Defoliation Frequency Research Articles

Comparison of Nutritive Values of Tropical Pasture Species Grown in Different Environments, and Implications for Livestock Methane Production: A Meta-Analysis.

Simple SummaryGlobally, tropical pasture species predominate in tropical and subtropical climates, and are the primary feed source for grazing livestock including dairy cattle. Therefore, this study aimed at systematically analysing the nutritive values of tropical pastures and the implications of potential methane gas production from tropical pasture species and livestock, in relation to the growing conditions and agronomic management approaches used (defoliation frequency and intensity) across different climates. This analysis allowed us to understand the better performing tropical pasture species grown across wider geographical regions, in order to improve pasture-based livestock production systems. Results revealed that pasture quality and methane gas production varied among and within species, and were significantly affected by the climate and by the agronomic management regime as well.The demand for dairy products is ever increasing across the world. The livestock sector is a significant source of greenhouse gas (GHG) emissions globally. The availability of high-quality pasture is a key requirement to increase the productivity of dairy cows as well as manage enteric methane emissions. Warm-season perennial grasses are the dominant forages in tropical and subtropical regions, and thus exploring their nutritive characteristics is imperative in the effort to improve dairy productivity. Therefore, we have collated a database containing a total of 4750 records, with 1277 measurements of nutritive values representing 56 tropical pasture species and hybrid cultivars grown in 26 different locations in 16 countries; this was done in order to compare the nutritive values and GHG production across different forage species, climatic zones, and defoliation management regimes. Average edaphoclimatic (with minimum and maximum values) conditions for tropical pasture species growing environments were characterized as 22.5 °C temperature (range 17.5–29.30 °C), 1253.9 mm rainfall (range 104.5–3390.0 mm), 582.6 m elevation (range 15–2393 m), and a soil pH of 5.6 (range 4.6–7.0). The data revealed spatial variability in nutritive metrics across bioclimatic zones and between and within species. The ranges of these nutrients were as follows: neutral detergent fibre (NDF) 50.9–79.8%, acid detergent fibre (ADF) 24.7–57.4%, crude protein (CP) 2.1–21.1%, dry matter (DM) digestibility 30.2–70.1%, metabolisable energy (ME)3.4–9.7 MJ kg−1 DM, with methane (CH4) production at 132.9–133.3 g animal−1 day−1. The arid/dry zone recorded the highest DM yield, with decreased CP and high fibre components and minerals. Furthermore, the data revealed that climate, defoliation frequency and intensity, in addition to their interactions, have a significant effect on tropical pasture nutritive values and CH4 production. Overall, hybrid and newer tropical cultivars performed well across different climates, with small variations in herbage quality. The current study revealed important factors that affect pasture nutritive values and CH4 emissions, with the potential for improving tropical forage through the selection and management of pasture species.

Prescribed defoliation strategies influence soil carbon and nitrous oxide potential in pastures

AbstractCool‐season perennial grasslands are commonly used for livestock pasture. However, understanding of the belowground effects of forage defoliation (selective pressure applied by grazing) management is nascent. We investigated how defoliation management affects aboveground (forage productivity) and belowground processes (soil C/N), microbial nutrient cycling, and potential nitrous oxide [N2O] emissions). We hypothesized that rotational (moderate frequency) defoliation at low severity will increase soil organic matter (SOM) storage and microbial capacity to cycle C, N, and P, but that these changes would also lead to greater soil N2O emission potential. Data were collected from organically (OF) and conventionally managed (CF) farms with differing botanical composition in West Virginia, where three frequencies and two severities of forage defoliation were imposed. At OF, more severe defoliation decreased labile soil C content (–26%), while moderate defoliation resulted in a 39% reduction in microbial enzymatic capacity to cycle C, but not at CF. The N2O emission potential (ratio of nirK/nosZ functional gene abundance), was differentially affected by defoliation treatments at both sites. At OF, defoliation severity altered N2O emission potential, whereby low severity resulted in an 82% decrease in potential N2O emissions compared with high severity treatments. At CF, continuously defoliated plots exhibited a 71% lower N2O emission potential relative to less frequent defoliation. Belowground microbial parameters were more responsive to defoliation at OF, suggesting past management may influence how grazing management asserts belowground changes. Results suggest that defoliation management could enhance soil C storage, but potentially at the risk of increased N2O emissions.

