Defoliation Management Research Articles

Defoliation management and grass growth habits modulated the soil microbial community of turfgrass systems.

Grass species selection and regular mowing are essential for maintaining aesthetic and environmentally sound turfgrass systems. However, their impacts on the soil microbial community, the driving force for soil N cycle and thus the environmental fate of N, are largely unknown. Here, the high throughput sequencing of 16S rRNA gene and internal transcribed spacer (ITS) region was used to evaluate how long-term defoliation management and grass growth habits (propagation types and photosynthetic pathways) modulated the soil microbial community. The investigation included three cool-season C3 grasses (creeping bentgrass, Kentucky bluegrass, and tall fescue) and three warm-season C4 grasses (bermudagrass, St. Augustinegrass, and zoysiagrass). Creeping bentgrass and bermudagrass were managed as putting greens with a lower mowing height; tall fescue spread in a tussock manner via tiller production whereas other grasses propagated in a creeping manner via rhizomes and/or stolons. Ordination analysis showed that both bacterial and fungal communities were primarily separated between putting green and non-putting green systems; and so were N-cycle gene relative abundances, with the putting greens being greater in N mineralization but lower in nitrification. Compared to warm-season grasses, cool-season grasses slightly and yet significantly enhanced the relative abundances of Chloroflexi, Verrucomicrobia, and Glomeromycota. Tall fescue yielded significantly greater bacterial and fungal richness than non-tussock grasses. As the main explanatory soil property, pH only contributed to < 18% of community compositional variations among turfgrass systems. Our results indicate that defoliation management was the main factor in shaping the soil microbial community and grass growth habits was secondary in modulating microbial taxon distribution.

Harvest Management Effects on Canopy Height and Light Interception of ‘Performer’ Switchgrass and its Relationship with Weed Infestation

Defoliation management can determine the presence or absence of desirable forage species. Canopy characteristics and light interception are two critical determinants of productivity and can influence weed pressure. The objectives of this study were to determine the effect of the factorial combination of four defoliation heights (clipped to 10, 20, 30, and 40 cm; DH) and four defoliation frequencies (clipped every 3, 6, 9, and 12 wk; DF) on light interception, canopy height, and weed canopy cover and frequency for ‘Performer’ (Panicum virgatum L.) switchgrass and to relate the abovementioned responses to previously reported productivity measurements. The experiment was conducted for 2 yr (2016 and 2017) at the Central Crops Research Station, Clayton, NC. The 16 treatments were allocated in a randomized complete block design replicated four times. Across years, light interception before harvest ranged from ∼45 to 88%, canopy height ranged from 35 to 97 cm, and weed cover and frequency ranged from 0 to 75 and 0 to 95%, respectively. Greater canopy height was associated with greater light interception and lower weed infestation. Weed infestation occurred mainly for treatments harvested every 3 and 6 wk and defoliated to lower stubble heights; however, there was no impact of DH for DF treatments harvested every 9 and 12 wk. Canopy light interception values of at least 70% obtained in our study were associated with defoliation thresholds previously reported in the literature for sustained yields of ‘Performer’ switchgrass. Switchgrass canopy light interception values of at least 70% were achieved with canopy heights before harvest of ∼60 cm tall.

Modeling the Nutritive Value of Defoliated Tall Fescue Pastures Based on Leaf Morphogenesis

