Timing Of Defoliation Research Articles

Forage productivity is resilient to timing of post-wildfire defoliation in mixed-grass Prairie

Post-fire rangeland management recommends rest from grazing to allow forage regrowth and litter accumulation. In the first year after wildfire in the mixed-grass Prairie, we examined forage and litter mass responses to variable timing of defoliation in burned and non-burned areas. Total forage biomass did not differ between burned and non-burned areas by the second growing season. The July defoliation in both burned and non-burned areas reduced total forage biomass. Litter mass was decreased by wildfire and was further reduced by all defoliation treatments.

Partial and total defoliation during the filling period affected grain industrial and nutraceutical quality in soybean.

Little is known about soybean grain chemical composition response to defoliation. The objectives of our study were: (i) to quantify the impact of different levels and timing of defoliation during the filling period on soybean grain yield and grain chemical content and composition, including protein, oil, fatty acids, and isoflavones; and (ii) to establish associations between them and the level and timing of defoliation. Yield and grain chemical components were reduced by defoliation treatments, these effects being more pronounced as defoliation increased. Mild defoliation (33%) caused small or non-significant changes in yield, its components, protein, oil, and isoflavone contents and concentrations. However, it affected oil composition, increasing the degree of unsaturation, which became more accentuated as defoliation increased. Moderate defoliation (66%) produced similar relative reductions in protein and oil contents, with small effects in isoflavone content, resulting in a generally greater isoflavone concentration in defatted flour and a greater isoflavone/protein ratio in grain. Total defoliation (100%) produced greater relative reductions in oil and isoflavone contents than in protein content. These resulted in higher protein/oil ratio and protein concentration and lower isoflavone/protein ratio and isoflavone concentration. Analyzed variables were associated with cumulative solar radiation during grain filling; indeed, this parameter successfully captured the effects of defoliation intensity and timing. By exploring different levels and timings of defoliation during the filling period, our study provides novel and important information regarding the impact of light interception decreases on grain chemical components, with special emphasis on nutraceuticals. © 2022 Society of Chemical Industry.

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.

Grazing and Defoliation Timing Effects in Great Plains Ponderosa Pine Woodland Following a Large Summer Wildfire

Grazing and Defoliation Timing Effects in Great Plains Ponderosa Pine Woodland Following a Large Summer Wildfire

Status and types of Chiuri (Diploknema butyracea (Roxb.) H.J.Lam) owned by Indigenous Chepang Communities in Makwanpur, Nepal

Chiuri (Diploknema butyracea) is a medium-sized tree that inhabits in sub-Himalayan tracks of steep slopes and cliffs at an elevation of 400 to 1400 meters from west to east of Nepal. It belongs to Sapotaceae family of plant kingdom. This study was conducted to assess status of Chiuri tree in Raksirang Rural Municipality (RRM) with particular interest to location, khoria aspect, age and types. Primary data were collected through questionnaire survey, interviews, informal discussion, etc. whereas secondary data were collected through desk review. Biometric data such as seed size and seed count per kg of seeds were measured using measuring scale and weighing balance. Four types of Chiuri namely Wayo, Lanyo, Titiya and Tomyo were found in RRM depending on ripening time of fruit. Most of them have Chiuri older than 30 years of age and their khoria facing south direction. Chiuri takes 6-10 years to start fruiting from seedling. Based on survey, Wayo and Lanyo were found in lower elevation whereas Titiya and Tomyo were found in higher elevation. The timing of fruit ripening was different but followed a pattern of types located in lower elevation fruiting earlier. However, defoliation timing was different and was not influenced by elevation.

