Regrowth Period Research Articles

Lateglacial and Holocene chronology of climate‐driven postglacial landscape evolution in northeast Greenland

The Greenland Ice Sheet is highly sensitive to climate change, leading to significant retreat along its edges. This rapid ice loss contributes to rising sea levels and impacts the Earth's climate stability. Understanding the extent of recent glacier retreat is crucial in order to determine if it is unprecedented or within ranges of natural variability. Palaeoenvironmental studies aim to identify past glacial phases and landscape changes using advanced dating methods such as cosmic ray exposure (CRE) dating. In NE Greenland, CRE dating has helped establish the timing of glacial oscillations, yet a comprehensive understanding of glacial fluctuations during specific periods still needs to be developed. This study aims to chronologically constrain the postglacial landscape evolution of two NE Greenland valleys from the Young Sund–Tyrolerfjord area (74°N, 20–25°E) from the onset of deglaciation and throughout the Holocene to better understand glacial and postglacial changes. The chronological framework relies on 27 10Be cosmic‐ray exposure ages that constrain our interpretation of the geomorphological features in both valleys. Inconsistencies were observed in the ages dataset, highlighting potential bias associated with nuclide inheritance and post‐glacial dynamics. Despite limitations, the CRE results confirm the general pattern observed in NE Greenland: (i) major deglaciation and disconnection of glaciers from the main glacial systems during the Lateglacial and Early Holocene with a rapid but not homogeneous deglaciation within the range from ~14.3 to 11.9 ka; (ii) no evidence of glacial activity during the Middle Holocene, probably associated with the withdrawn position of the ice masses’ fronts; and (iii) glacier expansion during the Late Holocene, with a Little Ice Age advance as the last significant period of glacial regrowth.

Dynamics of Mulatto Grass Regrowth Depending on Rotational Cattle Grazing Management

This study was carried out to characterize the dynamics of forage accumulation during the regrowth of Mulatto grass submitted to rotational grazing strategies. The treatments corresponded to combinations between two pre-grazing conditions (95% and a maximum light interception during regrowth—LI95% and LIMax) and two post-grazing conditions (post-grazing heights of 15 and 20 cm), according to a 2 × 2 factorial arrangement and randomized complete block design, with four replications. Rates of leaf growth (LGR), stems growth (SGR), total growth (TGR), leaf senescence (LSR), grass accumulation (GAR) (kg·ha−1·day−1), and the senescence/canopy growth ratio during different stages of regrowth. There was no difference between the management strategies for TGR. However, a higher GAR was reported for pastures managed with LI95% relative to LIMax, of 161.7 and 120.2 kg DM ha−1·day−1, respectively. Pastures managed with LI95% have a lower SGR in the intermediate and final regrowth period, reflecting the efficient control in the stalks production. On the other hand, in pastures managed, the LIMax showed higher SGR and LSR in the final regrowth phase. Thus, the LAI was higher in pastures managed at LI95% compared to those managed at LIMax, of 163.9 and 112.7 kg DM ha−1·day−1, respectively. Mulatto grass pastures, which were managed at LI95% pre-grazing, corresponded to approximately 30 cm in height, showed higher LAI, and ensured a low SGR throughout the regrowth period, constituting a more efficient management strategy.

Morphogenesis, Structure, and Tillering Dynamics of Tanzania Grass under Nitrogen Fertilization in the Amazon Region

Nitrogen fertilization is one of the main management strategies for continuous pasture management with high productivity. We examined the effects of nitrogen fertilization on the morphogenic, structural, and tillering dynamic characteristics of Tanzania grass in the Amazon region in the state of Pará, Brazil. The study was conducted using a randomized block design with six treatments (0, 100, 200, 300, 400, and 500 kg N ha−1 year−1) and five replicates. The treatments were performed during the rainy season in 2016 and 2017 using urea as the nitrogen source. The leaf elongation rate was increased by 68.5% compared with that of the control treatment (p < 0.01). The leaf appearance rate and number of alive leaves increased with higher doses of nitrogen (p < 0.01, each). The regrowth period was reduced by approximately 13 days under 500 kg N ha−1 (p < 0.01), thus providing more production cycles. Nitrogen fertilization was also associated with a higher tillering rate (p < 0.01); however, the rate of this increase decreased with increasing nitrogen dose. Higher nitrogen doses thus improved the development of Tanzania grass; however, this became less pronounced at doses < 300 kg N ha−1.

