Adjacent Monocultures Research Articles

A Forage Allowance by Forage Type Interaction Impacts the Daily Milk Yield of Early Lactation Dairy Cows.

We tested for a forage allowance effect on the milk yield of early lactation dairy cow herds grazing swards sown with perennial ryegrass (Lolium perenne L.), white clover (Trifolium repens L.) and plantain (Plantago lanceolata L.) relative to perennial ryegrass alone. The examined allowances consisted of offering 12, 14, 16, 18, 20 or 25 kg of dry matter (DM)/cow per day of grazeable herbage, with diverse swards sown as mixtures and spatially adjacent monocultures. After adapting cows to their assigned forage type for 8 days, treatment effects on milk yield and composition, blood metabolites (beta-hydroxybutyrate, non-esterified fatty acids and urea concentrations), body weight change, forage intake and selection differentials for forage species and certain nutrients were monitored over 7 days. We confirmed a forage allowance effect on milk yield improvements in dairy cows grazing diverse swards relative to perennial ryegrass monocultures. Improvements in milk yield were evident at forage allowances of 14 to 20 kg of DM/cow per day, diminishing at the highest allowance of 25 kg of DM/cow per day. Improvements in milk yield for the mixture and spatially adjacent monocultures peaked at forage allowances of 18 and 16 kg of DM/cow per day, equalling increases of 1.3 and 1.2 kg of milk/cow per day, respectively.

Digging deeper: microbial communities in subsoil are strongly promoted by trees in temperate agroforestry systems

AimsTemperate alley-cropping agroforestry systems maintain agricultural production while offering several environmental benefits. Central benefits of agroforestry systems such as the ‘safety-net’-role of the trees for leached nutrients are mainly due to processes occurring below the soil surface: the subsoil. Microorganisms in the subsoil may play a key role in the ‘safety-net’-function as they can improve the capturing and uptake of nutrients by the trees. Systematic investigations of microbial communities in temperate agroforestry systems, however, are restricted to topsoil.MethodsWe quantified bacteria, fungi, and functional groups of microorganisms in the topsoil and subsoil of two alley-cropping systems using real-time PCR. Topsoil and subsoil samples were collected in the tree rows and at multiple distances from the trees within the crop rows of the agroforestry systems as well as at an adjacent monoculture cropland.ResultsMicrobial population size decreased with soil depth likely due to limited resource availability in subsoil. Tree rows in agroforestry systems not only promote soil microbial populations in both the topsoil and subsoil but the promotion also extends gradually into the crop rows of the systems. The promotion of microorganisms through trees is stronger in subsoil than topsoil, pointing at more intense resource scarcity in the subsoil than topsoil.ConclusionsWe propose that tree root-derived resources and root litter, which are scarce in agricultural subsoils, triggered the strong positive response of the subsoil community to the trees. Finally, we provide initial evidence that subsoil microorganisms contribute to the ‘safety-net’-role of the trees in agroforestry systems.

Early response of soil fungal communities to the conversion of monoculture cropland to a temperate agroforestry system.

BackgroundAlley-cropping systems in the temperate zone are a type of agroforestry in which rows of fast-growing trees are alternated with rows of annual crops. With numerous environmental benefits, temperate agroforestry is considered a promising alternative to conventional agriculture and soil fungi may play a key in maintaining productivity of these systems. Agroforestry systems that are established for more than 10 years have shown to increase the fungal biomass and impact the composition of soil fungal communities. Investigations of soil fungi in younger temperate agroforestry systems are scarce and the temporal dynamic of these changes is not understood.MethodsOur study was conducted in a young poplar-based alley cropping and adjacent monoculture cropland system in an Arenosol soil in north-west Germany. We investigated the temporal dynamics of fungal populations after the establishment of agroforestry by collecting soil samples half, one, and one and a half years after conversion of cropland to agroforestry. Samples were collected within the agroforestry tree row, at 1, 7, and 24 m distance from the tree row within the crop row, and in an adjacent conventional monoculture cropland. The biomass of soil fungi, Asco-, and Basidiomycota was determined by real-time PCR. Soil fungal community composition and diversity were obtained from amplicon sequencing.ResultsDifferences in the community composition of soil fungi in the tree row and arable land were detected as early as half a year following the conversion of monoculture cropland to agroforestry. In the tree row, soil fungal communities in the plots strongly diverged with the age of the system. The presence of young trees did not affect the biomass of soil fungi.ConclusionsThe composition of soil fungal communities responded rapidly to the integration of trees into arable land through agroforestry, whereas the fungal biomass was not affected during the first one and a half years after planting the trees. Fungal communities under the trees gradually diversified. Adaptation to spatially heterogeneous belowground biomass of the trees and understory vegetation or stochastic phenomena due to limited exchange among fungal populations may account for this effect; long-term monitoring might help unravelling the cause.

