Defoliation Intensity Research Articles

Potassium fertilization and defoliation intensity effects on forage characteristics of “BRS Zuri” guineagrass

Potassium fertilization and defoliation intensity effects on forage characteristics of “BRS Zuri” guineagrass

Defoliation level and timing affect popcorn yield traits in the Midwestern United States

Popcorn [Zea mays (L.) var. Everta] is an important field crop in the Midwestern United States. However, hailstorms are a major threat to ensuring high yield because of their effects on leaf photosynthesis, pollination, and stalk lodging. A multi-state study spanning six site-years (2020–2023) was conducted in two locations (Ohio and Nebraska) to determine how defoliation intensity at different stages affects yield loss in popcorn and compare these losses with current values in the National Crop Insurance Service (NCIS) Corn Loss Instructions. At each location the study was conducted in a randomized complete block design with four replicates. The treatments consisted of the combination of four levels of leaf loss (25, 50, 75 and 100 % leaf blade area removal) imposed at five developmental stages: V8 (10-leaf), V13 (15-leaf), VT, R2, and R4. The evaluated traits were plant population, grain yield, stalk lodging, and 100-kernel weight. All evaluated traits were affected by defoliation, except plant population. The treatments 100 % defoliation at VT and R2 stages were the most damaging in terms of grain yield reduction, number of ears per plant and 100-kernel weight for both locations. In Ohio, the greatest stalk lodging was observed at 100 %-R2 and in Nebraska, at 75 %-VT. For both locations, the actual yield losses in the defoliated treatments were lower than values currently listed in the NCIS Popcorn Leaf Loss Chart. These results indicate leaf loss chart values should be updated to accurately reflect yield losses from popcorn defoliation events. This evaluation did not impose damage to stalks (e.g., bruising) or to plant whorls as may be expected in natural events. Future research should incorporate other forms of plant damage such as those described to provide a better emulation of hail damage.

Defoliation modifies the impact of drought on the transfer of recent plant-assimilated carbon to soil and arbuscular mycorrhizal fungi

Abstract Aims The allocation of recent plant photosynthates to soil via arbuscular mycorrhizal (AM) fungi is a critical process driving multiple ecosystem functions in grasslands. Yet, our understanding of how defoliation modifies below-ground allocation of recent plant photosynthate and its response to drought, which is becoming more intense and frequent, remains unresolved. Methods Here we undertook a 13C pulse-labelling experiment in a mesotrophic temperate grassland to evaluate in situ how defoliation intensity modifies the transfer of recently assimilated 13C from plant shoots to roots, extraradical AM fungal hyphae, soil, and 13C-CO2 efflux (soil respiration) in response to simulated drought. Results We found that, individually, both defoliation and drought reduced initial plant 13C uptake, but when defoliation and drought were combined, we detected a significant reduction in below-ground 13C allocation to soil. Furthermore, while defoliation stimulated 13C transfer to plant roots and soil, high intensity defoliation amplified 13C-CO2 efflux relative to the amount of 13C taken up by plants. Drought stimulated 13C transfer to fungal hyphae relative to initial plant uptake. High intensity defoliation, however, suppressed both 13C enrichment of extraradical AM fungal hyphae and 13C transfer to fungal hyphae relative to initial uptake. Conclusions Our findings suggest that defoliation can reduce the transfer of recent photosynthate below-ground under simulated drought and provide new insights into how defoliation may influence grassland C allocation dynamics and cycling between plants and AM fungi in grasslands facing drought.

Defoliation modifies the response of arbuscular mycorrhizal fungi to drought in temperate grassland

Arbuscular mycorrhizal (AM) fungi predominate in grasslands, where they play a key role in enhancing plant water uptake and plant tolerance to drought. However, how plant defoliation, which is common to grazed and cut grasslands, modifies plant and AM fungi responses to drought remains unknown. Here, we examined how defoliation intensity modified plant and AM fungi responses to drought.This was done using an in situ factorial field experiment at Colt Park meadows, northern England, whereby mixed grassland communities were subjected to different intensities of defoliation in combination with simulated summer drought. We measured a range of plant, AM fungal, and soil microbial and chemical responses to defoliation and drought, both individually and in combination, and extracted neutral lipid fatty acid (NLFA) as an indicator of AM fungi energy storage status.High intensity defoliation significantly reduced root colonization by AM fungi, and the negative impact of drought on AM fungi extraradical hyphal length was amplified under high intensity defoliation. Drought had no effect on total shoot biomass but reduced specific root length and increased soil NLFA concentrations, indicating an increase in AM fungi energy reserves. However, defoliation dampened this response, implying that defoliation suppresses AM fungi energy reserves under drought.Our findings suggest that plant communities can maintain above-ground productivity under drought with the assistance of AM fungi symbiosis, but that defoliation suppresses positive plant-fungi interactions under drought. Taken together, our findings provide new insights into how drought and defoliation, a key feature of grassland management, combine to negatively impact the plant-AM fungi associations in grassland.

