Breeding to improve biomass production of switchgrass (Panicum virgatum L.) and big bluestem (Andropogon gerardii Vitman) for conversion to bioenergy began in 1992. The purpose of this study was (i) to develop a platform for uniform regional testing of cultivars and experimental populations for these species, and (ii) to estimate the gains made by breeding during 1992 to 2012. A total of 25 switchgrass populations and 16 big bluestem populations were planted in uniform regional trials at 13 locations in 2012 and 2014. The reference region was USDA Hardiness Zones 3 through 6 in the humid temperate United States. Significant progress toward increased biomass yield was made in big bluestem and within upland-ecotype populations, lowland-ecotype populations, and hybrid-derived populations of switchgrass. Four mechanisms of increasing biomass yield were documented: (i) increased biomass yield per se, (ii) later flowering to extend the growing season, (iii) combined later flowering from the lowland ecotype with survivorship of the upland ecotype in hybrid-derived populations, and (iv) increased survivorship of late-flowering lowland populations in hardiness zones that represent an expansion of their natural adaption zone. Switchgrass exhibited all four mechanisms in one or more improved populations, whereas improved populations of big bluestem were likely influenced by two of the four mechanisms. The uniform testing program was successful at documenting increases in biomass yield, identifying the mechanisms for increased yield, and determining adaptation characteristics and limitations of improved populations.

Big bluestem (Andropogon gerardii Vitman) and indiangrass (Sorghastrum nutans L.) were collected from remnant Midwestern prairies and evaluated as individual prairie accessions in replicated space‐transplanted nurseries near Mead, NE, Ames, IA, and West Lafayette, IN. The objective was to determine the extent of differences among the accessions for plant biomass (g plant−1) and biomass quality, the extent of strain × location interactions, and the relationship between geographical locations of collection sites and evaluation locations for plant biomass production. Plant biomass has been used previously as a measure of plant adaptation and fitness. Big bluestem and indiangrass accessions differed significantly (P < 0.05) for plant biomass at all locations. Strain mean squares for plant biomass were 10× greater than strain × location effects for big bluestem and were not significant for indiangrass, indicating a general lack of specific adaptation across the Midwest. Accessions were identified that had high plant biomass at all three locations. These accessions should have value in breeding programs and for use in revegetation. Regression analyses were used to test the effect of north‐to‐south, east‐to‐west, and direct distances between the collection sites and the evaluation locations on plant biomass. The most important distance effects were the north‐to‐south effects, which were significant for plant biomass for big bluestem at all locations and for indiangrass at West Lafayette. Moving northern big bluestem accessions south resulted in reduced plant biomass, with the opposite effect when southern accessions were moved north. Results support the regional adaptation of the best accessions and cultivars for these grasses.

Apparent ruminal digestibility of forage soybean-based silages, with and without pearl millet, was determined along with evaluation of silages on heifer performance and reproductive function. Fermenters were utilized in a Latin square design and randomly assigned to 1 of the following treatments: 1) control diet of alfalfa haylage (CON), 2) soybean silage (SB) or 3) soybean and pearl millet silage (SB×PM). All diets were formulated to meet or exceed nutrient requirements of replacement beef heifers targeted to gain 0.79 kg/d. These same diets were fed to 90 Angus-Simmental beef replacement heifers [body weight (BW) = 366 kg; body condition score (BCS) = 5.53; age = 377 ± 11 d] 65 d prior to timed artificial insemination (TAI). Heifers were randomly allotted by breed, BCS and BW to 1 of the 3 treatments, with 3 reps/treatment. Diets were terminated 21 d post-TAI and heifers were commingled and placed on a common diet. Pubertal status was determined by progesterone concentrations of 2 blood samples taken 10 d apart prior to both trial initiation as well as initiation of estrous synchronization. Ovulatory follicle diameter was determined at time of breeding by ultrasonography. Pregnancy diagnosis was accomplished 35 and 66 d post-TAI, respectively, to calculate TAI and end of season pregnancy rates. Neither SB nor SB×PM had an effect (P > 0.37) on apparent ruminal digestion of nutrients compared to the CON. Final BW (414 kg; P ≥ 0.10) and BCS (5.28; P ≥ 0.26) for the heifers were similar among treatments. Likewise, there were no differences in TAI (48%; P > 0.43) or overall breeding season (93%; P > 0.99) pregnancy rates. Ovulatory follicle diameters (11.7 mm) was not different (P > 0.19) among treatments. In summary, forage soybean-based silages, with and without pearl millet, was an acceptable alternative forage for developing replacement beef heifers.

