Effects of soil bulk density and strength on seedling growth of annual ryegrass and tall fescue in controlled environment

Grasses sown with minimal tillage commonly exhibit slower establishment and lower herbage yield than those sown into a conventionally tilled seedbed. Some of the difference in performance may be attributed to differences in bulk density between tilled and untilled ground. It is not known if performance rankings of grass cultivars established in clean‐tilled ground remain valid in more compacted soil characteristic of no‐till seeding. Seedlings of five cultivars of Italian ryegrass (Lolium multiflorum Lam.) [IRG] and five cultivars of tall fescue [Festuca arundinacea Schreb. also known as Lolium arundinaceum Schreb. (Darbysh.)] [TF] were grown in pots of Coyle or Stephenville series soils (sandy loam and loamy sand respectively) packed to 0·75, 0·88 or 1·00 of maximum packing densities, established as 1·47 and 1·68 g cm^?3 for Coyle and Stephenville soil respectively. Leaf appearance was measured until seedling harvest at 540 growing degree days after emergence. Increased bulk density decreased leaf appearance rates, reduced final leaf and tiller numbers and aerial and root biomass at harvest in both IRG and TF. Among cultivars within species, there was no difference (P > 0·05) in response to measured parameters to change in bulk density. Seedling growth and development of IRG were consistently greater than that of TF but showed greater reduction in response to increased soil bulk density. Soil strength provided a better indicator of likely seedling response to soil compaction than bulk density. The results suggest that cultivar rankings obtained under conventional tillage are likely to be valid with no‐till planting.     

Yield, persistency and chemical composition of Lotus species and varieties (birdsfoot trefoil and greater birdsfoot trefoil) when harvested for silage in the UK

The yield and chemical composition of thirteen Lotus corniculatus varieties and one Lotus uliginosus variety, when grown and ensiled in the UK, were investigated. Replicate plots of each variety were established in a randomized block design. Dry‐matter (DM) yield was measured over two harvest years. At cuts 1 and 2 of the first harvest year, 1 kg of each variety was ensiled and sub‐sampled for chemical analysis. At cut 2 of the second harvest year, sub‐samples of forage were analysed for condensed tannins. Two L. corniculatus varieties, Oberhaunstaedter and Lotar, had higher DM yields (with Oberhaunstaedter having the highest DM yield at cut 3) in both harvest years compared with other varieties (P < 0·001). Chemical analyses showed differences among silages of varieties of L. corniculatus (P < 0·001) and that the ammonia‐N concentration of L. uliginosus silage was higher than that of L. corniculatus (P < 0·001), despite its lactic acid concentrations being within the range observed for L. corniculatus (17 g kg^?1 DM vs. 13–19 g kg^?1 DM). Differences (P < 0·001) in HCl/Butanol test absorbance units were found among varieties of L. corniculatus, indicating possible differences in concentrations of condensed tannins. Overall, the variety Oberhaunstaedter was found to be the most suitable variety for silage production. Based on its agronomic performance, L. corniculatus does not compare well with other legumes such as red clover.     

The effects of temperature and fertilizer nitrogen on the spring growth of tall fescue and cocksfoot

A detailed study of the spring growth curves of two forage grasses, tall fescue and cocksfoot, over three successive years showed a large variability of growth over the vegetative phase. This variability was evident at levels of fertilizer N which were considered to be non-limiting (60 kg N ha^-1 in autumn plus 120 kg N ha^-1 in February).
At this level of N there was a relationship between yield in the vegetative phase and accumulated temperatures from the last cut in the autumn which was described by a regression common to the three years. The slope of this regression represents the potential growth of a variety. At a lower level of N a separate regression was needed in each year to relate growth to accumulated temperature.
Variation in spring growth was not related to accumulated net radiation. Growth in the reproductive phase was related to accumulated temperature and accumulated net radiation from the 10-cm ear stage.     