Free and glycosylated green leaf volatiles, lipoxygenase and alcohol dehydrogenase in defoliated Nebbiolo grapes during postharvest dehydration

Background and Aims Nebbiolo grapes are used to produce Sfursat wine, following partial dehydration. This research aimed to clarify the influence of fruit exposure to light and postharvest water loss on the concentration of green leaf volatiles (GLVs) and lipoxygenase (LOX) and alcohol dehydrogenase (ADH) activity of grapes. Methods and Results Nebbiolo grapes from Control vines (no defoliation) (ND) and from vines defoliated at fruitset (DFS) or defoliated post-veraison (DPV) were harvested at about 23°Brix and dehydrated at 10 and 20°C, 60% RH and air flow of 1.5 m/s. Berries were sampled at 10 and 20% mass loss (ML). Significant differences in crop yield, bunch mass and berry mass were observed. As expected, the higher the dehydration temperature, the faster the dehydration process: 20% ML at 20°C occurred between 18 and 25 days, the shortest time corresponding to ND and the longest to DFS; at 10°C, the dehydration lasted between 27 and 32 days. At 10°C, the ADH activity was almost double that at 20°C, and in DFS was much higher than in other samples. At harvest, LOX did not show any difference among the samples, while at 10°C and 10% ML, the enzyme activity increased significantly and then declined at 20% ML, especially in defoliated samples. At harvest, the total free GLVs associated with the metabolism of lipid oxidation were 9434, 7212 and 11 656 μg/kg dry weight (DW) in ND, DFS and DPV samples, respectively; the total bound GLVs lipid-derived were 7599, 18 486 and 15 409 μg/kg DW in ND, DFS and DPV samples, respectively. During dehydration at 10°C, the ML induced ADH + LOX activity, especially in defoliated samples, but the bound GLVs, produced by defoliation, greatly decreased. Conclusions Defoliation affected the response of Nebbiolo grapes to dehydration temperature: postharvest cold stress (10°C) and ML induced glycosylation of GLVs, alcohol formation (via ADH) and membrane oxidation (via LOX); a further stress effect was observed with leaf removal, regardless of the time of application. Significance of the Study The timing of defoliation and postharvest dehydration temperature are significant factors to mitigate the postharvest stress response of Nebbiolo grapes.

Phenolic profile of grapevine cv. Tempranillo skins is affected by timing and severity of early defoliation

Aim of study: To investigate the effects of three early leaf removal treatments on the phenolic compounds of cv. ‘Tempranillo’ (Vitis vinifera L.) grape skins.Area of study: The experiment was conducted in a vineyard located in Requena, Valencia (South-eastern Spain) over two consecutive seasons.Materials and methods: Four treatments were investigated over two seasons in drip-irrigated vines: Control (C), non-defoliated and three defoliation treatment, applied at different phenological stages and intensities where all leaves from the first 6 nodes were eliminated just before flowering (ED) and at fruitset (LD). The fourth defoliation treatment was performed at the same time of ED but only the leaves facing east of the eight first nodes were removed (EED). At harvest, thirty-eight phenolic compounds were quantified by HPLC in the grape skins, including anthocyanins, flavanols, flavonols, hydroxycinnamic acids and their tartaric derivatives.Main results: A general increase of the skin phenolic compounds concentration was found in response to the defoliation treatments. The largest and more significant effects were observed for LD in 2009 with relative increases with respect to the un-defoliated vines of 14.8, 86.0, 119.0, and 75.9% for anthocyanins, flavanols, flavonols and hydroxycinnamates, respectively. On the other hand, EED did not clearly modify any polyphenolic compound. In addition, the response of phenolic families analyzed to defoliation treatments was different. Malvidine derivatives were not altered by any of the treatments, while the contents of quercetin and kaempferol derivatives and ferulic and coumaric acids, increased in both years when LD was applied.Research highlights: The defoliation effects on specific phenolic substances were dependent on timing, severity, and the season. Skin phenolic compounds increase in response to defoliation treatments and flavonols and hydroxycinnamates were the most affected families.

Effects of Defoliation at Fruit Set on Vine Physiology and Berry Composition in Cabernet Sauvignon Grapevines.

