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Winter injury of alfalfa [Medicago sativa (L.)] in the northern United States decreases its economic and ecosystem benefits. Therefore, continued improvement in alfalfa cultivar winter survival (WS) is crucial for sustaining the productivity of this perennial crop. The North American Alfalfa Improvement Conference (NAAIC) standard test for WS recommends measuring the WS of spaced plants established in rows the previous spring. Measurement of WS of alfalfa grown in sward plots used by plant breeders would increase data collection and better reflect the potential for WS when grown in production fields. We conducted trials at seven location‐year environments spanning from Wisconsin to South Dakota in the northern United States. These trials involved six check cultivars and followed protocols from the NAAIC standard test. The objectives were to determine (1) if WS and biomass yield assessment from sward plots were similar to those from the standard spaced planted row ratings and (2) if location‐dependent environmental conditions affected the usefulness of alternative approaches for measuring WS. Estimation of WS using spaced plants and sward measurements was highly correlated, while correlations between the WS of the spaced planted rows and biomass yields were less. The number of locations required for spaced and sward plantings to determine cultivar differences was at least two, with four replications per location. Measuring WS from swards can enhance data collection and its relevance to on‐farm alfalfa production, as sward plots serve a dual purpose by allowing both WS testing and evaluation of yield, making them a practical choice in comparison to the exclusive use of spaced plants in rows for WS testing. Availability of sward‐plot WS descriptions of alfalfa cultivars will enhance decision making by producers. Core Ideas: Sward plot score correlation with Biomass yield is higher than that with spaced plant score.Measurement of Winter Survival of alfalfa grown in sward plots used by plant breeders would promote greater documentation of WS of alfalfa cultivars.Adopting sward scoring of alfalfa cultivars for WS will reduce the costs associated with establishing an independent spaced row trial. [ABSTRACT FROM AUTHOR]

Forage yield, nutritive value, and stand persistence are key metrics in alfalfa (Medicago sativa L.) management. The combination of cultivar improvement, longer growing seasons in the Midwest, and trends of shorter alfalfa rotations offer opportunity to reevaluate the effects of increasing cutting frequency (CF) on these metrics. We evaluated forage yield, nutritive value, milk production, and persistence of eight alfalfa entries with fall dormancy (FD) ranging from two (FD2) to five (FD5) under CF of four (CF4), five (CF5), or six (CF6) annual cuts during two production years in two environments in the upper midwestern United States. Nutritive value and milk kg–1 alfalfa increased with increased CF and differed among alfalfa entries. Cutting frequency and alfalfa entry interactively influenced forage yield and milk production ha–1 yet optimal CF depended on environment. At one environment, increasing CF from CF4 to CF5 and from CF5 to CF6 caused a 5 and 29% decrease in milk ha–1, respectively. At another environment, CF5 had about 16% greater milk production than CF4 and CF6. The CF6 reduced persistence of 3rd-year stand density with the effects especially severe for some entries. Alfalfa entry FD was not correlated to forage yield or persistence, but an entry with FD5 was consistently among those with the greatest in forage and milk yield ha–1 at CF5 and CF6. These results suggest that intensifying CF from four to five harvests per season of some cultivars can boost yield and nutritive value without negative effects on stand persistence in some environments. [ABSTRACT FROM AUTHOR]

Reduced lignin alfalfa (Medicago sativa L.) has the potential to improve alfalfa forage quality, yet forage morphology, biomass allocation, and stem and leaf forage nutritive value remains undetermined. The objectives of this study were to characterize changes in morphological development and forage nutritive value within stem and leaf fractions for reduced lignin alfalfa. Reduced lignin ('54HVX41') and reference ('DKA43‐22RR') alfalfa cultivars were sampled weekly from the mid‐vegetative stage through full flower during the seeding (2015) and first production (2016) year at two locations in Minnesota. Samples were staged to determine maturity, divided into stem and leaf fractions, weighed, and analyzed for forage nutritive value. Alfalfa cultivars were similar in stem and leaf yield, leaf to stem ratio (L/S), stem crude protein (CP), stem neutral detergent fiber (NDF), leaf CP, leaf NDF, leaf acid detergent lignin (ADL), and leaf NDF digestibility (NDFD). On average, reduced lignin alfalfa showed a 14% decrease in stem ADL and a 12% increase in stem NDFD compared to reference alfalfa. For both cultivars, increases in forage maturity increased stem and leaf yields and decreased L/S. Forage maturity also affected stem and leaf forage nutritive values; as maturity increased, NDF and ADL increased while CP and NDFD decreased. These results indicate that changes in forage nutritive value for reduced lignin alfalfa are largely a result of changes in ADL and NDFD within the stem fraction, and confirm that alfalfa forage nutritive value is negatively affected by forage maturity, particularly within the stem portion of the plant. [ABSTRACT FROM AUTHOR]