European Union Citizenship and the sorting of Europe

ABSTRACT Free movement is intended to bring Europeans together. This article suggests it may have the opposite effect: it may drive them apart. The mechanism involved is sorting. This happens when people are free to choose where to live, and choose a community which matches their preferences. This match can come about in different ways, but the result of them all is that people of particular preferences are clustered together, leading to society being structured as a series of adjacent mono-cultures. It is not a large step to suggest that this arrangement is likely to cause alienation between the communities. The fact of sorting means that they have less in common than they did before. For Europe, if sorting happens, this would imply that polarization between states would increase and the governability of the EU would be threatened. Free movement may be less a mechanism of integration than one of disintegration.

Transgressive overyielding in mixed compared with monospecific Scots pine (Pinus sylvestris L.) and oak (Quercus robur L., Quercus petraea (Matt.) Liebl.) stands – Productivity gains increase with annual water supply

Tree species mixing has become a crucial tool in European forest management as positive interactions between species have been found to promote the provision of multiple ecosystem services, while at the same time reducing the risks associated with climate change. However, mixing effects have proven to be strongly context-dependant and some species combinations have still not been studied in detail. Here we focus on mixed forests of Scots pine and oak, which are likely to become increasingly popular for balancing wood production and other ecosystem services under climate change. Using 20-year growth data from newly established triplets in Germany and Denmark, this study investigates how mean tree and stand characteristics as well as productivity in mixed Scots pine-oak stands compare with adjacent monocultures and how stable the observed productivity relation is, considering inter-annual variations in local climate. Species mixing on average resulted in 15% higher standing volume and 14% higher volume productivity compared with the weighted mean of the adjacent monocultures. Oak profited most in mixture, showing overyielding of 19%. Overyielding on the stand and species level increased in years with higher water supply. In mixture, standing volume of Scots pine was 25% higher than in monocultures. Both species were found to modify their morphology in mixture. Oak in mixture showed a significantly higher inequality in stem volume compared with monocultures. We hypothesise that the observed overyielding of Scots pine-oak mixtures mainly results from complementary light use, where differences in shade tolerance, crown architecture and leaf phenology may be contributing factors.

Pasture Production and Sheep Behavior in Mixed or Adjacent Monocultures Swards in Different Seasons of the Year

Pasture Production and Sheep Behavior in Mixed or Adjacent Monocultures Swards in Different Seasons of the Year

More milk from forage: Milk production, blood metabolites, and forage intake of dairy cows grazing pasture mixtures and spatially adjacent monocultures

