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Managing annual row crops on marginally productive croplands can be environmentally unsustainable and result in variable economic returns. Incorporating perennial bioenergy feedstocks into marginally productive cropland can engender ecosystem services and enhance climate resiliency while also diversifying farm incomes. We use one of the oldest bioenergy-specific field experiments in North America to evaluate economically and environmentally sustainable management practices for growing perennial grasses on marginal cropland. This long-term field trial called 9804 was established in 1998 in eastern Nebraska and compared the productivity and sustainability of corn (Zea mays L.) --both corn grain and corn stover--and switchgrass (Panicum virgatum L.) bioenergy systems under different harvest strategies and nitrogen (N) fertilizer rates. This experiment demonstrated that switchgrass, compared to corn, is a reliable and sustainable bioenergy feedstock. This experiment has been a catalyst for other bioenergy projects which have also expanded our understanding of growing and managing bioenergy feedstocks on marginal cropland. We (1) synthesize research from this long-term experiment and (2) provide perspective concerning both the knowledge gained from this experiment and knowledge gaps and how to fill them as well as the role switchgrass will play in the future of bioenergy. [ABSTRACT FROM AUTHOR]

Corn residue grazing is an economical winter feed resource for cows in the Midwest. However, questions about changes in the feeding value have been raised. A 2-yr experiment was conducted to evaluate the effects of corn grain yield on the quantity and quality of corn residue. In yr 1, 32 hybrids were evaluated from four locations in Nebraska. In yr 2, 31 hybrids were evaluated from three locations in Nebraska. Each hybrid was harvested from four replicate plots. Three of the locations were irrigated and four were rainfed. Observed grain yields ranged from 1,416 to 22,318 kg/ha (23 to 355 bushels/acre) with a mean of 12,704 kg/ ha (202 bushels/acre). As corn yield increased, the amount of grain relative to whole plant biomass (harvest index) increased (P < 0.01). Harvest index ranged from 48.4% to 67.6% and averaged 59.3%. The increase in harvest index indicates there was less residue produced per kilogram of corn grain produced in greater yielding corn. However, as expected, total amount of residue (kg/ha) still increased (P < 0.01) as grain yield (kg/ha) increased. Within the residue, the proportions of leaf and husk increased (P < 0.01) slightly, stalk decreased (P < 0.01) slightly, while the proportion of cob did not change (P = 0.62) as grain yield increased. On average, the observed plant proportions in this experiment were 15.8% husk, 18.6% leaf, 50.5% stalk and 15.1% cob (DM basis). As grain yield increased, the proportion of husk within residue increased from 14 to 21% and leaf increased from 17 to 24%. In contrast, the proportion of stalk within residue decreased from 53 to 41%. Cattle primarily consume leaf and husk when grazing corn residue, thus the availability and digestibility of those plant parts could be a key factor that affects diet quality of grazing cattle. Both the digestible organic matter (DOM, % of DM) in leaf and husk and the kilograms of DOM from leaf plus husk per 25.4 kilograms of grain declined (P < 0.01) as grain yield increased. On average, the DOM (% of DM) for husk was 69.3% but declined from 83.6 to 56.4% with increasing in grain yield. The average DOM (% of DM) for leaf was 55.6% and declined from 65.3 to 41.6% as grain yield increased. The average amount of DOM from leaf plus husk was 3.6 kg/25.4 kg of grain (8 lb/bushel) and declined from 5.8 to 2.5 kg/25.4 kg of grain (12.8 to 5.5 lb/ bushel) as grain yield increased. Thus, the concentration of nutrients in corn residue declined as grain yield increased, meaning greater yielding corn had reduced quality residue. The impacts of this decline in diet quality on cow performance should be further evaluated. [ABSTRACT FROM AUTHOR]