Potassium (K) is a critical macronutrient for alfalfa growth; however, reports of the effects of K fertilization on alfalfa yield, quality, and persistence have been inconsistent. Five K fertilizer rates ranging from 0 to 403 kg K ha-1 were applied to eight alfalfa cultivars during the establishment year (2011) and three subsequent production years (2012-2014) at three locations varying in baseline soil test potassium (STK) levels. Alfalfa yield, nutritive value, and STK were measured annually. During the final year, stem density and belowground traits were quantified. Forage yield, nutritive value, and root traits varied by cultivar, but there were no interactions between cultivar and K rate. Crown rot varied by cultivar but was not affected by K rate. Averaged across cultivars, the effect of K on yield varied by location and stand age. At the site with the lowest baseline STK values, K fertilizer had a positive quadratic effect on yield, which plateaued at a K rate of 296 kg K ha-1. There was no effect of K on yield at the site with the greatest baseline STK. Potassium fertilizer reduced forage nutritive value and increased forage K concentration. Aboveground and belowground biomass K concentration increased with K fertilizer at rates beyond those that maximized yield, indicating luxury consumption of K. However, mineralization of soil K resulted in a net increase in STK after accounting for K removal during harvest. Potassium removal rates that resulted in maintained STK were 167, 227, and 268 kg K ha-1 yr-1 at three locations. [ABSTRACT FROM AUTHOR]

Dry bean (Phaseolus vulgaris) can be grown as a local food source and as an alternative to soybean (Glycine max) to diversify organic crop rotations. To understand the benefits of diversification of organic cropping systems, the effects of preceding alfalfa (Medicago sativa) and corn (Zea mays) crops on yields of five dry bean types and one soybean type, and the effect of bean type on following spring wheat (Triticum aestivum) yields, were tested at four Minnesota locations. Dry bean and soybean yields following alfalfa were 25% greater than yields following corn at two of four locations, though bean yields following corn were greater at one location. A preceding alfalfa crop benefited bean yields at locations where hog manure or no manure was applied to corn, whereas bean yields following corn fertilized with cow manure were similar to or greater than bean yields following alfalfa. Among dry bean types, black bean yielded similarly to soybean at three of four locations, but dark red kidney bean consistently yielded 25–65% lower than soybean. Navy, pinto and heirloom dry bean types yielded similarly to soybean at two of four locations. Across locations, weed biomass was 3–15 times greater in dry bean than in soybean and dry bean yield response to weed competition varied among bean types. However, dry bean, regardless of the preceding crop, demonstrated the potential to produce yields comparable with soybean in organic systems and the substitution of dry bean for soybean did not affect subsequent wheat yields. More studies are needed to identify nitrogen fertility dynamics in organic systems as they relate to dry bean yield. [ABSTRACT FROM AUTHOR]

Organic crop production is a growing part of the agricultural economy. The transition from a conventional to an organic cropping system, while complying with certification guidelines, is financially and logistically challenging for growers. Therefore, it is important to develop strategies, perhaps using novel cropping systems, that can both mitigate economic challenges and quickly improve soil health. We evaluated the impact of perennial and annual cropping systems on soil health during the first two years of a three-year organic transition period at three research stations in Minnesota distinct in climate and soil conditions: Rosemount, St. Paul, and Lamberton. The sites were established in fall of 2017 by planting each of six cropping systems including 1) the novel perennial grain crop intermediate wheatgrass (IWG), 2) alfalfa, 3) an intermediate wheatgrass - alfalfa intercrop (IWGAlfalfa), 4) a winter wheat - red clover (WheatRC) rotation, 5) a corn – soybean (SoyCorn) rotation and 6) a corn - soybean rotation with a cereal rye cover crop (SoyCCorn). We measured root biomass and soil physical, chemical, and microbial parameters to evaluate soil health under the different cropping systems over time. IWG and IWGAlfalfa were consistently among the systems with greater root biomass and larger water stable soil aggregates, while SoyCorn systems had the least. Other soil health variables had site specific responses, with Lamberton and St. Paul the most influenced by cropping systems. At St. Paul and Lamberton soil pH increased in IWG and SoyCorn, and soil K decreased under WheatRC and alfalfa. Labile C and total C and N were not influenced by the different cropping systems. At Lamberton, increases in the biomass of microbial groups including bacteria, fungi, and actinomycetes were observed in IWGAlfalfa. The improvement in some health parameters at one or more sites by IWG and IWGAlfalfa after 2 years of the organic transition period could translate into building longer-term soil health for subsequent organically certified crops, but this is dependent on local soil and other characteristics. It will likely require more time for cropping systems to affect other important soil health parameters such as soil C in the C-enriched loamy soils of Southern Minnesota. • Perennials, especially Intermediate Wheatgrass (IWG), improved soil aggregate size. • IWG monocultures and IWG+alfalfa consistently had among the highest root biomass. • IWG and Soy/Corn maintained soil pH and K better than alfalfa and wheat/red clover cropping systems. • IWG+alfalfa increased fungal biomass, actinomycetes and bacteria in the second year at one site. • Soil health improvements varied by location, with the poorest quality and the least structured soils being most responsive. [ABSTRACT FROM AUTHOR]

