Craig C. Sheaffer

Intensive rotational grazing for dairy cattle feeding

A 2-year study compared milk production and profitability for confinement feeding versus rotational grazing. Guernsey and Guernsey x Holstein cows grazed perennial grass pastures from mid-May to October or were fed in confinement. Averaged over both years, confined cows produced 7% more milk; their milk was similar in fat concentration to that of grazing cows. Body weight changes and health of the two groups were similar. Net return per cow averaged

Base temperature for the application of the growing-degree-day model to field-grown alfalfa

64 higher for rotational grazing than for confinement because of lower costs for feeding, facilities, equipment, and labor. Intensive rotational grazing of pastures is a competitive alternative for dairy cow feeding. However, farmers in the northern U.S. will still require stored feeds from late fall through early spring.

MATURATION EFFECTS ON FORAGE QUALITY OF KENTUCKY BLUEGRASS

Abstract Base temperature ( T b ) selection for the field application of the growing-degree-day ( gdd ) model for predicting alfalfa ( Medicago sativa L.) harvest under a three-cutting management system was investigated, because current usage is based upon extrapolation of growth-chamber data and employs a constant T b despite microclimatic and physiological changes that take place during the growing season. Three methods of analysis and 11 station-years of climatic and alfalfa one-tenth-flower data from Rosemount and St. Paul, Minnesota, were used for successive growth periods to estimate T b . The best estimate of T b in the spring growth period, 3.5°C, was significantly less than the 5°C value currently used. For the succeeding summer periods, T b estimates were 7.5° and 10.0°C, the latter being significantly higher than the current T b . The gdd requirement, computed using the best estimates of T b , were 585, 425 and 425 for alfalfa to reach one-tenth flower in each successive period. When a constant T b was used, the gdd requirement to flower differed between growth periods, with the late summer period having a greater requirement.

Genetic diversity of rhizobia nodulating Trifolium ambiguum in North America

Kentucky bluegrass (Poa pratensis L.) is an important constituent of many permanent pastures in the northern United States and is an important source of livestock feed, but there is a paucity of information on its forage quality. The objective of this research was to assess changes with maturity in forage quality of whole herbage, leaves, and stems of Kentucky bluegrass compared with other important cool-season forage grasses. Kentucky bluegrass, orchardgrass (Dactylis glomerata L.), reed canarygrass (Phalaris arundinaceae L.), smooth bromegrass (Bromus inermis Leyss), timothy (Phleum pratense L.), and tall fescue (Festuca arundinacea Schreb) were sampled weekly beginning in mid-May until each species reached milk stage. Kentucky bluegrass had the highest or was among the grasses with the highest average leaf percentage, and leaf, stem, and whole herbage neutral detergent fiber (NDF) and acid detergent lignin (ADL) concentrations; and lowest average whole herbage, leaf, and stem in vitro digestible dry ma...

Associations between soil bacterial community structure and nutrient cycling functions in long-term organic farm soils following cover crop and organic fertilizer amendment

Kura clover (Trifolium ambiguum M.B.) is a persistent rhizomatous forage legume, whose use in the U.S.A. is limited by establishment difficulties in part attributable to nodulation problems. In this study, soil was collected from established stands of Kura clover growing in 9 diverse North American environments. Rhizobia were plant-trapped using Kura clover cv. Endura as host, then rhizobia from nodules fingerprinted using BOX-PCR. The diversity of isolates from North America was then contrasted to that of rhizobia from a single Caucasian environment (Russia), the center of origin for this species. Populations were characterized using clustering methods, and genetic diversity estimated using the Shannon-Weaver diversity index. The genetic diversity of the North American populations was extremely limited, all isolates being closely related to two of the strains found in a locally available commercial inoculant. In contrast, Russian isolates formed a distinct cluster with significant internal genetic diversity. Genetic diversity indices for the North American and Russian populations were 3.5 and 10.76, respectively. The implication of this and other studies is that Kura clover is highly specific in Rhizobium requirement. If the performance of this legume in the U.S.A. is to be improved, either by modifying current establishment practices or plant breeding, it is essential that these studies be paralleled by more collections and evaluation of rhizobia from its center of origin, given the extremely limited diversity of rhizobia found in North America.

Structure of bacterial communities in soil following cover crop and organic fertilizer incorporation

Agricultural management practices can produce changes in soil microbial populations whose functions are crucial to crop production and may be detectable using high-throughput sequencing of bacterial 16S rRNA. To apply sequencing-derived bacterial community structure data to on-farm decision-making will require a better understanding of the complex associations between soil microbial community structure and soil function. Here 16S rRNA sequencing was used to profile soil bacterial communities following application of cover crops and organic fertilizer treatments in certified organic field cropping systems. Amendment treatments were hairy vetch (Vicia villosa), winter rye (Secale cereale), oilseed radish (Raphanus sativus), buckwheat (Fagopyrum esculentum), beef manure, pelleted poultry manure, Sustane(®) 8-2-4, and a no-amendment control. Enzyme activities, net N mineralization, soil respiration, and soil physicochemical properties including nutrient levels, organic matter (OM) and pH were measured. Relationships between these functional and physicochemical parameters and soil bacterial community structure were assessed using multivariate methods including redundancy analysis, discriminant analysis, and Bayesian inference. Several cover crops and fertilizers affected soil functions including N-acetyl-β-d-glucosaminidase and β-glucosidase activity. Effects, however, were not consistent across locations and sampling timepoints. Correlations were observed among functional parameters and relative abundances of individual bacterial families and phyla. Bayesian analysis inferred no directional relationships between functional activities, bacterial families, and physicochemical parameters. Soil functional profiles were more strongly predicted by location than by treatment, and differences were largely explained by soil physicochemical parameters. Composition of soil bacterial communities was predictive of soil functional profiles. Differences in soil function were better explained using both soil physicochemical test values and bacterial community structure data than using soil tests alone. Pursuing a better understanding of bacterial community composition and how it is affected by farming practices is a promising avenue for increasing our ability to predict the impact of management practices on important soil functions.

