Herbage Density Research Articles

Влияние абиотических факторов на продуктивность тростника Phragmites australis в озёрах юга Западной Сибири

The article presents the results of studying phytomass, stem height and density of thickets (herbage) of Phragmites australis, one of the most common aerial-aquatic plant in the south of Western Siberia. This region is distinguished by a rare combination of chloride, sulfate and soda lakes in a relatively small space. As an eurybiont, reed is highly resistant to water and soil salinity, but high salinity adversely affects its growth and development. The aim of the work was to assess the degree of abiotic factors (pH, mineralization) effect on the quantitative characteristics of reed growing in water bodies with different water mineralization: from 0.005 to 387.6 g/L. In total, we studied 59 freshwater, brackish-water (oligo-, meso- and polyhaline) and hypersaline water bodies, located in various natural zones (southern taiga, forest, forest-steppe, steppe and dry-steppe) in the south of Western Siberia. The studies were carried out in late July – early August from 2012 to 2020 during the period of maximum vegetation of plants. As a result of the studies, it is shown that the optimal for reed growth and development is water mineralization from 0.5 to 5.0 g/L, when the highest values of biomass and plant height are observed. A model based on redundancy analysis (RDA) was built and a correlation analysis was carried out to assess the dependence of phytomass, shoot height and herbage density on abiotic factors. We took into account pH, salinity, and Ca2+, Na+, Mg2+, K+, HCO3-, Cl- and SO42- content. We found that pH and determined by Ca2+ water hardness are the limiting factors in freshwater lakes. In brackish-water meso- and polyhaline, as well as in saline hyperhaline water bodies reed phytomass is affected by a whole range of factors, while shoot height is affected by pH, chlorides, and water hardness, and grass stand density is affected by chlorides and sulfates.

Assessment of the state of vegetation cover of recultivated dumps of uranium deposits in Northern Kazakhstan.

The purpose of this study was to assess the processes of plant community formation on recultivated dumps of spent uranium-containing industrial waste from uranium deposit mines, as well as to identify the degree of impact of agro-climatic factors, agrochemical indicators of soils of recultivated dumps, and the level of residual ionizing radiation on the productivity of the emerging vegetation cover. Studies of plant colonization of recultivated Grachevsky and Shantobinsky uranium mine dumps located in Northern Kazakhstan were carried out. The mining and technical stage of reclamation consisted of planning a dump with slopes of 15° and covering it with a 1 m layer of chestnut soil. In total, 30-35 plant species are present in the dumps, the projective coverage is approximately the same (56.6-70.0%), and the herbage density is 15-16.6 plants/100 m2. As a result of the measures taken to recultivate the dumps, the intensity of the background ionizing radiation at the Grachevsky mine dump was in the range of 25-35 µR/hr and at the Shantobinsky mine dump 10-25 µR/hr, which indicates compliance with safety standards. The plant species which can be used for artificial plant colonization of uranium-containing waste dumps, were identified.

Phytocenotic and Biotopic Parameters Affect the Condition of European Spruce Cultures during the Establishment Stage in the South-East of the Leningrad Region

In the Boksitogorskiy district of the Leningrad oblast, the study was conducted regarding the influence of phytocenotic parameters (crowns density, height, herbage density, moss cover) and biotopic parameters (illumination, acidity, moisture and soil richness) on the morphometric parameters and vitality of European spruce (Picea abies (L.) H. Karst.) BRT (bare root trees) and RBT (root-balled trees) seedlings during the establishment phase under contrasting growing conditions: under the sparse aspen canopy left in clearings and in open spaces, outside the influence of tree crowns. The positive effect of undercanopy cultivation on the safety and viability of seedlings of both types has been statistically proven; with RBT seedlings having the best indicators of vitality and growth along the main axis. However, the herbaceous layer’s height and density under these conditions adversely affected the branching of seedlings. Unlike the undercanopy conditions, when growing in the open, the condition of seedlings was more susceptible to the influence of abiotic factors. Under these conditions, a close positive correlation was found between the viability of seedlings with BRT and the main soil parameters (humidity, acidity, and nitrogen supply). Due to the better illumination on plots without canopies, seedlings with BRT had consistently high growth rates along the main axis. Under these conditions, the grass cover at the stage of spruce establishment was found to have a protective effect, maintaining a more optimal moisture regime and shading the seedlings. The practicality of using the RBT cultures in open spaces was still substantiated, since they were less susceptible to the negative influence of factors.

