Simulated Rotational Grazing Research Articles

How Does Nitrogen Application Rate Affect Plant Functional Traits and Crop Growth Rate of Perennial Ryegrass-Dominated Permanent Pastures?

High doses of nitrogen (N) fertiliser input on permanent pastures are crucial in terms of N surplus and N losses. Quantitative analyses of the response of plant functional traits (PFT) driving crop growth rate (CGR) under low N input are lacking in frequently defoliated pastures. This study aimed to understand the significance of PFTs for productivity and N uptake in permanent grasslands by measuring dynamics in tiller density (TD), tiller weight (TW), leaf weight ratio (LWR), leaf area index (LAI), specific leaf area (SLA), as well as leaf N content per unit mass (LNCm) and per unit area (LNCa) in perennial ryegrass (Lolium perenne)-dominated pastures, in a simulated rotational grazing approach over two consecutive growing seasons. Annual N application rates were 0, 140 and 280 kg N ha−1. The phenological development of perennial ryegrass was the main driver of CGR, N uptake and most PFTs. The effect of N application rate on PFTs varied during the season. N application rate showed the greatest effect on TD, LAI and, to a lesser extent, on SLA and LNCm. The results of this study highlight the importance of TD and its role in driving CGR and N uptake in frequently defoliated permanent pastures.

Responses of biotic interactions of dominant and subordinate species to decadal warming and simulated rotational grazing in Tibetan alpine meadow.

Warming increases competition among plant species in alpine communities by ameliorating harsh environmental conditions, such as low temperatures. Grazing, as the main human activity, may mitigate the effect of warming, as previously reported. However, it is critical to refine the effects of warming on biotic interactions among species, for example, by taking the competitive ability of species into consideration. Based on a 10-year warming and grazing experiment in a Tibetan alpine meadow, we evaluated interspecific biotic interactions of dominant and subordinate species, using the approach of interspecific spatial associations. Warming significantly increased competition between subordinate and dominant species as well as among subordinate species, but not among dominant species. Moreover, facilitation of dominant-subordinate species also increased under warming. Simulated rotational grazing had similar effects to warming, with increasing interspecific competition. Our results show that, when studying the effects of warming on biotic interactions among species, it is necessary to characterize different species pairs relative to their competitive ability, and that simulated rotational grazing does not mitigate the effects of warming in the long term. Our results also provide evidence that the spatial pattern of species is a critical mechanism in species coexistence.

Yield and nutritional value of permanent grassland forage under simulated rotational grazing

A cutting experiment was conducted to test the changes in botanical composition, yield and nutritional value of forage, obtained in conditions of simulated rotational spring grazing on permanent grassland. The experiment was carried out on permanent pasture in vicinity of Sabac, Serbia in 2015 included three cuttings as a simulated rotational spring grazing. The highest share of grasses was noted in the first cut and decreased in the second and third cut, with increased forbs participation, and relatively constant percentage of legumes. The highest dry matter (DM) yield was obtained for the first harvest, followed by the second cut, and the lowest forage production was determined for the third harvest, with only 11.04 and 17.42% of the first and second cut yield. There were not found the significant differences between cuts for herbage DM and crude protein content. Markedly lower value for non-protein N concentration (p<0.05) was determined in the third cut. The fiber content increased during the grazing season (p<0.05), with the highest value determined in the herbage obtained in the second cut. The highest energy values (p<0.05) had the herbage produced in the first cut (DM basis), wherein the lowest values were found in the forage from the second harvest. These results indicate that especially herbage yield of analyzed grassland as chemical composition and nutrition value are highly variable during the growing season. The accurately defined optimal period for using is necessary to provide the high-quality forage for grazing animals.

Influence of simulated rotational grazing on the forage production of spring wheat, oats and rye in the Yellow River irrigation area

Influence of simulated rotational grazing on the forage production of spring wheat, oats and rye in the Yellow River irrigation area

Nutrient Runoff Potential from Fescue Pastures using Simulated Rotational Grazing of Lactating Dairy Cows

This study was designed to evaluate phosphorus (P) losses from rotationally grazed pastures. Sod of tall fescue was transplanted into boxes 100×18.4 cm2. Treatments (13) imposed in triplicate were a no P control, inorganic P at rotational requirements, inorganic P at seasonal requirements, and 10 plots representing a paddock in a 20‐day, alternate‐day grazing rotation. Treatments were isonitrogenous; three rotations were conducted. Inorganic fertilizers were applied on day 1 of the rotation. Dairy slurry from grazing cows was applied daily to the respective treatments. Rainfall was simulated after each rotation, and continuous runoff was collected for 30 min. Total and dissolved reactive P in runoff were lower from control than from P‐amended treatments. No differences were observed among P‐amended plots. The small size of the boxes and naturally high variability in fescue sod did not allow for an accurate assessment of the risk of P losses from rotationally grazed pasture.