Pre-eruptive magmatic processes at Taranaki volcano from an amphibole perspective

Amphibole phenocrysts in post-1 ka lava domes deposits of Taranaki volcano, an andesite arc volcano in New Zealand, provide an opportunity to explore late-stage changes in melt composition and volatiles in the run up to eruption. Amphibole is a subordinate phase (0–7% of modal phenocrysts) and the phenocrysts display three types of growth history. Type 1 are large compositionally and texturally uniform phenocrysts that have low MgO (<13 wt%) and high K2O (∼1–1.4 wt%) contents. In contrast, Type 2 have similar cores but have been partially resorbed and overgrown by a mafic rim distinguished by high MgO (up to 15 wt%) and low K2O (<1.0 wt%) contents. Type 3 are the least common, and have either normal zoned or concentrically zoned interiors with respect to MgO and FeO. Overall, elemental substitutions and zonation patterns are related to periods of resorption and regrowth that are best explained by changes in melt composition. Based on calculated equilibrium melt compositions, the amphibole crystallisation is consistent with an incrementally grown andesitic to dacitic (SiO2 58–67 wt%) crystal mush that was periodically recharged with more mafic magma (SiO2 ∼ 55 wt%). The melts span a compositional gap (SiO2 ∼ 60–65 wt%) that is not represented in eruption products from the last 8 ka. Such melts were likely brief stages during ongoing fractional crystallisation and magma mixing. Each recharge event disrupted an evolving system and mixed crystals from different parts of it. This concept supports triggering of eruptions by recharge of mafic melts, as also inferred from plagioclase zonation for some eruptions from Taranaki. The outermost rims (0–5 μm) of many amphibole phenocrysts are enriched in fluorine (up to 1.9 wt%) and surrounded by a thick opacitic decomposition growths. We interpret this as the result of slow magmatic ascent and extensive crystallisation that produced a late-stage halogen-rich interstitial melt. This likely extended the conditions for amphibole stability to lower pressure. If F enrichment was accompanied by comparable enrichments in other halogens that preferentially partition into an aqueous phase, then extensive degassing would have occurred during the dome extrusions.

In Vitro Gas Production of Common Southeast Asian Grasses in Response to Variable Regrowth Periods in Vietnam

In Vitro Gas Production of Common Southeast Asian Grasses in Response to Variable Regrowth Periods in Vietnam

Reusing livestock farming wastewater for Tifton 85 irrigation: productivity, morphological, and bromatological indicators

The utilization of wastewater from livestock farming (WLF) represents a common agricultural practice, but the absence of research on its agronomic impacts hinders its sustainable implementation. This study assesses the reutilization of WLF combined with nitrogen fertilization on the morphological, bromatological, and productivity attributes of a Tifton 85 pasture during the winter season. The study involved the application of different types of water via sprinkler: (I) stream water; (II) mixture of WLF and stream water at a 1:1 ratio; and (III) undiluted WLF combined with mineral nitrogen fertilization (0 and 45 kg N ha-1) administered at the commencement of the regrowth period. Irrigation was applied on a weekly basis, totaling 2,440 m3 ha-1. At 106 days post-regrowth, parameters including forage productivity, height, leaf-stem ratio, leaf area index, nitrogen nutrition index, crude protein content, acid detergent fiber, neutral detergent fiber, and mineral matter content were determined. Mineral fertilization at the prescribed dosage (45 kg N ha-1) did not have any discernible impact on the parameters under investigation. On average, the reuse of WLF raised the productivity from 2.50 to 5.12 t ha-1 and the Crude Protein from 12.35% to 14.58% compared to stream water. The reuse of WLF demonstrated superior outcomes (p &lt; 0.01) in terms of pasture productivity, nutritional quality, and nitrogen accumulation compared to irrigation solely with stream water. The reuse of diluted WLF (1:1) without fertilization proved adequate to sustain Tifton 85 pastures during the winter season in the Brazilian Cerrado region. Keywords: Cynodon dactylon, forage, irrigated pasture.