Evaluation of grass mixtures of a lawn type in the conditions of forest-steppe of the Middle Volga region

In 2019-2020, the quality of lawn-type grass mixtures based on creeping clover (Trifolium repens L.), meadow fescue (Festuca pratensis), pasture ryegrass (Lolium perenne) and meadow bluegrass (Poa pratensis) was evaluated in the conditions of the forest-steppe of the Middle Volga region (Penza region). The studied factors are the composition of the mixtures (creeping clover + bluegrass component), the seeding rates of the components (40 + 70 %; 55 + 55 %; 70 + 40 %) and the background of mineral nutrition (without fertilizers, P45K45, N30P45K45). The growing season during the years of research was characterized by arid conditions, the hydrothermal coefficient (HTC) for the period May-September in 2019 was 0.79, in 2020 - 0.76. On average, over two years of grass mixtures of creeping clover with meadow bluegrass at a seeding rate of 40 + 70 % and 70 + 40 % (from the seeding rate in pure form), creeping clover with meadow fescue with a seeding rate of 70 + 40 % components at all doses of mineral fertilizers had the highest comprehensive assessment of the quality of the lawn. The grass mixtures of creeping clover with meadow bluegrass (70 + 40 %) and creeping clover with meadow fescue (70 + 40 %) against the background of application of N30P45K45 had the maximum indicators in terms of herbage density (1425 and 1475 pcs/m2), which significantly exceeded the control and the variant with the introduction of Р45К45. In these variants, the highest indicators of projective cover (97.5 %) and a comprehensive assessment of "excellent" and "highest quality". According to weediness, the crops were estimated at 1 point (slightly weedy), per 1 m2 of annual and biennial weeds there were 24-27 pcs., rhizome weeds - less than 10 pcs. per 1 m2, the area of weed projective cover did not exceed 5 %.

Revisited the matter of the fodder galega new feed crop cultivation on the irrigated lands of the Lower Volga region

The research results carried out on light-chestnut soils in 2011-2017 are presented, in order to determine the rational parameters of the water, nutritional regimes of the soil and various varieties of fodder galega to create highly productive herbage with their long-term use. The study of the fertilizers calculated doses influence and various pre-irrigation soil moisture thresholds on the herbage density showed that the maximum number of shoots was formed in the Magistr variety crops while maintaining an 80% moisture threshold due to an improved nutritional background. Under the same growing conditions, the highest symbiotic activity and photosynthetic activity of plants were noted. The yield of the fodder galega was significantly influenced by the moisture supply and the nutritional medium. The pre-irrigation soil moisture threshold maintaining at 80% minimum water capacity and the fertilizers application contributed to the formation of 47-83 t / ha of green mass, which meets the high requirements for the feed quality assessment. The accumulation of the root mass contributed to the enrichment of the soil with organic matter and nitrogen, most of which was obtained through the work of nodule-forming bacteria.

The effect of grazing by cattle and sheep on diverse pastures>

The aim of this research was to assess differences in pasture properties associated with grazing diverse swards. A total of six fields were studied on commercial farms in the west of the UK, with three fields being permanent pastures (M1, V2 and M2) and three temporary ley pastures (V1, V3 and M3). Each field was monitored monthly for three months during the autumn when all fields were being grazed. Pastures included a diverse range of grass, legume, herb, flower and weed species. Pasture properties assessed included measurements of grass content, greenness (both %), height (in centimeters), pasture cover (fresh and dry matter in kg per hectare) and pasture density (fresh and dry matter in kg per hectare per centimeter) and nutrient concentrations. The nutrient concentrations measured were dry matter, crude protein, acid detergent fibre (ADF), neutral detergent fibre (NDF), sugars, ash, digestible organic matter in the dry matter (DOMD), oil, nitrate nitrogen, and metabolisable energy (ME). A linear mixed model was used to assess the effect of field, month of study and grazing on pasture properties. This study showed that across fields studied grazed swards were shorter with a higher grass content and fresh/dry herbage density compared to ungrazed swards. Across diverse pastures studied grazed swards had higher nutrient concentrations of dry matter, ADF, NDF and nitrate nitrogen, but lower concentrations of crude protein, sugars and ash. There was no difference in digestibility among grazed and ungrazed swards. While grazing may reduce pasture biomass and certain nutrient concentrations within a pasture, it appears to enhance the grass content and density of the sward, which may provide more sustainable grassland systems.