Effects of Defoliation at Different Fertility Stages on Material Accumulation, Physiological Indices and Yield of Cotton

In recent years, severe hailstorms have caused damage to cotton leaves and stalks. In order to identify the effects of cotton leaf damage on its dry matter accumulation, protective enzyme activity and yield in different periods, in this experiment, different intensities of hail were simulated by manual leaf cutting. In this study, the effects of leaf damage on dry matter accumulation, chlorophyll fluorescence, POD (peroxidase), SOD (superoxide dismutase) and MDA levels (malondialdehyde), and yield of cotton were studied in field experiments at three stages (bud, full bud and flower boll stages) and in sub-plots with different artificial defoliation intensities (0%, 25%, 50%, 75% and 100%). Removing the leaf sources had differently sized effects on the “sink” at each stage, and these are ordered as follows: flowering and boll stage > full bud stage > pregnancy stage. The greater the intensity of leaf removal, the greater the impact on the “sink”. Among them, after removing 50% of the leaves at the full bud stage, the total dry matter of the cotton plant increased by 12.46% compared to that of the control, and the boll formation rate per plant increased by 14.99%, resulting in overcompensation. Mo, Vj and φDo all showed a tendency to decrease and then increase with the increase in defoliation intensity at different periods of the treatment, and the lowest values of Mo, Vj and φDo, and the largest values of φpo, ψo and φEo were found in the 50% defoliation treatment at the gestational bud stage. The values of ψo and φEo were at the maximum in the 25% defoliation treatment at the full bud stage. The values of Mo and Vj in the different defoliation treatments at the bolling stage showed a tendency to increase and then decrease with the increase in defoliation intensity, with the highest values in the 25% treatment and the smallest values of φpo, ψo and φEo in the 25% defoliation treatment. The POD enzyme activity level was elevated in the defoliation treatments at the three different periods, and the highest value was observed in the 50% defoliation group at the full bud and boll stages, which is a reflection of supercompensation. The SOD enzyme activity level tended to increase with the intensity of defoliation, and defoliation at the gestational and full bud stages first enhanced and then weakened the stress on the cotton plants. The differences between treatments decreased after 12 weeks. The stress of defoliation on cotton plants was weakened at the boll stage. With the increase in defoliation intensity, the content of MDA showed a gradual increasing trend. The cotton MDA content was higher than that of the other treatments at 75% defoliation at both the post-fertilized bud and full bud stage.

Connecting competitor, stress-tolerator and ruderal (CSR) theory and Lund Potsdam Jena managed Land 5 (LPJmL 5) to assess the role of environmental conditions, management and functional diversity for grassland ecosystem functions

Abstract. Forage offtake, leaf biomass and soil organic carbon storage are important ecosystem services of permanent grasslands, which are determined by climatic conditions, management and functional diversity. However, functional diversity is not independent of climate and management, and it is important to understand the role of functional diversity and these dependencies for ecosystem services of permanent grasslands, since functional diversity may play a key role in mediating impacts of changing conditions. Large-scale ecosystem models are used to assess ecosystem functions within a consistent framework for multiple climate and management scenarios. However, large-scale models of permanent grasslands rarely consider functional diversity. We implemented a representation of functional diversity based on the competitor, stress-tolerator and ruderal (CSR) theory and the global spectrum of plant form and function into the Lund Potsdam Jena managed Land (LPJmL) dynamic global vegetation model (DGVM) forming LPJmL-CSR. Using a Bayesian calibration method, we parameterised new plant functional types (PFTs) and used these to assess forage offtake, leaf biomass, soil organic carbon storage and community composition of three permanent grassland sites. These are a temperate grassland and a hot and a cold steppe for which we simulated several management scenarios with different defoliation intensities and resource limitations. LPJmL-CSR captured the grassland dynamics well under observed conditions and showed improved results for forage offtake, leaf biomass and/or soil organic carbon (SOC) compared to the original LPJmL 5 version at the three grassland sites. Furthermore, LPJmL-CSR was able to reproduce the trade-offs associated with the global spectrum of plant form and function, and similar strategies emerged independent of the site-specific conditions (e.g. the C and R PFTs were more resource exploitative than the S PFT). Under different resource limitations, we observed a shift in the community composition. At the hot steppe, for example, irrigation led to a more balanced community composition with similar C, S and R PFT shares of aboveground biomass. Our results show that LPJmL-CSR allows for explicit analysis of the adaptation of grassland vegetation to changing conditions while explicitly considering functional diversity. The implemented mechanisms and trade-offs are universally applicable, paving the way for large-scale application. Applying LPJmL-CSR for different climate change and functional diversity scenarios may generate a range of future grassland productivities.