Evaluation of marandu palisadegrass regrowth intervals in silvopastoral and monoculture systems

Silvopastoral systems (SPS) offer a sustainable alternative for animal production in tropical ecosystems. This study aimed to evaluate the effects of deferment days on herbage accumulation, plant-part composition, and canopy structural characteristics of Marandu palisadegrass (Urochloa brizantha Hochst. ex A. Rich.) in SPS with Eucalyptus urophylla and monoculture (MC). The experiment was conducted using a randomized block design, with each system individually allocated at the center of each plot in a 3 x 4 factorial arrangement, consisting of three systems: monoculture, and silvopastoral systems with tree row spacings of 12 m and 18 m, and tree intra-row spacing of 2 m, across four regrowth periods (60, 90, 120, and 150 days), each with three replications. Increasing deferment days reduced the proportion of green components in the forage, affecting tiller population density (TPD), leaf dry mass (LDM), and leaf/stem ratio. Maximum LDM production occurred at approximately 88 days with 0.63 Mg ha-1, while peak green dry mass (GDM) was at 94 days, reaching 1.11 Mg ha-1. Both dead material dry mass (DMDM) and total dry mass (TDM) increased linearly with regrowth periods, although TDM comprised about 47% dead forage. A regrowth period of 94 days from March is feasible for Marandu palisadegrass in SPS with 12 m and 18 m between tree rows, demonstrating that this spacing does not hinder forage production.

PECULIARITIES OF THE ACCUMULATION OF GLUCOFRUCTANS IN THE ABOVE-GROUND PART OF THE SPECIES OF THE GENUS ALLIUM (AMARYLLIDACEAE)

The specifics of the accumulation of fructose-containing carbohydrates (glucofructans) in the above-ground parts of Allium L. species were studied. High molecular weight glucofructans (polyfructans) were present in significant amounts (6.9–10.1%) during the spring regrowth period in the leaves of A. jesdianum Boiss. &amp; Buhse and A. victorialis L. During active growth and budding, their content dropped sharply (up to 0–3.6%). In A. victorialis, at the end of the growing season, the amount of polyfructans in the leaves of the second generation increased markedly (up to 9.7–11.8%). Since the leaves of this species are preserved under the snow all winter, fructans, probably, have a protective function, increasing their resistance to low temperatures.&#x0D; In all the studied species, polyfructans were accumulated in the underground part in much greater quantities than in the leaves, except for A. victorialis, where their content in the aboveground and underground parts was similar in the same phenophases, or in the leaves they were contained in larger quantities.&#x0D; The content of low molecular weight glucofructans (oligofructans) in leaves at the beginning of the growing season varied from 2.9 to 11.7% in different species. During the period of active growth and budding their content increased significantly up to 4.6–18.9%. The leaves of A. aflatunense B. Fedtsch., A. jesdianum, A. hollandicum R.M. Fritsch, A. rosenbachianum Regel, belonging to the subgenus Melanocrommyum (Webb &amp; Berthel.) Rouy, and A. victorialis, belonging to the subgenus Anguinum (G.Don ex W.D.J.Koch) N.Friesen, are the richest in oligofructans. In A. obliguum L. and A. saxatile M. Bieb., belonging to the subgenus Polyprason Radić, the content of oligofructans in the leaves was significantly lower than in the previous species.&#x0D; Considerable amounts of fructans were accumulated in the inflorescences of A. victorialis and A. obliquum.

Mathematical models for predicting protodioscin in tropical forage grasses

Protodioscin is a saponin present in grasses that can lead to losses in animal production. Our hypothesis was that mathematical models can accurately and precisely predict the protodioscin concentration in tropical grasses. We evaluated the ability of four mathematical models to describe the protodioscin concentration in Brachiaria and Panicum cultivars with different regrowth periods. Six cultivars of Panicum: Aruana, Massai, Mombaça, Tanzânia, Tamani, and Zuri; and five of Brachiaria-grass: Marandu, Paiaguás, Piatã, Xaraés and Basilisk. Protodioscin concentration evaluations were carried out at 51, 84, 110, and 111 days of age. Linear, Quadratic, Exponential, and Logarithmic models were evaluated, and the adequacy of the models was verified. The models were compared for accuracy and precision by pairwise mean squared error analysis and the delta Akaike information criterion. The models did not differ from each other in terms of accuracy and precision. The exponential model showed a high ability to explain the observed variability between protodioscin concentration and plant age for Brachiaria grasses. Panicum grasses have constant protodioscin concentration. Mathematical models are capable of predicting the protodioscin concentration in grasses of the genus Brachiaria based on plant age. We recommend Exponential model to predict the concentration of protodioscin in Brachiaria grasses.