Grapevine canopy defoliation is a fundamentally important technique for the productivity and quality of grapes. Leaf removal is a pivotal operation on high-density vines which aims to improve air circulation, light exposure, and leaf gas exchange. The effects of leaf removal (LR) on vine physiology and berry composition in Cabernet Sauvignon grapevines were studied during the 2018–2019 growing season in the Bolgheri area, Tuscany, Italy. The basal leaves were removed at fruit set at two severity levels (removal of four basal leaves of each shoot (LR4) and removal of eight basal leaves (LR8)). The two treatments were compared with the not defoliated control (CTRL). The following physiological parameters of vines were measured: leaf gas exchange, leaf water potential, chlorophyll fluorescence and indirect chlorophyll content. The results showed that defoliation increased single leaf photosynthesis. In addition, qualitative grape parameters (phenolic and technological analyses) and daytime and night-time berry temperature were studied. The results showed that leaf removal had an impact on total soluble solids (°Brix), titratable acidity, and pH. The LR8-treated grapes had higher titratable acidity, while those in the LR4 treatment had higher °Brix and extractable anthocyanin and polyphenol content. Berry weight was not significantly influenced by the timing and severity of basal defoliation. Therefore, this research aims to investigate the effects of defoliation at the fruit set on vines performance.

Effects of cotton genotype, defoliation timing and season on fiber cross-sectional properties and yarn performance

Cotton fiber cross-sectional properties influence the performance of ring spun yarns. The spinning performance of two Gossypium hirsutum L. Upland cotton genotypes known to have inherently different fiber fineness properties were compared. Genotypes were grown together in field experiments conducted over two growing seasons, and crops were subjected to early and late defoliation treatments. The aim was to quantify the differences in yarn properties following changes targeting fiber fineness properties in isolation from other fiber properties. For the first time, the percentage difference in yarn properties was captured along with the associated changes made to alternative fiber fineness properties within the base micronaire 3.50 to 4.90 G5 range. As expected the genotype with lower fiber micronaire, linear density, and perimeter, spun yarns that were stronger and more even. Late defoliated cotton plants produced fibers that were higher in micronaire and maturity ratio, and were bigger in perimeter, which demonstrated that the fibers had expanded during the secondary wall thickening phase of development. However, the defoliation treatment effect on fiber fineness properties was smaller compared with the effect of genotype, and no change to any yarn property was detected. In terms of environmental effects, the first season cotton had smaller perimeter finer fibers that spun stronger and more even yarns. In contrast, the second season cotton had bigger perimeter fibers that spun weaker and less even yarns.

Biomass yield, chemical composition and in vitro digestibility of maize leaves defoliated at different times

This experiment was conducted to determine the effect of defoliation time on the productivity of maize, forage and in vitro digestibility of maize leaves (ML). The response of grain yield, plant height, days to 50% silking, ear height and leaf yield as well as the chemical composition of ML variety "Obasuper" to defoliation time were evaluated in a randomized complete block design with four defoliation treatments 3, 6, 9 weeks after planting (WAP) and undefoliated treatment replicated four times. Results showed that defoliating maize at 9 WAP and beyond did not have any significant (P>0.05) effect on the grain and leaf yield as well as other yield components of maize. Grain and leaf yield at 9 WAP averaged 2778.35 and 975.74 DM kg/ha respectively. The DM, crude protein (CP) and fibre fractions contents of ML varied significantly (P<0.05) among the defoliation treatments with maize defoliated at 9 WAP having a CP content of 12.6%. Ether extract and ash contents were not affected (P>0.05) by defoliation time. The in vitro digestibility of ML decreased significantly (P<0.05) with increase in the time of defoliation ranging from 59.2 and 66.4%. IT was concluded that maize variety "Obasuper" can produce forage of high quality and quantity when defoliated 9 weeks after planting wihout any anyadverse effect on the grain yield of maize.