Two experiments were conducted to evaluate the effect of feeding corn modified wet distillers grain plus solubles (MWDGS; 48% DM) co-ensiled with chopped whole plant corn (WC) on growth performance, dietary intake, and nutrient digestibility of beef cattle. In Exp. 1, 96 Angus-crossed heifers (2 yr old; 522 ± 49.1 kg BW; 5.3 ± 0.1 BCS) were stratified and blocked according to BW and stratified by BCS in each block in a randomized complete block design (24 pens; 4 heifers/pen; 6 treatment replications). Groups were assigned to 1 of 4 dietary treatments for a 62 d trial. Treatments were 1) corn silage (CS) and soybean meal (CON), 2) MWDGS co-ensiled with chopped whole plant corn (WC; CO-EN), 3) CS mixed with MWDGS at feeding (CS+WDG), and 4) CS mixed with dry distillers grain plus solubles (DDGS) at feeding (CS+DDG). In Exp. 2, 4 crossbred beef steers (initial BW = 278 ± 18 kg) fitted with permanent ruminal cannulas were used in a balanced 4 × 4 Latin square to test the effects of feeding MWDGS co-ensiled with WC on DM intake, ruminal fermentation characteristics, and total tract digestibility. There were four 14-d periods, with 10 d for diet adaptation and 4 d for samples collection. Orthogonal contrasts were used and compared CON vs. diets containing distillers grains (DGD), CO-EN vs. diets where distillers grains were mixed at feeding (MIX), and CS+WDG vs. CS+DDG. In Exp. 1, the CON fed heifers resulted in greater G:F (P = 0.04) compared with those fed DGD. However, ADG (P = 0.03), final BW (P = 0.04), and BW gain (P = 0.03) were greatest for DGD diets compared with CON and greatest (P = 0.04) for CO-EN when compared with MIX. Apart from a slightly greater acetate concentration (P = 0.05), which resulted in a greater acetate to propionate ratio (P = 0.03) for the CON diet compared with DGD, no important differences were observed on intake, diet digestibility, or fermentation characteristics when comparing the CON treatment with DGD or when comparing CS+WDG with CS+DDG. However, the CO-EN diet resulted in decreased DMI (P = 0.05) and consequently decreased OM (P = 0.05), N (P = 0.04), and NDF (P = 0.02) intakes compared with MIX. Data from these studies suggest that MWDGS co-ensiled with WC can successfully replace traditional corn-based diets supplemented with soybean meal and corn silage diets supplemented with distillers grains without compromising digestibility and growth performance in pregnant heifers.

Two experiments were conducted to evaluate the effects of feeding corn modified wet distillers grain plus solubles (MWDGS) co-ensiled with direct-cut forage (DC) to beef steers, on feedlot performance and total tract digestibility. In Exp. 1, sixty-four crossbred Angus steers (n = 64; 329 ± 43 kg) were blocked by BW and randomly assigned to 1 of 4 dietary treatments: 1) corn-silage and soybean meal (CON), 2) DC co-ensiled with MWDGS (CO-EN), 3) haylage mixed with MWDGS at feeding (H+WDG), and 4) haylage mixed with dry distillers grains plus solubles at feeding (H+DDG). Steers were harvested when they reached an endpoint of 1.1 cm of 12th-rib back fat. In Exp. 2, four ruminally cannulated beef steers (initial BW = 556 ± 31 kg) were used in a 4 × 4 Latin square to evaluate digestibility of diets used in Exp. 1. Experimental periods were 14 d in length with 10 d for diet adaptation and 4 d for sample collection. Three linear orthogonal contrasts were used to compare effects of 1) CON vs. diets containing distillers grains (DGD), 2) CO-EN vs. diets where distillers grains were mixed at feeding (MIX), and 3) H+WDG vs. H+DDG. In Exp. 1, DMI was less (P < 0.001) for steers fed CON compared with those fed DGD and greatest (P < 0.001) for steers fed CO-EN compared with MIX. Corn-silage- and soybean-meal-fed steers had more days on feed than those fed DGD (P = 0.001). Body weight gain (P = 0.02) was greater for CO-EN compared with MIX. Fat thickness at the 12th and 13th ribs was greater (P = 0.03) for DGD steers compared with CON steers. Hot carcass weight was greater (P = 0.03) for steers fed CO-EN compared with those fed MIX. Steers fed CON resulted in greater marbling scores (P = 0.01) compared DGD-fed steers. Longissimus muscle area was greater (P = 0.01) for CON-fed steers compared with all other treatments. In Exp. 2, no differences (P > 0.10) in DM, OM, or N intakes were observed. Apparent total tract DM (P = 0.01) and N (P = 0.02) digestibility were greatest in steers fed CON compared with all others. Steers fed DGD had less (P = 0.02) rumen NH3 concentrations compared with CON. The CON diet resulted in greater molar concentrations of VFA (P = 0.03) and decreased acetate to propionate ratio (P = 0.03) compared with all DGD. These data suggest that feeding MWDGS co-ensiled with direct-cut forage results in reduced diet digestibility but equal or greater feedlot performance and similar carcass and characteristics when compared with a corn diet supplemented with soybean meal and diets where MWDGS and DDGS were added at the mixer.

