Effects Of Defoliation Frequency Research Articles

Forage productivity and morphogenesis of Mesosetum chaseae under defoliation frequency

The effect of defoliation frequency (14, 21, 28, 35, 42, 49 and 56 days) on forage production and morphogenic and structural characteristics of Mesosetum chaseae (Luces) was evaluated under natural field conditions during the dry season, in the savannas of Roraima. The reduction in pasture defoliation frequency resulted in higher green dry matter (GDM) yields, number of tillers plant-1, number of leaves tiller-1, tiller leaf area, leaf senescence rate and average leaf size. The relationship between defoliation frequency and GDM production was quadratic, with the maximum value estimated at 53.8 days of regrowth. Absolute rates of growth and leaf appearance and expansion were inversely proportional to defoliation frequencies. The highest rate of leaf expansion was obtained at 49.7 days of regrowth. Aiming to reconcile forage productivity with the optimization of the morphogenic and structural characteristics of the grass, the most appropriate period of use of its pastures is between 42 and 49 days of regrowth.

Forage productivity and chemical composition of Megathyrsus maximus cv. Tamani under defoliations regimes

The effects of defoliation frequency (21, 28, 35 and 42 days) and defoliation intensity (20, 30 and 40 cm above the ground) on green dry matter (GDM) yield, and chemical composition of Megathyrsus maximus cv. Tamani were evaluated under natural field conditions at the Roraima´s savannas. Defoliation regimes affect productivity and chemical composition of M. maximus cv. Tamani forage. The decrease in the pasture defoliation frequency and intensity improved the accumulation of forage, however it reduces the tissue concentrations of N, P, Ca, Mg and K. Irrespective of defoliation frequencies, the highest levels of N (25.31 g kg-1), P (2.11 g kg-1), Mg (2.78 g kg-1) and K (21.13 g kg-1) were recorded for the defoliation intensity at 40 cm above the ground, except for Ca (4.31 g kg-1), where the greatest concentration was obtained with defoliations at 30 cm above the ground. The use of defoliation frequency around 32 days and defoliation intensity of 28 cm above the ground can be considered adequate for the management of pastures of M. maximus cv. Tamani, in order to provides higher forage productivity and quality, regrowth vigor, larger efficiency of forage utilization, greater tissue renewal and canopy structure more favorable to grazing.

Forage productivity and chemical composition of Panicum maximum cv. Mombaça under defoliations intensities and frequencies

The effects of defoliation frequency (28, 35, 42 and 49 days) and defoliation intensity (30, 40 and 50 cm above the ground) on green dry matter (GDM) yield, and chemical composition of Panicum maximum cv. Mombaça were evaluated under natural field conditions at the Roraima´s savannas. Defoliation regimes affect productivity and chemical composition of grass forage. The decrease in the pasture defoliation frequency and intensity improved the accumulation of forage, however it reduces the tissue concentrations of N, P, Ca, Mg and K. Irrespective of defoliation frequencies, the highest levels of N (23.99 g kg-1), P (2.12 g kg-1), Ca (4.22 g kg-1), Mg (2.87 g kg-1) and K (21.45 g kg-1) were recorded for the defoliation intensity at 40 cm above the ground. The use of defoliation frequency around 42 days and defoliation intensity of 42,9 cm above the ground can be considered adequate for the management of pastures of P. maximum cv. Mombaça, in order to provides higher forage productivity and quality, regrowth vigor, larger efficiency of forage utilization, greater tissue renewal and canopy structure more favorable to grazing.