Preliminary studies on allelopatic effect of some woody plants on seed germination of rye-grass and tall fescue

In order to investigation of allelopathic effects of some ornamental trees on seed germination of rye-grass (Lolium prenne) and tall fescue (Festuca arundinaceae), this experiment was conducted in a randomized complete block design with 3 replicates at the laboratory of Horticultural Sciences Department of Ferdowsi University of Mashhad, during 2008. In this research, we studied the effect of aqueous and hydro-alcoholic extracts of Afghanistan pine (Pinus eldarica), arizona cypress (Cupressus arizonica), black locust (Robinia psedue acacia) and box elder (Acer negundo) leaves that prepared in 1:5 ratio on seed germination percent and rate for two grasses. The results showed that all extracts decreased statistically seed germination in compared to control treatment. The highest germination percentage and germination rate of tested grass detected in control treatment. Hydro-alcoholic extracts of all woody plants (15, 30%) were completely inhibited seed germination of rye-grass and tall fescue. Also aqueous extract of arizona cypress was completely inhibited seed germination of tall fescue and had more inhibitory activity than other aqueous extracts on rye-grass. Between aqueous extracts, the highest and lowest seed germination of rye-grass was found in Afghanistan pine and arizona cypress, respectively.     

Nodulation and root growth of forage legumes sown into tall fescue swards

Establishing forage legumes into endophyte‐infected tall fescue (Festuca arundinacae Schreb.) pastures is problematic, especially in well‐established stands. A oversowing field experiment determined if this problem was because of poor nodulation. Four renovation techniques, clipped sward (treatment A), herbicided + rye seeding in the previous autumn (treatment B), herbicided in the autumn and spring (treatment C) and herbicided to suppress the sward (treatment D), were investigated to determine their effect on nodulation and root growth of lucerne (Medicago sativa L.), red clover (Trifolium pratense L.) and white clover (T. repens L.) at 16, 22 and 29 d after sowing the legumes. A pot experiment was also conducted under optimal growth conditions and using the same soil to determine the nodulation and root growth potentials of these legume species. At adequate rhizobial populations (>6 × 10⁴ cfu g^?1 soil), substantial nodulation of all species occurred by 29 d after sowing in treatments C and D, whereas nodulation of clovers was usually reduced in treatment A. Total root lengths for all sampling dates, species and treatments were severely restricted, especially under treatment A. A general correspondence of nodulation with root growth was observed for all species, with high correlations (r ≥ 0·85) between these variables for all legume species and treatments, suggesting that soil moisture, and possibly competition for light, were the limiting factors. These results demonstrate that weak stands of forage legumes, typically found when sown into tall fescue swards, are probably not because of inadequate nodulation. Rather, inhibition of root growth by detrimental physical/chemical conditions or allocation of limited photosynthate to shoots instead of roots is suggested.     

Effect of soil solarization on true potato (Solanum tuberosum L.) seed germination, seedling growth, weed population and tuber yield

Summary True potato seed of 17 progenies were evaluated during 2002-03 and 2003-04 crop seasons for 12 characters related to seed germination, seedling growth and weed population in nursery beds and tuber yield of transplanted seedlings under non-solarized field conditions. Solarization was found to have beneficial effect on seed germination, seedling growth and yield of transplanted seedlings. Total weeds and major annual weedCornopus didymus were reduced to a great extent due to solarization. However solarization had no effect onCyperus rotundus. Progenies also showed significant differences among themselves for the various characters studied. The progeny x solarization interaction was also significant for all the characters. Yield increase in present study shows that the approach involving raising of seedlings in solarized nursery beds and subsequent transfer of seedlings to non-solarized field would be cost-effective and profitable for raising true seed crop of potato.     

How planting configuration influences plant secondary metabolites and total N in tall fescue (Festuca arundinacea Schreb.), alfalfa (Medicago sativa L.) and birdsfoot trefoil (Lotus corniculatus L.): Implications for grazing management

Theories suggest that incorporating alfalfa (Medicago sativa L.; Alf) or birdsfoot trefoil (Lotus corniculatus L.; BFT) into endophyte‐infected tall fescue (Festuca arundinaceas Schreb.; E+TF) pasturelands may improve livestock production. We investigated how planting configuration might influence plant secondary metabolites (PSM) and nitrogen concentration in these forages. Total nitrogen (N), in addition to condensed tannins (CT), saponins and ergovaline (EV), was compared in BFT, Alf and E+TF, respectively, when forages grew in monocultures and all possible two‐way “mixtures” using a block design with repeated measures in three blocks. Ergovaline (p < .01) and N (p < .001) concentrations in E+TF were greater when growing adjacent to legumes than when growing in monoculture, and N and EV concentrations in E+TF were positively correlated (r = .51; p = .001). No differences in saponins or CT were found when Alf or BFT grew in monoculture or in two‐way mixtures (p > .10). We conducted an in vitro trial to determine whether CT or saponins isolated from BFT and Alf, respectively, would bind to EV in water. Ergovaline bound to saponins to a greater extent (39%; SE = 0.25) than CT (5.1%; SE = 5.13; p < .05). Because EV was lower in E+TF monocultures than in E+TF–legume mixtures, and because CT and saponins may form complexes with EV which may alleviate fescue toxicosis, animals may benefit from systems which allow them to graze monoculture patches of E+TF and Alf or BFT rather than grass–legume mixtures.     