'Homestead' (Reg No CV-255, PI 655522) Canada wildrye (Elymus canadensis L) was developed cooperatively by USDA-ARS and the University of Nebraska and was released in 2008 for use in the Great Plains and the Midwest USA, a region for which no adapted cultivars were previously available It was developed by means of the Ecotype Selection Breeding System from a collection made in a remnant prairie in Eastern Nebraska USA Homestead, which was tested as NE3, is adapted to Plant Adaptation Region (PAR) 251-5 (Temperate Prairie Parkland-Plant Hardiness Zone 5), which is its origin, and in which it has been evaluated in both space-transplanted and sward trials This region is equivalent to USDA Plant Hardiness Zone 5 of the tallgrass-prairie ecoregion of the Midwest, USA When grown in its area of adaptation, it produces more forage than the previously available, unadapted cultivar of the species and its forage has higher in vitro dry matter digestibility than another adapted experimental strain to which it was compared in sward forage yield trials Its primary use will be as a native cool-season grass component of conservation, roadside, and grassland seeding mixtures

Sorghum brown midrib (bmr) mutants have reddish-brown vascular tissues in their leaves and stems as a result of changes in lignin content and subunit composition. Past research at Purdue University has generated a set of bmr sorghum mutants via chemical mutagenesis and established some to be allelic to each other. More recently, we identified additional spontaneous mutants in true breeding lines with marked phenotype and a range of agronomic characteristics. One such mutant, bmr-26, is of particular interest because it arose in a drought-tolerant sorghum line. Analysis of testcross hybrids between this spontaneous bmr mutant and the chemically induced mutants, bmr-6 and bmr-12, showed that the bmr-26 allele was allelic to bmr-12 and not to bmr-6. Both the bmr-12 and the bmr-26 mutations significantly reduced lignin content in leaf, blade, sheath, stem, and panicle tissue. The effect of the mutation was relatively more severe in bmr-12 than in bmr-26. The impact of the two mutations on cell wall composition in different tissues varied. The biggest effect of the bmr-12 mutation was in reduction of lignin in the sheath, whereas lignin content in panicles was more affected by the bmr-26 mutation. This suggested an allele-specific effect in tissue lignin reduction of these mutants. Cellulose and hemicellulose concentrations were also significantly higher in certain tissue types for both the induced and spontaneous mutants. Forage quality traits including percent NDF and ADF were significantly increased by both mutations. Improvement in in vitro dry matter digestibility as a result of the bmr-26 mutation was relatively small and was not proportional to the reduction in the lignin content. Key words: Acid detergent fiber (ADF), bmr, brown midrib, in vitro dry matter digestibility (IVDMD), lignin, neutral detergent fiber (NDF), Sorghum bicolor.

Fertilization with K and P impacts alfalfa (Medicago sativa L.) yield, but how these nutrients influence taproot reserves and gene expression is unknown. Our objectives were to determine how P and K impact (i) alfalfa yield and yield components, (ii) accumulation and use of taproot carbon (C) and nitrogen (N) pools, and (iii) transcript levels for β‐amylase, sucrose synthase, and the high molecular weight vegetative storage protein in alfalfa taproots. Yield and yield components were determined at 30‐d intervals beginning in late May. Roots were sampled after the late June harvest (Day 0) and 1, 3, 6, 10, 14, 21, and 30 d thereafter. Addition of P and K increased forage yield by enhancing mass per shoot. High P resulted in rapid starch use, while taproots of plants fertilized with K had low sugar concentrations. Transcripts decline by Day 6 and by Day 10 were below detection limits. Transcripts for β‐amylase and sucrose synthase accumulated rapidly after Day 10 in taproots of plants fertilized with both P and K. Balanced P and K nutrition resulted in the accumulation and effective utilization of C and N reserves and in improved alfalfa adaptation to defoliation.