Effect of Herbage Density, Height and Age on Nutrient and Invertebrate Generalist Predator Abundance in Permanent and Temporary Pastures

The aim of this research was to assess differences in the quantity and quality of herbage and invertebrate generalist predator abundance among permanent and temporary pastures. Two permanent pastures and four temporary ley pastures (either one year or two years since being sown) were monitored weekly for 10 weeks in the spring. Permanent pastures included a diverse range of native UK grass species, and temporary ley pastures were predominantly perennial ryegrass (Lolium perenne) with or without white clover (Trifolium repens). Weekly measurements of herbage height (in centimeters), herbage cover (fresh and dry matter in kg per hectare) and herbage density (fresh and dry matter in kg per hectare per centimeter) were obtained for each field, along with lycosid spider and carabid beetle abundance. Weekly pasture samples were used to obtain nutrient concentrations of dry matter, crude protein, neutral detergent fibre (NDF), acid detergent fibre (ADF), ash, oil, sugars, digestible organic matter in the dry matter (DOMD) and metabolisable energy (ME) in the herbage as a measure of forage quality for grazing or harvesting. A linear mixed model was used to assess the effect of sward age, herbage density and height on herbage production, nutrient concentrations and invertebrate abundance. Although this study showed that permanent pastures were associated with lower nutrient concentrations of crude protein, ash, oil and ME compared to younger and predominantly perennial ryegrass pastures, the older pastures were associated with higher carabid numbers. Furthermore, permanent pastures had a higher density of dry matter herbage compared to younger pastures, and more dense and taller swards were associated with higher lycosid numbers. The study suggests that within pastures of 3 to 20 cm height, increasing the height and density of swards increases both ME and oil concentrations in herbage, therefore enhancing forage nutrient quality. Older and more permanent pastures can be beneficial for plant and invertebrate generalist predator populations, and still provide a useful source of nutrients for forage production.

Effects of sheep and cattle alternate grazing on sheep parasitism and production

Production of sheep (nursing ewes) grazing alternately with cattle (growing weaned heifers) was compared to the production of sheep or cattle grazing alone (controls). Pasture production and sheep parasitism were also monitored. The herbage allowance was higher for the control heifers than for the alternate heifers, but the leaf to green material ratio (LGMR) was lower, and no difference on heifer growth was revealed (443 vs. 431g.d(-1), P = 0.54). The LGMR was higher for the alternate sheep (+3 points) than for the control sheep, except during the dry season, when the herbage density was lower. The effects of parasitism on the packed cell volume of alternate ewes and lambs were lower than those of control ewes and lambs. However, the infection of sheep by Cooperia sp. (better adapted to cattle) was significantly higher for the alternate sheep than for the controls, and some indication of cattle infection by Haemonchus contortus was suggested. The 70-day lamb weight was higher in the alternate grazing system than in the control (+0.76,+1.11 and+0.61kg for the dry, intermediate and rainy seasons, respectively), and the average 70-day lamb production per ewe exposed was 21.42kg in the alternate grazing system vs. 18.59kg in the control (P = 0.003).

A comparison of diploid and tetraploid perennial ryegrass and tetraploid ryegrass/white clover swards under continuous sheep stocking at controlled sward heights. 3. Sward characteristics and animal output, years 4–8

