Kenneth J. Moore

Biomass yield and quality of 20 switchgrass populations in southern Iowa, USA

Renewable bioenergy could be supplied by high yielding grass crops, such as switchgrass (Panicum virgatum L.). Successful development of a bioenergy industry will depend on identifying cultivars with high yield potential and acceptable biofuel quality. The objective of this study was to evaluate 20 switchgrass populations in a field study planted in May 1997 in southern Iowa, USA. The populations included released cultivars and experimental germplasm of both upland and lowland ecotypes. Yield, plant height, stand, lodging, leaf:stem ratio, cell wall fiber, total plant nitrogen, and ash were determined on all entries between 1998 and 2001. Ultimate and proximate analyses together with chlorine and major oxide determinations were made on three cultivars in 2000 and 2001. Biomass yield was determined from a single autumn harvest each year. The lowland cultivars ‘Alamo’ and ‘Kanlow’ produced the most biomass, exceeding the production of the widely recommended upland cultivar ‘Cave-In-Rock’. Other traits differed among the cultivars, although the range was less than that for yield. The differences among years were substantially greater for the ultimate, proximate, and major oxide analyses than differences among cultivars. The highest yielding cultivars had low ash, slightly lower fiber concentrations, and moderate levels of important minerals, suggesting that excellent germplasm is available for biofuel production. The persistence of the lowland cultivars in southern Iowa may need more research because the winters during the experiment were mild.

Genetic mapping and analysis of quantitative trait loci affecting fiber and lignin content in maize

Abstract.Plant cell walls of forage provide a major source of energy for ruminant animals. Digestion of cell walls is limited by the presence of lignin, therefore the improving the digestibility of forages by reducing lignin content is a major goal in forage crop breeding programs. A recombinant inbred line maize population was used to map quantitative trait loci (QTL) for neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) of leaf-sheath and stalk tissues. All traits were positively genetically correlated. The larger genetic correlations were between NDF and ADF in sheaths (r = 0.84), NDF and ADF (r = 0.96), ADF and ADL (r = 0.83), and NDF and ADL (r = 0.76) in stalks. Twelve QTL were detected for NDF and 11 QTL for ADF in leaf-sheaths. Eight QTL detected for both traits were defined by the same or linked marker loci. Eight QTL were associated with leaf-sheath ADL. Eleven QTL were detected for NDF and ADF, and 12 QTL for ADL in stalks. Nine of eleven QTL detected for both NDF and ADF in stalks coincided in their genomic position. A high proportion of QTL detected for these traits had the same parental effects and genomic locations, suggesting that it is only necessary to select on one fiber component (NDF or ADF) to improve digestibility. Favorable correlated responses of unselected fiber components are expected due to coincident genomic locations of QTL and the high genetic correlation between fiber components. Several QTL detected in this study coincided in their positions with putative cellulose synthase genes from maize.

Vegetation diversity, growth, quality and decomposition in managed grasslands

The relationship between vegetation growth rate, quality, litter decomposition and diversity was investigated in four grazed grasslands differing in topography, management and fertility in the southern North Island of New Zealand. Vegetation samples were clipped at two sampling times (summer and autumn) from 0.5 m 2 areas excluded from grazing. Crude protein (CP), in vitro dry matter digestibility (IVDMD), neutral detergent fiber (NDF), average daily growth (ADG) rate, species composition and the relative extent of tissue degradation by soil microorganisms were determined for the vegetation samples. It was hypothesized that vegetation diversity would be negatively related with measures of vegetation growth, quality and decomposition. Comparisons made across all environmental and management conditions agreed with the hypotheses. Higher vegetation diversity was associated with lower ADG rate, lower CP concentrations, lower IVDMD and higher NDF concentrations. Comparisons within management regimes (MR), however, were less consistent and possible reasons for this are examined. Litter decomposition extent was closely related to the tissue quality characteristics of the vegetation, especially NDF concentration, but not species diversity. The observed local-scale relationships between the vegetation diversity, growth, quality and decomposition characteristics were contended to be largely the result of the influence of environmental resource richness on community structure of the managed grasslands studied. There is a need to promote a functionally diverse plant community over the entire managed area rather than promoting high localized species diversity within grasslands.