Agronomic characteristics of Tamani grass managed under different combinations of frequency and intensity of defoliation

Background: Management strategies may affect plant growth and herbage characteristics. Thus, understanding its impact may help to define appropriate management. Objective: To evaluate the effect of different defoliation intensities and frequencies on the structural characteristics, biomass components and the potential use of NDVI (normalized difference vegetation index) in pastures with Megathyrsus maximus cv. BRS Tamani. Methods: A randomized block design in a 2x3factorial arrangement was adopted, with two defoliation frequencies (85 and 95% of interception of photosynthetically active radiation (IPAR) and three defoliation intensities (residual leaf area index (LAIr) of 0.8, 1.3 and 1.8). Results: The frequency of defoliation affected the pre-defoliation leaf area index, height, total harvestable forage biomass (HTFB), and harvestable leaf blade (HGLB), with greater values for pastures managed at 95% of IPAR. The effect of intensity of defoliation was observed for the HTFB and HGLB variables, where pastures with lesser LAIr presented greater biomass values. Pastures managed at 95% of IPAR and higher LAIr reached the level of saturation of the normalized difference vegetation index more quickly. Pastures managed under the combination of 95% IPAR and LAIr of 0.8 showed greater production of harvestable green stem biomass and harvestable dead forage biomass. The combination of 95% of IPAR with LAIr of 0.8 or 1.8 enabled a greater number of new live leaves when compared to pastures with 85% of IPAR. Conclusions: Tamani grass must be managed with a frequency of defoliation of 95% of the interception of photosynthetically active radiation, maintaining a residual leaf area index between 0.8 and 1.3.

Consórcio de gramíneas para a alimentação de ruminantes

ABSTRACT An integrative review was conducted to identify which intercrops, composed of grasses from tropical or temperate climates, are most commonly used in ruminant feeding and which result in higher productivity. The review followed a developed and tested protocol according to the PVO strategy to formulate the guiding question. Data were collected from articles published in the electronic databases SCOPUS (Elsevier), Web of Science (Main Collection), and SciELO Citation Index (Web of Science) through a single cross-reference search. It was not carried out temporally, regionally, nor limited to Brazil. Among the selected studies, the genera found were Lolium (26.7%), Avena (26.7%), Brachiaria (20.0%), Cynodon (13.4%), Panicum (6.6%), and Sorghum (6.6%). The technologies adopted in the articles were target height (50.0%), reseeding (33.3%), and defoliation intensity (16.7%). The animal species used were beef cattle, dairy cattle, and goats - 50.0%, 33.3%, and 16.7%, respectively. It was possible to observe that the use of different cultivars yields positive results; this was most evident with the grasses most used in intercropping: ryegrass (Lolium multiflorum Lam) and black oats (Avena strigosa Schreb); which showed higher productivity values compared to monoculture.