Results for years 4–8 of a long‐term grazing experiment on swards of a diploid perennial ryegrass (Lolium perenne), var. Contender (D swards), a tetraploid ryegrass, var. Condesa (T swards) and Condesa with S184 white clover (Trifolium repens) (TC swards), direct sown in May 1987, are presented. The swards were continuously stocked with sheep from 1988 to 1990, as previously reported, and for a further 5 years, 1991–95, at a target sward surface height (SSH) of 4–6 cm. Control of sward height was successfully achieved by variable stocking, except in 1993 when paddocks were set stocked and the resulting mean SSH was 9·3 cm. Grass swards received on average 160 kg N ha−1 year−1; grass/clover swards were mainly not fertilized with N with the exception that they were given 30 kg N ha−1 as a remedial mid‐summer application during a period of low herbage mass on offer in 1994 and 1995.Mean white clover content of the swards fell from 18·2% of herbage dry‐matter (DM) in 1992 to 8·5% in 1993, whereas stolon lengths fell from 120 to 58 m m−2. A return to lower sward heights in 1994–95 resulted in an increase in white clover content to 12·8% by the final sampling in August 1995. Perennial ryegrass content of the grass swards remained high throughout (mean 96·7% in 1995). Perennial ryegrass tiller densities recorded in August 1991, 1993 and 1994 showed consistently significant (P < 0·001) sward differences (3‐year mean 16 600, 13 700 and 10 100 perennial ryegrass tillers m−2 for the D, T and TC swards). In 1994, the year after lax grazing, a low perennial ryegrass tiller density (9100 m−2) and low white clover content (mean 4·3%) in the TC swards resulted in a much lower herbage bulk density than in the grass swards (April–July means 72, 94 and 44 kg OM ha−1 cm−1 for the D, T and TC swards). There was a consistent 40 g d−1 increase in lamb liveweight gain on the TC swards over the T swards, except in 1994. In that year there was a reduction in lamb liveweight gain of 33 g d−1 on the TC swards and a significant increase in ewe liveweight loss (117 g d−1) associated with low herbage bulk density despite optimal sward height. Lamb output (kg liveweight ha−1) on TC swards reflected white clover content, falling from a similar output to that produced from grass given 160 kg N ha−1, at 18% white clover DM content, down to 60% of grass + N swards with around 5% clover. A 6% greater output from the T than the D swards was achieved mainly through higher stocking rate. The experiment demonstrated a rapid, loss in white clover under lax grazing, and showed that the relationship between performance and sward height is also dependent on herbage density. High lamb output from a grass/clover sward was only achieved when the clover content was maintained at 15–20% of the herbage DM.

Herbage density of third-stage larvae of goat strongyles during the dry season in Guadeloupe.

The objective of this study was to determine the main sources of variation in herbage densities of infective third stage larvae of goat strongyles during the marked dry season of 1994 in Guadeloupe (FWI). Herbage samples were collected for L3 density (LD) determination by an accurate method, 4 times at 4-week intervals in 58 paddocks of 21 farms spread out in five regions of the archipel of Guadeloupe. At the same time, FEC of each grazing animal and fecal culture for parasite genus determination according to sex and age were carried out. Stocking rate, dry matter content of soil, and daily climatic data were also recorded. An index of egg development in larvae (IEDL) was calculated as the ratio of LD to the eggs deposed during the 4th, 3rd, and 2nd weeks before sampling. Medians of LD in herbage were 3397, 1853, 1410, and 324 L3/kg DM for all parasites, Haemonchus, Trichostrongylus, and Oesophagostomum, respectively. Date of sampling, region, and irrigation practice in the northern windward region were the main sources of variation in LD and in frequency of each parasite. LD decreased as the dryness lasted, but it remained important (500 L3/kg DM) despite the drought. LD in windward regions were higher than in other regions. The region, the farm, and the paddock were the main sources of variation of IEDL. LD of each parasites were inversely correlated to global radiation recorded 1 to 3 weeks before herbage sampling, but no relation was found with rainfall data. Trichostrongylus frequency in L3 population increased as the dryness lasted. A dryness axis was extracted from environmental variables (climatic data, dry matter of soil, duration of dryness) by a multiple factorial procedure. LD and Haemonchus frequency in L3 population were inversely correlated to dryness axis (p < 0.01). In contrast, Trichostrongylus frequency was positively correlated to the dryness component.

Vertical distribution of trichostrongylid larvae on herbage and in soil

Vertical distribution of trichostrongylid larvae on herbage and in soil. International Journal for Parasitology 16: 241–244. The vertical migration of third stage trichostrongylid larvae (L 3) on herbage was studied at controlled temperatures and humidities to help quantify the relationship between weather and the movement of L 3 onto pasture. Pots of grass and clover were seeded on top of the soil with approx. 1000 L 3 of Teladorsagia spp. and Trichostrongylus spp. of sheep nematodes. Pots were sampled for viable L 3 at daily intervals over 4 days. On average we recovered 8 times more L 3 in soil than on herbage, and the proportion of 1.3 on herbage did not increase significantly ( P=0.44) with time, that is there was no significant positive migration from soil onto herbage. We recovered a mean of 20.0% of the initial population of L3 over 4 days. Only 2.0% of these were on herbage, with 1.3% found below 2 cm. Seventy-one percent of the L 3 which were recovered were concentrated within 2 cm of the soil-herbage interface. Recovery of L 3 on herbage was significantly ( P=0.001) dependent on temperature and humidity. There was no significant ( P > 0.30) difference in the percentage of L 3 recovered from grass and clover. Neither the ratio of Teladorsagia spp. to Trichostrongylus spp. in the L 3 populations nor herbage density significantly affected percentage of L 3 found on herbage.