Canopy morphology and nutritional quality traits as potential grazing value indicators for Lolium perenne varieties

Twelve perennial ryegrass (Lolium perenne L.) varieties of different ploidy and maturity classifications were compared under a frequent cutting management in their second harvest year, equivalent to the simulated rotational grazing system employed in UK testing protocols. Varietal differences in canopy structure (proportion of lamina, green leaf mass, sward surface height, extended tiller height, bulk density) and in herbage nutritive value factors (water-soluble carbohydrate content and proportion of linoleic and α-linolenic fatty acids) were assessed and their importance evaluated with reference to total herbage production. Significant variety variation (P<0·001) was recorded in the annual means of all the canopy structure characteristics. Significant differences associated with ploidy were also recorded, with tetraploid varieties having significantly higher values than diploids in most plant characters, indicating better intake characteristics for these grasses. Temporal patterns of variation associated with maturity were also observed in several characters, thus making it impossible to designate a single assessment that would be representative of the annual ranking of varieties. Water-soluble carbohydrate concentration differed significantly (P<0·001) between varieties and although the tetraploids tended to have high contents, the highest value of all was recorded in a diploid variety, which had been selectively bred for this trait. The varieties did not differ in total lipid content but there were significant differences in the proportion of linoleic acid between varieties (P<0·001) while the proportion of α-linolenic acid differed between varieties (P<0·001), ploidy (P<0·001) and maturity (P<0·05) classes.Overall evaluation of the extensive variety variation highlighted the need for better quantification of animal responses to differences of these magnitudes, before the high workload of including them in routine variety testing protocols could be justified. Potential for breeding improvement in these factors was also indicated and the future prospects for their use in farmer decision support systems was considered.

Effect of soil-N and urine-N on nitrate leaching under pure grass, pure clover and mixed grass/clover swards

During six annual drainage periods (DP O to DP 5), the drainage water, the NO 3 concentration of the drainage water and the total leached N were compared under bare soils and under ryegrass/white clover, pure ryegrass and pure white clover stands in 80 deep lysimeters with 3m 2 area. For each soil cover, the sensitivity of the variables to the soil N supplying capacity at sowing was measured, using a set up of 32 lysimeters. This initial capacity to supply mineral N (SoilN) varied from 90 to 230 kg N ha −1 year −1. The stands were managed in a simulated rotational grazing system, without addition of fertilizer N. During the first drainage period after sowing (DP 0), N leaching increased significantly with the initial SoilN under the bare soils, the pure grass and the mixture, but was not influenced under the pure clover. In the following drainage periods, N leaching increased according to the sequence pure grass (1–5 kg N ha −1 year −1), mixed swards (1–19 kg N), pure white clover (28–140 kg N) and bare soils (84–149 kgN ha −1 year −1). It was only slightly greater under the mixture than under the pure grass, despite the N harvest and the N animal returns were much higher. Under the mixed stands, N leaching became independent of the initial SoilN in DP 1 and DP 2 and decreased with increasing initial SoilN in DP 3, DP 4 and DP 5. This inversion of the SoilN effect in time and the limited amounts of leached N demonstrated that adaptations in the ecosystem tend to counteract the SoilN effect on the N losses. In the mixed stands, the accumulated N leaching represented 12 and 21% of the accumulated N at harvest for the initially rich and poor soils, respectively and 32% of the accumulated N harvest in the mixed clover, whatever the initial SoilN. N leaching also represented 13% of the urine-N above 80 kgN ha −1 year −1. The low values of N leaching under the mixed swards make them sustainable for environment quality. Mechanisms which regulate the N fluxes are discussed, using published data on the soil and some results concerning the harvests in the same experiment.

Differences in the nitrogen use efficiency of perennial ryegrass varieties under simulated rotational grazing and their effects on nitrogen recovery and herbage nitrogen content

Eight varieties of perennial ryegrass (six new varieties and two old ones) grown at five levels of applied fertilizer (100, 200, 300, 400 and 500 kg of N ha–1) were cut monthly during two growing seasons (March to October in 1997 and 1998) and their herbage dry‐matter (DM) yield and nitrogen (N) content were determined. Herbage leaf content and the N content of young fully expanded leaves were also measured in 1997, and monthly recovery of applied N was determined in both the first and second harvest years by using 15N.The rank order of varieties was similar for annual yield of DM and N at all five fertilizer levels. Proportional differences between varieties in DM yield were greatest in the first cut of each year, the late‐heading candidate variety Ba12151 out‐yielding the old late‐heading variety S23 by more than 70%. However, differences in annual DM yield were much more modest than in early spring yield, up to 10% in 1997 and up to 21% in 1998. The relatively small differences in total annual DM yield were attributed to only a small proportion of the applied N being recovered during a single regrowth period, most of the remainder becoming available for uptake in subsequent regrowth periods.There were small but highly statistically significant differences among varieties in the N content of their leaves, leaf N content being inversely related to yield of DM and N. This lends further support to the hypothesis that the metabolic cost of protein synthesis and turnover is a key factor controlling genetic variation both in leaf yield and in annual DM and N yield under frequent harvesting. Seasonal variation in herbage N content was much greater than differences among varieties in mean N content over all harvests. In May of both years at all applied fertilizer levels, herbage N content fell below the 20 g N kg–1 DM level required by productive grazing animals.