Composition and decomposition of rhizoma peanut (Arachis glabrata Benth.) belowground biomass

Roots and rhizomes can play an important role in nutrient cycling, however, few studies have investigated how their decomposition pattern is affected by defoliation and time of the year. This 2-year study evaluated root-rhizome composition and decomposition of a warm-season rhizomatous perennial legume [rhizoma peanut (RP; Arachis glabrata Benth.)] under continuous stocking or when defoliated by clipping every 56 days. A 168-days incubation trial was performed to determine disappearance of biomass and N and changes in acid detergent fiber (ADF), acid detergent insoluble N (ADIN), and C:N ratio. Additionally, three 56-days incubations were performed each year to evaluate the disappearance coefficient (B0) and relative decay rate (k). There were no treatment differences in any response for the 168-days incubation. After 168 days, 21 and 60% of initial biomass and initial N remained, respectively. Relative decay rate for OM and N were 0.0088 and 0.0035 g g−1 day−1, respectively. Carbon-to-N ratio decreased from 29 at day 0 to 17 at day 168. Concentration of ADIN increased from 6.9 to 19.3 g kg−1, plateauing at day 79. The B0 and k for remaining OM and N were greater in late than early season and could be explained by greater N concentration and lesser C:N ratio. Rapid decomposition, difference in C:N ratio from day 0 to 168, and the increase in ADIN concentration during incubation indicate large amounts of root-rhizome-soluble C at initiation of incubation. These data indicate that RP root-rhizome turnover is more responsive to season than defoliation frequency.

Effect of Defoliation Frequency on Rytidosperma Virescens Plants and Arbuscular Mycorrhizal Fungi Colonization

Rangelands provide different ecosystem services to satisfy human needs. Although grazing management in southern Patagonia is mostly characterized by extensive continuous grazing, rotational grazing management may improve plant productivity and its associated microbiome. Arbuscular mycorrhizal (AM) symbioses play an important role in the functioning of arid rangelands. However, in most arid and semiarid grasslands, little is known about the environment-plant-symbiont interaction under different defoliation frequencies and contrasting growth conditions. In this context, the objective of the present study was to evaluate the response of Rytidosperma virescens native grass and the associated AM fungi under different defoliation frequency treatments (plants undefoliated, two clippings with 50-d intervals between defoliations, four clippings with 30-d intervals, and six clippings with 21-d intervals) and two growth conditions (field and greenhouse) in a 150-d experiment. Defoliation frequency with 21-d clipping intervals negatively affected plants and AM colonization. We found a negative linear relationship between AM colonization and removal of aboveground biomass and a positive relationship with root biomass and leaf area of R. virescens plants. We determined that the appropriate recovery period for rotational grazing systems should be at least 50 d (threshold) to optimize forage production and AM symbiosis during spring-summer seasons. Sustainable grazing management practices should be designed to improve or restore AM communities to maintain positive feedback with plant development.

Functional contribution of two perennial grasses to enhance pasture production and drought resistance under a leaf regrowth stage defoliation criterion

AbstractLolium perenne L. (Lp) is the main pasture species in New Zealand, but climate change increases the likelihood of drought during summer and consequently lowers its growth rates. Bromus valdivianus Phil. (Bv) tolerates better the summer soil water restriction, but its competitiveness in a diverse pasture relates to the defoliation management and soil moisture levels. The performance of both species in terms of production, persistence and feed quality across seasons under different defoliation regimens was evaluated when the species were mixed and in monoculture. The treatments were applied in a randomised complete block design with three blocks. Bromus valdivianus and Lp monocultures and the 50/50 mixture (Mx) were grazed at low and high defoliation frequencies (i.e. based on Bv and Lp optimal leaf regrowth stage [LS], respectively). Herbage mass production was 15% higher in the Mx, mainly due to an increase in production in spring and summer. In spring, there was complementarity growth between the species, while during summer/early autumn, the Mx production relayed in the higher participation of Bv. Root biomass at depth (31–70 cm) was 38% greater for Bv monoculture and the Mx compared with Lp monoculture, which demonstrated the contribution of Bv to a better production of the mixture during and following the dry periods. In addition, the maintenance of the Bv tiller population and the higher growth rate during dry periods demonstrated its better fitness to low soil water availabilities than Lp. Although herbage mass was not modified by the defoliation frequency, forage quality of Bv showed values at low defoliation frequency that could compromise animal production during spring. However, there was an increase in root biomass under low defoliation frequencies, which suggested that a flexible grazing management across seasons would increase the niche utilisation between species in the mixture. The defoliation frequency of the mixture could be based on Lp LS during spring and winter, and slowed down, following Bv criteria, during summer and autumn.