There is interest in the reincorporation of legumes and forbs into pasture-based dairy production systems as a means of increasing milk production through addressing the nutritive value limitations of grass pastures. The experiments reported in this paper were undertaken to evaluate milk production, blood metabolite concentrations, and forage intake levels of cows grazing either pasture mixtures or spatially adjacent monocultures containing perennial ryegrass (Lolium perenne), white clover (Trifolium repens), and plantain (Plantago lanceolata) compared with cows grazing monocultures of perennial ryegrass. Four replicate herds, each containing 4 spring-calving, cross-bred dairy cows, grazed 4 different forage treatments over the periods of early, mid, and late lactation. Forage treatments were perennial ryegrass monoculture (PRG), a mixture of white clover and plantain (CPM), a mixture of perennial ryegrass, white clover, and plantain (RCPM), and spatially adjacent monocultures (SAM) of perennial ryegrass, white clover, and plantain. Milk volume, milk composition, blood fatty acids, blood β-hydroxybutyrate, blood urea N concentrations, live weight change, and estimated forage intake were monitored over a 5-d response period occurring after acclimation to each of the forage treatments. The acclimation period for the early, mid, and late lactation experiments were 13, 13, and 10 d, respectively. Milk yield (volume and milk protein) increased for cows grazing the RCPM and SAM in the early lactation experiment compared with cows grazing the PRG, whereas in the mid lactation experiment, milk fat increased for the cows grazing the RCPM and SAM when compared with the PRG treatments. Improvements in milk production from grazing the RCPM and SAM treatments are attributed to improved nutritive value (particularly lower neutral detergent fiber concentrations) and a potential increase in forage intake. Pasture mixtures or SAM containing plantain and white clover could be a strategy for alleviating the nutritive limitations of perennial ryegrass monocultures, leading to an increase in milk production for spring calving dairy cows during early and mid lactation.

Subsoil Phosphorus Loss: A complex problem with no easy solutions

Subsoil Phosphorus Loss: A complex problem with no easy solutions

The influence of season on lambs' feeding preference for plantain, chicory and red clover

The objective of the three studies reported here was to examine the grazing preference and diet selection of lambs for plantain (Plantago laceolata), chicory (Cichorium intybus L.) and red clover (Trifolium pratense) compared with New Zealand’s conventional ryegrass (Lolium perenne) pasture. Study One investigated the diet selection of lambs for 7 days at the beginning of March, using transects with tagged plants on a mixed plantain, chicory and red clover sward. Study Two was an outdoor preference experiment conducted in both March and May by observation of lambs on adjacent monocultures of plantain, chicory and red clover. Study Three was an indoor feeding trial that aimed to determine the intake rate and relative preference of weaned lambs for two herbages (chicory and plantain), two legumes (lucerne and red clover) and ryegrass pasture, in both spring (November) and summer (March). Study One determined that when grazing the mixed sward for a period of 7 days, the mean day that lambs commenced grazing red clover, chicory and plantain was Day 1.6 ± 0.1, 4.8 ± 0.2 and 6.2 ± 0.2, respectively, with significant (P < 0.05) differences between all species. In relation to preference as observed in Study Two, more lambs (P < 0.05) were seen to be grazing red clover at any time, and more lambs were grazing chicory (P < 0.05) than plantain. There was, also an interaction of season with preference, with plantain becoming more acceptable (P < 0.05) to the lambs in May (late autumn) versus March (early autumn). In Study Three, the term ‘preference’ refers to the natural logarithm of the ratio of amounts eaten between the forage being tested and the alternative forage offered simultaneously. This was established in triplicate by offering pairs of all the plant species side by side to individually penned lambs. The results indicated that plantain was consumed at a similar rate (P > 0.05) to that of ryegrass, whereas red clover and chicory had higher voluntary feed intakes, likely due to lower fibre content. The intake rate of chicory was greater in summer than spring and may be related to increased palatability due to the increased water-soluble carbohydrate content of chicory in summer. Regardless of season, average preference for red clover was always higher (P < 0.05) than that of chicory, plantain and ryegrass. Plantain was considerably less preferred in summer than spring. Differences in diet selection and preference may offer a unique opportunity to manipulate utilisation of pastures using a diverse range of plant species.