Addition of P and K fertilizer can increase alfalfa (Medicago sativa L.) yield and stand persistence, but the yield components associated with P‐ and K‐induced variation in agronomic performance are not clear. Our objectives were: (i) to determine the impact of P and K nutrition on productivity of a relatively old alfalfa stand; and (ii) determine which yield components are associated with changes in alfalfa forage yield. Treatments were a factorial combination of four P and five K rates replicated four times. Forage harvests occurred four times annually. Plant populations were determined in early December and late May each year. When compared to unfertilized plots, addition of P and K increased forage yield each year. Fertilization with P decreased plants m−2 at all K application rates, but especially in plots fertilized with P, but not K. By comparison, plots fertilized with K, but not fertilized with P, had the higher plant population densities. Although regression analysis eventually revealed a positive association between forage yield and shoots m−2 in 2003 and 2004, the greatest forage yields were not obtained in plots with the greatest plant population densities, shoots plant−1 or shoots m−2 Regression and path analysis revealed that improved forage yield in P‐ and K‐fertilized plots was consistently associated with greater mass shoot−1

Canada wildrye (Elymus canadensis L.) and Virginia wildrye (Elymus virginicus L.), which are native to the USA, were collected from remnant Midwest prairies. The objectives of this study were to determine the genetic variability among the collected accessions for biomass yield and other traits, determine the extent of genotype × environment interactions for these traits across Midwest environments, and to determine the relationship between the geographical location of the collection site and evaluation sites for these accessions for plant biomass yield which can be used as a measure of adaptation. Seed collected from six Midwest states was bulked by collection site to form individual accessions. Space transplanted evaluation nurseries were established at Mead, NE, Ames, IA, and West Lafayette, IN, and accessions were evaluated on a plot basis for 2 yr. There was significant genetic variation among accessions for post‐heading forage yield, heading date, height, pre‐heading in vitro dry matter digestibility (IVDMD) and crude protein (CP) concentration, and post‐heading CP concentration. Strain × location (S × L) interaction effects were only significant for post‐heading IVDMD and height indicating that for the other traits, the relative ranking of the strains was similar at all three locations over the two evaluation years. Regression analyses of the effect of distance of the collection site from the evaluation site (direct, east or west, and north or south) on biomass yield were largely nonsignificant or had very low R2 values. These regression results along with the nonsignificant S × L effects from the analysis of variance indicate that longitudinal or latitudinal adaptation gradients for plant biomass yield are lacking for Canada wildrye accessions from Midwest prairies. All but five of the Canada wildrye accessions had higher biomass yield than the only released cultivar, Mandan, indicating that this germplasm can be used to develop improved cultivars that should be adapted to the region represented by the collection and evaluation sites.

Phosphorus and K fertilization increases alfalfa (Medicago sativa L.) yield and stand persistence, but the changes in yield components as affected by P and K fertility level are not known. Our hypothesis is that P and (or) K fertilization will increase one or more alfalfa yield components, and those component responses may change with stand age. The objectives of this field study were to determine the impact of P and K fertilization on alfalfa forage yield and yield components during the initial 3 yr after establishment. Treatments were the factorial combinations of four P rates (0, 25, 50, and 75 kg P ha(-1)) and five K rates (0, 100, 200, 300, and 400 kg K ha(-1)) arranged in a randomized complete block design with four replications. Forage harvests occurred four times annually, and yield, mass shoot(-1), and shoots area(-1) were determined. Plant populations were determined in early December and late May each year. Incremental additions of P and K increased alfalfa yield in each year. Potassium fertilization did not influence plant population, while robust P-responsive alfalfa plants apparently crowded out smaller, less vigorous plants thus decreasing plants m(-2). Stand assessments based on shoot counts, or aboveground plant counts may not accurately indicate alfalfa yield potential. Shoots plant(-1) was not affected by application of either nutrient, while shoots m(-2) generally declined with increased P and K fertilization. Improved forage yield of P- and K-fertilized plots was consistently associated with greater mass shoot(-1). Because fertilizer-responsiveness is closely associated with greater mass shoot(-1), cultivars possessing this trait may be relatively more productive under well-fertilized conditions.