3种植物生长调节剂对棉种萌发及棉苗生长的影响

采用药剂浸种回干技术,分析了稀土微量元素、芸薹素、甲哌3种植物生长调节剂浸种处理对棉花种子萌发、出苗及幼钅翁苗生长的影响,以期为棉花生产提供参考.结果表明:1000 mg·L-1稀土微量元素、0.01 mg·L-1芸薹素、50 mg·L-1甲哌对棉花种子萌发和幼苗促生效果较好.     

盐胁迫对不同基因型紫苏种子萌发、幼苗生长 和生理特征的影响

本文对苏引1、紫野7和紫野10三个不同基因型紫苏在不同浓度（0,50, 100, 150, 200,250mmol/L）盐胁迫下种子萌发、幼苗生长、根系活力、丙二醛及可溶性糖含量、过氧化物酶活性等进行了研究。结果表明：种子发芽率、发芽势、种子活力指数等发芽指标均随盐浓度增加而降低。不同盐浓度胁迫下幼苗培养3周后,随盐浓度增加,幼苗株高、幼苗活力指数、存活率、鲜重、干重和根系活力降低,MDA和可溶性糖增加,POD呈先增加后降低的趋势。三个紫苏品种在种子发芽、幼苗生长和生理变化上均表现出不同的耐盐能力,苏引1 耐盐能力最强,紫野7居中,紫野10对盐胁迫最敏感。     

模拟酸雨对花生种子萌芽及幼苗生长的影响

以人工模拟酸雨试验研究不同酸度酸雨对花生种子萌发和幼苗生长的影响，试验结果表明，pH值4．5以下的酸雨可显著地降低花生种子的发芽率，使胚根长度变短，活力指数下降，高酸度的模拟酸雨胁迫使花生幼苗叶总数显著减少，叶片出现明显的受害症状，pH值2．5的模拟酸雨胁迫使叶绿素含量明显下降，过氧化氢酶活性显著增强，酸雨还对土壤具有酸化作用。     

抗旱剂对大豆出苗及幼苗生长的效应

在干旱胁迫下，抗旱拌种剂加浸种剂复合处理能够提高大豆种子的发芽率，促进幼苗根系生长，增加根冠比，加强水分的吸收和利用。同时能提高叶绿素和可溶性糖含量，幼苗体内脯氨酸含量降低，植株保水力明显增强。试验结果表明抗旱剂浸种8h后2％拌种处理效果最好。     

Effects of systemic fungal endophytes on the performance of meadow fescue and tall fescue in mixtures with red clover

A symbiosis between grasses and systemic fungal endophytes exists in both natural and agricultural grassland communities. Our objective was to examine the effects of systemic endophytes on the competitive ability of two agronomically important grass species: meadow fescue [Festuca pratensis (Huds.) syn. Schedonorus pratensis (Huds.) P. Beauv] and tall fescue [Festuca arundinacea (Schreb.) syn. Schedonorus phoenix (Scop.)]. Plants of meadow and tall fescue were grown for 48 days in replacement series of interspecific mixture with a legume (red clover, Trifolium pratense L.) in different nutrient environments in a greenhouse. Neither of the grass species gained endophyte‐promoted competitive advantage over red clover in grass–clover mixtures. Endophyte infection increased the growth of meadow fescue monocultures by 89% compared to endophyte‐free monocultures in high‐nutrient soils, but plant competition or the cost of endophyte infection to the meadow fescue decreased the yield in resource‐limited conditions. On average, endophyte‐infected and endophyte‐free meadow fescues produced 0·15 and 0·17 g, and 0·14 and 0·14 g dry biomass per plant in mixtures with red clover in high‐ and low‐nutrient soils respectively. In contrast to meadow fescue, endophyte‐promoted growth of tall fescue monocultures was not detected. Endophyte‐infected and endophyte‐free tall fescue monocultures produced 0·76 and 0·95 g biomass per pot, respectively, in the high‐nutrient environment. Endophyte infection can increase the performance of the host grass, but the positive effects depend on the host species, the species composition and soil nutrient availability.     

