Polyphenol oxidase (PPO) in red clover (RC) has been shown to reduce both lipolysis and proteolysis in silo and implicated (in vitro) in the rumen. However, all in vivo comparisons have compared RC with other forages, typically with lower levels of PPO, which brings in other confounding factors as to the cause for the greater protection of dietary nitrogen (N) and C18 polyunsaturated fatty acids (PUFA) on RC silage. This study compared two RC silages which when ensiled had contrasting PPO activities (RC+ and RC−) against a control of perennial ryegrass silage (PRG) to ascertain the effect of PPO activity on dietary N digestibility and PUFA biohydrogenation. Two studies were performed the first to investigate rumen and duodenal flow with six Hereford×Friesian steers, prepared with rumen and duodenal cannulae, and the second investigating whole tract N balance using six Holstein-Friesian non-lactating dairy cows. All diets were offered at a restricted level based on animal live weight with each experiment consisting of two 3×3 Latin squares using big bale silages ensiled in 2010 and 2011, respectively. For the first experiment digesta flow at the duodenum was estimated using a dual-phase marker system with ytterbium acetate and chromium ethylenediaminetetraacetic acid as particulate and liquid phase markers, respectively. Total N intake was higher on the RC silages in both experiments and higher on RC− than RC+. Rumen ammonia-N reflected intake with ammonia-N per unit of N intake lower on RC+ than RC−. Microbial N duodenal flow was comparable across all silage diets with non-microbial N higher on RC than the PRG with no difference between RC+ and RC−, even when reported on a N intake basis. C18 PUFA biohydrogenation was lower on RC silage diets than PRG but with no difference between RC+ and RC−. The N balance trial showed a greater retention of N on RC+ over RC−; however, this response is likely related to the difference in N intake over any PPO driven protection. The lack of difference between RC silages, despite contrasting levels of PPO, may reflect a similar level of protein-bound-phenol complexing determined in each RC silage. Previously this complexing has been associated with PPOs protection mechanism; however, this study has shown that protection is not related to total PPO activity.

A three-year experiment was conducted near Scottsbluff, NE, to evaluate the selectivity of POST-applied imazethapyr for weed control in alfalfa, birdsfoot trefoil, cicer milkvetch, red clover, sainfoin, and yellow sweetclover. Imazethapyr injured all legumes 15 DAT. Imazethapyr also reduced the height of birdsfoot trefoil, cicer milkvetch, red clover, and yellow sweeclover 28 DAT. Legume first cutting yields were not reduced by imazethapyr and with alfalfa, birdsfoot trefoil, cicer milkvetch, and sainfoin, first cutting yields were increased by imazethapyr. Imazethapyr reduced weed biomass in all legume seedings. Weed biomass in new seedings of alfalfa was reduced more than that of the other legumes.

Data obtained from two experiments were used to identify and describe factors affecting crop loss due to weeds in forage stands. Timothy (Phleum pratense L. ‘Champ′) was established in presence or absence of barley (Hordeum vulgare L. ‘Bruce′), red clover (Trifolium pratense L. ‘Florex′), broadleaf weeds, and grass weeds. Botanical composition, soil water, soil nutrients, light interception, and plant cover were determined 4 and 6 weeks after seeding, and crop yield was determined at periodic forage harvest dates. Principal components analyses permitted the extraction of 12 factors and regression analyses demonstrated that these factors can be used to describe crop yield. Each factor can be estimated either by obtaining the rotated factor scores or by selecting a representative variable that can be substituted for the rotated factor scores in the regression models. The approach described in this paper should be tested with other crops and other weed complexes. It is suggested to use weed density in combination with weed and crop cover data to predict crop loss.

Sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} and RO-13-8895 {acetone-O-[d-2-[p-[(α,α,α-trifluoro-p-tolyl)-oxy]phenoxy]propionyl]oxime} were evaluated for quackgrass [Agropyron repens (L.) Beauv. ♯ AGRRE] control in ‘Norcen’ birdsfoot trefoil [Lotus corniculatus (L.)], ‘Monarch’ cicer milkvetch [Astragalus cicer (L.) Hook.], and ‘Arlington’ red clover [Trifolium pratense (L.)]. None of the herbicide treatments applied to weed-free legumes 3, 15, and 30 cm tall reduced crop ground cover or seed yield. Postemergence treatments of sethoxydim and RO-13-8895 applied to quackgrass in the one- to four-leaf stage, at rates from 0.56 to 1.1 kg ai/ha, gave control of 57 to 91% in September of the seedling year. Legumes in all postemergence herbicide-treated plots produced more seed than legumes in untreated plots, regardless of time of application. Sequential applications of sethoxydim, RO-13-8895, or fluazifop {(±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]propanoic acid} at 0.14 plus 0.14 kg ai/ha gave more effective quackgrass control and greater legume ground cover than single applications at 0.28 kg ai/ha.