Association Mapping of Biomass Yield and Stem Composition in a Tetraploid Alfalfa Breeding Population

Alfalfa (Medicago sativa L.), an important forage crop that is also a potential biofuel crop, has advantages of high yield, high lignocellulose concentration in stems, and has low input costs. In this study, we investigated population structure and linkage disequilibrium (LD) patterns in a tetraploid alfalfa breeding population using genome‐wide simple sequence repeat (SSR) markers and identified markers related to yield and cell wall composition by association mapping. No obvious population structure was found in our alfalfa breeding population, which could be due to the relatively narrow genetic base of the founders and/or due to two generations of random mating. We found significant LD (p < 0.001) between 61.5% of SSR marker pairs separated by less than 1 Mbp. The observed large extent of LD could be explained by the effect of bottlenecking and selection or the high mutation rates of SSR markers. Total marker heterozygosity was positively related to biomass yield in each of five environments, but no relationship was noted for stem composition traits. Of a total of 312 nonrare (frequency >10%) alleles across the 71 SSR markers, 15 showed strong association (p < 0.005) with yield in at least one of five environments, and most of the 15 alleles were identified in multiple environments. Only one allele showed strong association with acid detergent fiber (ADF) and one allele with acid detergent lignin (ADL). Alleles associated with traits could be directly applied in a breeding program using marker‐assisted selection. However, based on our estimated LD level, we would need about 1000 markers to explore the whole alfalfa genome for association between markers and traits.

Alfalfa yield and quality as influenced by establishment method

management of a companion crop is critical to successful establishment of perennial forages (Albrecht and Hall, Weed control during alfalfa (Medicago sativa L.) establishment is 1995). a primary concern of forage producers. Companion crops and clearWeed management is important for decreasing comseeding with an herbicide are commonly used methods for establishing alfalfa. This study evaluated an alternative method in which alfalfa petition with alfalfa and for increasing alfalfa yield and is seeded into a winter-killed mulch residue from a fall-seeded winter quality during the establishment year (Chapko et al., cover crop of oat (Avena sativa L.) and compared it with seven other 1991; Hall et al., 1995). Weed control, during legume establishment methods: (i) drilled with postemergence application of establishment without a companion crop, is critical to imazethapyr {( )-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxoobtain a productive stand (Zollinger and Meyer, 1996). 2-imidazol-2-y1]-5-ethyl-3-pyridinecarboxylic acid}, (ii) drilled with Herbicide use, when seeding alfalfa alone, reduces weed postemergence application of sethoxydim {2-[1-(ethoxyimino)butyl] densities and allows better stands of pure alfalfa to be 5-[2-(ethylthio)propo]-3-hydroxy-2-cyclohexen-1-one}, (iii) drilled with obtained in the seeding year (Schmid and Beherns, no oat and no herbicide, (iv) oat companion crop harvested for silage, 1972). Competition, provided by weeds or companion (v) oat companion crop harvested for grain, (vi) spring-planted oat crops, reduces the total season alfalfa yield compared drilled with postemergence application of sethoxydim, and (vii) broadcast seeding without weed control. Field studies were conducted at two with alfalfa seeded alone with an herbicide (Sheaffer Iowa locations in 1996 and 1997. The oat companion-crop treatment et al., 1988). Lanini et al. (1991) found similar weed harvested for silage yielded the greatest forage dry matter (DM) in percentages in alfalfa treatments established with a comthe establishment year. However, drilled treatments without an oat panion crop or alone with an herbicide. Weed control companion crop, including the control, resulted in greater alfalfa stand during establishment also increased alfalfa shoot weight densities. Treatments with sethoxydim had lower grass weed densities and leaf number (Stout et al., 1992). in the establishment year while the drilled control and oat residue Clear-seeding is a planting method that provides an mulch treatment had the greatest. Treatments containing oat, and alternative to using a companion crop. This method clear-seeded with imazethapyr, had the lowest broadleaf weed densiprovides decreased competition from companion crops ties in the establishment year. During the establishment year, forage and increases in harvested alfalfa yields in the establishquality was greatest where alfalfa density was high and weed density was low. Because no significant yield or quality differences were found ment year (Simmons et al., 1992). Herbicides are necesamong treatments in the year after establishment, method chosen for sary for weed control and are advantageous for firstestablishment should be based on forage needs during the establishyear yields of clear-seeded alfalfa (Sheaffer et al., 1988). ment year. Imazethapyr is a postemergence selective herbicide that was labeled for use on alfalfa in January 1995 (Dahmer, 1995). Imazethapyr gives excellent control of annual A has traditionally been established in the grass and broadleaf weeds. Some short-term plant stuntMidwest with a companion crop such as oat (Chapko ing, however, can occur for alfalfa plants, but this does et al., 1991; Simmons et al., 1995). Companion crops not lead to phytotoxic effects by harvest time (Zollinger are advantageous to alfalfa during establishment beand Meyer, 1996). cause they suppress weed germination, growth, and A method of establishing alfalfa that utilizes the attricompetition and decrease the potential for soil erosion butes of both companion cropping and herbicide use (Wollenhaupt et al., 1995). Companion crops can inwas introduced in the late 1980s (Twidwell et al., 1993). crease total dry matter (DM) production during the Sethoxydim is a postemergence herbicide that can be establishment year (Sturgul et al., 1990; Chapko et al., used during alfalfa establishment to control grass weeds 1991). Companion crops can also negatively affect alor oat (Twidwell et al., 1993). Sethoxydim application falfa during establishment by competing for light, moisto alfalfa and oat is very effective in killing the companture, and nutrients, which can lead to reduced yield ion crop and other grass weeds that might be present. (Hall et al., 1995) and decreased plant density (Lanini This provides a pure stand of high quality alfalfa forage et al., 1991; Nickel et al., 1990). Appropriate harvest for harvest (Stute and Posner, 1993). A postemergence application of sethoxydim to oat growing with alfalfa can also optimize alfalfa yields in the establishment year Dep. of Agron., Iowa State Univ., Ames, IA 50011-1010. Journal (Curran et al., 1990; Twidwell et al., 1993). Another Paper no. J-18704 of the Iowa Agric. and Home Econ. Exp. Stn., Ames. Project no. 2899, supported by Hatch Act and State of Iowa funds. Received 25 Aug. 2000. *Corresponding author (kjmoore@ Abbreviations: ADF, acid detergent fiber; ADL, acid detergent lignin; iastate.edu). CP, crude protein; DM, dry matter; IVDMD, in vitro dry matter digestibility; NDF, neutral detergent fiber. Published in Agron. J. 94:65–71 (2002).