Impact of spatial heterogeneity of plant species on herbage productivity, herbage quality and ewe and lamb performance of continuously stocked, perennial ryegrass–white clover swards

AbstractThe benefits of white clover (Trifolium repens L.) in pastures are widely recognized. However, white clover is perceived as being unreliable due to its typically low content and spatial and temporal variability in mixed (grass‐legume) pastures. One solution to increase the clover proportion and quality of herbage available to grazing animals may be to spatially separate clover from grass within the same field. In a field experiment, perennial ryegrass (Lolium perenne L.) and white clover were sown as a mixture and compared with alternating strips of ryegrass and clover (at 1·5 and 3 m widths), or in adjacent monocultures (strips of 18 m width within a 36‐m‐wide field). Pastures were stocked by ewes and lambs for three 10‐month grazing periods. Over the 3 years of the experiment, spatial separation of grass and clover, compared with a grass–clover mixture, increased clover herbage production, although its proportion in the sward declined through time (0·49–0·54 vs 0·34 in the mixture in the first year, 0·28–0·33 vs 0·15 in the second year and 0·03–0·18 vs 0·01 in the third year). Total herbage production in the growing season in the spatially separated treatments decreased from 11384 kg DM ha−1 in the first year to 8150 kg DM ha−1 in the third year. Crude protein concentration of clover and grass components in the 18‐m adjacent monoculture treatment was greater than the mixture treatment for both clover (310 vs 280 g kg−1 DM) and grass (200 vs 180 g kg−1 DM). There was no clear benefit in liveweight gain beyond the first year in response to spatially separating grass and clover into monocultures within the same field.

Diet Composition and Dry Matter Intake of Beef Steers Grazing Tall Fescue and Alfalfa

ABSTRACTAlkanes are a noninvasive method to estimate dry matter intake (DMI) of grazing herbivores. Other cuticular wax components such as long chain fatty alcohols (LCOH) have been used for estimation of diet composition of ruminants eating mixed diets. This study estimated diet composition using n‐alkanes and LCOH and estimated DMI using naturally occurring and dosed n‐alkanes. Beef steers (Bos taurus) (16 mo. old, 358 ± 9 kg) grazing vegetative adjacent monocultures of tall fescue (Festuca arundinacea Schreb.) and alfalfa (Medicago sativa L. subsp. sativa) were used in this study, which also evaluated diet preference. The LCOH (C26, C28, and C30) added additional characterization of the forages, but diet composition estimates were not different (P ≥ 0.22) than when estimated using four n‐alkanes (C27, C29, C31, and C33). Diet composition estimation indicated that steers consumed similar (P = 0.13) diets of 79 and 70% alfalfa in Year 1 and Year 2, respectively, corresponding to previous work showing a partial preference for legumes. Dry matter intake in Year 2 was lower (P = 0.0002, 4.7 kg d−1) than Year 1 (9.2 kg d−1), likely due to hot weather in Year 2. This study suggests that if n‐alkane profiles of the forages being grazed are distinct, the additional analysis needed to determine LCOH concentrations may not be necessary. Analyzing preliminary forage and fecal samples for n‐alkanes to estimate diet composition could reduce labor and expenses by eliminating additional laboratory analyses.

Grazing Behavior of Steers on Different Annual Ryegrass and White Clover Forage Systems

ABSTRACTStudying grazing behavior of ruminants may help increase the understanding of the use of forage systems of varying forage types and composition. This study was conducted during 2008 at Raymond, MS, to evaluate grazing time by ruminants on various forage systems to examine any relationship with pasture composition and stocking rate (SR). Annual ryegrass (Lolium multiflorum Lam. ‘Marshall’) and white clover (Trifolium repens L. ‘Durana’) were used to create forage system treatments of either monoculture grass (MG) or monoculture legume (ML), a binary mixture of grass and legume (MIX), or a spatial system of adjacent grass and legume monocultures in a 50:50 land area ratio within the same paddock (SS). Two levels of SR (3 or 6 steers [Bos taurus] ha−1) were imposed on each of the four forage systems to give a 4 × 2 factorial arrangement of treatments with two replicate paddocks of each treatment combination in a completely randomized design experiment. Two Angus crossbred yearling beef steers (236 ± 24 kg initial body weight [BW]) were randomly assigned to each of the 16 paddocks. Time spent grazing per animal on continuously stocked pastures was recorded for 10 d selected randomly during the months of April and May, with each day of observation lasting for 14 h (0615 to 2015 h). Forage system had an effect (P < 0.001) on time spent grazing daily. Animals grazing MG and MIX spent similar time grazing (mean = 442 min per animal), which was greater than daily grazing time on SS (380 min per animal). Grazing time was least on ML (341 min per animal). Also, SR had an effect (P < 0.001) on daily grazing time. Animals on high SR (431 min per animal) spent greater time grazing than those on low SR (371 min per animal). There was no difference in time spent grazing on each component of the adjacent monocultures of grass and legume within the SS (P = 0.23; 197 [the monoculture legume component of a SS] vs. 182 min per animal [monoculture grass component of a SS]). Less grazing time by animal on SS than MG and MIX may have implications for performance of animals grazing such a system because of expected lesser energy expenditure for grazing.