Methods for prediction of morphophysiological variables of Brachiaria decumbens grass

AbstractThe purpose of this study was to evaluate different methodologies used in the field in order to find the one that could most effectively relate to the morphophysiological condition of Brachiaria decumbens cv. Basilisk (syn. Urochloa decumbens cv. Basilisk Stapf R.D. Webster). Two light interception frequencies (LI, 85% and 95%) and two defoliation intensities were adopted as targets for the residual leaf area index (RLAI 1.3 and 1.8). The treatments consisted of evaluating different methods of measuring the canopy height (CH) through its ability to correlate with the morphophysiological variables of species B. decumbens cv. Basilisk. High correlations between the methods CH, compressed height (CHe), weighted height 1 (WH1) and weighted height 8 (WH8) were observed mainly with the variables total forage biomass (TFB) and leaf area index (LAI) in both residual and pre‐grazing conditions. The path analysis showed degrees of multicollinearity, which determined the use of the “k” constants in order to correct the distortions of the diagonal elements of the correlation matrix X'X. Path analysis provided direct cause/effect indexes on TFB using LAI = 0.1435, photosynthesis (A) = −0.1061, CH = 0.1616, CHe = 0.0913, WH1 = 0.1386 and WH8 = 0.0575; on LAI using CH = 0.2404, CHe = 0.2164, WH1 = 0.2307 and WH8 = 0.2183; and on photosynthesis rate (A) using LAI = 0.2895, CH = 0.0203, CHe = −0.1170, WH1 = 0.0352 and WH8 = 0.0937. Similarity was observed between intercepts and slope coefficients for TFB prediction using CH, CHe, WH1 and WH8, providing mean values of 1069.57 and 204.06, respectively. Methods CH and WH1 presented a significant correlation with most morphophysiological variables and can be used to quantify TFB and LAI, while CH and WH8 can be used only for TFB.

Increasing spruce budworm defoliation increases catchment discharge in conifer forests

Forest insect outbreaks cause significant reductions in the forest canopy through defoliation and tree mortality that modify the storage and flow of water, potentially altering catchment runoff and stream discharge patterns. Despite a growing understanding of the impacts of insect outbreaks on the hydrology of broadleaf forests, little is known about these impacts to catchment hydrology in northern conifer-dominated forests. We measured the effects of cumulative defoliation by spruce budworm (Choristoneura fumiferana) on stream discharge and runoff in 12 experimental catchments (6.33–9.85 km2) across the central Gaspé Peninsula in eastern Québec, Canada over a three-year period (2019–2021). Six catchments were aerially treated with BtK (Bacillus thuringiensis kurstaki) insecticide to suppress the outbreak and six catchments were left untreated, leading to a defoliation gradient across the study sites. Stage-discharge relationships were established between June and October from 2019 to 2021. Stream volumetric discharge (r = 0.71, p < 0.01, t(34) = 5.85), runoff (r = 0.55, p < 0.01, t(34) = 3.81) and runoff ratios (r = 0.67, p < 0.01, t(33) = 5.19) were all strongly positively correlated with cumulative defoliation intensity, likely by reducing available water storage in the catchment and therefore enhancing runoff generation. Seasonally, volumetric discharge, runoff, and runoff ratios were more strongly correlated with defoliation in the summer than autumn months, likely because available catchment storage was more limited following the freshet. Overall, we found that insect defoliation impacts forested catchment hydrology similar to other landscape disturbances, and such consequences should be considered in forest management and the control of forest insect outbreaks.

A cost-benefit analysis for the management of Gonipterus platensis by comparing chemical and augmentative biological control

Around 1.5 million ha of the Iberian Peninsula is currently occupied by Eucalyptus globulus, the preferred species for commercial plantations due to its fast growth and wood technological properties. However, these economically important plantations are being heavily damaged by Gonipterus platensis (Col: Curculionidae), an invasive species native to Australia which was established in the Peninsula, in the nineties. A classical biological control with the release of the egg parasitoid Anaphes nitens (Hym: Mymaridae) was launched in the Peninsula. Yet, in the colder regions, in the North of the Peninsula, the parasitoid is not efficient enough to control the weevil population. The resulting damage overcomes more than 200 million euros every year.Current control strategies rely on the application of insecticide (acetamiprid) or augmentative biological control (ABC) with yearly releases of A. nitens in spring. However, uncertainties about the best option persist. In this study, chemical and ABC treatments were submitted to a cost-benefit analysis with the aim of determining their viability against the weevil, based on a treatment efficacy and stand productivity trade-off analysis.A simulation tool (3-PG.d) was used to simulate the growth of E. globulus stands, under four defoliation intensity scenarios mimicking the removal of 25, 50, 75 and 100% of the spring new leaves biomass. Each defoliation scenario was combined with three treatments: (i) chemical (acetamiprid), (ii) ABC+ (optimistic approach), and (iii) ABC- (pessimistic approach). For each treatment, several plans of yearly treatments were tested. The Net Present Value (NPV) and the harvested volume were used to compare all treatment alternatives.The best treatment decision, based on a cost-benefit analysis comparing economic results and harvested volume, varied with the intensity of defoliation. Treating was always better than doing nothing, except for the 25% defoliation scenario. ABC+ offered the best economic results, relative to other treatments, for 25, 50 and 75% defoliation scenarios. ABC- was only as good as the chemical treatment for the 25 and 50% defoliations. Under the heaviest weevil attack (100%), applying insecticide was the best alternative, overcoming both ABC treatments. These results show that augmentative biological control was a strategy to consider for this study, and thus, may be a strategy to be considered in the future.The 3-PG.d simulator showed that it can be an asset for forest managers aiming at integrating chemical and/or biological treatments against forest pests in stand management decisions.