Response of perennial ryegrass varieties to annual changes in sward management

AbstractThe effect of annually switching sward management between cutting regimes that simulated rotational grazing and those for forage conservation vs. maintaining a constant management regime was studied by testing for ranking‐order changes between six perennial ryegrass varieties.Total dry‐matter (DM) yields were found to change in response to an annual switch in management. When under a conservation management and switched in the next year to simulated grazing, all six varieties yielded more in that year than when they were maintained constantly under simulated grazing. Similarly, when under a simulated grazing management and switched in the next year to conservation, all six varieties yielded less than when maintained constantly under a conservation management. These yield differences were largely expressed in spring of the year following the management switch.Differences in the ranking order of varieties were observed between the constant sward management treatments and the alternating managements. However, in these changes in variety ranking, no variety was consistently favoured or disadvartaged by the annual switch in management. Therefore, no clear evidence was produced that an alternating management system had any consistent effect on variety ranking and the observed changes were possibly due to the normal year‐to‐year variation frequently recorded in variety performance trials.

Long‐term effects of different rotational grazing schedules on the productivity and floristic composition of Tall Grassveld in KwaZulu‐Natal

Abstract Nine simulated rotational grazing systems, comprising combinations of three different periods of occupation (2, 10 and 20 days) and three periods of absence (20, 40 and 60 days), were applied to Tall Grassveld for 24 years (1967–1991), using sheep. All camps were rested every fourth year during which recovery growth yields were measured. Differences in floristic composition between camps at the end of the trial were small and were associated with spatial variations in composition on the experimental site rather than with the applied grazing treatments. Although palatable grasses, such as Themeda triandra and Tristachya leucothrix, were still dominant in 1991, the unpalatable grass Aristida junciformis increased in abundance in all treatments during the last seventeen years of the trial. The extent of this increase did not, however, vary (P≥0.05) between treatments. The mean recovery yield over all rest years did not differ (P≥0.05) between treatments because of inconsistencies in treatment effect...

The effect of veld condition on the quality of diet selected by cattle grazing the Natal Sour Sandveld

The quality of diet selected by steers fistulated at the oesophagous was related to veld condition in a simulated rotational grazing system on the Natal Sour Sandveld. Six camps, ranging in veld condition score from 8,5 to 53%, were grazed simultaneously for a two‐week period in spring, summer, autumn and winter. Fistula samples were collected on the first, middle and last day of a period of occupation in a camp. Samples were analysed in terms of crude protein (CP), in vitro digestibility (IVD) and plant‐part (% leaf, % stem and % dead material) composition. Dietary quality in terms of CP, IVD and plant‐part composition was not related to veld condition but was dependent largely (P≤0,01) upon season and to a lesser extent upon period of occupation in a camp. It was concluded that in sourveld areas, where dietary quality may be limiting, the veld condition score may be a poor index of potential animal production.

The effects of height of stubble left after simulated rotational grazing on regrowth of star grass

Abstract Star grass (Cynodon aethiopicus cv. No. 2) was grazed to leave stubble of 5, 15 or 25 cm in height after grazing. In the first year (1972–73) 350 kg N and 39 kg P per ha, and in the second year (1974–75) 500 kg N and 39 kg P per ha, were applied. Grazing was done at 15‐day intervals although in the first year this was not always possible because of poor rainfall which affected growth. In both years amounts of herbage harvested above the three stubble heights decreased as the height of stubble left after grazing increased. The relative proportions of green leaf, dead leaf and stem were similar with all stubble heights although there was slightly less green leaf in the 5 cm stubble.

Screening of legumes for veld reinforcementpeulgewastoets vir veld verbetering

Abstract In order to test their suitability for veld reinforcement, Desmodium intortum, D. sandwiceme, D. uncinatum,Glycine wightii, Listia heterophylla, Lotononis bainesii, Macroptilium atropurpureum, Stylosanthes fruticosa, S. humilis and three strains of S. guianensis were seeded in December 1970 in disced veld at Marandellas (sand) and near Mazoe (clay). Starting in December 1971 the legumes were grazed in common at two stocking intensities during the wet season only, the dry season only or year‐round, using a simulated rotational grazing system. Legume seedling mortality was high on the sand and only M. atropurpureum and the five Stylosanthes lines had plant densities in the second season greater than 1 plant/m2. On the clay establishment was better and all legumes except L. heterophylla had densities greater than 1 plant/m2. Oxley fine‐stem stylo was the only legume to persist and spread on the sand but on the clay a much wider range of legumes persisted, although all were adversely affected by a ho...