Khakiweed (Alternanthera pungens) control with contact and residual herbicides

Abstract Khakiweed is a perennial broadleaf weed that is difficult to control because of its multiple means of reproduction, vigorous growth, and deep taproot. Khakiweed reduces the performance of pasture, pecan, and turf areas by choking out desirable grass and legume species. Because information on the effectiveness of contact and residual herbicides for control in pecan and pasture areas is limited, greenhouse studies were conducted to determine the effect of application timing, mode of action, and rate on khakiweed control. Preemergence and postemergence herbicides were applied to mature khakiweed plants at 0.25X, 0.5X, 1X, or 2X the label recommended rate for general broadleaf control. Biomass was collected 3 wk after application. Plants regrew from roots in the greenhouse until a second biomass harvest was collected at 6 wk after treatment (WAT). Metsulfuron-methyl, indaziflam, or pendimethalin was applied preemergence to the soil surface. All rates of preemergence herbicides provided high-efficacy control of regrowth (&gt;85%) compared to the nontreated control. The efficacies of postemergence-applied metsulfuron-methyl, metsulfuron-methyl + nicosulfuron, indaziflam, aminopyralid + florpyrauxifen-benzyl, 2,4-D amine, and 2,4-D amine + florpyrauxifen-benzyl were also examined. All postemergence herbicide treatments exhibited control compared to the nontreated plants at both sample timings (3 and 6 WAT) and increased with herbicide application rate. No herbicide provided high-efficacy control during the initial postspray period (0 to 3 WAT). During the regrowth period (3 to 6 WAT), metsulfuron-methyl alone and in combination gave &gt;85% control of khakiweed biomass, indicating that the sulfonylurea herbicides used in this study are well suited to controlling khakiweed.

Succession and climatic stochasticity induce long-term decline of a forest browser.

Removal of predators and creation of early seral habitat have, in many systems, caused substantial population growth of herbivores. Hyperabundant herbivores, in turn, induce cascading ecosystem effects, but few studies have investigated long-term browser density trends in relation to succession and stochastic climate events. Here, we use annual, empirical population estimates of a forest browser to relate forest succession to long-term decline of an herbivore that prefers early seral habitat. From 2007-2021, concurrent with reduced timber harvest, we used line-transect distance sampling to document annual changes in Columbian black-tailed deer (Odocoileus hemionus columbianus) density on a mid-sized (17.3km2) predator-free island. We documented successional changes associated with forest aggradation and decreased forage quality for deer: early successional shrub/scrub habitat declined 3.8%/year; timber volume increased 4.5%/year; and canopy coverage increased 2.5%. In 2007-2008, deer densities were the greatest observed (~44/km2), but then an historic snowstorm reduced deer density by 39%. From 2010-2021, as forests continued to mature, deer density decreased 4.0%/year, declining to 20 deer/km2. Using a multivariate approach to combine habitat variables (i.e., early seral coverage, timber volume, and canopy closure) into a measure of forest maturation, we found a significant negative relationship between deer density and forest aggradation. Thus, consistent with predictions for bottom-up limited browsers, we observed significant annual declines in a deer population throughout an extended period of forest regrowth. Despite declines, deer density on the island exceeds mainland densities, and overbrowsing likely continues to disrupt ecosystem processes.