Frost seeding alfalfa (Medicago sativa L.) can be convenient and economical for establishing or renovating forage stands; however, premature seedling emergence triggered by unusually warm temperatures followed by fatally cold temperatures can lead to seedling mortality and stand failure. Delaying germination could improve establishment success in frost-seeded stands. Our objective was to measure the effect of temperature and water potential (Ψ) on germination across a range of alfalfa varieties. Germination rate (1 divided by days to 50% germination) was estimated for 11 varieties at nine constant temperatures (-1.1 to 10°C) and three Ψ (0, -0.2, and -0.6 MPa). Linear regression between temperature and germination rate was tested for all variety-Ψ combinations. Base temperature (Tb; minimum temperature for 50% germination) and thermal constant (DD; time to 50% germination in growing degree-days) were determined by calculating the intercept on the temperature axis and the inverse of the slope parameter from each regression, respectively. The Tb ranged from -0.55 to 0.49°C across varieties and was greater in low Ψ conditions. The DD was negatively correlated with Tb, which supports the hypothesis that seeds with lower Tb require more degree-days to germinate. Selecting alfalfa varieties with higher Tb could delay germination and reduce the risk of frost mortality; however, these varieties are also likely to have higher DD, which would expedite seedling emergence and potentially offset delays from high Tb. Based on small variations in germination parameters compared with field temperatures, no variety was identified as superior for frost-seeding success. [ABSTRACT FROM AUTHOR]

Perennial grain crops are being developed to reduce the negative environmental impacts of tillage and chemical inputs related to annual row-crop agriculture. To further improve the ecological benefits of perennial grains like Kernza® intermediate wheatgrass (IWG) [ Thinopyrum intermedium (Host.) Barkw. & D.R. Dewey], intercropping with perennial legumes has the potential to diversify grain production systems and reduce mineral N fertilizer requirements; however, the facilitative vs. competitive effects of various legume species on perennial grain yields are unknown. We compared grain and biomass yields, tissue C:N ratio, and δ15N of IWG in response to either mineral fertilizer treatments or intercropping with one of six legume species at three locations for three years. IWG tissue C:N ratio increased through time at all sites suggesting a consistent increase in N limitation. Although no legume intercrop consistently affected grain yields through time or across sites, very rarely did an intercrop reduce grain yields to levels less than fertilized and unfertilized IWG monocultures. However, legume biomass in year 1 was negatively correlated with IWG grain yields in year 1, suggesting that negative effects of competition may outweigh positive effects of N fixation and transfer the year following establishment. The relationship between legume biomass and IWG grain yield became positive by year 3, indicating a potential lag in the positive effects of legume intercrop on grain yield. At one location, red clover (Trifolium repens L.) biomass was higher than all other legume treatments in year 1 and declined through time, giving way to a subsequent increase in IWG biomass and grain yields through time. At this site, N transfer from legumes to IWG determined by δ15N was positive by year 3 for red clover and two other legume species. This study provides evidence that legume intercrops can benefit IWG production under certain conditions, but outcomes are site-specific and may depend on conditions related to soil N levels, temperature and precipitation patterns, and weed pressure. Research is needed to identify specific traits that promote legume coexistence and facilitation with IWG, and how these traits might rank in importance depending on environmental conditions. • Intermediate wheatgrass (IWG) grain yields were similar when intercropped with legumes compared to monocultures. • Total aboveground biomass increased with some legume/IWG intercrops compared with monocultures. • Nitrogen transfer from legumes to IWG was detected and varied by legume species. • Year 3 IWG grain yield was positively correlated to year 1 legume yield indicating a delayed effect of legume intercropping. [ABSTRACT FROM AUTHOR]