Leaf stage as a defoliation criterion for the production of high-vigour annual ryegrass seeds

Previous research demonstrated that the interval between defoliation treatments based on the leaf stage is a promising tool for the management of annual ryegrass (Lolium multiflorum L.) pasture. The use of this tool, which is based on the physiological status of the plant, could also benefit the seed production. We assessed the effects of the time of defoliation based on leaf stage on seed yield and quality of annual ryegrass cut to three residual stubble heights (RSH) (50%, 25% and 0% of plant height pre-defoliation) and a second defoliation applied to certain treatments based on the leaf stage of the plant regrowth (two or three leaves per tiller). Higher defoliation intensities (lower RSH) increased the amount of harvested forage to 4.0 t DM ha–1. Moderate defoliation (50%) undertaken at the 3-leaf stage combined with intense defoliation (25% and 0%) at the 2-leaf stage resulted in the highest seed yields (1.8 t ha–1). However, lower RSH reduced mean seed weight and physiological seed quality, which was also associated with lower seed starch and protein content. Accelerated ageing (AA) tests were used to compare seed vigour between treatments. A second defoliation at the 3-leaf stage plus intense defoliation (RSH 0%) resulted in seed lots with a high rate of lipid peroxidation after the AA test, followed by lower catalase activity, germination, and seedling growth. The combination of a second defoliation at the 3-leaf stage and the retention of higher RSH (50%) promoted a greater proportion of leaf blades in the stubble, with a strong positive correlation with seed production and vigour. Antioxidant enzyme activity after the AA test is an important marker of annual ryegrass seed quality.

Effects of defoliation timing on plant nutrient resorption and hay production in a semi-arid steppe

Abstract Aims Nutrient resorption is a key plant nutrient conservation strategy, and its response to environmental and management changes is linked to nutrient cycling and production of ecosystems. Defoliation is a major pathway of mowing affecting plant nutrient resorption and production in grasslands, while the effect of defoliation timing has not been unexplored. The aim of this study was to examine the effect of defoliation timing on plant nutrient resorption and production in a steppe ecosystem. Methods We conducted a field experiment in a semi-arid steppe of Inner Mongolia including four treatments: early defoliation, peak defoliation, late defoliation and non-defoliation. We measured plant nitrogen (N) and phosphorus (P) resorption at species and community levels, and quantified plant N and P fluxes in resorption, litter return and hay output. Plant production in the mowing system was assessed by hay production and quality. Important Findings Peak and late defoliation, but not early defoliation, reduced plant community N and P resorption proficiency; and late defoliation reduced N resorption efficiency but not P resorption efficiency. Peak and late defoliation, but not early defoliation, reduced plant nutrient resorption flux and litter nutrient return flux. Defoliation timing did not alter root nutrient accumulation as nutrient uptake from soil likely compensated the deficit of nutrient resorption. Peak defoliation had the highest hay production and quality, while early defoliation had the lowest. Our results provide new insights into the nutrient cycling in mowing grassland, and imply that the mowing timing can be used as a tool to mediate the balance between conservation and production of steppes, and the early mowing before plant peak biomass period is recommended for conservation of the steppes while keeping sustainable pastoral production.

Variable Fall Climate Conditions on Carbon Assimilation and Spring Phenology of Young Peach Trees.

Variable fall temperature and moisture conditions may alter leaf senescence of deciduous fruit trees, influencing carbon assimilation before dormancy and phenology the following spring. This study explored gas exchange of young peach trees (Prunus persica (L.) Batsch) when senescence proceeded normally or was delayed during the fall under two soil moisture treatments: Well-irrigated trees or water deficit. Results showed leaf carbon assimilation was similar between the senescence treatments, but whole tree assimilation was estimated to be greater in delayed senescence trees compared to normal senescence trees based on timing of defoliation and total leaf area. The effect of soil moisture on carbon assimilation was not consistent between years. Delayed sap flow and bloom time resulted as a consequence of delayed senescence the previous fall, but soil moisture did not affect spring phenology.