Defoliation Frequencies of Forage Legumes: Effects on Yield and Nutritive Value for Beef Cattle Production

A study was conducted to determine the effect of cutting frequencies for 2 temperate (Trifolium pratense and Trifolium repens) and 2 tropical (Stylosanthes guianensis and Centrosema molle) forage legumes on dry matter yield and nutritive value for beef cattle production in a cool tropical environment of Jos, Nigeria. It was a factorial experiments with four forage legumes and three defoliation frequencies (4 x 3) making twelve treatments combinations arranged in a randomized complete block design and replicated four times. The study was conducted in 2016 and 2017. The result showed that total dry matter yield (DMY) was higher (p<0.05) in T. pratense in 2017 (3.06 t/ha), while C. molle produced least DMY (1.01 t/ha). The temperate species performed better after each cut in DMY. Crude protein content was higher (p<0.05) in T. repens (26. 12 %) at the third cut. The tropical species were higher (p<0.05) in fibre contents. Dry matter intake (3.88 %), digestible dry matter (71.24 %) , total digestible nutrients (70.2 %) and relative feed value (214.53) were all higher (p<0.05) in T. repens at third cut. The temperate forage legumes generally showed more resilience to cuttings compared to the tropical species. Therefore the crops can be grown in the cool tropical environment of Jos, Nigeria as supplementary forage feeds.

Physiological and sanitary quality of ryegrass seeds submitted to different defoliation frequencies

ABSTRACT: This study determined the effect of different defoliation frequencies in a long-cycle ryegrass cultivar on yield components and the physiological and sanitary quality of seeds. Four defoliation frequencies were applied (without, one, two, and three defoliations). The time between defoliations was 350 degree-days. At the first, second, and third defoliation time, the plants were 15 cm, 20 cm, and 35 cm, respectively, and were lowered to half their height. The yield components and plant structure were evaluated through the tillers, along with the physiological quality of the seeds, which was verified by germination tests, first germination count, accelerated aging, tetrazolium test, field emergence, and weight of a thousand seeds. For the sanitary quality analysis, the percentage (%) of fungi incidence in the seeds was verified. The second defoliation determined the seeds’ high physiological and sanitary quality due to the higher amount of primary and secondary tillers produced concerning the other treatments. However, there was no significant difference for the third defoliation since the aerial tillers issued the same quality of seeds originated from primary and secondary tillers. The average incidence of fungi such as Colletotrichum sp., Fusarium sp., Phoma sp., and Dreshslera spp. was lower in ryegrass plants subjected to three defoliations.

Dissimilarity between Andropogon lateralis ecotypes under different defoliation frequencies and heights

ABSTRACT: Andropogon lateralis Nees is a native grass of southern Brazil and is one of the most frequent specie found in native grasslands. The species is widely distributed and has a high degree of phenotypic plasticity, which makes it highly adaptable to different edaphoclimatic conditions and management. This study aimed to evaluate the behavior of twelve ecotypes of A. lateralis, collected in different regions of the state of Rio Grande do Sul and cut to three different heights and subjected to two different defoliation frequencies. From September to February, the ecotypes were evaluated for total dry matter, leaf and stem yields. In addition, total, vegetative and reproductive tillers and plant height were measured. These characteristics are important for the selection of superior genotypes in terms of genetic variability and forage production. Total dry matter and leaf dry matter are characteristics with agronomic importance and they showed the highest correlation (r = 0.77), enabling an indirect selection for one of these characteristics. The natural selection of plants resulted in distinct structural, morphological and productive characteristics with heterogeneity that allows the selection and grouping according to the characteristics, ecotypes with superior agronomic characteristics can be included in breeding programs.