Grazing Behavior and Diet Preference of Beef Steers Grazing Adjacent Monocultures of Tall Fescue and Alfalfa: II. The Role of Novelty

ABSTRACTDomestic ruminants select a mixed diet when grazing heterogeneous pastures. Adjacent monocultures allow diet preference to be evaluated without certain constraints that could influence diet selection; however, few forage species have been evaluated. Adjacent monocultures of tall fescue (Festuca arundinacea Schreb.) and alfalfa (Medicago sativa L. ssp. sativa) were used to test the theories that selection of mixed diets is influenced by a plant's “novelty,” and that regardless of forage species, cattle will have a partial preference for legumes over grasses. Cattle without previous experience eating alfalfa spent 78% of total grazing time eating alfalfa, whereas after having experience grazing alfalfa they spent less (P = 0.04) time grazing alfalfa (72%). Overall, proportion of the day spent grazing was less (P = 0.001) when alfalfa was novel (40%) than when steers were experienced with both forages (46%). Proportion of the day spent idling was greater (P < 0.001) when alfalfa was novel (35%) than when both forages were familiar (26%). The proportion of grazing time in alfalfa was greater (P = 0.02) in the afternoon (76.8%) than in the morning (72.1%), differing from previous studies that reported a decline in legume preference over the day with an increased grass preference in the afternoon. Application of adjacent monocultures in production systems would benefit from additional research on performance of cattle grazing in this paddock arrangement.

Grazing Behavior and Diet Preference of Beef Steers Grazing Adjacent Monocultures of Tall Fescue and Alfalfa: I. Spatial Allocation

ABSTRACTAdjacent forage monocultures are a valuable tool to study the diet preference of grazing animals. Previous research has suggested that cattle will exhibit a partial preference for a legume over a grass regardless of forage species. The objective of this study was to determine if beef steers have a partial preference for alfalfa (Medicago sativaL. subsp.sativa) over tall fescue (Festuca arundinaceaSchreb.). These forages have not been evaluated previously as adjacent monocultures. Behavior data recorders, global positioning system (GPS), and pedometers were used to evaluate grazing behavior and diet preference of beef steers grazing tall fescue monocultures or adjacent monocultures of tall fescue and alfalfa at proportions (by ground area) of 50:50, 25:75, and 75:25. Steers exhibited a partial preference for alfalfa, grazing it for 61 to 65% of the time regardless of the proportion offered. A diurnal pattern of preference was not observed. Steers grazing tall fescue monocultures spent more time ruminating (p= 0.02) and tended to graze less time (p= 0.06) than steers in adjacent monoculture treatments. Time spent idling, number of prehensions and mastications, and bite rate were similar (p> 0.05) among treatments. Steers grazing tall fescue monocultures spent less time standing, more time lying, were less active, and took fewer steps (p≤ 0.05) than steers in adjacent monoculture treatments. These results support the proposal that cattle have a partial preference for legumes over grasses.