Modern technologies for cultivation of winter wheat on leached chernozems of the Republic North Ossetia-Alania

The purpose of the research was to study and use modern agrobiological principles of adaptive intensification of the technology for cultivating promising introduced varieties of winter wheat, their responsiveness to growth stimulants and winter hardiness of plants, as well as to identify inhibitory functionality in the destruction of weeds, reducing the incidence and number of pests on leached chernozems of the Republic North Ossetia–Alania. The processes of pre-vegetation were studied and it was found that the energy of seeds germination had a positive correlation with air temperature within the range of r=0,68–0,84. A slightly lower correlation coeffi cient (r=0,61–0,68) was noted when taking into account laboratory seeds germination. The maximum weight of 1000 seeds was observed in the varieties Aivina, Vassa and Kameya – 44,8–51,9 g, which was 1,2–8,3 g higher than in the control. High resistance to low temperatures was determined with normal autumn development of plants with sugar content in within 30 % or more. A recommended method for pre-sowing treatment of winter wheat seeds consists of soaking in a 0,1 % aqueous solution of sodium selenate (Na2SeO4) for 0,5–1 hour, enveloping with soil from the rhizosphere of Galega eorientalis Lam., thereby increasing the productivity and fertility of soils without additional costs for nitrogen fertilizers. The infl uence of seeding rates and predecessors such as clover and peas on the yield of Batko variety on leached chernozems of the foothill zone of the Republic of North Ossetia-Alania was revealed. The optimal germination rate was 89,5 %, when sowing after peas with a seeding rate of 4,5 million pcs/ha, the yield reached 3,7 and 3,8 c/ha after clover and peas, respectively, with a profitability level of 77,7 % for due to the lack of additional technological methods. It was revealed that the biological product Nikfan in mixed with sulfur-containing mineral water as a top dressing for crops during the spring regrowth period after various predecessors contributed to an increase in yield and quality indicators of grain, a profitability level of 51,9 % and a reduction in prime-cost to 5,77 rub./kg.

Formation and Quasi‐Periodic Variation of Equatorial Jet Caused by Planetary‐Scale Waves in the Venusian Lower Cloud Layer

AbstractThe equatorial jet in the Venusian lower cloud layer (47–55 km altitudes) and its quasi‐periodic variation are found in a general circulation model (GCM). The equatorial jet is produced by the 5.8‐day wave and destroyed by the 7‐day wave, and its quasi‐periodic variation with a timescale of about 280 days is caused by the alternating development of these waves in the GCM. The 5.8‐day wave, which is excited by the Rossby‐Kelvin instability, produces the equatorward angular momentum (AM) flux, and accelerates the zonal‐mean zonal wind in the equatorial region. The 7‐day wave, newly found in the present study, is a planetary‐scale wave antisymmetric about the equator, although it has not yet been observed. It is excited by the coupling among the lower‐altitude equatorial Rossby mode, the mid‐latitude Rossby mode, and the high‐latitude Rossby mode. In the growth period, the 7‐day wave produces the poleward (equatorward) AM flux around the equatorward (poleward) critical latitude. As a result, the zonal‐mean zonal wind is decelerated (accelerated) in the equatorial region and high latitudes (mid‐latitudes). In the regrowth period, the lower‐altitude equatorial Rossby mode disappears due to the disappearance of the equatorial jet, but the high‐latitude Rossby mode is still enhanced by the coupling with the mid‐latitude Rossby mode. These results could provide a possible explanation of the equatorial jet inferred from the recent Akatsuki observation, although it should be investigated by further observations.

Rooting dynamics of ‘kustee’ honeybush (Cyclopia genistoides) as affected by seasonality and the manipulation of stock plant characteristics

Honeybush (Cyclopia spp.), a legume endemic to the Fynbos biome of South Africa, has gained popularity as a herbal tea, particularly for its unique honey-like flavour, low tannin content and high antioxidant status. However, extensive wild-harvesting practices are a concern as this continued practice is placing pressure on natural stands. To ensure a sustainable supply of high-quality tea, a switch to clonal cultivation is required. In this study, the rooting potential of cuttings from four clonal types of Cyclopia genistoides was evaluated, following rejuvenation of stock plants over various regrowth periods, with cutting material collected over different seasons and phenological phases. The highest rooting success of >90 % was achieved following either six- or nine months of regrowth in winter and spring. Cutting dry weight positively correlated with rooting percentages in summer and autumn rooted cuttings. Extended periods of regrowth highlighted clonal differences in rooting success whilst no clonal differences occurred in shorter regrowth periods of less than a year. Cuttings (clones ‘GK3’ and ‘GK5’) made following regrowth of more than 12 months differed significantly, with ‘GK3’ rooting percentages that were lower in comparison to ‘GK5’ cutting material, when harvested in winter (30 %; 82 %) and the following autumn (37 %; 100 %), but were comparable when harvested in the preceding summer, autumn and spring. Stock plant phenology of C. genistoides at harvesting influenced rooting as low rooting percentages consistently coincided when the harvesting of cutting material coincided with the flowering period. The use of terminal cuttings collected from the current season's growth during a vegetative phase, following a six- or nine-month regrowth period, is recommended for C. genistoides stock plants to achieve acceptable to high rooting success in cutting material.