Systematic performance trials have been conducted in several states for more than 20 yr to evaluate agronomic performance of annual ryegrass (Lolium multiflorum Lam.). Despite development and testing of many annual ryegrass cultivars, the first improved cultivar, Gulf, has remained one of 10 to 12 cultivars recommended for planting in the southeastern USA. Our objectives were to evaluate cultivar yield performance across 12 yr at five locations, to assess cultivar yield distribution within growing seasons, and to estimate cultivar yield stability (consistency of relative performance environments). Efficacy measures were early-season yield (total before 1 March), late-season yield (total after 1 March), and total annual yield. Overall means for all cultivars and individual cultivar performance (for common years) were compared with Gulf or Marshall. Neither location effects nor cultivar X location interactions were found. Cultivar and year effects, plus cultivar X year interactions were detected (P < 0.05) for all three yield responses. Mean early season yields ranged from 2.3 to 4.6 Mg [ha.sup.-1], with mean late-season yields ranging from 5.1 to 7.4 Mg [ha.sup.-1]. No trend existed for mean total yield relative to Gulf or Marshall to increase over time in association with availability of newer cultivars. Given large yearly fluctuation in yields, it is apparent that unpredictable environmental factors, including climate and perhaps pests, are the primary determinants of annual ryegrass performance rather than differences in yield potential among cultivars. Thus, yield stability may be an appropriate selection factor to include among the criteria for development of improved annual ryegrass cultivars., DURING THE PAST 50 YR, annual ryegrass has become an important cool-season forage plant in the southeastern USA. The development of the first improved cultivar for the region, Gulf annual [...]

Differences among annual ryegrass (Lolium multiflorum Lam.) cultivars for weight gain of grazing steers have been reported, even though plot experiments suggest that forage dry matter yield among cultivars should not be a limiting factor. Likewise, forage nutritive value differences among cultivars have not been assessed. The objectives of this research were to evaluate differences in cumulative forage yield, yield distribution, and nutritive value among `Gulf', `Jackson', `Marshall', `Rio', `Rustmaster', and `Surrey' annual ryegrass. Plots were harvested six times beginning in December at approximate 30-d intervals during the 1997-1998 and 1998-1999 growing seasons. Nutritive value measurements included crude protein (CP), neutral detergent fiber (NDF), in vitro true digestibility (IVTD), and digestible NDF (DNDF). There were no differences among cultivars for cumulative forage yield (P = 0.99). However, for the January harvest, Surrey and Gulf averaged 1030 (± 65) kg DM [ha.sup.-1], whereas Marshall yielded only 672 (± 79) kg DM [ha.sup.-1]. For the March harvest, yields of all varieties were similar and averaged 1350 (± 95) kg DM [ha.sup.-1]. At the May harvest, Marshall and Jackson yielded 1232 (± 123) kg DM [ha.sup.-1], whereas Gulf yielded only 929 (± 74) kg DM [ha.sup.-1]. Crude protein concentration differed significantly among harvests with a general decrease from 260 to 120 g CP [kg.sup.-1] as the growing mason progressed. Similar declines in nutritive value occurred for NDF, IVTD, and DNDF. Trends in yield distribution and forage quality may indicate a need for cultivar specific recommendations based on intended forage need and season of use., BEEF AND DAIRY CATTLE PRODUCERS require a consistent supply of high-quality forage to maintain economical levels of animal production. Beef and dairy cattle producers in the southeastern USA rely primarily [...]

Energy availability from forages is limited by fiber concentration because fiber is slowly and incompletely digested, whereas cell solubles are almost completely digested. Thus, the proportion of fiber to cell solubles is a major determinant of energy availability in forages. Grasses normally have more fiber than legumes, especially in leaves. Grass fiber is more digestible than that of legumes, but that of legumes digests at a faster rate. Ruminants digest 40-50% of legume fiber and 60-70% of grass fiber. Some fiber cannot be digested no matter how long it remains in the rumen. Lignin is thought to interfere with microbial degradation of fiber polysaccharides by acting as a physical barrier and by being cross-linked to polysaccharides by ferulate bridges. In addition to the effects of lignin, physical and structural barriers may limit fiber digestibility. Because the middle lamella and primary wall of thick-walled cells are so highly lignified, many cells can be digested only from the interior of the cell. For many cells, access to cell interiors is limited because of large particle sizes. Forage digestibility could be improved by reducing the amount of lignified cells or by developing improved cultivars so that lignified cells are more digestible. KEY WORDS: energy availability digestible fiber lignin cell wall structural barriers