Chemical and acidic composition of Longissimus dorsi muscle of Comisana lambs fed with Trifolium subterraneum and Lolium multiflorum

Aim of this study was to evaluate the effects of grazing on Trifolium subterraneum and Lolium multiflorum, as pure or associated crops, on the chemical composition and on the fatty acid profile of the intramuscular lipids of the meat of lambs. Forty Comisana male lambs, on average weighing 13.75 ± 1.90 kg, were divided into four homogenous groups of ten and called, in relation to the diet: group T those grazing on T. subterraneum; Group L on L. multiflorum; Group TL on adjacent monocultures of T. subterraneum and L. multiflorum (66.6 and 33.3% of surface, respectively); Group LT on adjacent monocultures of T. subterraneum and L. multiflorum (33.3 and 66.6% of surface, respectively). Every 10 days, samples of forage species ingested by grazing lambs were collected and analysed. At 90 days of age, with an average live weight of 25.44, 23.44, 24.69 and 24.75 kg for T, L, TL and LT group, respectively, all lambs were slaughtered and a sample of Longissimus dorsi muscle for each animal was collected to study the chemical and acidic composition. No significant differences among the groups were observed for the growth performance and for the chemical composition of the meat. As regards the fatty acid classes, significant differences ( P < 0.05) were observed for the monounsaturated fatty acids, which were lower in the group T (35.46%) than those of the groups L (38.24%), TL (38.63%) and LT (38.59%), whereas, significant higher values for the group T were observed for the polyunsaturated fatty acids of the n-3 (4.49%) and n-6 (8.26%) series than those of the n-6 series for group L (6.79%; P < 0.05) and than those of both series for group LT (n-3 = 3.64%; P < 0.05 and n-6 = 6.43%; P < 0.05). The fatty acids that have significantly determined the modifications of the acidic classes were: oleic acid, which showed significant ( P < 0.05) lower values in the group T (26.70%) than the levels observed in the groups L (30.33%), TL (30.39%) and LT (30.63%) and the linoleic, linolenic and rumenic acids which were significantly ( P < 0.05) higher in the groups T (linoleic = 5.13%; linolenic = 1.97%; rumenic = 0.46%) and TL (linoleic = 4.75%; linolenic = 1.82%; rumenic = 0.41%) than those of the groups L (linoleic = 4.10%; linolenic = 1.52%; rumenic = 0.26%) and LT (linoleic = 3.95%; linolenic = 1.42%; rumenic = 0.33%). These differences could be due to the different dynamic activity of the cellulolytic bacteria in the rumen, related to the different levels of fibrous fractions of the diets. No significant difference was observed for saturated fatty acid, unsaturated/saturated fatty acids ratio and Atherogenic and Thrombogenic indices among the groups, whereas, PUFA/SFA ratio showed significant ( P < 0.05) higher value in group T than that in the group LT. T. subterraneum monoculture grazed as monoculture (T) and in mixture with L. multiflorum (66/33, TL) increased the linoleic, linolenic and rumenic acids improving the dietetic-nutritional characteristics of the lamb meat.

An update on the nutrition of dairy sheep grazing Mediterranean pastures

In the light of recent findings in sheep nutrition and feeding behaviour, the diets of grazing dairy sheep should be based on forages encompassing a variety of complementary nutritional values and containing moderate levels of diverse plant secondary metabolites, until recently regarded as “anti-nutritional”. In lactating sheep, pastures of tannin-containing legumes like sulla ( Hedysarum coronarium) and chicory ( Cichorium intybus) can be integrated with annual grasses for establishing artificial pastures under rainfed conditions. Diets based on these forages, while ensuring high milking performance, can mitigate the unbalance of CP to energy ratio of grazing sheep. By grazing sulla and Italian ryegrass (50:50 by area) as spatially adjacent monocultures or in timely sequence (complementary grazing) sheep eat more and perform better than by grazing the ryegrass pasture only. Concentrate supplementation of lactating sheep should be preferably based on sources rich in digestible plant fiber (soyhulls or beet pulps), particularly from mid-lactation onwards and when supplementation levels are high. Milk urea concentration is confirmed as a useful monitoring tool to balance protein nutrition and curb the waste of N at animal and system level. Finally, challenging tasks for future research on dairy sheep grazing management and nutrition are on-farm application of recent technological advances, such as image-based estimation of pasture biomass and quality, evaluation of sheep dietary quality by faecal Near Infrared Reflectance Spectrometry, and establishment of remote control systems.