Phenology of the Antyllis vulneraria L. in Moscow region

The research topic is the study of the biological characteristics of the local flora protected species Anthillis vulneraria L., under conditions of field experience in the Moscow region. The purpose of this research was to study the phenological cycle and the influence of meteorological factors on the timing and duration of phenophases. In the period from 2017 to 2022, a reduction in the duration of the shoot regrowth period, budding and flowering phases was revealed due to an increase in the sum of average daily temperatures and a decrease in precipitation. The resistance of plants to the conditions of the winter season in plants of the 1st-2nd year is 60-84 %, in plants of the 3rd year 50 %. A. vulneraria goes through a full phenological cycle in 175-190 days, blooms and bears fruit annually, forms a viable self-seeding, starting from the 2nd year of vegetation, grows in one place for up to 6 years, with the lifespan of individual plants up to 3 years. Pre-sowing preparation of seeds - wet stratification for 2 months, increases their germination rate to 53-65 %. The results of the study are relevant for maintaining the number of A. vulneraria that is a protected species of local natural flora in the Moscow region.

Shortened first regrowth interval of grass silage as a harvesting strategy to improve nutrient supply for dairy cows: a case study

Dairy cows have a highly valuable ability to convert grass into milk. A modification of the normal three-cut harvesting strategy was evaluated consisting of shortened first grass regrowth period to increase the energy value of the silage crop over the whole growing season under Boreal conditions. Grass was ensiled from timothy-meadow fescue-red clover swards over two years at three consecutive harvests within the growing season. Diets based on the silages (D1, 1st cut; D2, 2nd cut and D3, 3rd cut) were fed to dairy cows in two milk production experiments using change-over designs and an average concentrate proportion of 0.41 on dry matter basis. Consistently high energy value in silages was achieved and despite minor differences in silage D-values, feed intake was highest for D1. The differences in energy-corrected milk yield between treatments were limited to an increase for D2 in Exp 2 so that feed energy conversion into milk was decreased with D1. A shortened first regrowth interval for grass silage harvest was a viable option, but forage area per animal and other farm specific factors should be considered when choosing the silage harvesting strategy.

Physiology of the forage cactus cultivate Opuntia stricta (Haw.) Haw under different irrigation frequencies in the Semiarid

The objective of this work was to evaluate the physiological variables of the cultivar Opuntia stricta (Haw.) Haw in the first cycle and in the regrowth, under different frequencies of drip irrigation, cultivated in the Agreste da Paraíba mesoregion. Therefore, a randomized block design was used, with 2 treatments (irrigation frequencies) and 4 replications (blocks), with each treatment repeated 3 times within the block (triplicate) totaling 24 experimental plots. For physiological variables, data were evaluated by analysis of variance (ANOVA) and means compared by t test at 5% probability using SAS ® (2002). The present study shows that the stress of environmental conditions had a greater impact on the frequency of irrigation every 28 days, since the forage cactus irrigated every 7 days had the highest internal concentration of CO2; CO2 absorption rate; instant efficiency in water use; intrinsic efficiency of water use; instantaneous carboxylation efficiency, both in the first cycle and in the regrowth period. Respiratory rate and stomatal conductance did not differ between irrigation frequencies for both cycles, showing the good adaptation of the cultivar to the semiarid region.