Glandular-haired alfalfa ( Medicago sativa L.) cultivars resistant to potato leafhopper [ Empoasca fabae Harris] (PLH) have not been evaluated for forage quality across a wide region. Our objective was to compare forage quality of PLH resistant and susceptible alfalfa cultivars with and without insecticide control of PLH across the Midwest USA. Six commercially released PLH resistant and five susceptible cultivars were evaluated from 1996 to 1997 in field experiments in Ohio, Indiana, Wisconsin, and Minnesota. The resistant cultivar group was more mature at harvest but equal to or higher ( P ≤ 0.05) in crude protein (CP) concentration than the susceptible group regardless of insecticide treatment. Averaged over all harvests, the CP advantage for the resistant group was 11 to 13 g kg −1 for insecticide treated and untreated controls, respectively. Without insecticide, the resistant group was equal to or lower ( P ≤ 0.05) in neutral detergent fiber (NDF) and equal to or higher ( P ≤ 0.05) in in vitro digestible dry matter (IVDDM) than the susceptible group, except at harvests when PLH severely stunted the susceptible cultivars, which likely increased leaf/stem ratio. With insecticide, the resistant group was lower in NDF by 15 to 25 g kg −1 and higher in IVDDM by 19 g kg −1 than the susceptible group. Potato leafhopper feeding had less effect on forage quality and maturity of PLH resistant cultivars than susceptible cultivars. The PLH resistant cultivars we evaluated generally had higher forage quality than susceptible cultivars when grown with or without insecticide application despite being more mature at harvest.

ABSTRACTIn vitro dry matter digestibility (IVDMD) was improved by three cycles (C) of recurrent selection in a switchgrass (Panicum virgatum L.) population but significant winter kill occurred in the Cycle 4 (C4) mass selection nursery. Stand density losses in strains differing in IVDMD also were noted in pastures intensively grazed for 3 yr. Two studies were conducted to evaluate the effect of genetic changes in IVDMD on plant survival of switchgrass. Seed was harvested from the original high IVDMD C3 parent clones to produce half‐sib family seedlings that were planted into a replicated half‐sib progeny evaluation nursery in 1991 at Mead, NE. This nursery was harvested in 1993 and 1995 for biomass yield after plants had headed, forage was analyzed for IVDMD, and plant survival was determined. There were significant differences among the families for biomass yield, IVDMD, and plant survival. Among the half‐sib families, the correlations of 1993 and 1995 IVDMD with 1995 survival were not significant nor were the correlations between 1993 and 1995 yields and 1995 stands. In the C3 high IVDMD populations, some families had decreased winter survival but other families had high IVDMD and good survival. Randomly selected plants from pasture trials (PC or pasture clones) of ‘Trailblazer’ and ‘Pathfinder’ were polycrossed and the resulting bulk populations were evaluated with parent populations in replicated sward trials at three locations along with the High IVDMD C3 population and its derived winter survival (WS) population produced by harvesting bulk seed from surviving plants in the C4 selection nursery. Differences among populations for stand were not detected in the sward trials, likely because survival and IVDMD have low correlations within populations. It should be feasible to continue to breed for high IVDMD in switchgrass but survival will need to be an additional selection criterion.

Addition of phosphorus (P) and potassium (K) fertilizer is vital to maintain alfalfa productivity. The objective of this study was to examine how P and K fertilizer application increases alfalfa yield, nutrient use, and plant persistence. Replicate plots of P (0, 50, 100, 150 lbs P2O5/acre) and K (0, 100, 200, 300, 400 lbs K2O/acre) treatments were arranged in a factorial design. Forage harvests occur-red four times annually for 3 years and yield, mass per shoot, shoots per area, and herbage nutrient concentrations were determined. Roots were dug in May and December of each year to ascertain plant populations and determine whether plants were dying during the summer (May to December) or during the winter (December to May). Total annual yield increased with application of P and K, but K application did not increase first harvest yield. Yield increases were due to greater mass per shoot. Addition of P decreased plant populations, whereas K did not alter stand populations. Removal rates of K exceeded K application each year even at the highest (400 lbs K2O/acre/yr) rate.