Leaf and root necrosis of soybean are associated with black walnut and Fusarium solani in a tree- based intercrop

In tree-based intercropping, trees are established in rows, creating alleys that allow the mechanized production of crops. In 2004–2005, soybean (Glycine max) diseases were surveyed at the University of Guelph Agroforestry Research Station (established in 1987–1988, Guelph, Ont., Canada). This intercropping experiment is composed of 10 tree species, including black walnut (Juglans nigra). Areas within the soybean intercrop with symptoms of stunting, root rot, and interveinal chlorosis or necrosis were observed. In 2004 and 2005, these patches covered 253 and 738 m2, respectively, in the intercrop and were all found in the vicinity of black walnut. No patches were found in an adjacent soybean monoculture. Fusarium solani was isolated from diseased plants and Koch postulates completed, but the pathogen did not induce the stunting symptoms observed in the field. A role for juglone, an allelopathic compound produced by black walnut, as a predisposing factor to F. solani infection was investigated. The growth rate of F. solani at 1 × 10 4 mol/L juglone was reduced in vitro by 0.9 mm/day but not at a concentration of 0, 1 × 10−7, 1 × 10−6, and 1 × 10 −5 mol/L. In a hydroponic system, soybean was challenged with juglone (1 × 10−6 1 × 10−6, and 0 mol/L) and F. solani. Growth of soybean was severely reduced at 1 × 10−5 mol/L juglone, which can explain the observed stunting. Six days after infestation, plants challenged with juglone and F. solani had significantly fewer leaves (juglone × Fusarium effect, F = 7.90, P = 0.0057), shorter total root length (F = 11.06, P = 0.0013), and exhibited more root browning (F = 14.91, P = 0.0003) than plants challenged only with juglone, but there was variability among repetitions and in the development of leaf symptoms. Field and controlled environment observations point to an association, previously unreported to our knowledge, among F. solani, black walnut, and soybean disease. Tolerance of the pathogen to juglone and soybean stunting due to juglone are also novel findings, but more data are needed to conclusively prove the link with the allelopathic compound.

Evaluation of the effect of eprinomectin in young dairy heifers sub-clinically infected with gastrointestinal nematodes on grazing behaviour and diet selection

Inappetence is commonly associated with parasitism and has been observed in both housed and pastured ruminants. In seeking a functional explanation for these observations, it has been hypothesised that parasitized animals may feed more selectively in order to proportionally increase the protein content of their diet and thus partially compensate for their reduced feed intake. Support for this theory is found principally in studies in housed animals under carefully controlled experimental conditions. Grazing animals face a far more heterogeneous environment and a multiplicity of potentially confounding factors that could influence diet selection. Controlled grazing of adjacent monocultures of grass and clover can mitigate some of these variables and was used in the current study to examine the dietary preference of dairy heifers with sub-clinical parasitic gastroenteritis when compared to those receiving regular anthelmintic treatments. Grazing behaviour and herbage intake rates were determined through the use of jaw-movement recorders, direct observation and short-term liveweight change. Consistent with previous observations and despite evidence that nematode burdens were low in the untreated control heifers, a reduction in daily grazing time of 56 min ( P = 0.054) was observed in the control animals. There was, however, no evidence that the control heifers showed greater preference for clover compared with ryegrass: partial preference for clover was 73.0% in the untreated controls and 75.5% in the treated heifers. Furthermore control heifers were observed grazing the clover swards significantly ( P = 0.032) less frequently than the treated heifers. This study provides additional evidence in grazing cattle for parasite-induced inappetence, manifest as a reduction in grazing time and in subtle changes in ingestive behaviour. The observed partial preference for clover in both treated and control cattle was not significantly affected by the level of parasitism.