Lotus tenuis and Schedonorus arundinaceus co-culture exposed to defoliation and water stress

The present study aimed to investigate the effect of defoliation frequency (low and high) and water stress (excess or deficit) on biomass production, P and N nutrition, and symbiosis with native soil microorganisms on a Lotus tenuis and Schedonorus arundinaceus co-culture in a pot experiment. Combined effects of defoliation frequency and water stress affected plant accumulated shoot biomass. L. tenuis root biomass decreased in response to defoliation and water stress, while S. arundinaceus root biomass was similar between non-defoliated and defoliated plants, at all water levels. Low and high frequencies of defoliation in a waterlogged soil can be considered the most stressful scenario for L. tenuis and S. arundinaceus co-culture. Colonization of arbuscular mycorrhizal fungi in L. tenuis roots and dark septate endophytes colonization in S. arundinaceus roots were affected by both factors, whereas arbuscular mycorrhizal colonization in S. arundinaceus was affected only by water stress. Both plants tolerated defoliation and water stress due to the interaction between the translocation of nutrients and carbon compounds from roots to shoots, and P and N absorption (plus N2 fixation in L. tenuis). Highlights: Both plants tolerated defoliation and water stress due to the interaction between the translocation of nutrients and carbon compounds from roots to shoots, and P and N absorption (plus N2 fixation in tenuis). Low and high frequencies of defoliation in a waterlogged soil can be considered the most stressful scenario for tenuis and S. arundinaceus co-culture. Defoliation frequency increased AM colonization in plant roots under well watered and water deficit conditions. arundinaceus roots were co-colonized by AM fungi and DSE. Promoting the presence of tenuis through low defoliation frequency would improve forage yield and quality with the maintenance of AM symbiosis in legume–grass communities.

Effects of defoliation frequencies on above- and belowground biodiversity and ecosystem processes in subtropical grasslands of southern Brazil

The links between vegetation and soil biota are responsible for a variety of ecosystem processes and services that can be affected by grazing. In this study, we aimed to evaluate the effects of grazing frequency in natural grasslands’ biodiversity (plant and collembola communities) and on ecosystem processes (decomposition and biomass accumulation). For so, we carried out a clipping experiment over a natural area of subtropical grassland in southern Brazil. The plots were submitted during three years to three different clipping frequencies (high, intermediate, and low) to simulate defoliation caused by grazing. We found the highest aboveground biomass accumulation and detritivore activity in the low defoliation frequency, which also promoted the dominance of tussocks. The synergies between higher vegetation height and biomass tend to provide microclimatic conditions that favors decomposition, which releases nutrients to plants, promoting their growth. The defoliation frequencies applied in this study were not sufficient to provide effects on plant community, since its co-evolutionary history with grazing. The Collembola community was not affected by defoliation. It seems to be more influenced by other factors associated with grazing.

Response of Bromus valdivianus (Pasture Brome) Growth and Physiology to Defoliation Frequency Based on Leaf Stage Development