Changes in Forage Quality and Cattle Performance with Short-Duration Grazing of Mesic Meadows in the Intermountain West

Managers tasked with balancing livestock production and wildlife habitat in mesic meadows face a unique set of challenges. These challenges are compounded in the arid western United States because mesic areas comprise only a small portion of the landscape yet provide vital forage and water resources to livestock and wildlife and are essential to underlying ecosystem integrity and function. Our objectives were to compare the effects of short-duration grazing treatments that varied by season and intensity on the quantity and nutrient quality of pasture forage and average daily gains (ADG) of yearling cattle. We established pastures (n = 15 total pastures) in mesic meadows at the University of Idaho Rinker Rock Creek Ranch in south-central Idaho and stocked them with heifers during 2019 and 2020. Heifers grazed six pastures in June (early-season; 16 d) and six pastures in August (late-season; 16 d) at moderate (30−40%) and high (70-80%) relative utilization levels (n = 3 pastures per treatment). Three pastures were not grazed by cattle representing controls. Forage was collected and analyzed for nutrient quality at pregrazing, postgrazing, and after a period of regrowth in late September. Contrasted against all other treatments, early-season grazing at a high-intensity produced forages with the highest crude protein (P < 0.001) and lowest neutral-detergent fiber (P ≤ 0.04) after regrowth. ADGs of yearling heifers were greater (P ≤ 0.01) during the first year of the trial than the second year. Differences in ADG were not associated with grazing season (P = 0.08) or intensity (P = 0.12), despite numeric differences. Forage quantity and quality and heifer ADG responses varied between years, likely due to spring and annual precipitation differences. This study demonstrates the effectiveness of early-season grazing at a high intensity for improving forage quality and increasing ADG of livestock grazing mesic meadows.

Evaluation of the Role of Silt Content on the Flocculation Behavior of Clay‐Silt Mixtures

AbstractThe interactions and impacts of silt content on clay‐silt mixture flocculation processes and settling and floc properties were investigated from a series of laboratory experiments. The results demonstrate that the silt content in clay‐silt mixtures has an impact on the time‐evolution average floc size, peak floc size, and equilibrium floc size. Increasing the silt content reduces the floc strength, recovery factor, and average floc size. The silt fraction can present both cohesive and noncohesive characteristics in silt‐clay suspensions. The bulk concentration of clay‐silt mixtures was found to reasonably correlate with the average floc sizes under equilibrium conditions and with maximal floc sizes under both equilibrium and nonequilibrium conditions. The results also show that the flux‐settling velocities increase with increasing silt content. Specifically, the flux‐settling velocities are 0.66, 0.87, and 1.39 mm/s for mixing ratios of clay‐silt of 1:0.5, 1:1, and 1:2.5, respectively, under equilibrium conditions. Under growth‐breakup‐reflocculation (G‐B‐R) conditions, the percentage changes in the flux‐settling velocities of flocs during the regrowth period are 22%, 41%, and 42% less than those under equilibrium conditions. Therefore, both the silt content and hydrodynamic conditions need to be taken into consideration when determining the flux‐settling velocities under variable shear conditions. The findings from this research provide better insight into the highly complex role of silt in the flocculation process of clay‐silt mixtures in natural water environments.

Effect of Ammonia-Oxidizing Bacterial Strains That Coexist in Rhizosphere Soil on Italian Ryegrass Regrowth.

Potted Italian ryegrasses (Lolium multiflorum L.) were used to investigate the effect of ammonia-oxidizing bacterial (AOB) strain that coexisted in rhizosphere soil on Italian ryegrass regrowth. The results showed that the isolated and screened AOB strain (S2_8_1) had 100% similarity to Ensifer sesbaniae. The inoculation of S2_8_1 on day 44 before defoliation caused its copy number in rhizosphere soils to increase by 83-157% from day 34 before defoliation to day 14 after defoliation compared with that in Italian ryegrass without S2_8_1 inoculation, indicating that S2_8_1 coexisted permanently with Italian ryegrass. The coexistence promoted the delivery of root-derived cytokinin to leaves and to increase its cytokinin concentrations; thus, the Italian ryegrass regrowth accelerated. During the 14-day regrowth period, the S2_8_1 coexistence with Italian ryegrass caused its leaf and xylem sap cytokinin concentrations, rhizosphere soil nitrification rates, net photosynthetic rates, and total biomass to increase by 38%, 58%, 105%, 18%, and 39% on day 14 after defoliation, respectively. The inoculation of S2_8_1 on day 2 before defoliation also increased the regrowth of Italian ryegrass. Thus, the coexistence of AOB with Italian ryegrass increased its regrowth by regulating the delivery of cytokinins from roots to leaves.