Growth response of oaks to insect defoliation: Immediate and intermediate perspectives

In this study, we investigate the immediate and short-term consequences of defoliation by the spongy moth Lymantria dispar on secondary growth of oaks (Quercus robur L. and Quercus petraea (Matt.) Liebl.), including the interplay between defoliation and water availability during the defoliation period within a large-scale field experiment in south-eastern Germany. Furthermore, the impact of defoliation on oak secondary growth is explored retrospectively based on tree core measurements.Within the large-scale filed experiment, secondary growth of 880 oaks in 44 oak-dominated stands was monitored using permanent girth tapes over a three-year period following a spongy moth outbreak. Insecticide treatments were applied to half of the plots to obtain trees without defoliation, and canopy cover dynamics were subsequently monitored ground based and from satellites in all plots.We found that moth defoliation significantly reduced oak secondary growth by 10–60% during the outbreak year, with the impact on secondary growth being directly proportional to defoliation intensity. The negative impact of defoliation on secondary growth was aggravated by increased water availability during the outbreak year.In the post-outbreak year, secondary growth of oaks that had endured mild defoliation was no longer different from that of non-defoliated oaks. In contrast, oaks that had experienced substantial defoliation still exhibited a significant 10–30% reduction in secondary growth. Regardless of defoliation intensity, no further reduction in secondary growth was detected two years after the event compared to control trees. Our complementary retrospective analysis, utilizing core samples from oaks previously subjected to a defoliation event under distinct weather conditions, disclosed a strikingly analogous recovery of secondary growth from defoliation instigated by the spongy moth. Thus, validating that our experimental findings possess broad temporal transferability.

Bahiagrass (Paspalum notatum CV. Inia Sepé) responses to defoliation intensities

AbstractDefoliation management is determinant of forage production and plant persistence. The objective of this study was to identify grazing suitability and stability of herbage production of INIA Sepé subjected to four intensities of defoliation (represented for sward canopies of 3, 10, 17 and 24 cm maintained constant through weekly cuts) and two rates of nitrogen fertilization (100 and 300 kg ha−1). The response variables studied were: botanical/morphological composition of the herbage mass, herbage accumulation, nutritive value, tiller population density (TPD), tiller weight (TW), leaf area index (LAI) and nitrogen nutrition index (NNI) and calculations performed relative to the tiller size × density compensation mechanism (SDC). Taller swards had smaller population of large tillers, with greater individual leaf area, showing a tiller × size density compensation response. Calculations indicated that the regression coefficient for the linear regression between TW and TPD in a log scale was close to −2.5, in agreement with the −5/2 self‐thinning rule, with variable LAI and R (ratio between tiller leaf area and volume). The exception was during year 1 for the 100 kg N ha−1, when the regression coefficient was close to −1.5. During year 2 only one replication of the 3 cm and 100 kg N ha−1 did not follow the SDC line. LAI and herbage accumulation were positively correlated with the distance between points of log(TW) × log(TPD) and an hypothetical −3/2 SDC line (p &lt; .0001). Paspalum notatum cv. INIA Sepé shows stability of herbage accumulation and ability to adjust tiller size and population density.