Effect of defoliation on spring-sown winter-type canola (

Context In Australia’s high-rainfall zone (>550 mm/year), winter-type canola (Brassica napus L.) can be sown in spring and grazed as a forage crop during its vegetative phase, producing a canola grain crop in late spring of the second year. The timing, length and intensity of grazing or defoliation that can be imposed on canola before a grain yield penalty occurs remains largely unknown. Aim Our research aimed to determine the impact of grazing spring sown canola during summer and autumn on the subsequent canola grain yield. Methods A paddock-scale field experiment was conducted over 2 years, 2013–14 and 2015–2016, at Hamilton, Victoria, Australia, with two winter-type canola treatments and three grazing–defoliation sub-treatments replicated four times in a replicated block design. The canola cultivars used were Hyola971CL and Taurus in 2013–14 and Hyola971CL and Brazzil in 2015–16. The three grazing–defoliation sub-treatments were: NG, no grazing; VG, grazing with sheep for a 10-week period during the vegetative phase over summer–autumn; RG, grazing with sheep as per the VG sub-treatment and then in the reproductive phase, either cutting the canola for silage in August (2013–14) or grazing with sheep between 28 July and 17 August 2016 (2015–16). Key results The VG sub-treatment resulted in no grain-yield penalty (P > 0.05) relative to NG in either year. In 2014, canola grain yields from VG for Hyola971CL and Taurus were 2.32 and 2.13 t/ha, compared with NG grain yields of 2.66 and 2.19 t/ha. In 2016, grain yields from VG for Hyola971CL and Brazzil were 2.14 and 1.74 t/ha, compared with NG grain yields of 1.87 and 1.90 t/ha. The RG sub-treatment reduced (P < 0.05) canola grain yield by ~65% in 2014 and 80% in 2016 compared with NG and VG. Conclusions Spring-sown winter-type canola can be grazed during summer and autumn in southern Australia with no grain-yield penalty relative to ungrazed canola. However, further grazing or defoliation in winter once bud elongation commences can result in large grain-yield penalties. Implications Spring-sown winter-type canola is a viable forage option for filling the summer–autumn feed gap in southern Australia while also providing a dual-purpose income in mixed-farming systems.

Light Interception and the Growth of Pastures under Ideal and Stressful Growing Conditions on the Allegheny Plateau.

Pasture-based livestock production is impacted by management and weather. In pastures, there is conflict between leaf retention for plant growth and leaf harvest for animal nutrition. Defoliated pastures with low light interception (LI) may have a low forage growth rate (FGR), while excessive growth shades leaves, reducing FGR and resulting in an S-shaped regrowth curve. To optimize production, it is best to keep FGR linear. Three studies were conducted to evaluate the impact of management and weather on FGR. Replicated pastures were used to measure FGR when grazed from 25 to 10 cm and allowed to regrow. The impact of alternative defoliation timings and intensities on FGR were studied using clipped treatments at three recovery intervals and two stubble heights. Variability in FGR was studied using a field validated plant growth model. Of the 24 growth periods studied, two displayed exponential, 12 linear and 10 linear-plateau growth. There was no effect of FM on growth curve form. In May and June, LI increased with canopy height, up to 0.93. Stubble height and days of growth impacted FGR with an interaction. There was no treatment impact on root density. Weather caused variation in FGR. A low FGR risk occurs at high elevations; greater risk occurs east of the plateau.

Interactions of Spring Cereal Genotypic Attributes and Recovery of Grain Yield After Defoliation.