Core Ideas The leaf morphogenetic‐based model predicted the pasture nutritive value variance generated by in an ad hoc experiment. Variation in fiber digestibility with the age and length of leaves is the main driver for declines in pasture digestibility of vegetative regrowth. The morphogenetic approach was designed to enable its potential integration with some of the available pasture growth models. The model provided mechanistic understanding and predictions that allow for the exploration of new management strategies. The leaf morphogenesis of plants is the most important determinant of the nutritive value dynamics in vegetative pasture regrowth. The aim of this study was to develop a simulation model of the pasture nutritive value dynamics based on a morphogenetic approach that takes into account the effects of leaf age and leaf length on forage digestibility in relation to defoliation management. The model was developed and evaluated with detailed data from two independent experiments (Exp. 1 and Exp. 2, respectively) on tall fescue [Lolium arundinaceum (Schreb.) Darbysh.], including descriptions of morphogenesis, neutral detergent fiber (NDF) and digestibility of NDF (NDFD) and dry matter (DMD) of leaf blades. The model precisely and accurately simulated the forage digestibility dynamics of pasture regrowth observed under different residual pasture heights in Exp. 2. The main calculated statistics for NDF, NDFD, and DMD were root mean square deviation &lt; 4% points, R2 ≥ 0.92, concordance correlation coefficient ≥ 0.86 and bias correlation factor ≥ 0.89. The evaluated model was used to investigate the responses of forage nutritive value to several combinations of residual pasture heights (2–15 cm) and defoliation intervals (one to five leaves per tiller). This study highlights the inclusion of the NDFD trait associated to leaf morphogenesis as a mechanistic way to improve predictions of DMD dynamics in vegetative regrowth under different defoliation managements.

Leaf area response in dual purpose wheat submitted to different defoliation managements and seeding densities

Leaf area response in dual purpose wheat submitted to different defoliation managements and seeding densities

Phenotypic Plasticity and Other Forage Responses to Grazing Management of Ecoturf Rhizoma Peanut

Forage–livestock systems in the southeastern United States are based on N‐fertilized perennial grass pastures, with minimal legume contribution. The legume rhizoma peanut (RP, Arachis glabrata Benth.) can persist and spread in grazed mixtures with C4 grasses, and Ecoturf RP is of particular interest because it is relatively decumbent and may vary its growth habit in response to defoliation management. The objective was to quantify effects of grazing frequency and intensity of Ecoturf on herbage accumulation (HA), canopy characteristics, storage organ mass, and total nonstructural carbohydrate (TNC) concentration. Treatments were the factorial combinations of three levels of regrowth interval (RI; 1, 4, and 7 wk) between grazing events and two levels of post‐grazing stubble height (SH; 4 and 8 cm). For the 4‐cm SH, HA increased from 8.4 to 10.5 Mg ha−1 in 2015 and from 9.8 to 13.6 Mg ha−1 in 2016 as RI decreased from 7 to 1 wk. The effect of RI was less pronounced for the 8‐cm SH. When grazed to a 4‐cm SH, herbage bulk density and post‐grazing leaflet mass increased linearly as RI decreased from 7 to 1 wk in both years. Changes in root‐rhizome mass and TNC pool during 2 yr of grazing were not affected by SH or RI. Ecoturf adapted to frequent, close grazing by increasing herbage bulk density and positioning leaves close to the soil surface, allowing rapid regrowth after defoliation without depleting reserves. Ecoturf is tolerant of a range of grazing strategies, showing promise for use in pastures.

Development of the Moorepark St Gilles grass growth model (MoSt GG model): A predictive model for grass growth for pasture based systems

Abstract In humid-temperate regions grazed grass is the most economical means of feeding ruminant livestock. Grass growth is often highly variable and therefore difficult to predict. It is influenced by many factors including climatic conditions, soil type and soil nutrients. The Moorepark St. Gilles Grass Growth model (MoSt GG model) is a dynamic model developed in C++ describing daily grass growth at the paddock level. It was developed by adapting an existing grass growth model to include a nitrogen (N) component and a soil water component. The model is effective in grazing and cutting scenarios. Inputs include weather data, grazing management decisions and N fertiliser application. Outputs include daily grass growth, soil mineral N content, grass N uptake, grass N content and NO3− leaching. The MoSt GG model was evaluated against measured data using 2 years data from an experimental farm; the predicted and measured biomass for each paddock was compared. The mean root mean square prediction error (RMSPE) at the measurement level was 505 kg DM/ha. When averaged by week of year, the RMSPE was reduced to 321 kg DM/ha. The MoSt GG model was also evaluated against a range of management scenarios including N fertiliser application rate (from 0 to 650 kg N/ha per year) and defoliation management, and weather conditions. The grass growth response to N fertiliser application was, on average, 9.6 kg DM/kg N applied with a minimum response of 0.8 kg DM/kg N applied and a maximum response of 16.2 kg DM/kg N applied, which is in the range of previously published studies. The MoSt GG model responds to daily weather conditions, patterns and methods of sward defoliation, and describes daily variations in soil mineral and organic N content.