Long-Term Biomass Yield and Species Composition in Native Perennial Bioenergy Cropping Systems

Incorporation of organic material into soils is an important element of organic farming practices that can affect the composition of the soil bacterial communities that carry out nutrient cycling and other functions crucial to crop health and growth. We conducted a field experiment to determine the effects of cover crops and fertilizers on bacterial community structure in agricultural soils under long-term organic management. Illumina sequencing of 16S rDNA revealed diverse communities comprising 45 bacterial phyla in corn rhizosphere and bulk field soil. Community structure was most affected by location and by the rhizosphere effect, followed by sampling time and amendment treatment. These effects were associated with soil physicochemical properties, including pH, moisture, organic matter, and nutrient levels. Treatment differences were apparent in bulk and rhizosphere soils at the time of peak corn growth in the season following cover crop and fertilizer application. Cover crop and fertilizer treatments tended to lower alpha diversity in early season samples. However, winter rye, oilseed radish, and buckwheat cover crop treatments increased alpha diversity in some later season samples compared to a no-amendment control. Fertilizer treatments and some cover crops decreased relative abundance of members of the ammonia-oxidizing family Nitrosomonadaceae. Pelleted poultry manure and Sustane® (a commercial fertilizer) decreased the relative abundance of Rhizobiales. Our data point to a need for future research exploring how (1) cover crops influence bacterial community structure and functions, (2) these effects differ with biomass composition and quantity, and (3) existing soil conditions and microbial community composition influence how soil microbial populations respond to agricultural management practices.

Palatability and nutritive value of native legumes

Biomass yield is an important factor when recommending native perennial plants and mixtures for bioenergy production. Our objective was to determine long-term biomass yields in fertilized and unfertilized native plant monocultures and mixtures that show promise for bioenergy across diverse environments in the Upper Midwest. We measured biomass yields, species composition, and diversity annually in monocultures and mixtures ranging from 4 to 24 planted species including grasses, legumes, and other forbs; each managed with and without 67 kg N ha–1 fertilizer applied annually at nine locations for 7 yr. Without N fertilization, switchgrass (Panicum virgatum L.) monocultures and an eight-species mixture of grasses and legumes produced the most biomass over locations and years (5.1 Mg ha–1). With N fertilizer, switchgrass monocultures and a four-species mixture of grasses produced the highest yields (6.8 and 6.4 Mg ha–1). Over time, biomass yields increased for switchgrass, decreased for Canada wild rye (Elymus canadensis L.), and remained stable for the high diversity mixtures. Other mixtures had nonlinear changes in yield, likely related to changes in species composition. Although the relative abundance of individual species changed over time, Shannon diversity was constant except for the four-species legume mixture where it decreased. Contrary to other studies, N fertilization did not decrease species diversity through time. Diversity was positively related to biomass yield following establishment, but the strength of the relationship diminished with stand age. Native plant mixtures managed with and without N fertilizer can yield similar biomass compared with highly productive monocultures in the Upper Midwest.

Physical sod suppression as an alternative to herbicide use in pasture renovation with clovers

Native perennial legumes have potential for use as components of grazing systems. Palatability affects forage utilization by grazing livestock, but relative palatability of native legumes is unknown. We determined the palatability of these native legumes of the Fabaceae family based on relative leaf consumption: false indigo (Amorpha fruticosa L.), Illinois bundleflower (Desmanthus illinoensis (Michx.) MacMill. ex B.L. Rob. & Fernald), blue wild indigo (Baptisia australis (L.) R. Br.), wild senna (Senna hebecarpa (Fernald) Irwin & Barneby), and purple prairie clover (Dalea purpurea Vent.); compared with temperate forage legumes (Fabaceae): alfalfa (Medicago sativa L.) and birdsfoot trefoil (Lotus corniculatus L.). Purple prairie clover and Illinois bundleflower were among the most palatable native legumes each year and were readily consumed by grazing sheep (Ovis aries L. [Bovidae]). False indigo, a shrub, was the least palatable native legume. The leafiness, plant maturity, and nutritive value of leaves varied among legumes but were not associated with palatability.Sheaffer CC, Wyse DL, Ehlke NJ. 2009. Palatability and nutritive value of native legumes. Native Plants Journal 10(3): 224–231.

Annual legumes as green manure and forage crops in winter canola (Brassica napus L.) rotations

Using herbicides for sod suppression during pasture renovation by legume sod-seeding often results in the loss of potentially usable forage, weed encroachment, and inadequate legume:grass ratios. Physical sod suppression methods could alleviate some of the problems associated with suppression via herbicide. A study was conducted in Quebec, Canada, to investigate, as an alternative to herbicide, sod suppression by sheep grazing or mowing before and after spring no-till seeding of red clover (Trifolium pratense L.) or white clover (T. repens L.). Sod-suppression treatments included six physical suppression methods: mowing or sheep grazing, to 5 or 10 cm, at seeding and when the grass sward reached 30 cm during the first 2 mo of clover establishment, or similarly managed mowing or sheep grazing to 5 cm with an additional defoliation the previous fall. Additional treatments included suppression by herbicide (glyphosate [N-(Phosphonomethyl) glycine] at 2.6 kg a.i. ha–1) and two controls: sod-seeding with no so...