Effect of vernalisation on the diurnal changes in fatty acid profile and nutrient composition of chicory in response to defoliation frequency

ABSTRACT The effect of defoliation frequency and severity on FA and nutrient composition of forage chicory (Cichorium intybus L.) before and after vernalisation were compared. Before vernalisation, the FA and nutrient components exhibited little variation with defoliation frequency and severity irrespective of the time of day. After vernalisation, total FA more than halved compared with pre vernalisation levels (52.2 versus 19.2 mg/g DM). Concentrations of total FA and polyunsaturated FA: linoleic and linolenic declined by 63%, 50%, and 74%, respectively. Furthermore, extending the defoliation frequency from 300 to 600 growing degree-days after vernalisation caused a decline of 28% of linoleic, 40% of linolenic and 33% of total FA concentrations. Diurnal fluctuations were detected for linoleic and oleic acids after vernalisation (P < 0.01). In terms of nutrient composition, vernalisation decreased CP, digestibility and ME, while fibre contents increased. Between morning and afternoon, there were general declines in CP and fibre contents as well as increases in soluble sugars the herbage regardless of vernalisation. Overall, the feeding value and the concentration of FA were greater on chicory herbage managed under shorter regrowth intervals than that under longer regrowth intervals, which is likely to favour animal production and the concentration of the desirable FA in ruminant products.

Effect of defoliation strategies on the productivity, population and morphology of plantain (Plantago lanceolata)

This trial provided information about effects of defoliation frequency, defoliation intensity and winter management (grazing or rest) on the productivity, morphology and plant population of a 3-year-old plantain (Plantago lanceolata) stand. Plant population density declined drastically over time independently of grazing management, with the greatest decrease in summer. Winter grazing had a critical effect on the productivity and population remaining 6 months later. Frequent grazing during summer increased plantain contribution. Grazing intensity reduced crown weight and diameter of individual plants. Further studies are required to determine the interactions of defoliation management with pastures of different age including the natural reseeding as a mechanism to maintain plant recruitment. Keywords: defoliation, grazing, morphology, population

Defoliation frequency effects on winter forage production and nutritive value of different entries of Agropyron cristatum (L.) Gaertn

The objective of this study was to evaluate the effect of different defoliation frequencies on winter forage production and nutritive value of improved population of Agropyron cristatum (L.) Gaertn. Four entries, a) base population, b) selected plants from mass honeycomb selection (MHS), c) selected plants from pedigree honeycomb selection (PHS) and d) selected plants from pedigree honeycomb selection using the combined criterion CC = x¯2 (1 – CV) / CV [PHS (CC)] were tested under four defoliation frequencies: 1) frequent, 2) moderate, 3) infrequent and 4) control. Dry matter production under moderate defoliation treatment was 9% and 107% respectively higher than frequent and infrequent the first harvest year, while the second harvest year the corresponding percentages were 26% and 44%. The selected populations of A. cristatum consistently exceeded in herbage production the base population under all defoliation treatments during winter. Among the selected entries, [PHS (CC)] had consistently higher DM production compared to MHS and PHS for the two experimental years. The CP content was significantly higher, while NDF, ADF and ADL contents were lower in the increased defoliation frequency compared to the control in both harvest years. There were no significant differences of the nutritive value among the entries (P &gt; 0.05). Generally, herbage production of the moderate defoliation frequency was more stable through the years with relatively high nutritive value.

Defoliation frequency effects on winter forage production and nutritive value of different entries of Dactylis glomerata L.

The objective of this study was to evaluate the effect of different defoliation frequencies on winter forage production and nutritive value of improved populations of Dactylis glomerata L. Four entries: (a) base population, (b) selected plants from mass honeycomb selection (MHS), (c) selected plants from pedigree honeycomb selection (PHS), and (d) selected plants from pedigree honeycomb selection using the combined criterion CC = x 2 (1 ‐ CV)/CV (PHS(CC)) were tested under four defoliation frequencies: (1) frequent, (2) moderate, (3) infrequent, and (4) control. Dry matter (DM) production under the frequent and moderate defoliation frequencies was 17% and 7% respectively more than under infrequent defoliation in the first year. However, in the second year, DM production under infrequent defoliation was 41% and 46% higher than under frequent and moderate defoliation, respectively. The DM production of the selected populations (b, c and d) of D. glomerata consistently exceeded that of the base population (a) under various defoliation frequency regimes during winter. Among the selected entries, MHS and PHS(CC) had consistently higher DM production than PHS for the two experimental years. Under increased defoliation frequencies, crude protein content significantly increased and neutral detergent fibre and acid detergent fibre significantly decreased compared with the control defoliation treatment in both years. There were no significant differences (P > 0.05) in nutritive value among the entries. Generally, DM production was more stable under infrequent defoliation, while nutritive value met the demands of small ruminants for maintenance and lactation.