Defoliation Management Affects Productivity, Leaf/Stem Ratio, and Tiller Counts of ‘Performer’ Switchgrass

Core Ideas Defoliation management resulted in a wide range of plant responses that varied by year, with deleterious responses more evident in the second year. Greater leaf/stem ratios occurred with more frequent defoliation treatments. Frequent defoliations such as every 3 wk should maintain a stubble height of at least 40 cm, defoliation frequencies ≥6 wk to 20‐cm stubble height, and ≥9 wk to 10 cm stubble height are warranted to ensure stand persistence. ‘Performer’ switchgrass (Panicum virgatum L.) was released in 2006 by the USDA‐NCSU forage program because of its greater digestibility compared to standard cultivars grown in the southeastern United States. Forages with greater digestibility have potential to positively impact animal responses, however, defoliation management can influence its productivity and persistence. The objectives were to determine the effect of the factorial combination of four defoliation heights (DH) (clipped to 10, 20, 30, and 40‐cm) and four defoliation frequencies (DF) (clipped every 3, 6, 9, and 12 wk) on productivity, leaf/stem ratio, and tiller counts. The experiment was conducted in 2016 and 2017 at the Central Crops Research Station, Clayton, NC. The 16 treatments were allocated in a complete randomized block design replicated four times. In 2016, total dry matter (DM) yield ranged from 4.2 to 13.1 Mg ha−1 being greatest for the 9‐ and 12‐wk DF at 10‐ and 20‐cm DH and lowest for all DH at 3‐wk defoliation frequency. In 2017, the DM yield range was wider ranging from 0.5 to 14.0 Mg ha−1 with lower tiller counts for the 10‐ and 20‐cm DH, 3‐wk DF treatments. Leaf/stem ratio was greater for the more frequently defoliated treatments in both years. ‘Performer’ switchgrass is a productive forage and on the basis of total DM harvested, leaf/stem ratio, and tiller counts, frequent defoliations such as every 3 wk to 40‐cm stubble height, ≥6 wk to 20‐cm stubble height, and ≥ 9 wk to 10 cm stubble height, are warranted to ensure stand persistence.

Optimal defoliation management of brachiaria grass–forage peanut for balanced pasture establishment

AbstractA well‐established canopy is crucial for a stable mixed grass–legume forage pasture. The aim of this study was to assess a defoliation intensity that can ensure the establishment of mixed pasture of brachiaria grass (Brachiaria brizantha) intercropped with forage peanut (Arachis pintoi). The treatments comprised four canopy heights: 10, 20, 30 and 40 cm, maintained throughout the first 3 years of pasture establishment. Canopy structure, morphogenetic and structural characteristics were measured. A block design was used with four replicates, and seasons of the year were considered using repeated measurements over time. Light interception during the experimental period was 86.3%, 95.9%, 97.6%, and 99.1% for 10, 20, 30 and 40 cm of defoliation respectively (p &lt; .001). Competition for light in taller canopies (at 30 and 40 cm) caused etiolation of forage peanut (greater internode, petiolate and stolon lengths). This response promoted its upward growth, leading to a lower stolon density compared with 10 and 20 cm. The treatment at 10 cm displayed a predominance of forage peanut (up to 0.614), potentially compromising community stability. Overall, the 20 cm canopy height showed a desired botanical composition (from 0.20 to 0.45 of legume in forage mass) and thus was considered an ideal defoliation intensity for establishment of mixed canopies of brachiaria grass and forage peanut.