Soybean harvest leaves little residue, potentially subjecting the soil to negative environmental impacts. Additionally, integrated livestock producers with crops and cattle identified a need to fill early spring forage deficiencies. Planting winter-hardy cereal cover crops after soybean harvest provides ground cover until the next cash crop is planted and has potential for early spring grazing before perennial pastures are ready. A 3-year study was conducted near Mead, Nebraska to evaluate the grazing potential of winter wheat, winter triticale, and cereal rye when planted after soybean harvest. A 7.3-ha field was split into nine 0.81-h paddocks and paddocks were then randomly assigned to a small cereal species (n = 3 paddocks per treatment), then divided further into 2, 0.4 ha paddocks to allow for rotational grazing within the assigned paddock. Growing steers were stratified by body weight (BW) and randomly assigned to paddock with 6 steers per paddock in years 1 and 2, and 5 steers per paddock in year 3. Steers were limit-fed at 2% of BW to equalize gut fill and weighed before and at the conclusion of grazing. Grazing was initiated when a paddock reached 13 cm. The initial BW did not differ among treatments (P > 0.05) with steers weighing 303, 335, and 372 kg in years 1 through 3, respectively. The final BW did not differ among treatments (P > 0.05). There was a treatment by year interaction (P = 0.01) for average daily gain (ADG). There were no differences (P > 0.05) in ADG among treatments in year 1 (1.9 kg/d) or year 3 (1.3 kg/d). However, in year 2, steers grazing rye gained more (P < 0.01) at 1.4 kg than wheat (0.83 kg) and triticale (0.67 kg), which did not differ (P > 0.05). There were no differences (P > 0.05) among treatments for animal unit months (AUM) per hectare. Year 1 provided the most (P < 0.01) grazing at 5.1 AUM/ha, year 2 provided the least (P < 0.01) at 2.4 AUM/ha, and year 3 was intermediate at 3.1 AUM/ha. For gain per hectare (GPH), there were no differences (P > 0.05) among treatments. Steers in year 1 had greater (P < 0.01) GPH (390 kg/ha) than subsequent years, with year 2 (93 kg/ha) being less (P < 0.01) than year 3 (151 kg/ha). For all 3 years, there were no differences among treatments in pre-graze (P > 0.05) or postgraze biomass (P > 0.05). These data suggest that during early spring there are no major differences in the grazing potential and growing cattle performance for wheat, rye, or triticale in eastern Nebraska. [ABSTRACT FROM AUTHOR]

Shading patterns when two forage species are intercropped may be different than in a monocrop environment. Our objectives were to quantify yield and forage quality response of forage soybean [Glycine max (L.) Merr.] intercropped with forage sorghum [Sorghum bicolor (L.) Moench] and compare to the measurements of monocrop soybean. Soybean plants were harvested from the middle portion of individual rows in plots containing only soybean and from plots having alternating soybean and sorghum rows spaced 76 cm apart. Morphological and forage quality measurements were determined on leaf and stem fractions. Morphological measurements included main stem length, node number, leaf area ratio (LAR), specific leaf weight (SLW), and stem diameter. Forage quality constituents included in vitro dry matter disappearance (IVDMD), neutral detergent fiber (NDF), hemicellulose, and cellulose, and crude protein (CP) concentrations. Intercropped soybean had 6 more plants [m.sup.-1] of row, less advanced morphological development, and 2.3 Mg [ha.sup.-1] less dry matter than monocrop soybean. Leaf IVDMD, NDF, hemicellulose, and cellulose did not differ between intercrop and monocrop soybean. However, stem IVDMD was 33 g [kg.sup.-1] greater for intercropped than monocrop soybean, reflecting the 36 g [kg.sup.-1] decrease in NDF concentration. Intercropped soybean was lodged both years more than monocrop soybean, which may have been due to the significant decrease in stem NDF. Leaf CP concentration was 25 g [kg.sup.-1] greater for monocrop soybean than intercropped soybean; however, stems from intercropped soybean had 12 g [kg.sup.-1] greater CP than monocrop soybean stems. Soybean exhibited a high degree of morphological plasticity, presumably in response to increased competition for solar radiation. Although forage quality of intercrop soybean was greater than monocrop soybean, intercropping forage-type soybean with another tall-growing forage does not appear to be practical because of the decrease in dry matter accumulation., Interplant competition is usually mediated through competition for soil water, available nutrients, and solar radiation, although other factors such as temperature fluctuation and pest infestations may be equally important (Buxton [...]