Genotypic variation and selection of traits related to forage yield in tall fescue under irrigated and drought stress environments

Development of a standard evaluation protocol has been a pressing problem for the selection of drought‐resistant genotypes of tall fescue (Festuca arundinacea). This study was conducted to evaluate the association of forage yield with specific phenological and morphological traits to find a proper model for indirect selection under irrigated (normal) and drought‐stress conditions in tall fescue. A random sample of seventy‐five genotypes were clonally propagated and evaluated in normal and drought‐stress environments in the field during 2009 and 2010. Results showed that water stress had a negative effect on forage yield and most of the morphological traits measured and reduced genotypic variation for most of them. Forage yield had the highest genotypic variation, whereas days to pollination had the lowest variation. Low broad‐sense heritability estimates were obtained for dry‐matter yield, but heritability for the traits of number of stems per plant, plant height and crown diameter was moderately high. These traits were identified as the main components of forage yield. The importance of these components and their direct and indirect effects on forage yield was different in normal and drought‐stress conditions. This suggests that indirect selection for developing high‐yielding, drought‐tolerant varieties should be performed under drought‐stress conditions with a specific model.     

The influence of leaf area,light interception and season on potato growth and yield

Summary Light interception in the photosynthetically active radiation (PAR) range (400 700 nm) was measured over two years in potato crop canopies. Light interception increased linearly with increasing leaf area index (L) up to values of 2.25, light interception increased at a decreasing rate until L=4.0 was attained when around 95% of the incoming radiation was intercepted. The equation I_l=I_oe^kl accounted for 92% of the variance in the relationship between light interception and L, where I_l is the irradiance on a horizontal plane below a leaf area index of L., and k (light extinction co-efficient)=0.335+0.151 (L) 0.0129 (L)². Crop growth rate was found to be linearly related to the PAR intercepted by the canopy in 1980, in the absence of any apparent water-stress. The photosynthetic conversion efficiency of the canopy (g dry weight MJⁱ PAR intercepted) was 3.42 and 2.49 for 1980 and 1979, respectively. Tuber yields were also found to be linearly related to PAR intercepted by the canopy over the whole season.

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Zusammenfassung In den Jahren 1979 und 1980 wurde die Lichtaufnahme der photosynthetisch aktiven Strahlung (PAR) im Bereich von 400–700 nm in Kartoffelbest?nden im Vereinigten K?nigreich gemessen. Die meteorologischen Daten zeigten, dass der Niederschlag in den Jahren sehr unterschiedlich war (Abb. 2); 1979 war überwiegend trocken, vor allem in der sp?teren Vegetationszeit, w?hrend 1980 allgemein ein nasses Jahr war. Die Lichtaufnahme stieg linear mit dem zunehmenden Blattfl?chenindex (L) bis zu L=2,25 an (wobei rund 73% der einfallenden Strahlung aufgenommen wurde) und über L=2,25 nahm die Lichtaufnahme mit einer abnehmenden Rate bis zu L=4,0 zu, wobei rund 95% der einfallenden Strahlung aufgenommen wurden (Abb. 3). Die Gleichung I_L=I_oe^kL gilt für 92% der Varianz in der Beziehung zwischen Lichtaufnahme und Blattfl?chenindex (L), wobei I_L=Strahlung auf einer horizontalen Fl?che unter einem Blattfl?chenindex von L und k (Lichtextinktionskoeffizient)=0,335+0,151(L)−0,0129(L)². Wenn die Konstante k (=0,72) verwendet wurde (Abb. 3) entsprach die Varianz für das ausgew?hlte Modell 88%. Zwischen dem Gesamttrockengewicht (TDW) und der PAR, die aufgenommen wurde, bestand in beiden Jahren ein signifikantes lineares Verh?ltnis. Abb. 4 zeigt die Daten für 1980. Durch den Nullpunkt geführt ergibt sich ein TDW=3,42 (PAR) und 2,49 (PAR) für 1980 bzw. 1979, das bedeutet, dass die Umwandlung von Lichtenergie in Trockensubstanz ohne ersichtlichen Wassermangel 1980 wirkungsvoller war. Abb. 5 zeigt die photosynthetische Wirksamkeit (g Trockengewicht MJ^l PAR) w?hrend der Vegetationszeiten zusammen mit den ?nderungen im Blattfl?chenindex L. Die Wachstumsrate des Bestandes stand 1980 in einem linearen Verh?ltnis zu der von den Bl?ttern aufgenommenen PAR, w?hrend sich für 1979, wo der Bestand stark unter Trockenheit litt, eine Abweichung ergab (Abb. 6). Obwohl w?hrend der beiden Jahre die photosynthetische Wirksamkeit (g Knollentrockengewicht MJ^l PAR, aufgenommen w?hrend der gesamten Vegetationszeit) für das Knollengewicht unterschiedlich war: Knollentrockengewicht=1,97 (PAR) und 2,37 (PAR) für 1979 bzw. 1980, zeigen die Daten, dass ein gesteigertes Wachstum entsprechend einer h?heren Lichtaufnahme zu h?heren Knollenertr?gen führt, unabh?ngig von einer Reihe ackerbaulicher Massnahmen.

