bridger, MT, in 1961. Line M-27 was planted on 0.4 ha under isolation, and breeder seed (Syn 1) was produced from 1962 through 1969. The name Trailhead was derived from the proximity of the collection site to the origin of the 1989 Montana Centennial Cattle Drive. Trailhead has been evaluated in 105 NRCS field plantings throughout Montana and Wyoming. It has been evaluated for use as wildlife habitat, mineland reclamation, winter livestock grazing, stabilization, field barriers, and reclamation of saline or acidic soils. Trailhead consistently had superior establishment, vigor, and persistence at arid sites compared with other basin wildrye lines, including 'Magnar', the only other known cuitivar of basin wildrye (1). Replicated forage yield trials of Trailhead have been conducted at Bridger, Bozeman, Cardwell, and Moccasin, MT. In five trials at sites receiving >350 mm of precipitation annually, mean forage yields of Trailhead (100%) and Magnar (107%) were not significantly different (P = 0.05). However, at one site receiving less than 250 mm of annual precipitation, forage yields over a 6-yr period for Trailhead were significantly (P = 0.10) higher than those Magnar. Trailhead basin wildrye was released based on its superior performance under dry conditions. Trailhead is recommended for range and disturbed-site reclamation in the western USA and Canada. The major use of Trailhead is for late summer or winter grazing by livestock and wildlife (2).