Defoliation frequency and cultivar effects on the storage and utilisation of stolon and root reserves in white clover

The effects of defoliation frequency (2 or 6 defoliations over a 91-day period) on the reserve status and growth rate of 2 white clover cultivars, cvv. Irrigation (medium-leafed) and Haifa (large-leafed), were examined over the final 42 days of the defoliation treatments. The clover plants consisted of single stolons growing in a sand/scoria mix in an unheated glasshouse, and were fertilised weekly with a solution containing essential nutrients excluding nitrogen. More frequent defoliation reduced the leaf appearance rate, stolon elongation rate, and plant size, and increased stolon death, with all of these effects being less pronounced in Irrigation than in Haifa (18% v. 30%, 60% v. 80%, and 23% v 34%, respectively, for leaf appearance rates, stolon elongation rates, and the proportion of stolon length that died). With infrequent defoliation, the combined utilisation of starch and water-soluble carbohydrate (WSC) reserves in the first 14 days after defoliation was equivalent to 15% of the plant weight at defoliation, and to 95% of the new leaf produced during that period. Frequent defoliation reduced the reserve content and remobilisation less in Irrigation than in Haifa, with the combined mass of remobilised starch and WSC over the first 14 days after defoliation being 2.9% and 2.0% of the plant weight at defoliation, and 29% and 19% of leaf production over that period, for Irrigation and Haifa, respectively. The greater reserve mobilisation in Irrigation than in Haifa plants under frequent defoliation probably contributed to their higher growth rates and reduced stolon death. These cultivar differences with frequent defoliation suggest that Irrigation is more suited to frequent defoliation than Haifa.

Defoliation frequency and genotype effects on stolon and root reserves in white clover

The effect of defoliation frequency (1 or 3 defoliations over a 42-day period) on the starch, water soluble carbohydrate (WSC), and nitrogen contents of 3 white clover cultivars (Haifa, Irrigation, and S184) was examined. The clover plants consisted of single stolons growing in a sand/scoria mix in an unheated glasshouse and fertilised weekly with a nitrogen-free solution. Starch concentrations ranged from 1·3% in frequently defoliated Haifa to 15·3% in infrequently defoliated S184 plants. However, there was no interaction between cultivar and defoliation frequency, with the starch concentration in S184 (11·2%) being twice that in Irrigation (6·0%) and 3 times that in Haifa (3·8%). The starch concentration was also less with frequent (3·7%) than with infrequent (10·3%) defoliation. The starch was localised in the old stolon material (12·2%), with lower levels of starch in both the young stolon (6·0%) and roots (4·0%). Furthermore, the cultivar and defoliation frequency effects on the starch concentrations were most pronounced in the old stolon. More frequent defoliation also resulted in a small reduction in the WSC and nitrogen concentrations in both the young and old stolons of Haifa, but not of Irrigation. It was concluded that although starch reserves were the principal method of reserve storage in white clover, WSC and nitrogen reserves will form a relatively large fraction of the reserve pool when starch reserves are depleted under conditions such as frequent defoliation.

Effect of defoliation frequency on an irrigated perennial pasture in northern Victoria. 1. Seasonal production and sward composition

A field experiment was carried out to investigate whether changes in winter and post-winter defoliation frequency would increase the white clover content of an irrigated perennial ryegrass–white clover pasture in northern Victoria. Pastures defoliated every 4 weeks during winter had higher white clover growing point (stolon apices with at least 2 nodes) density at the end of winter than pastures defoliated every 8 weeks or those receiving a single defoliation after 16 weeks, but these differences did not affect the clover content in the spring. Reasons for this are suggested. Pastures defoliated at 8-week intervals in winter were the most productive over winter{early spring. Less frequent defoliation (4 v. 2 weeks) during the post-winter, September–May period reduced white clover growing point and perennial ryegrass tiller densities. However, the white clover growth rate during this period was increased by less frequent defoliation, whereas the ryegrass growth rate was reduced, resulting in an increase of 10% in the white clover content, and a 1·9 t dry matter (DM)/ha increase in total DM produced. This higher clover content and pasture yield during spring–autumn with less frequent defoliation has important implications for the management of irrigated perennial pastures for the dairy industry in northern Victoria.