Biorational and chemical management of defoliators on soybean

Biorational and chemical management of defoliators on soybean

Defoliation management affects morphogenetic and structural characteristics of mixed pastures of brachiaria grass and forage peanut

A sound understanding of the effects of defoliation management in a grass–legume pasture is key in balancing populations between species. The aim of this study was to quantify the morphogenetic and structural characteristics and forage production of brachiaria grass and forage peanut mixtures under four defoliation strategies. A two-year experiment was carried out in Brazil (Cwa climate), where the following treatments were studied: rest period interruption by cattle grazing when the canopy attained light interception (LI) of 90%, 95% and 100%, and grazing performed every 42 d. Morphogenetic and structural characteristics of both species were measured. The forage and leaf accumulation rates were also quantified. The design was randomised blocks, with three replications, and repeated measurements over time. The 100% LI had greater stem and stolon elongation rates and a lower leaf appearance rate in both species and fewer tillers or stolons when compared with the other strategies. Conversely, rest periods of 90–95% LI promoted an increase of about 30% on forage and leaf accumulation rates of both grass and legume. Therefore, to enhance productivity and stability when these species are associated we recommend defoliating at 90–95% LI, which represents a canopy height ranging from 26 to 32 cm.

White clover: the forgotten component of high-producing pastures?

The contribution of white clover (Trifolium repens L.) to nitrogen fixation and feed quality in mixed pastures is indisputable, but the benefits of clover inclusion to total herbage accumulation (HA) are less clear. Results from four experiments comparing mixed pastures of white clover–perennial ryegrass (Lolium perenne L.) with perennial ryegrass monocultures are presented. These experiments covered a range of environments (dryland northern New Zealand and irrigated southern New Zealand), management inputs (nitrogen (N) fertiliser rates and defoliation management), and genotypes of ryegrass and white clover. Mixtures resulted in a significantly greater HA than did monocultures in 7 of the 8 years for which data were available; the interaction between pasture type (monoculture or mixture) and N rate was significant in six of those years, with a greater advantage in HA for mixtures under low N rates (mean = 3.08 t DM/ha.year) than under high N rates (mean = 1.54 t DM/ha.year). Two-thirds to four-fifths of the yield advantage under grazing was due to the direct effect of clover contribution (which ranged between 10% and 30% of total annual yield) to HA, most of which accrued in summer. The remainder was due to the capture of additional clover-derived N by the grass component of the mixture, estimated to equate to 50–60 kg N/ha under low N-fertiliser rates and 15–35 kg N/ha under high N rates. The magnitude and consistency of the yield advantages observed here indicates that there are unrealised yield and other benefits not currently being captured in New Zealand dairy production systems, largely because they are negated by the use of high N-fertiliser rates. The agronomic practices required to support clover-rich mixed pastures receiving moderate rates of N fertiliser are well documented and can be applied to help deal with nutrient loss limits required by environmental regulations plus volatility in farm-gate milk prices.

Evaluation of Continuous and Multipaddock Grazing on Vegetation and Livestock Performance—a Modeling Approach

Although the impact of optimal stocking rate on rangeland health and ranch profitability has been extensively studied, grazing management practice has received far less attention in mathematical modeling analyses. This paper uses a mathematical model to examine the impacts of continuous grazing and multipaddock (MP) grazing on vegetation and livestock forage consumption. Simulations are carried out using parameters applicable to the southern tallgrass prairie of North America. On small areas of land with no difference between defoliation rates across different grazing methods, the performance of MP grazing is no better than continuous grazing. At the scale of commercial ranches, MP grazing with improved defoliation management improves grass composition and productivity, as well as livestock consumption relative to continuous grazing, especially with heavier stocking rates and unfavorable initial biomass composition. The advantages of MP grazing, however, are reduced with favorable rainfall conditions, light stocking, low levels of undesirable plants, and inadequate recovery periods.