Dual-purpose crops are grazed during their vegetative phase and allowed to regrow to produce grain. Grazing slow-developing winter cereals (wheat, barley, and triticale) is common, but there is also potential to graze faster-developing spring cereals used in regions with shorter-growing seasons. Defoliation in faster-developing genotypes has risks of larger yield penalties, however, little is known about genotypic characteristics that may improve recovery after grazing. Four experiments examined 7 spring wheat and 2 barley cultivars with differing physiological attributes (phenological development rate, putative capacity to accumulate soluble carbohydrates, and tillering capacity) that may influence the capacity of spring wheat to recover after defoliation. Defoliated and undefoliated crops were compared to assess physiological differences between cultivars including recovery of biomass, leaf area and radiation interception at anthesis, and subsequent crop grain yield and yield components. All genotypes had similar responses to defoliation treatments indicating that the physiological attributes studied played little part in mitigating yield penalties after defoliation. Despite some differences in yield components amongst cultivars, defoliation did not adversely affect cultivars with different yield component combinations under non-water limited conditions. Later and intense defoliation (around GS30/31) resulted in large yield penalties (40%) which reduced both grain number and kernel mass. However, earlier defoliation (before GS28) induced small or insignificant yield penalties. Defoliation often reduced canopy radiation interception and crop biomass at anthesis but this rarely translated into large yield penalties. These studies further demonstrate that shorter season spring cereals can provide valuable forage (up to 1.2 t DM/ha) for grazing during early vegetative growth without inducing large yield penalties. This study suggests that beyond appropriate phenology, there were no other specific characteristics of cultivars that improved the recovery after grazing. Hence farmers don’t need specific dual-purpose cultivars and can still focus on those that optimize grain yield potential for a particular environment and sowing date. The timing and intensity of defoliation appear to be larger drivers of yield recovery in spring cereals and better understanding of these relationships are needed to provide grazing management guidelines that mitigate risk of yield penalties in dual-purpose cereal crops.

Functional Traits, Morphology, and Herbage Production of Vernalised and Non-Vernalised Chicory cv. Choice (Cichorium intybus L.) in Response to Defoliation Frequency and Height.

Chicory (Cichorium intybus L.) used in pastoral systems has the attributes required of a forage species to reduce animal urinary nitrogen loading to soil, increase milk production, and enhance milk fatty acid profile to improve pastoral farm systems for matching increasing global demand for dairy products and environmental standards of livestock systems. Greater adoption of chicory requires confidence in management decisions that can control risks to farm production, namely bolting after vernalisation or a decline in persistence of chicory swards, which have slowed its adoption in pastoral systems. We, therefore, measured functional traits, morphology and herbage production of chicory under irrigated field conditions before and after vernalisation in Canterbury, New Zealand. The experimental site was laid out in a complete randomized block design with four replications where two regrowth intervals and two defoliation heights were applied. Regrowth interval had a stronger influence over functional traits and herbage production than defoliation height, with more pronounced effects after vernalisation. Plants managed under shorter regrowth intervals had narrower roots with lower concentration of sugars than plants under longer intervals, which might compromise their longevity. In addition, plants managed under shorter intervals remained mostly vegetative with heavier and longer leaves, though with reduced photosynthetic capacity than those managed under longer intervals. The thermal time to initiate stem elongation in plants managed under longer intervals was ~274 growing degree-days, with a mean stem elongation rate increasing linearly at 1.4 ± 0.08 mm/growing degree-days. The key outcomes of this research quantify the growing degree-days to initiate stem elongation post vernalisation, which provides management directive for timing of defoliation of chicory in order to maintain feed quality for grazing livestock. Alternating frequent and infrequent defoliation regimes might be used to optimise vegetative growth, root reserves, and pasture persistence.

The Impact of Herbicide Application and Defoliation on Barley Grass (Hordeum murinum subsp. glaucum) Management in Mixed Pasture Legumes