Effect of defoliation frequency and summer irrigation on survival of perennial (Lolium perenne) and biennial (Lolium multiflorum) ryegrass in the subtropics

Summary. The present study investigated, in a subtropical environment, the timing of defoliation treatments in spring and summer irrigation management on the survival of perennial (Lolium perenne cv. Yatsyn) and biennial (L. multiflorum cv. Noble) ryegrass in a mixed ryegrass–white clover (Trifolium repens) pasture over the first summer, and seedling recruitment the following autumn. Defoliation options were related to various ryegrass plant development stages such as the number of leaves per tiller attained during regrowth, stem elongation and seed set. The criterion for timing of frequent defoliation was 1 leaf/tiller regrowth and infrequent defoliation 3 leaves/tiller. Both pasture types were defoliated either frequently or infrequently at specific times from sowing to mid summer. Half the plots were irrigated from 30 November to 6 April while the remaining plots were not irrigated over this period. There was no survival of biennial ryegrass plants into autumn of the second year and pasture production was entirely from seedling recruitment of seed set in the previous spring. The maximum seedling recruitment (plant population 89% of spring in establishment year) was achieved by infrequent defoliation in mid spring and then cessation of defoliation until mid summer to allow plants to set seed. However, this resulted in a production loss of 3094 kg dry matter/ha of ryegrass and clover. In contrast, production of perennial ryegrass in the second year was reliant almost exclusively on individual ryegrass plants surviving the summer, as there was little seed set and virtually no seedling recruitment. There would appear to be 2 contrasting defoliation requirements to optimise perennial ryegrass persistence. Infrequent defoliation from sowing to early spring (22 March–2 September) and frequent defoliation in early summer (19 November–3 February) resulted in maximum plant survival and minimum tropical grass incursion. Frequent, compared with infrequent, defoliation up to 2 September decreased root dry matter in February by 45% to 1.66 g dry matter/plant. However in early summer, frequent defoliation maximised survival, presumably by reducing shading by tropical grasses, and preventing a closed canopy which encourages ‘rust’ infestation of the ryegrass. Irrigation of ryegrass over summer, in situations likely to become waterlogged, will only be of benefit in dry years and if scheduling is frequent enough to benefit ryegrass rather than tropical grass. These results highlight the importance of maintaining an infrequent defoliation interval to maximise persistence of perennial ryegrass in the subtropics. More frequent defoliation may be necessary in late spring/early summer to reduce the impact of leaf rust.

Effect of defoliation frequency on an irrigated perennial pasture in northern Victoria 2*Part 1, Aust. J. Agric. Res., 1997, 48, 811 - 17.. Individual plant morphology