Forage quality as it relates to plant maturity is well established; however, strategies for improving fiber digestion in switchgrass populations have not been determined. The objectives of this study were to determine fiber digestion of sward components within switchgrass (Panicum virgatum L.) populations and which aspects of fiber digestion dynamics caused in vitro dry matter disappearance (IVDMD) differences of six switchgrass populations. This study was conducted in 1993 near Ames, lA, and Mead, NE. The experimental design was a randomized complete block design with a split-plot arrangement of treatments with four replicates at each location. Whole plots were populations and subplots were sward maturity. `Trailblazer', `Pathfinder', `Cave-in-Rock', and three experimental switchgrass populations were used in this study. Populations were harvested on 9 June, 19 July, and 27 August al Ames and on 10 June, 27 July, and 26 August at Mead. Fiber composition and digestibility were determined on leaf blade, leaf sheath, and stem fractions of the primary growth stages. Significant differences for theoretical true digestibility (TD) and neutral detergent fiber (NDF) existed for morphological components at each sward maturity. However, digestion characteristics of the sward components were not stable across primary growth stages. Rate of fiber digestion was faster for most sward components at Ames than Mead, although stems of elongating tillers from elongating swards digested faster on plants grown at Mead than Ames. Rate of fiber digestion of stems was typically slower than either leaf blades or sheaths, but in several instances they were similar or stems had faster rates of fiber digestion. Although phenotypic selection can increase fiber digestibility, plant maturity remains an important factor, and selections may require evaluation at different stages of morphological development. Thus, improvements in forage digestion, at least in switchgrass, may only be manifested for the growth stage at which it was selected., Improved ruminant animal production can be achieved by selectively breeding forages for increased IVDMD. Vogel et al. (1981) showed that it was possible to select switchgrass for increased and decreased [...]

Winter-hardy small grains offer an opportunity to improve soil health as a cover crop, and they can also be used as a forage source for cattle. Winterhardy small grains differ in the time needed to reach various maturity stages. Species selection may also impact yield and nutritive value. A two-year study was conducted in eastern Nebraska to determine the effect of species and maturity on yield and nutritive value of winter-hardy small grains used for silage. Three species were evaluated; cereal rye, winter wheat, and winter triticale at four stages of maturity: boot, anthesis, milk, and soft dough. The experimental design was a randomized complete block design with four blocks per year. Small grain species were considered whole plots with maturity at harvest considered sub-plot. Each year, the small grain species were randomly assigned within each block. Within each plot, maturity was randomly assigned to one quarter of each plot. Dry matter (DM) forage yield, crude protein (CP), digestible organic matter (DOM), and nutrient yield per hectare were measured and analyzed using the mixed procedure of SAS. Forage yield increased for all species (P < 0.01) with maturity, except for wheat, where there was a decrease at soft dough. Forage yield of cereal rye and triticale did not differ (P>0.05), except at soft dough where triticale was greater (P < 0.01) than cereal rye. Forage yield of triticale and cereal rye yield was greater (P£0.05) than wheat at anthesis and soft dough. Crude protein (% DM) decreased (P < 0.01) with maturity across all species. Among species, CP for cereal rye was greater (P£0.01) than triticale at boot, anthesis, and soft dough, but not different (P³0.10) from wheat at boot, milk, and soft dough. At boot, anthesis, and milk stages, CP of triticale was not different (P³0.07) than wheat, but triticale was lower than wheat (P < 0.01) at soft dough. The DOM (% DM) decreased (P < 0.01) with maturity, except at soft dough. The DOM of cereal rye and wheat did not differ (P > 0.05), but both were greater (P < 0.01) than triticale. Cereal rye and triticale had greater (P £ 0.05) nutrient yields than wheat in terms of energy (DOM) and CP. There was no difference for CP yield across stages (P = 0.10), but there was an effect of maturity on DOM yield. The DOM yield increased from boot to anthesis, (P = 0.05), anthesis and milk did not differ (P = 0.08) and increased (P < 0.01) again at soft dough. This suggests that planting either cereal rye or triticale resulted in the greatest nutrient yield per acre. Harvest at anthesis had increased yield compared to boot with minimal loss in nutritive value; for maximizing energy yield per acre, harvesting at soft dough was the best option. [ABSTRACT FROM AUTHOR]