Barley grass (Hordeum murinum subsp. glaucum.) is an annual weed associated with grain revenue loss and sheep carcass damage in southern Australia. Increasing herbicide resistance led to a recent investigation into effective integrated weed management strategies for barley grass in southern Australia. Field studies in Wagga Wagga, New South Wales (NSW) during 2016 and 2017 examined the effect of post-emergent herbicide applications and strategic defoliation by mowing on barley grass survival and seed production in a mixed legume pasture. Statistically significant differences between herbicide-only treatments in both years showed propaquizafop to be more than 98% effective in reducing barley grass survival and seed production. Paraquat was not effective in controlling barley grass (58% efficacy), but led to a 36% and 63.5% decrease in clover and other weed biomass, respectively, after 12 months and increased lucerne biomass by over three-fold after 24 months. A single repeated mowing treatment resulted in a 46% decline in barley grass seedling emergence after 12 months and, when integrated with herbicide applications, reduced other weed biomass after 24 months by 95%. Resistance to acetyl-CoA carboxylase (ACCase)-inhibiting herbicides observed in local barley grass populations led to additional and more focused investigation comparing the efficacy of other pre- and post-emergent herbicides for barley grass management in legume pastures. Haloxyfop-R + simazine or paraquat, applied at early tillering stage, were most efficacious in reducing barley grass survival and fecundity. Impact of defoliation timing and frequency on barley grass seedlings was also evaluated at various population densities, highlighting the efficacy of repeated post-inflorescence defoliations in reducing plant survival and seed production. Results highlight the importance of optimal environmental conditions and application timing in achieving efficacious control of barley grass and improving pasture growth and biomass accumulation.

Harran Ovası Sulu Koşullarında İkinci Ürün Olarak Yetiştirilen Mısırda Koçan Üstü ve Altı Yaprakların Hasat Zamanının Yeşil Ot ve Tane Verimine Etkileri Üzerinde Bir Araştırma

Bu araştırma, Harran Üniversitesi Ziraat Fakültesi Araştırma ve Uygulama Alanında 2002 yılı ikinci ürün yetiştirme sezonunda bölünmüş parseller (Split-Plot) deneme desenine göre 3 tekrarlamalı olarak yürütülmüştür. Yaprak uzaklaştırma yeri ana parselleri, yaprak uzaklaştırma zamanı (çiçeklenme, süt olum, hamur olum) ise alt parselleri oluşturmuştur. Araştırmada, koçan altındaki veya koçan üstündeki yaprakların uzaklaştırılmaları arasında önemli farklılıklar saptanmamıştır. Buna karşın yaprakların erken dönemde uzaklaştırılması, incelenen bütün özelliklerde verilerin azalmasına neden olmuştur. Yaprak uzaklaştırma zamanı geciktikçe tane verimi önemli derecede artmıştır. Yeşil ve kuru yaprak verimleri uzaklaştırma şekli ve zamanından etkilenmemiştir.

Managing forage and turf‐type bahiagrass for seed production

AbstractBahiagrass (Paspalum notatum Flüggé) is the most extensively cultivated perennial warm‐season grass in the southeastern United States for pasture, utility turf, cover cropping, and soil stabilization. The University of Florida Institute of Food and Agricultural Sciences bahiagrass breeding program has recently selected several improved forage‐ and dwarf‐turf‐type tetraploid breeding lines. However, seed production and seed quality quantification is needed before proposing any of these lines for cultivar release. The objectives of this study were (a) to evaluate seed production in seven tetraploid bahiagrass breeding lines (two forage‐type apomictic hybrids, and five turf‐type facultative apomicts) and the cultivar ‘Argentine’, and (b) to determine the optimum management practices (defoliation timing [May, June] and N rate [0, 60, and 120 kg N ha−1]) to increase seed yield and quality. Six seed traits were evaluated during 2 yr (first and second production year) under a randomized complete block design in a strip‐split‐plot arrangement with three replications. Eight genotypes (main plot), two defoliation timings (subplot), and three N fertilization rates (sub‐subplot) were tested. All breeding lines produced viable seed comparable with Argentine, although some of them exhibited very low reproductive efficiency. Nitrogen fertilization improved seed yield by increasing inflorescence density but did not affect seed quality traits. Defoliation in May produced greater seed yield, whereas defoliation in June resulted in greater seed quality, especially for turf‐type genotypes. The information generated in this study will guide cultivar release(s) and will be used to develop targeted recommendation practices for seed production in the species.