The increase in drought events due to climate change have enhanced the relevance of species with greater tolerance or avoidance traits to water restriction periods, such as Bromus valdivianus Phil. (B. valdivianus). In southern Chile, B. valdivianus and Lolium perenne L. (L. perenne) coexist; however, the pasture defoliation criterion is based on the physiological growth and development of L. perenne. It is hypothesised that B. valdivianus needs a lower defoliation frequency than L. perenne to enhance its regrowth and energy reserves. Defoliation frequencies tested were based on B. valdivianus leaf stage 2 (LS-2), leaf stage 3 (LS-3), leaf stage 4 (LS-4) and leaf stage 5 (LS-5). The leaf stage development of Lolium perenne was monitored and contrasted with that of B. valdivianus. The study was conducted in a glasshouse and used a randomised complete block design. For Bromus valdivianus, the lamina length, photosynthetic rate, stomatal conductance, tiller number per plant, leaf area, leaf weights, root growth rate, water-soluble carbohydrates (WSCs) and starch were evaluated. Bromus valdivianus maintained six live leaves with three leaves growing simultaneously. When an individual tiller started developing its seventh leaf, senescence began for the second leaf (the first relevant leaf for photosynthesis). Plant herbage mass, the root growth rate and tiller growth were maximised at LS-4 onwards. The highest leaf elongation rate, evaluated through the slope of the lamina elongation curve of a fully expanded leaf, was verified at LS-4. The water-soluble carbohydrates (WSCs) increased at LS-5; however, no statistical differences were found in LS-4. The LS-3 and LS-2 treatments showed a detrimental effect on WSCs and regrowth. The leaf photosynthetic rate and stomatal conductance diminished while the leaf age increased. In conclusion, B. valdivianus is a ‘six-leaf’ species with leaf senescence beginning at LS-4.25. Defoliation at LS-4 and LS-5 was optimum for plant regrowth, maximising the aboveground plant parameters and total WSC accumulation. The LS-4 for B. valdivianus was equivalent to LS-3.5 for L. perenne. No differences related to tiller population in B. valdivianus were found in the different defoliation frequencies.

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.

Canopy structural variations affect the relationship between height and light interception in Guinea Grass

The study of canopy structures is essential for the precise management of local forage. Although the relationship between the canopy height (CH) and light interception (LI) allows the best use of forage, there are other characteristics of the canopy that, if not observed, can lead to errors in grazing management. This study analyzes the effect of the defoliation frequencies (DF) and season on the productive and structural characteristics of Guinea grass and defines whether tiller population density (TPD) should be considered in the mathematical models that relate CH to LI. The experimental design used includes randomized blocks with six defoliation frequencies (DF) of 14, 21, 28, 35, 42, and 49 days, over three seasons: rainy season 2015 (RS2015), dry season (DS), and rainy season 2016 (RS2016), in the Amazon biome. Yield characteristics and forage structure were evaluated. The interaction between the DFs and seasons in all evaluated variables included forage accumulation, proportions of stem, leaves and dead material, tiller population density (TPD), CH, LI, and leaf area index. The curve steepness constant (CSC) of the nonlinear models between CH and LI was different from that of the DFs. A DF of 14–28 days averaged a TPD of 616 tillers m−2 and CSC of 0.0407, and a DF of 35–49 days averaged a TPD of 496 tillers m−2 and CSC of 0.0368. An agreement index (d) of 0.87, a bias of 1.5 %, and a determination coefficient (R²) of 0.6187 were obtained for the model that estimated a CH with the inclusion of LI and TPD when validated with data from studies published in the literature. TPD associated with CH and LI allowed for more precise management of the ideal defoliation moment.

Development of a lucerne model in APSIM next generation: 1 phenology and morphology of genotypes with different fall dormancies

Prediction of lucerne phenological and morphological development is important for optimising the defoliation schedule and time of other management events. A challenge for any lucerne phenology module is to capture the seasonality of development processes in response to environment, management and genotype. To date, lucerne phenological modules have not been evaluated under different defoliation regimes or with genotypes of different fall dormancy (FD) classes. This research integrated data of lucerne phenological development into the Agricultural Production Systems sIMulator (APSIM) next generation (APSIM NextGen) model framework to develop and verify a phenology module. Relationships derived from the FD5 genotype, grown under a 42 day (LL) defoliation treatment were used for model development. These were further tested for two genotypes with contrasting FD (FD2 and FD10) under frequent (28 day: S) or long (84 day: H) defoliation regimes, all under irrigated conditions. Development was parameterized based on thermal time targets to reach specific phenological stages and modified by photoperiod responses. Development stage and node appearance were shown to be independent of defoliation treatment and FD class. Simulation results showed good agreement for prediction of development stages (NSE of 0.77 for days to buds visible and 0.67 for days to flowering stage) and number of main stem nodes (NSE values were ranged from 0.53 to 0.84). However, both defoliation management treatment and FD classes affected stem height. For FD5, there was good agreement for the 84 day treatment (NSE of 0.83) and the 42 day treatment (NSE of 0.66), but it was poor for the 28 day treatment (NSE of -0.08). This was probably due to reduced stem extension rates, limited by low C and N reserves in perennial organs under the frequent (28 day) defoliation regime. For FD2 and FD10, two separate sets of parameters were used to improve model prediction of height to account for their contrasting seasonal C partitioning patterns. These results show that the APSIM NextGen lucerne phenology module was able to simulate crops grown under unconstrained growing conditions. However, the reason for under estimation of stem height for the 28 day treatment needs further investigation.