The effect of 5 winter and 2 post-winter defoliation frequencies on the morphology of medium-leafed and large-leafed white clover and perennial ryegrass plants in an irrigated perennial pasture in northern Victoria was investigated. Measurements included leaf appearance rates, axillary bud development and survival, stolon elongation and survival, and tiller production and survival. White clover leaf appearance rate was affected little by either defoliation frequency or cultivar, ranging from 0·4 leaves/week in July to 1·1 leaves/week in February. In contrast, perennial ryegrass leaf appearance rate in the same period ranged from 0·35 to 0·7 leaves/week. Axillary bud production on clover stolons was highest in winter and spring and lowest through summer, and was usually greater in the medium-leafed than in the large-leafed cultivars. When the swards were not defoliated through winter, the rate of bud production was reduced in late winter; this was followed by a high rate of bud production in early spring, resulting in little treatment difference in the number of buds per stolon by mid spring. Bud survival was greater when initiated in winter than in summer. The rate of stolon death in spring was higher in the swards not defoliated during winter and higher in the large-leafed than in the medium-leafed cultivar. These effects were associated with the stolon elongation rate in late winter; the medium-leafed cultivar was unaffected by defoliation frequency, whereas in the large-leafed cultivars the rate of stolon elongation increased as the defoliation interval lengthened and canopy shading increased. Perennial ryegrass tiller production was greater with frequent than infrequent winter or post-winter defoliation, but never exceeded 1·2 daughter tillers/tiller, with 44% of the reproductive tillers failing to replace themselves. The low leaf appearance rate and tiller production of the perennial ryegrass may contribute to its poor competitiveness and persistence in this environment.

Leaf number as a criterion for determining defoliation time for Lolium perenne: 2. Effect of defoliation frequency and height

AbstractThe object of this study was to determine the importance of frequency and height of defoliation on regrowth potential of Lolium perenne. Defoliation interval was based on stage of the regrowth cycle, as indicated by leaves per tiller.Simulated swards of Lolium perenne cv Yatsyn were grown as individual plants in a glasshouse kept at a day/night temperature of 25°C/15°C.Treatments imposed were defoliation at 2, 5 or 12 cm residual height, and low and high water soluble carbohydrate (WSC) level obtained by varying defoliation interval, i.e. defoliating at the 1‐leaf or 3‐leaf stage of the regrowth cycle. Regrowth after frequent short defoliations was only 65% of the less frequently defoliated plants taken over the full regrowth cycle. This was associated with a lower stubble WSC content (2·15 vs 17·5% in stubble) and a twenty‐seven‐fold difference in the amount of WSC in the stubble per plant. This difference in total WSC was a combined effect of more and heavier tillers and higher WSC content in stubble of plants defoliated less frequently at the end of the regrowth cycle. The regrowth of plants with WSC levels depleted by frequent defoliation when defoliated at 2 cm was significantly below that of those defoliated at 5 and 12 cm.The results indicate the desirability of defoliating plants at the 3‐leaf stage of the regrowth cycle. This not only allows the full regrowth potential to be expressed in that growth cycle, but also in the next cycle, by allowing the replenishment of WSC reserves and optimizing tiller status. The potential to regrow appears then to be based more on the total amount of WSC than the proportion of WSC in stubble.

Reproductive‐Resource Allocation in Rhizoma Peanut

Partitioning of energy reserves between sexual (flower and seed) and asexual (rhizome) reproduction in rhizoma peanut (Arachis glabrata Benth.), a perennial, tropical‐forage legume, appears to be affected by environmental stress. If so, seed production may be enhanced by manipulating the growing environment. To investigate this possibility, the effect of defoliation frequency on the energy‐allocation balance of sexual vs. asexual reproduction of rhizoma peanut was determined. Four defoliation frequencies (nondefoliated, weekly, every 4 wk, and every 8 wk) were imposed on ‘Florigraze’ rhizoma peanut. Aboveground and rhizome biomass were sampled prior to treatment initiation (6 June 1988 and 15 June 1989) and every 4 wk until frost (24 wk in 1988 and 16 wk in 1989). During the first 8 wk, aboveground biomass of the non‐defoliated treatment nearly doubled. Concurrently, aboveground biomass of all defoliated treatments remained the same or declined. Rhizome biomass of all treatments declined during the same period but in most cases, recovered by the latter part of the growing season. Generally, aboveground biomass ranked (P &lt; 0.05) 1 wk &lt; 4 wk ≤ 8 wk &lt; nondefoliated, and rhizome biomass ranked (P &lt; 0.05) 1 wk = 4 wk = 8 wk &lt; nondefoliated. Flowering was synchronous for all treatments, but sexual reproductive effort constituted &lt;0.5% of total‐plant biomass because seeds were never produced. Defoliation positively affected (P &lt; 0.05) both flower dry matter (DM) production and sexual:asexual ratio with treatments generally ranked nondefoliated = 1 wk &lt; 4 wk = 8 wk. This study indicates that the partitioning of energy to sexual or asexual reproduction in rhizoma peanut can be altered in response to stress.

