Annual medic (Medicago spp.) pastures that produce high levels of good quality forage are well suited to grazing and are used extensively throughout dryland farming regions of the world. In these regions, they are normally an integral component of cropping rotations because they allow for reductions in weed and disease problems in addition to increasing soil N levels for subsequent crops. The objective of this research was to investigate the performance of 17 annual medic cultivars and experimental lines for their potential use as self‐regenerating annual pastures in the dryland cropping region of southeastern Wyoming. Dry matter and seed production capabilities were recorded over three seasons, 1996 to 1998. Growth phase development following different emergence times was evaluated in two seasons, and the forage quality was assessed for medic cultivars and lines grown in the 1997 season. Results revealed that the M. rigidula (L.) All. line, SA10343, consistently produced the greatest level of dry matter, with more than double the amount of forage than nearly all other cultivars. Dry matter production was related to the period of growth and development where higher yielding cultivars showed extended periods of vegetative growth. In general, the southeastern Wyoming climate substantially reduced the growth and development periods of medic cultivars bred in southern Australia. Given the overall performance of all cultivars, it was determined that the M. rigidula species had the greatest potential for further development in this environment.

Plant improvement to increase the water‐use efficiency of affalfa (Medicago sativa L.) has been limited. This study compared leaf color variants (pale and dark) to evaluate the effect of alfalfa leaf chlorophyll on water relations and yield of alfalfa. Leaf color populations were selected from ‘Ladak 65’ and visually selected sub‐populations evaluated under controlled‐environment and field conditions. Seven moisture regimes were established in controlled environment studies in which a commercial root medium with high water‐holding capacity was used. The field study was at Laramie, WY, on a Wyocolo soil (fine, loamy, mixed Borollic Haplargid) and consisted of irrigated and nonirrigated treatments. Traits measured for the two populations included leaf chlorophyll (Chl), leaf photo‐synthesis (as CO2 exchange rate: CER), transpiration (T), stem pressure potential (ψw), water‐use efficiency (WUE), leaf area, forage yield. Controlled. environment conditions produced pale plants that contained 15% less total Chl than dark‐leaved variants. The Chl concentration of pale variants was equal between the moisture extremes, while the dark variants decreased 20% for the low‐moisture (compared with high moisture) regime in the controlled environment. The WUE in the controlled environment of pale and dark leaf types averaged 1.47 and 1.22 g dry forage kg−1 water, respectively. This difference in WUE was attributed mostly to the greater growth of pale leaf types. The CER and CER/T ratio of the dark leaf types were more sensitive to moisture stress than the pale types. In the 2‐yr field study, the pale leaf types had a 22% lower CER than the dark leaf types across moisture regimes and 19% lower T under the irrigated regime. Even though leaf photosynthesis was lower for the pale leaf types, the forage yield was 25% higher under the irrigated regime.

Sod‐seeding establishment of small‐seeded legumes and grasses has great potential for increasing forage production on previously non‐tillable lands. However, consistently successful stand establishment has been difficult to achieve via sod‐seeding. Even when adequate stands are obtained, they often lack the vigor associated with conventional establishment. A delay between the spraying of a non‐selective chemical for sod control and seeding with a minimum‐till drill has been suggested to improve sod‐seeding stand establishment. We conducted two field experiments to determine the optimum time interval needed between spraying glyphosate [N‐(phosphonomethyl) glycine] and sod‐seeding various grass and legume species with minimum‐till drills. The soils were classified as Cumulic Haploborolls and Ustic Tomfluvents in the first experiment and Udic Haploborolls and Typic Eutrochrepts in the second. A 14 day interval between spraying glyphosate and sodseeding alfalfa (Medicago sativa L.), alsike clover (Trifolium hybridum L.), and tall fescue (Festuca arundinacea Schreb.) with either the John Deere Powr‐till drill or the Melroe 701 No‐till drill was needed for adequate establishment at Laramie, Wyoming in 1978. In 1979, a 7 to 14 day spray‐plant interval was needed for adequate establishment of alfalfa, alsike clover, creeping meadow foxtail (Alopecurus mundinaceus Poir.), and meadow bromegrass (Bromus biebersteinii Roem. & Schult.) when seeding with the John Deere drill. When seeding with the Melroe drill in 1979, no differences among spray‐plant intervals were obtained for the same species. At Kalipell, Montana in 1978, a 28 day delay between spraying glyphosate and sod‐seeding alfalfa with the John Deere drill was needed for adequate establishment; whereas ladino clover (Trifolium repens L.) required a 14 day interval between spraying and seeding. In 1979 at Kalispell, a 28 day spray‐plant interval was needed for adequate establishment of alfalfa. Ladino clover establiihment was very poor for all spray‐plant intervals. Inadequate legume establishment was associated with slug (Agriolimax reticulatum Müller) predation. Spraying 28 days prior to seeding allowed sufficient time for grass desiccation. This permitted sunlight to penetrate the canopy which dried out the furrow thereby providing a less favorable slug environment.

We calculated seasonal accumulation of dry matter and crude protein in sainfoin and alfalfa and feed quality at three stages of maturity when species were grown on irrigated and dryland. Maximum accumulation of dry matter and crude protein occurred between 2 and 45% bloom for alfalfa and at 100% bloom for sainfoin on irrigated land. Dry matter and crude protein yield trends for both crops were similar on irrigated land and dryland. The maximum dry matter and crude protein contents for both sainfoin and alfalfa occurred at about the same calendar date on dryland but at different dates under irrigation. Decreases in the percentage of crude protein were similar in both species with time. At all sampling dates crude protein percentage of alfalfa was greater than for sainfoin. At similar stages of maturity alfalfa was consistently higher than sainfoin in crude protein, ash, calcium, and crude fiber; and with few exceptions it was lower in nitrogen‐free extract, total digestible nutrients, and P. At the point of maximum yield for each species (10% bloom for alfalfa, 100% bloom for sainfoin) crude fiber and total digestible nutrient content was similar, but alfalfa contained 6% more protein and 9 to 10% less nitrogen‐free extract than sainfoin. We concluded that sainfoin hay would supply adequate protein to meet the needs of beef animals, and that it would supply total available energy equal or superior to that of alfalfa.

Cuttings from alfalfa (Medicago sativa L. cv. ‘Mesa‐Sirsa’) genotypes which exhibited a wide range in leaflet size were grown under spaced‐planted and nonspaced‐planted conditions and used to determine the relation. ships between leaflet anatomy, leaflet morphology, and CO2 exchange. These same relationships were evaluated under controlled environmental conditions using alfalfa population MSE‐6 which has a broad germplasm base.Area per leaflet and leaflet width were negatively associated with photosynthetic rate per unit leaf area. Specific leaf weight (SLW) was positively correlated with photosynthesis; however, the correlation coefficients were consistently lower than the r values for leaflet size vs photosynthesis. Photosynthesis expressed as total CO2 uptake per plant was not significantly associated with SLW and leaflet size. Plants with small leaves had the greatest SLW, palisade tissue thickness, and leaf thickness. A positive association was observed between palisade tissue thickness and photosynthesis expressed on a leaf area basis. The significance of leaflet size as a selection tool for photosynthetic rate in alfalfa is discussed.