Management of defoliation in Trifolium vesiculosum S. for the production of seeds

ABSTRACT The present study aims to determine the appropriate defoliation management for the production of seeds and forage in arrowleaf clover via trail analysis. The results obtained demonstrated that defoliation practices have a great influence on the composition of seed yield and germination power. In addition, when the goal is the maximum balance between dry matter production and seed yield, this can be achieved in up to two defoliation practices. These results are confirmed by analyzing the positive association between the weight of a thousand seeds and the seed yield. When the third defoliation practice is performed, it negatively correlates with the weight of a thousand seeds, suggesting that, with the increase in defoliation frequency, there is a lower weight of a thousand seeds, and, therefore, lower seed yield. Therefore, management planning in Trifolium vesiculosum Savi that aims at natural reseeding, maximum yield and seed germination must prioritize one to two defoliation practices, aiming to promote favorable conditions for the perennialization of the species. In this context, the trail analysis proved to be a useful tool as a criterion for obtaining the ideal management aiming at the production of seeds and forage in vesicular clover.

Seedling defoliation may enhance survival of dominant wheatgrasses but not Poa secunda seeded for restoration in the sagebrush steppe of the Northern Great Basin.

Restoration of dryland ecosystems is often limited by low seedling establishment and survival. Defoliation caused by insects and small mammals could be an overlooked cause of seedling mortality. In the sagebrush steppe, we examined the effect of seedling defoliation on the survival of perennial grasses commonly used as restoration materials. Under field conditions, seedlings of three perennial bunchgrass species (non-native Agropyron cristatum, and native grasses Poa secunda and Pseudoroegneria spicata) were defoliated at two intensities (30 % and 70 % leaf length removal) and frequencies (one or two clippings) and compared to a non-defoliated control. Following emergence the first year, clippings occurred at the two-leaf stage; a second clipping occurred 1 month later for repeated defoliation treatments. We monitored seedling survival and tillering for 2 years. We expected higher defoliation intensity and frequency to reduce survival for all species, but only a few treatments reduced Po. secunda survival. Conversely, larger-statured Triticeae (wheatgrasses) benefited from some defoliation treatments. In both years, A. cristatum survival increased with repeated defoliation at both intensities. Defoliation did not affect Ps. spicata survival in the first year, but a single defoliation in the second year resulted in increased survival. In both A. cristatum and Ps. spicata, higher-intensity defoliation reduced the boost to survival resulting from defoliation frequency. Seedlings with more tillers had greater survival probabilities, but tiller number was unaffected by defoliation. Further research may elucidate mechanisms seedlings use to compensate for or benefit from defoliation. In the meantime, managers should aim to select defoliation-tolerant species if they anticipate herbivory will be problematic for restoration sites.

Collaborative Adaptive Rangeland Management, Multipaddock Rotational Grazing, and the Story of the Regrazed Grass Plant