Ensiling Corn Stover: Effect of Feedstock Preservation on Particleboard Performance

Ensilage is a truncated solid‐state fermentation in which anaerobically produced organic acids accumulate to reduce pH and limit microbial activity. Ensilage can be used to both preserve and pretreat biomass feedstock for further downstream conversion into chemicals, fuels, and/or fiber products. This study examined the ensilage of enzyme‐treated corn stover as a feedstock for particleboard manufacturing. Corn stover at three different particle size ranges (<100, <10, and <5 mm) was ensiled with and without a commercial enzyme mixture having a cellulase:hemicellulase ratio of 2.54:1, applied at a hemicellulase rate of 1670 IU/kg dry mass. Triplicate 20 L mini‐silos were destructively sampled and analyzed on days 0, 1, 7, 21, 63, and 189. Analysis included produced organic acids and water‐soluble carbohydrates, fiber fractions, pH, and microorganisms, including Lactobacillusspp. and clostridia were monitored. On days 0, 21, and 189, the triplicate samples were mixed evenly and assembled into particleboard using 10% ISU 2 resin, a soy‐based adhesive. Particleboard panels were subjected to industry standard tests for modulus of rupture (MOR), modulus of elasticity (MOE), internal bonding strength (IB), thickness swell (TS), and water absorption at 2 h boiling and 24 h soaking. Enzyme addition did improve the ensilage process, as indicated by sustained lower pH (P < 0.0001), higher water‐soluble carbohydrates (P < 0.05), and increased lactic acid production (P < 0.0001). The middle particle size range (<10 mm) demonstrated the most promising results during the ensilage process. Compared with fresh stover, the ensilage process did increase IB of stover particleboard by 33% (P < 0.05) and decrease water adsorption at 2 h boiling and 24 h soaking significantly (P < 0.05). Particleboard panels produced from substrate ensiled with enzymes showed a significant reduction in water adsorption of 12% at 2 h boiling testing. On the basis of these results, ensilage can be used as a long‐term feedstock preservation method for particleboard production from corn stover. Enzyme‐amended ensilage not only improved stover preservation but also enhanced the properties of particleboard products.

Improving Map Accuracy of Soil Variables Using Soil Electrical Conductivity as a Covariate

Accurate characterization of soil properties across a field can be difficult, especially when compounded with the diverse landscapes used for pastureland. Indirect methods of data collection have the advantage of being rapid, noninvasive, and dense; they may improve mapping accuracy of selected soil parameters. The objective of this study was to determine if the use of soil electrical conductivity (EC) as a covariate improved mapping accuracy of five soil variables across four sampling schemes and two sampling densities in a central Iowa, USA pasture. In this study, cokriging methods were compared to kriging methods for the measured soil properties of soil pH, available P and K, organic matter and moisture. Maps resulting from cokriging each of the soil variables with soil EC exhibited more local detail than the kriged maps of each soil variable. A small, but inconsistent, improvement occurred in kriging variance and prediction accuracy of non-sampled sites when cokriging was implemented. The improvement was generally greater for soil variables more highly correlated with soil EC. This work indicates that cokriging of EC with less densely and invasively collected soil parameters of P, K, pH, organic matter (OM) and moisture does not consistently and substantially improve the characterization accuracy of pasture soil variability.