A Resource-Based Approach to Assessing Interseeding Success in Reconstructed Tallgrass Prairies

Interseeding is a common method used to increase species richness within established reconstructed grasslands. This process depends upon the ability of the practitioner to produce resource conditions that facilitate seedling emergence in systems where such emergence is often limited. We tested effects of a mowing disturbance on interseeding success by seeding a mix of 10 common tallgrass prairie species into 1-m2 plots within two warm-season grass dominated grasslands. We clipped the vegetation on a subset of the plots once or repeatedly and measured environmental variables including litter depth, soil surface light, soil moisture, and soil nitrate within the first growing season. While clipping consistently increased soil surface light, seeded species emergence varied in response to measured environmental resources between sites. In the lowland site, emergence over two growing seasons was primarily explained by microsite and early season light availability. In the more recently burned upland site, emergence was primarily limited by later season light conditions associated with clipping. Despite this variation, seed additions increased plot-scale species richness irrespective of clipping effects mainly as a result of high establishment of wild bergamot ( Monarda fistulosa ) in both sites. It appears that effects of season-long defoliation management on seedling emergence depend on microsite conditions at seeding and we conclude that soil surface and established vegetation management are necessary when interseeding to increase grassland species richness.

Effects of autumn and spring defoliation management on the dry‐matter yield and herbage quality of perennial ryegrass swards throughout the year

AbstractA small‐plot experiment was conducted in south‐west Ireland to investigate (i) the effects of pre‐closing regrowth interval and closing date on dry‐matter (DM) yield and sward structural and composition characteristics, during the autumn–winter and spring opening periods, and (ii) subsequent carryover effects. The study used a randomized block design with a factorial arrangement of treatments (4 closing dates × 2 opening dates) with a split plot (two pre‐closing regrowth intervals). The long pre‐closing (LPC) interval began on 9 August, and the short pre‐closing interval (SPC) started on 15 September. The autumn closing dates were as follows: 1 October (CD1), 15 October (CD2), 1 November (CD3) and 14 November (CD4). Plots were defoliated again on 1 February (EOD) or 1 March (LOD). On the LPC treatment, herbage yield increased from CD1 (2463 kg DM ha−1) to CD3 (3185 kg DM ha−1). On the SPC treatment, herbage yield was similar for CD3 and CD4, indicating a ceiling in herbage accumulation. For each 1‐d delay in closing date between CD1 and CD4, the opening herbage yield was reduced by 10 kg DM ha−1. Herbage quality decreased as the closing date was delayed; DMD and CP decreased by 0·06 and 12 g kg DM−1, respectively, between CD1 and CD4. The EOD resulted in increased leaf and decreased dead proportions over the LOD treatments. A balance between autumn CD and spring OD needs to be achieved to ensure a sufficient supply of high‐quality grass in spring.

Eco-friendly approaches for the management of defoliators on onion

Eco-friendly approaches for the management of defoliators on onion

Reproductive Development of &amp;lt;i&amp;gt;Lotus tenuis&amp;lt;/i&amp;gt; (Fabaceae) Crop Defoliated at Different Times and Intensities

Lotus tenuis forage yield has been quantified under defoliation conditions in pastures, grasslands and under dual-purpose production of both livestock forage and seeds. However, little is known about the effects of defoliation management on L. tenuis flower and pod production and subsequent seed yield. Two field experiments were conducted to study the response of L. tenuis to defoliation at different flowering stages and intensities. In Experiment 1, crops were defoliated at the beginning of the flowering (DBF), mid-flowering (DMF) or full flowering (DFF). In Experiment 2, defoliation was in vegetative stage at low (LDI) or high (HDI) intensities. Defoliation in Experiment 1 neither affected plant cover nor the photosynthetically active radiation intercepted by the crop during pod production. There were less umbels with dehiscent (shattered) pods in the DFF treatment than in Control, DBF and DMF treatments. Flower peak occurred first in the Control, DBF and DMF treatments, and eight days later in DFF plots, however, seed yield was not affected (1324 ± 32.8 kg·ha-1). Defoliation intensity did not affect seed yield (962 ± 25.9 kg·ha-1) because of self-compensation which increased harvest index in HDI (14.5% ± 0.6%) compared to the Control and LDI (12.0% ± 0.3%) treatments. Plant survival was not affected by defoliation treatments in any of the experiments. Flowering can be synchronized through defoliation. The blooming of large numbers of flowers in a short time was achieved, reducing the number of shattered pods. Compensatory responses through plant plasticity conferred L. tenuis the ability to overcome defoliation without affecting seed yield. Lotus tenuis defoliation as management tool will be considered in future researches because it is possible to harvest forage and to increase seed yield through a reduction of shattered pods.