Frequent, severe defoliation reduces grass production and can alter plant species composition in grasslands. Multipaddock rotational grazing has been proposed as a grazing strategy that may reduce the frequency and intensity of defoliation on palatable grass plants without altering stocking rates. Previous studies evaluated this hypothesis using small, homogeneous paddocks and nonadaptive rotation schedules and found small and inconsistent differences between continuous and rotational grazing systems. Using a stakeholder-driven collaborative adaptive management (CAM) framework, we conducted the first ranch-scale experimental investigation into tiller defoliation patterns in the context of adaptive multipaddock rotational grazing. We monitored tiller defoliation frequency and intensity in 10 paired 130-ha pastures assigned to either a collaborative adaptive multipaddock rotational grazing treatment (CARM, one livestock herd) or a season-long continuous grazing treatment (traditional rangeland management [TRM]; 10 separate herds) in shortgrass steppe. Consistent with previous studies, we observed that frequencies of grazing and regrazing on a palatable, cool-season grass (western wheatgrass, Pascopyrum smithii) were much more sensitive to stocking rate than grazing system. Under moderate stocking rates used in both CARM and TRM treatments, roughly two-thirds of western wheatgrass tillers remained ungrazed annually, regardless of grazing system. Thus, season-long rest is present in season-long continuous and rotational grazing systems. Frequencies of tiller regrazing were low (5−15%) and similar between CARM and TRM treatments. Although defoliation patterns were similar between treatments at the whole-ranch scale, CARM enhanced spatial and temporal heterogeneity in defoliation frequencies among individual pastures. Pastures grazed earlier in the season or for longer experienced more defoliation. Managers implementing adaptive, multipaddock rotational grazing could use this heightened and predictable variability to strategically manage impacts of grazing on western wheatgrass at the individual pasture scale. The CAM model enabled our team to identify and directly address key stakeholder hypotheses and resulted in coproduction of management-relevant research.

THE IMPACT OF THE GRASSLANDS FERTILIZATION. CASE STUDY –FERTILISATION IN THE LOWER PLAIN OF BANAT ROMANIA

In the case of meadows, it is very important to correlate the productive capacity (given by the rating notes) and the correct animal load. Thus, the rating notes indicate the average potential in the current state of exploitation and conservation of soils, potential that can be improved considering the fact that some indicators such as reaction, humus reserve, and porosity are properties that in case of applying measures that widen the area. Manifestation of them as well as of other properties of the environmental factors taken in the calculation of the rating notes. The detailed knowledge of the factors that contribute to the increase or decrease of the production capacity of each part of the territory can ensure for the decision maker an effective tool for choosing working procedures that favor an efficient use of land resources. Nutrient-rich grasslands are dominated by fast-growing species, and nutrient-poor grasslands are dominated by slow-growing conservative species. Traditionally managed grasslands have been widely used in mowing and grazing and have hardly received artificial fertilizers, providing a wide range of habitats that support high biological diversity. But due to the intensive management of pastures, the high intake of nutrients and the increased frequency of defoliation, on the one hand, and the abandonment of marginal pastures, on the other hand, the biodiversity of grasslands has suffered a dramatic decline in recent years. Human activities have significantly altered the availability of nitrogen (N) in most terrestrial ecosystems, with consequences for community composition and ecosystem functioning.

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.

Decreasing Defoliation Frequency Enhances Bromus valdivianus Phil. Growth under Low Soil Water Levels and Interspecific Competition

Bromus valdivianus Phil. (Bv) is a water stress-tolerant species, but its competitiveness in a diverse pasture may depend on defoliation management and soil moisture levels. This glasshouse study examined the effect of three defoliation frequencies, based on accumulated growing degree days (AGDD) (250, 500, and 1000 AGDD), and two soil water levels (80–85% of field capacity (FC) and 20–25% FC) on Bv growth as monoculture and as a mixture with Lolium perenne L. (Lp). The treatments were applied in a completely randomised block design with four blocks. The above-ground biomass of Bv was lower in the mixture than in the monoculture (p ≤ 0.001). The Bv plants in the mixture defoliated more infrequently (1000 AGDD) showed an increase in root biomass under 20–25% FC compared to 80–85% FC, with no differences measured between soil water levels in the monoculture. Total root length was highest in the mixture with the combination of infrequent defoliation and 20–25% FC. Conversely, frequent defoliation treatments resulted in reduced water-soluble carbohydrate reserves in the tiller bases of plants (p ≤ 0.001), as they allocated assimilates mainly to foliage growth. These results provide evidence that B. valdivianus can increase its competitiveness relative to Lp through the enhancement of the root growth and the energy reserve in the tiller base under drought conditions and infrequent defoliation in a mixture.