Greenhouse studies were conducted using bentgrass (Agrostis tenuis Sibth. ‘Highland′) as a bioassay species to measure herbicidal activity of 3.4 kg/ha of the isopropylamine salt of glyphosate [N-(phosphonomethyl)glycine] when applied directly to the soil surface prior to bentgrass emergence. Activity of glyphosate also was examined by applying glyphosate to a moist soil surface and placing alfalfa (Medicago sativa L. ‘Vernal′) and red clover (Trifolium pratense L. ‘Kenstar′) seeds on the sprayed surface 3, 6, 9, and 24 h later. In two high-organic soils, glyphosate reduced bentgrass growth in each of four experiments, even when applied up to 5 days before bentgrass emergence. Significant glyphosate activity was measured in one of the experiments in another organic soil and in three of the experiments in a Chehalis sandy loam soil. Germination and growth of alfalfa and red clover were reduced when seeds were distributed on a sprayed soil surface up to 24 h after glyphosate application. These results show that glyphosate, at least under certain conditions, can cause significant crop injury when used prior to planting or emergence of some species.

Allelopathy has been suggested as a mechanism of interference in several weed species. Allelochemicals released from certain weed species influence the growth and yield of crop species. Several laboratory studies present circumstantial evidence of the occurrence of allelopathy as a causative agent in weed–crop agroecosystems. Field evidence, however, is still lacking. In this paper, the significance of field studies is argued in terms of a multifaceted approach to allelopathy, and mugwort is used as an example. Previous research demonstrated the allelopathic potential of mugwort; however, experiments were not carried out in a natural environment. Inderjit and Foy (1999) have demonstrated that chemical characteristics (pH, inorganic ions, and phenolics) of soil amended with mugwort leaf leachate were altered when compared to unamended soil. We have analyzed the mugwort-infested field soil and compared its chemical characteristics with those of amended soils. No definite trend, in terms of influence of mugwort on soil chemistry, was observed. Results indicate the importance of field studies in order to obtain ecologically relevant data from laboratory studies. Field situations are often complex in terms of the presence of interfering flora. Cyanobacteria, for example, play an important role in weed–crop interactions in rice paddy soils. Allelochemicals released from weed species present in the paddy field may influence nitrogen-fixing cyanobacteria in addition to their phytotoxic effects to the paddy crop. Significance of phytotoxic effects of weed species on crop growth, and N2-fixing potential of cyanobacteria in paddy soils is discussed.

Genetic diversity of a red clover global collection was assessed using 36 simple sequence repeat (SSR) primers representing all seven linkage groups (LGs). The number of fragments amplified ranged from 1 to 6 for all the primers. Primer RCS0060 detected highest number of fragments, whereas four SSRs viz., RCS0899, RCS1594, TPSSR40 and RCS6927 amplified single fragment. Size range of amplicons generated by all the primers varied from 100 to 400 bp. Polymorphism information content values ranged from 0.301 to 0.719 with an average value of 0.605. LG wise diversity analysis showed that LG 3 was most diverse (I = 0.65, Ht = 0.44), whereas LG-1 showed minimum diversity (I = 0.48, Ht = 0.26) for the microsatellites used. Bayesian model-based clustering inferred three genetically distinct populations in the red clover germplasm holding and showed considerable admixture in individuals within clusters. Neighbour-joining analysis showed intermixing of accessions within groups. Principal component analysis plot complemented the clustering shown by Structure and distinguished three populations to greater extent. Analysis of molecular variance showed that 91% of the genetic variation was residing within populations, while 9% variation was among populations. Overall, the results showed that a high level of genetic diversity is prevailing in this worldwide collection of red clover, which can be exploited for its genetic improvement through breeding approaches.

Ex situ seed banks provide an effective conservation and utilization system for crops and their wild relatives. Efforts are made to reduce genetic drift in conservation, where regeneration is a critical step. In the present study, we examined eight wild populations of red clover (Trifolium pratense L.) according to 13 morphological and phenological traits. Samples of original collected seed were grown and compared with plants from first and second ex situ generation, with commercial cultivars and landraces being included for purposes of comparison. Variance analysis and Tukey multiple comparisons of means showed that the commercial cultivars and landraces were clearly distinct from the wild populations and were excluded from the further analysis. Despite the fact that the wild accessions were collected from a geographically delimited region in Norway, they exhibited significant differences in several of the measured traits. The main phenotypic patterns remain after ex situ regenerations. However, the mean values for four of the examined traits (across accessions) did change significantly from one generation to the next. Two of the eight accessions had significantly changed from one generation to the next, a tendency was observed across all the studied traits. The results were discussed in terms of regeneration circumstances. Observed changes appeared to be directional, going from populations with predominantly wild morphological types towards plants more closely resembling the commercial cultivars. Such a directional change implies that selection or gene flow has been acting on the accessions during regeneration, rather than random changes owing to genetic drift.