Differential sensitivity of above- and belowground plant biomass to drought and defoliation in temperate grasslands

Multi-year droughts combined with other stressors such as defoliation are likely to have substantial ecological impacts. However, grasslands vary significantly in their response to drought and defoliation, and interpretations rarely address the importance of roots despite evidence showing roots are likely to respond differently to drought and defoliation than shoots. Here, we conducted a three-year manipulative experiment, combining a reduction in rainfall treatment (drought, 45% of ambient) with each of a time-of-defoliation (early vs. late) and an intensity-of-defoliation (none, light, heavy) treatment at seven temperate grassland sites to test three a priori hypotheses: 1) defoliation early relative to late in the season would exacerbate drought impacts on aboveground net primary productivity (ANPP) and root biomass; 2) ANPP and root biomass would progressively decrease with increasing intensity of defoliation early in the growing season under drought; 3) drought and defoliation effects on ANPP and root biomass would vary along a gradient of long-term mean annual precipitation of study sites. Across all seven sites, the combined effects of drought and defoliation led to greater changes in root biomass than ANPP. Under drought conditions specifically, defoliation early in the growing season reduced root biomass, but not ANPP, compared to defoliation late in the growing season. The decline in root biomass under drought was more substantial when the intensity of early-season defoliation increased from none to heavy. Furthermore, variation in the timing and intensity of defoliation altered root biomass more in mesic than arid grasslands, while their effects on ANPP remained unchanged across the seven sites. These results indicate that root systems may be more responsive than ANPP to simultaneous drought and defoliation, and could lead to long-term changes in plant productivity.

P77 Defoliation intensity impacts on feeding station exploration by dairy cows

P77 Defoliation intensity impacts on feeding station exploration by dairy cows

Prediction of the nutritional values by INRA (2018) feed evaluation system of Megathyrsus maximus subjected to different grazing strategies

Grazing management is a key element to optimize growth cycle of forages, which are enhanced in their chemical composition leading to the reception of greater nutritive values for feeding ruminants. Several studies have showed that the accuracy and precision of the feeding values are critical to achieve this goal, unfortunately, in Ecuador there are not referential data, despite of Megathyrsus maximus is the most forage used by livestock farmers. The predominant aim of the current study was to approach and estimate the feeding values by INRA feed evaluation system of Tanzania grass (Megathyrsus maximus) subjected at different grazing strategies. The statistical design was a randomized complete block, with a 3 × 2 factorial arrangement. Where the treatments were combinations of three grazing frequencies (GF) (30 d; termed GF30, 45 d, GF45 and 60 d, GF60) and two cutting heights (CHs; 30 and 45 cm). The agronomic data did not vary by season effect (P = 0.24 to 0.82), but GF60 had higher plant heigh and dry matter (DM) contents (P &lt; 0.001) than other GF, although with less tiller populations (241 vs. 304 tiller/m2). By CHs effect, Tanzania grass at 30 cm had a greater DM content than 45 cm of CHs (5565 vs. 4221 ± 603 kg/ha-1; P = 0.073). All chemical determinations were affected by GF, CHs and their interaction (P &lt; 0.001 to 0.004) with the exception on ADF between CHs (P = 0.50). Whereas only the CP and ADF values were conditioned by season effect (P = 0.001 to 0.011). Subsequently, Tanzania grass subjected at moderate rest periods and low defoliation intensities showed greater energy and proteins values than traditionally used GF60. Based in these findings, the defoliation frequency had influence on agronomic and chemical characteristics, whilst the feeding values was mainly affected by grazing intensities and weather conditions. So, the best combination regarding nutritive values should be at GF30 and GF45 combined with 45 cm of CHs.

Stocking method effects on forage accumulation, canopy attributes, and nutritive value of grazed Mulato II brachiariagrass pastures

AbstractRotational stocking (RS) is generally associated with the intensification of pasture‐based animal production systems, although many studies have shown little advantage over continuous stocking (CS). The objective of this research was to describe and explain the effects of two average canopy heights (20 and 30 cm) and three stocking methods (CS; rotational stocking with lenient defoliation, RSL; and rotational stocking with moderate defoliation, RSM) on forage accumulation (FA), vertical distribution of plant‐part components, and nutritive value of ‘Mulato II’ hybrid brachiariagrass (Brachiaria spp. syn. Urochloa spp.) during two summer rainy seasons in Piracicaba, São Paulo, Brazil. Pastures were maintained at average canopy height of 20 and 30 cm under CS, and treatments under RSL and RSM were imposed by variations of ±20 and 30% of the average canopy heights, representing defoliation intensities of 33 and 47% of the pre‐graze heights, respectively. The FA was not affected by CS, RSL, RSM stocking methods, averaging 8090 kg DM ha−1 year−1. Canopy bulk density and distribution of plant‐part components in the canopy profile were better at the average canopy height of 20 cm, accompanied by the greater nutritive value. The leaf bulk density was generally greater in RSM compared to CS. Pastures under CS had greater crude protein and in vitro digestible matter, and lesser neutral detergent fibre concentrations. Mulato II brachiariagrass should be managed at an average height of 20 cm under CS.