Effect of Defoliation Frequency and N-P-K Fertilization on Maidencane

Effect of Defoliation Frequency and N-P-K Fertilization on Maidencane

Persistence of a Lolium perenne-Trifolium subterraneum Pasture under Differing Defoliation Treatments

Effects of defoliation frequency and intensity on persistence of a perennial ryegrass (Loliumperenne)-subclover (TrYohm subterraneum) pasture were studied near Corvallis, Ore., during 1980 to 1983. While canopy cover of individual plant species did not differ between defoliation frequency or intensity treatments (p6.05) within years, all defoliated plots differed from the undefoliated control plots. Canopy cover of perennial ryegrass declined from its initial value of 43% in 1980 to an average of 30% and 1% in defoliated and undefoliated plots in 1983, respectively. Perennial ryegrass in defoliated plots was apparently replaced by subclover, whose canopy cover increased by 33% during the j-year period. On undefoliated plots, however, both perennial ryegrass and subclover were replaced by annual grasses, whose canopy increased from approximately 2% in 1980 to 48% in 1983. Density of perennial ryegrass plants at the end of the trial in 1983 was highest when plots were defoliated once every 21 or 35 days compared to those defoliated every 7 days, 49 days, or the undefoliated control plots. Root biomass per plant, however, increased linearly as defoliation interval increased from 7 to 49 days between defoliation events. Viewed together, these data suggest that underutilization of grass-clover pastures may be potentially as damaging to pasture persistance as overutilization.

Effect of defoliation frequency on simulated swards of ryegrass, tall fescue, and a 50/50 mixture of the 2 species

Abstract Simulated swards of ryegrass, tall fescue, and a 50/50 mixture of the 2 species were established in pots, placed in a controlled-environment room, and harvested at intervals of lO'h, 21, 42, and 63 days. Dry matter production increased with less frequent defoliation but tiller numbers were highest under the 101⁄/22-day defoliation interval. Digestibility tended to decline at defoliation intervals longer than 21 days. In the mixed sward, tall fescue was more competitive under a 63-day defoliation interval and less competitive under a 21-day defoliation interval. These results highlight the importance of assessing competition between pasture species in a mixed sward under more than one defoliation regime.

Effects of defoliation frequency and nitrogen and phosphorus nutrition on performance of 4 white clover cultivars

Abstract White clover plants, defoliated either 3-or 6-weekly, were grown in potted soil with a range of phosphorus and nitrogen additions. Four cultivars (‘Grasslands Huia’, ‘Grasslands Pitau’, S100, and Blanca RVP), were used as examples to investigate the effect of defoliation frequency on expression of genetic variation for response to P and N treatments. Defoliation 3-weekly favoured the detection of genetic variation in DM yield response to P treatment whereas the converse was true for response to N treatment. The P main effects and interactions were linear in form, but the cultivar × N interaction was bimodal. Reasons for these contrasting responses are discussed and the importance of careful definition of defoliation frequency when screening white clover is stressed.

Effect of defoliation frequency on growth and survival of four accessions of Psoralea eriantha

Four accessions of the semi-arid shrub legume Psoralea eriantha were evaluated under three six and nine week cutting regimes for 72 weeks in pots in the glasshouse. Total yield increased in all accessions with increasing intervals between cutting. Yield in the three week cutting interval was only 36 per cent of the yield in the nine week cutting interval. The one erect accession, though giving the highest average yield, also suffered the highest mortality under the frequent defoliation. The other accessions suffered little mortality. Defoliation frequency affected root and stubble weights and these were closely correlated with total dry matter yields. Frequent defoliation also markedly reduced the number of primary and secondary shoots. It is suggested that survival under grazing may be more important than a higher yielding ability.