A primary challenge of managing vegetable production on a small land base is the maintenance and building of soil quality. Previous studies have demonstrated the benefits of cover crops for improved soil quality; however, small growers struggle to fit cover crops into rotations. Small-scale growers with limited available land are under significant pressure to maximize their saleable yield and often work to maximize output by using intensive cropping practices that may include both early and late season crops, thus limiting the typical shoulder season windows in which cover crops can be grown. In-season living mulches may be an effective strategy to provide small-scale growers the benefits of cover crops with less land commitment than cover crops used in typical rotations. However, research on living mulches is generally not suited to small-scale organic production systems due to the typical reliance on chemical herbicide to suppress mulches. An experiment was designed with the goal of evaluating living mulch systems for space-limited organic vegetable production. In a 2-year study, four living mulch crops (buckwheat (Fagopyrum esculentum), field pea (Pisum sativum), crimson clover (Trifolium incarnatum) and medium red clover (Trifolium pratense)) and a cultivated control with no mulch cover were planted in early spring each year. Snap beans (Phaseolus vulgaris var. Tavera), transplanted bell peppers (Capsicum annuum var. Revolution), and transplanted fall broccoli (Brassica oleracea var. Imperial) were then planted directly into living mulches. During each summer growing season, living mulches and weeds were mown between-rows and hand-weeded in-row approximately every 10–14 days as needed for management. Labor times for mowing and cultivation were found to be higher in all treatments relative to the cultivated control. An inverse relationship between living mulch biomass and weed biomass was observed, demonstrating that living mulches may contribute to weed suppression. However, lower vegetable yields were seen in the living mulch treatments, most likely due to resource competition among vegetables, living mulches and weeds. High pre-existing weed seedbank and drought conditions likely increased competition and contributed to reduced vegetable yield.

Twenty-four twin-bearing mature Mule ewes were used to evaluate the effects of feeding ensiled red clover (Trifolium pratense), lucerne (Medicago sativa) or perennial ryegrass (Lolium perenne) during late pregnancy on subsequent ewe and lamb performance. Eight weeks prior to lambing the ewes were individually penned and offered one of the treatment forages ad libitum (no. = 8 per silage). All ewes were supplemented with molassed sugar-beet shreds to avoid dietary energy being a limiting factor and to ensure the responses were primarily attributable to the forage protein content. Individual intakes of the ewes were determined daily and weekly measurements of ewe live weight and body condition score were made. The ewes were also scanned weekly for depths of subcutaneous fat and longissimus dorsi (LD) muscle. Blood samples were taken at 6, 4, 2, and 1 week(s) before lambing, 24 h after lambing and at 3 weeks after lambing and were analysed for serum concentrations of total protein (TP), albumin, urea, beta-hydroxybutyrate (BHB) and plasma concentrations of glucose and non-esterified fatty acid (NEFA). After lambing all ewes and their lambs were turned out to graze together on a ryegrass sward. The lambs were weighed at birth and at weekly intervals thereafter until 12 weeks post partum. The lucerne silage offered had a higher dry matter (DM) content than the red clover and ryegrass silages (367, 305 and 314 g DM per kg fresh matter, respectively; P < 0·001). Forage type significantly affected crude protein (CP) concentration (240, 215 and 182 g CP per kg DM for lucerne, red clover and ryegrass silages, respectively) and metabolizable energy (ME) density (11·1, 11·6 and 10·8 MJ ME per kg DM respectively). Ewes offered the legume silages had higher intakes of DM, CP and ME than ewes offered ryegrass silage (P < 0·05), which was reflected in higher ewe live-weight gain (P < 0·05) but not in litter birth weight (P > 0·05). Silage treatment affected serum concentrations of TP, albumin, globulins and urea during the last 4 weeks of pregnancy (P < 0·05). Lambs born from ewes offered lucerne and red clover silages prior to lambing had higher growth rates from birth to 3 weeks of age than those from ewes offered ryegrass silage (320, 323 and 282 g/day, respectively; P < 0·05). Lamb live weight at 12 weeks of age was higher for lambs from ewes that had been offered the red clover silage, at 29·1 kg compared with 26·7 and 27·1 kg for lambs from ewes previously offered lucerne and ryegrass silages (P < 0·05). In conclusion, the results showed that red clover and lucerne silages are better able to meet nutrient requirements of ewes in late pregnancy than grass silage.