A management proposition to preserve functional identity of grasses in mixed swards

AbstractThe diversity of traits plays a key role in the maximization of ecosystems' multi‐functionality, but interspecific competition in defoliated swards can lead to unpredictable changes in the functional traits over the plant community. However, we hypothesize that interrupting canopy regrowth at a height corresponding to critical leaf area index (LAI), associated with moderate intensity of defoliation, can be an effective management to preserve the functional traits of contrasting growth strategy grasses cultivated as a mixture. A 2‐year experiment was conceived to assess continuously several traits of three cool‐season perennial grasses (Arrhenatherum elatius [exploitative], Dactylis glomerata [moderately exploitative] and Festuca arundinacea [conservative]) cultivated as single species stand or as a mixture. Dactylis glomerata was the less productive stand but no difference was observed between the mixture and the most productive monocultures. No change was observed in functional traits, whether the species were cultivated as monoculture or as a mixture. The dissimilarities over traits and, therefore, the functional identity of contrasting growth strategy grasses growing in multi‐specific swards was preserved when canopy regrowth was interrupted at a height corresponding to the critical LAI associated with moderate intensity of defoliation. Since the diversity of traits maximizes ecosystem multi‐functionality, our findings provide a step forward towards designing management practices that enhance ecosystems services delivered by cultivated multi‐specific grasslands.

Cladosporium spp. associado a crosta negra em seringueira no Brasil

ABSTRACT In recent years, a disease called black crust has caused damage to rubber trees in Brazil, since it leads to rapid leaf fall and consequently low latex production. Until the 1990s, black crust was associated with the fungi Phyllachora huberi and Rosenscheldiella heveae, but in 2022, after analysis of samples collected in the states of Minas Gerais and São Paulo, different species of the fungus Cladosporium ssp. were isolated from rubber tree leaves showing black crust in their leaflets. After morphological and phylogenetic analysis, using partial sequences of ITS-5.8S rDNA, α-elongase and actin regions, the isolates were identified as Cladosporium pseudocladosporioides, C. tenuissimum, C. cladosporioides, C. perangustum and C. xanthochromaticum. Pathogenicity tests with these isolates, in a greenhouse, demonstrated rapid appearance of symptoms such as apical death, damage to stems, intense defoliation and presence of black crust on stems and leaves. All isolates were pathogenic but had variable aggressiveness. This is the first report of Cladosporium causing black crust on rubber trees in Brazil.

Estadios fenológicos de crecimiento de árboles de guanábana (Annona muricata L.) utilizando la escala BBCH extendida

The soursop is a species of tropical fruit well accepted by consumers due to its creamy white pulp and excellent flavor. Currently, Mexico is the largest producer and consumer; however, the agronomic practices in use were established without a systematic knowledge of A. muricata L. phenology. The objective of this work then, was to conduct such a study in two of the main producing regions of Mexico: Tepic and Compostela (both in the state of Nayarit). For this, a total of 20 ungrafted trees were selected and their growth stages described using the extended BBCH-scale (Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie). Overall, eight main phenological stages were identified over the course of a year. These were: the development of buds (stage 0), leaves (stage 1),and shoots (stage 3), the emergence of flowers (stage 5), flowering (stage 6), fruit development and maturity (stages 7-8), and senescence of branches (stage 9). In addition, 37 secondary growth stages were also described and quantified. The highest number of vegetative shoots occurred from March-July, 2017 and the biggest increase in floral structures from July–September, 2017. Fruit setting to physiological maturity took an average of 114 days in both Tepic and Compostela, with the most intense defoliation occurring in October, 2017 in the former (Tepic) and in December, 2016 in the latter (Compostela). Hopefully, improved agronomic practices will be established using this information, as well as suitable protocols for future physiological studies.