Soil respiration and carbon balance in a subtropical native forest and two managed plantations

From 1999 to 2003, a range of carbon fluxes was measured and integrated to establish a carbon balance for a natural evergreen forest of Castanopsis kawakamii (NF) and adjacent monoculture evergreen plantations of C. kawakamii (CK) and Chinese fir (Cunninghamia lanceolata, CF) in Sanming Nature Reserve, Fujian, China. Biomass carbon increment of aboveground parts and coarse roots were measured by the allometric method. Above- and belowground litter C inputs were assessed by litter traps and sequential cores, respectively. Soil respiration (SR) was determined by the alkaline absorbance method, and the contribution from roots, above- and belowground litters was separated by the DIRT plots. Annual SR averaged 13.742 t C ha−1 a−1 in the NF, 9.439 t C ha−1 a−1 in the CK, and 4.543 t C ha−1 a−1 in the CF. For all forests, SR generally peaked in later spring or early summer (May or June). The contribution of root respiration ranged from 47.8% in the NF to 40.3% in the CF. On average, soil heterotrophic respiration (HR) was evenly distributed between below- (47.3∼54.5%) and aboveground litter (45.5%–52.7%). Annual C inputs (t C ha−1 a−1) from litterfall and root turnover averaged 4.452 and 4.295, 4.548 and 2.313, and 2.220 and 1.265, respectively, in the NF, CK, and CF. As compared to HR, annual net primary production (NPP) of 11.228, 13.264, and 6.491 t C ha−1 a−1 in the NF, CK, and CF brought a positive net ecosystem production (NEP) of 4.144, 7.514, and 3.677 t C ha−1 a−1, respectively. It suggests that native forest in subtropical China currently acts as an important carbon sink just as the timber plantation does, and converting native forest to tree plantations locally during last decades might have caused a high landscape carbon loss to the atmosphere.

Dietary selection and ingestive behaviour of fallow deer and sheep grazing on adjacent monocultures of white clover and tall fescue

The experiment compared dietary selectivity, in terms of both herbage intake and feeding behaviour, of fallow deer and sheep grazing on two types of pasture consisting of adjacent, one-area monocultures of Trifolium repens (C), at low standing mass availability (SM = 0.6 t DM ha −1) and compressed sward height (CSH = 4.5 cm), and Festuca arundinacea (F) in two proportions by ground area: 25%C:75%F (pasture type 1) or 75%C:25%F (pasture type 2). A split plot design was carried out in two blocks, each comprising two 0.50 ha plots of different pasture type. Every plot was grazed sequentially by two herds of six 1-year-old animals of either Dama dama (live weight (LW) = 28.5 kg) or sheep (LW = 47.4 kg), for two consecutive 9-day grazing periods. A total of four herds were used, by moving over the herds grazing on the same type of pasture from block to block, at the end of the first grazing period. The grazing measurements were recorded on the last 3 days of every grazing period. The time spent grazing either grass or legume was evaluated from a visual scan of each animal, while dietary composition, herbage intake and digestibility were estimated by the n-alkane method, after correcting the faecal patterns of markers by their individual recovery, evaluated in a companion trial for fallow deer. Application of the n-alkane method provided an estimation of dietary selectivity, for both deer and sheep, coherent with well-established principles of herbivore nutrition. Indeed, under the conditions of vegetation geography and herbage abundance mentioned above, which would have allowed animals to gather monospecific diets on both pasture types, mixed diets were selected, largely dominated by the most extensive plant species. Deer grazed higher proportions of clover than sheep (53% versus 37%; P < 0.05) and displayed a preference for the legume, the inclusion of which tended to increase diet digestibility. In comparison with the lighter deer, sheep showed a higher total intake (1.62 kg DM d −1 versus 1.12 kg DM d −1; P < 0.01), thus attaining a comparable feeding level (90 g DM kg −1LW −0.75 versus 91 g DM kg −1 LW −0.75) by consuming a greater amount of fescue at a higher rate of intake. On average, both ruminant species spent more time grazing on clover than fescue monocultures (257 min/d versus 164 min/d). The low SM and short CSH of clover introduced physical constraints which probably compelled animals to trade off their preferred diet with total daily herbage intake, resulting in a mixed diet with a lower proportion of clover than expected, particularly in the heavier and thus more demanding sheep. Deer exhibited longer nocturnal grazing activity, while sheep preferred afternoon and evening grazing, with little activity at night.