Defoliation, Shoot Plasticity, Sward Structure and Herbage Utilization in Pasture: Review of the Underlying Ecophysiological Processes

Sward structure affects herbage growth, pasture species dynamics, and herbage utilization. Defoliation management has a major impact on sward structure. In particular, tiller size-tiller density compensations allow for the maintenance of herbage growth. Tiller size and tiller density are determined by several major morphogenetical components. Defoliation affects these morphogenetical components, depending on its frequency and its intensity, through several direct and indirect physiological and environmental processes. Due to the implications of leaf area removal, defoliation has a direct effect on the mobilization of C and N reserves and their supply to growing leaves. In addition, defoliation has an indirect effect on leaf and tiller morphogenesis, due to its impact on the light environment within the canopy as well as plant responses to light signals (blue light, red far red ratio). Defoliation may also in some cases have a direct negative effect on leaf growth by damaging leaf meristems. Understanding the respective role of these various physiological and environmental processes requires studies where defoliation, photosynthetic active radiation and light signals are manipulated independently. Past and recent knowledge on these direct and indirect effects of defoliation on plant morphogenesis are discussed, leading to an overall integrated view of physiological and environmental processes that lead to adaptations of sward structure in response to defoliation management. Major consequences for herbage utilization efficiency are presented.

Flubendiamide, a novel insecticide for management of lepidopteron defoliators in soybean

Flubendiamide 20 WG, a benzenedicarboxamide compound with novel mode of action was evaluated against the major lepidopteron defoliators of soybean namely, Chrysodeixis acuta (Walker), Diachrysia orichalcea (Fabricius), Gesonia gemma Swinhoe, and Spodoptera litura (Fabricius) during 2010 and 2012 rainy seasons under the field conditions at Indore. Three application rates; 50, 60 and 120 g a.i. ha-1 of Flubendiamide 20 WG were tested in comparison to the conventional insecticides viz., Endosulfan 35 EC @ 250g a.i. ha-1 (2010) and Triazophos 40 EC @ 320 g a.i. ha-1 (2012). The application rate of 60 g a.i. ha-1 of Flubendiamide 20 WG was found most effective with better incremental cost benefit ratio as compared to the check insecticides. It has provided significantly better protection to soybean crop from the lepidopteron defoliators up to 15 days after spraying.

A comparison between cutting and animal grazing for dry‐matter yield, quality and tiller density of perennial ryegrass cultivars

AbstractPerennial ryegrass (Lolium perenneL.) evaluation trials are often conducted under simulated grazing to identify the most productive cultivars. It is unclear whether simulated grazing identifies the most productive cultivar for animal‐grazed swards. Ten cultivars were established as plots and managed concurrently under simulated grazing (SG), animal grazing (AG) and conservation (CON). The experiment lasted 3 years with dry‐matter (DM) off‐take, digestibility, tiller density and ground‐cover score recorded in all years. A good relationship existed betweenDMoff‐take underSGandCON(R2 = 0·73). The relationship betweenSGandAGwas strongest in year 2 and 3 (R2 = 0·53 and 0·55 respectively). HighDMproduction was observed inSGswards in year 1; this was weakly related to theDMproduction of theAGsward. Across the 3 years, theCONtreatment had higher yields than either of the other two treatments and was poorly correlated toDMyield underAG, confirming that cultivars should be evaluated under a similar defoliation frequency to their intended use. Tiller density declined quickest underCONand slowest underAG. Some reranking of cultivars occurred between defoliation managements. The results show that simulated grazing is a useful indicator ofDMyield performance of animal‐grazed swards.

Flubendiamide, a novel insecticide for management of lepidopteron defoliators in soybean

Flubendiamide, a novel insecticide for management of lepidopteron defoliators in soybean