Intake, digestion, and nitrogen balance of sheep fed shrub foliage and medic pods as a supplement to wheat straw

Abstract Low animal performance in arid and semi-arid areas of Morocco is mainly due to protein and energy deficiencies of available forages. A metabolism trial was conducted to evaluate the influence of supplementation with shrub foliage and medic ( Medicago sp.) pods on nitrogen (N) utilization by sheep fed low-quality roughage. Diets were wheat ( Triticum aestivum L.) straw (WS), WS plus alfalfa ( Medicago sativa L.) hay (AH), WS plus oldman saltbush ( Atriplex nummularia Lindl.) foliage (AN), WS plus blue wattle ( Acacia cyanophylla Lindl.) foliage (AC), and WS plus medic pods (MP). Alfalfa feeding level was set to provide a crude protein (CP) concentration of 90 g kg −1 dry matter (DM) in the diet. Shrub foliage and medic pods were offered ad libitum. Average intake levels for AN, AC, and MP were 37.2, 32.4, and 47.2% DM, respectively. Chemical composition and in vitro dry matter disappearance (IVDMD) were measured. Digestible dry matter intake (DDMI) was greatest ( P −0.75 ), followed by the alfalfa diet (30.0 g kg −0.75 ). Unsupplemented wheat straw and blue wattle diets had the lowest DDMI (21.3 g kg −0.75 ). The daily N balance for the supplemented diets was greatest ( P −1 ). A degradability trial was then conducted to investigate the rate and extent of DM and CP digestion of the same forages in the rumen. Forage samples were incubated for 0, 2, 4, 8, 12, 24, 48, and 72 h. Rate and extent of DM digestion were highest ( P P −1 ). Extent of CP degradation was greatest ( P

Browse foliage and annual legume pods as supplements to wheat straw for sheep

Abstract Cereal stubble and straw are widely used as animal feeds for sheep in arid areas of Morocco. The inherently low protein concentration of these feeds limits their intake and therefore potential of production. A 14-week feeding trial was conducted to investigate the effect of supplementation with browse foliage or medic ( Medicago sp.) pods on wheat ( Triticum aestivum L.) straw intake and ewe lamb live weight. Diets were wheat straw (WS), WS plus alfalfa ( Medicago sativa L.) hay, WS plus oldman saltbush ( Atriplex nummularia Lindl.) foliage, WS plus blue wattle ( Acacia cyanophylla Lindl.) foliage, and WS plus medic pods. Alfalfa and urea feeding levels were set to provide a crude protein (CP) concentration of 90 g kg −1 DM in the diet. Shrub foliage and medic pods were offered ad libitum. Atriplex and Acacia foliage supplementation resulted in the highest and lowest straw intake increases, respectively. These findings would contribute to explain why animals receiving Atriplex foliage in addition to wheat straw were the only ones to maintain weight over a 14-week period. Medic pod supplementation resulted in an insignificant weight loss. These results showed that foliage from palatable shrubs and medic pods can be effective protein supplements for livestock consuming wheat straw. Implementing such strategies would require that farmers plant oldman saltbush ( Atriplex nummularia Lindl.) shrubs on their private land and manage medic pasture to produce enough pods to be grazed in summer.

Comparison of common lignin methods and modifications on forage and lignocellulosic biomass materials.

BACKGROUND A variety of methods have been developed for estimating lignin concentration within plant materials. The objective of this study was to compare the lignin concentrations produced by six methods on a diverse population of forage and biomass materials and to examine the relationship between these concentrations and the portions of these materials that are available for utilisation by livestock or for ethanol conversion. RESULTS Several methods produced lignin concentrations that were highly correlated with the digestibility of the forages, but there were few relationships between these methods and the available carbohydrate of the biomass materials. The use of Na₂SO₃ during preparation of residues for hydrolysis resulted in reduced lignin concentrations and decreased correlation with digestibility of forage materials, particularly the warm-season grasses. CONCLUSION There were several methods that were well suited for predicting the digestible portion of forage materials, with the acid detergent lignin and Klason lignin method giving the highest correlation across the three types of forage. The continued use of Na₂SO₃ during preparation of Van Soest fibres needs to be evaluated owing to its ability to reduce lignin concentrations and effectiveness in predicting the utilisation of feedstuffs and feedstocks. Because there was little correlation between the lignin concentration and the biomass materials, there is a need to examine alternative or develop new methods to estimate lignin concentrations that may be used to predict the availability of carbohydrates for ethanol conversion.