Glandular‐haired alfalfa ( Medicago sativa L.) cultivars developed for resistance to potato leafhopper [ Empoasca fabae Harris] (PLH) have not been evaluated across a wide geographic area. Our objective was to evaluate forage growth, yield, insect damage, and stand density of glandular‐haired and standard alfalfa cultivars with and without insecticide control of naturally occurring PLH infestations across the Midwest USA. Nine glandular‐haired and five standard cultivars were evaluated from 1996 to 1998 in field experiments in Ohio, Indiana, Wisconsin, and Minnesota. Scheduled insecticide applications increased total yield of all cultivars, the response declining with increasing latitude (yield advantage = 32.7 − 0.72 × latitude; r 2 = 0.86, P = 0.05). Depending on location, total yield loss due to PLH damage ranged from 5 to 23% for the standard cultivars and 1 to 10% for the glandular‐haired, commercially released cultivars (GR). Yield loss from PLH feeding in the GR cultivars was less than half of that observed in standard cultivars in environments where PLH stress was high. The GR cultivars yielded 1.1 Mg ha −1 more per year on average than the standard cultivars without insecticide under high PLH stress in Ohio and Indiana. Potato leafhopper nymph densities were lower in glandular‐haired cultivars than in standard cultivars. Cultivars had similar yield when treated with insecticide or when PLH populations were low. Glandular‐haired alfalfa cultivars were not immune to PLH damage; however, they can substantially reduce yield losses caused by this pest and provide a useful new tool for integrated pest management strategies.

Alfalfa (Medicago sativa L.) cultivars are available that produce high-quality forage; however, information is lacking on the consistency of cultivar forage quality over environments and the influence of stand age on quality. Our objectives were to evaluate alfalfa cultivars for consistency of forage quality over time and environments and to test the validity of sampling seeding-year stands for forage quality. We sampled eight alfalfa entries (seven cultivars and one experimental germplasm) at bud and flower maturity stages in the seeding year (one harvest) and first production year (two harvests) in six states (Indiana, Kentucky, Minnesota, New York, Washington, and Wisconsin). ANOVA and orthogonal contrast analyses were conducted to assess entry X environment interactions for forage quality. First-cut forage in the first production year had lower forage quality than third-cut forage, and differences between entries were more pronounced at the first cutting. Including seeding-gear data in the ANOVA produced a complex Location X entry X stand age interaction, indicating that seeding year data alone cr ere insufficient to characterize alfalfa entries for forage quality. 'Cimarron VR', 'Arrow', and '5432' had the greatest stability for forage quality and could serve as high, medium, and low forage-quality checks, respectively, in forage quality testing trials. 'WL 322 HQ' and 'Pacesetter' often had high quality, but were not stable for forage quality over environments, Correlations between crude protein, acid detergent fiber (ADF), neutral detergent fiber (NDF), and in vitro digestible dry matter were consistent across locations, entries, cuttings, and maturities. The high correlation between NDF and ADF (r greater than or equal to 0.97, P less than or equal to 0.05) suggests that it may not be necessary to use both procedures to predict entry differences in forage quality.

Crop ScienceVolume 36, Issue 6 cropsci1996.0011183X003600060051x p. 1713-1713 Registration of Cultivars Registration of ‘Shawnee‘ Switchgrass K. P. Vogel, Corresponding Author K. P. Vogel dpl@unity.ncsu.edu Corresponding author (dpl@unity.ncsu.edu).Search for more papers by this authorA. A. Hopkins, A. A. HopkinsSearch for more papers by this authorK. J. Moore, K. J. MooreSearch for more papers by this authorK. D. Johnson, K. D. JohnsonSearch for more papers by this authorI. T. Carlson, I. T. CarlsonSearch for more papers by this author K. P. Vogel, Corresponding Author K. P. Vogel dpl@unity.ncsu.edu Corresponding author (dpl@unity.ncsu.edu).Search for more papers by this authorA. A. Hopkins, A. A. HopkinsSearch for more papers by this authorK. J. Moore, K. J. MooreSearch for more papers by this authorK. D. Johnson, K. D. JohnsonSearch for more papers by this authorI. T. Carlson, I. T. CarlsonSearch for more papers by this author First published: 01 November 1996 https://doi.org/10.2135/cropsci1996.0011183X003600060051xCitations: 43AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume36, Issue6November–December 1996Pages 1713-1713 RelatedInformation