Grassland dynamics of radioiodine: A filtration model simulation

The importance of certain air-pasture-herbivore-foodstuff pathways in a radiological impact assessment of airborne radioiodine necessitates a reliable quantitative simulation of the dynamics along each step of those pathways. Iodine's transport to and dynamics within a grass canopy are investigated, using a previously formulated filtration model as a contending simulator. The model's prediction is severally fitted (with high quality) to experimental data on the grassland retention of intercepted iodine, providing consistent model parameterisations, namely, that of the surface-lodged iodine, ≈20% is dislodged and ≈4% is assimilated per day. However, the model is not severely tested by the short experimental durations (up to one month) and shallow grassland canopies (up to 0·2 kg m −2 dry herbage density) for which predictions of retention depart insubstantially from exponentiality. The model is potentially a strong candidate for estimating the necessity for, and duration of, interdiction of radioiodine-contaminated grazing land — in respect of either actual contamination or a postulated contaminating scenario.

Grazing by sheep and the distribution of species through the canopy of a red clover‐perennial ryegrass sward

AbstractA trial was carried out to investigate whether or not sheep grazing at stocking rates of 22 (low) and 44 (high) ha−1 select red clover from a red clover‐perennial ryegrass sward, The distribution of botanical and morphological components was assessed in consecutive 5‐cm layers through the canopy inside and outside exclosure cages moved every 2 weeks for 6 weeks. The difference between inside and outside cages for a given layer was an indication of the amount of each component consumed from that position in the sward, and the corresponding difference for clover content was considered an indication of selection.Evidence of selection was observed over the third and fourth weeks of grazing, especially in the high stocking rate treatment. Laminae of red clover were selected in preference to other plant parts and were grazed throughout the depth of the canopy in contrast to grass. The basal layer at the high stocking rate during weeks 5 and 6 was not grazed suggesting that the crown of red clover may be protected from severe overgrazing by accumulation of dead matter.It was concluded that the low herbage density of red clover‐grass swards allowed the occurrence of selection which was most pronounced when the sward was being grazed down relatively quickly.

Variations in the surface characteristics of the sward and the short‐term rate of herbage intake by calves and lambs

AbstractThe results are reported of an examination of detailed measurements on the ingestive behaviour of calves and lambs in response to variations in the surface characteristics of swards under strip‐grazing and continuous stocking managements. It is shown that intake per bite and the short‐term rate of herbage intake were both sensitive to the height of the surface horizon above ground level but, at least under strip‐grazing management, not to variations in herbage density in the grazed horizon. The rate of biting was less sensitive to variations in sward conditions, particularly under strip‐grazing.Both intake per bite and rate of intake were more sensitive to variations in grazing height under strip‐grazing, where sward changes were rapid, than under continuous stocking, where they were slow. Under continuous stocking, ingestive behaviour was more sensitive to changes in sward conditions in lambs than in calves.

Interception and retention of radioactive aerosols by vegetation

The efficiency of vegetation as a filter for nuclides deposited on the earth's surface is examined. The proportion of the fallout initially retained in the herbage, p, is assumed to be related to an uptake coefficient μ (m 2 kg −1) by the relation 1 − p = exp − μw, where w is the herbage density in kg m −2 dry matter. Experimental values of μ lie in the range 2.3 to 3.3 m 2 kg −1, and there does not seem to be any marked dependence on the physical form of the activity. The rate of loss of activity by weathering from foliage is next considered. The field loss coefficient λ b has been found to be of order 0.05 days −1 in field experiments during the growing season, but lower values (corresponding to longer retention periods on the foliage) have been observed in winter. Representative values of p and λ b are then used to calculate the normalised specific activity of herbage continuously exposed to fallout, where N.S.A. = Activity per kg dry matter on foliage Activity deposited day −1 m −2 of ground The calculations give N.S.A. values ranging from 27 to 55 m 2 days kg −1 depending on the value assumed for λ b and for the time T 0 between successive croppings of the herbage. Finally, surveys of the activity of 90Sr and 137Cs in the U.K. and abroad are used to deduce the N.S.A. of foliage exposed to world-wide fallout from weapon tests. Good agreement with the calculated values is obtained, but there is evidence of enhanced N.S.A. values in poor growing conditions.