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Résumé L'interception des radiations actives pour la photosynthèse (PAR), dans des longueurs d'onde de 400 à 700 nm, est mesurée durant très différente les deux années; 1979 fut particulièrement sec, surtout en fin de saison, alors que 1980 fut une année humide. La quantité de lumière interceptée, augmente linéairement avec l'index de surface foliaire (leaf area index) jusqu'à une valeur de L=4,25 (correspondant à 73% de radiations interceptées) et pour des valeurs supérieures, l'interception augmente à une vitesse décroissante jusqu'à L=4,0 correspondant à 95% de radiations captées (fig. 3). La relation I_L=I_oe^kL interpréte 92% de la variation dans la liaison entre la lumière interceptée et l'index de surface foliaire (L), où I_L est le rayonnement atteignant un plan horizontal situé sous un index foliaire L et K (coefficient d'extinction lumineuse)=0,335+0,151(L) −0,0129(L)². Si on fixe k à 0,72 (fig. 3), la part de variation expliquée par le modèle est de 88%. Une relation linéaire significative entre la matière sèche totale (TDW) cumulée et le PAR intercepté cumulé, a été établie pour les deux années et les données de 1980 sont portées dans la figure 4. Si on fait passer la régression par l'origine, on écrira pour 1979: TDW=2,49× deux années, 1979 et 1980, dans des cultures de pomme de terre du Royaume-Uni. Selon les données météorologiques, la pluviométrie fut et pour 1980: TDW=3,42×PAR. Ces relations indiquent que la conversion de lumière en matière sèche a été plus efficace en 1980 en l'absence de déficit hydrique. L'efficacité de la conversion photosynthétique (g de matière sèche/PAR intercepté) au cours de la saison, est indiquée avec les variations de L dans la figure 5. La vitesse de croissance de la culture est liée linéairement au PAR capté par la végétation en 1980, alors que cette liaison s'écarte de la linéarité en 1979, lorsque la culture est affectée par la sécheresse (fig. 6). Bien que l'efficacité de la conversion photosynthétique (g de poids sec de tubercule/PAR captée durant toute la saison) pour le poids de tubercules soit légèrement différente pour les deux années (en 1979 elle est égale à 2,37 (PAR), en 1980 elle est égale à 1,97 (PAR)). Les données indiquent que l'augmentation de la croissance de la récolte totale, expliquée par l'augmentation de la lumière captée, résultent également du rendement de plus en plus grand des tubercules (fig. 7), sur une série de traitements agronomiques.

     

温度和盐胁迫对油葵种子萌发及幼苗生长的影响

通过测定不同温度和盐胁迫浓度对油葵种子发芽势、发芽率和幼苗生理生化特性指标的影响,发现相同温度条件下,随着盐浓度的升高,油葵种子的发芽势、发芽率呈降低趋势,发芽时间延迟,胚根的生长受到抑制,胚根长、子叶鲜重均呈现下降的趋势;油葵幼苗的叶片和根系的电解质相对外渗率,SOD、POD活性均呈现先升后降的趋势.相同浓度盐胁迫下...     

Effect of salt stress on seed germination and seedling growth of three salinity plants

Seeds of three halophyte species included Limonium sinense Kuntze, Glycine soja sieb. and Sorghum sudanense Stapf. were used to investigate the effects of different salinity concentrations on their germination percentage, germination energy, germination index, relative germination rate, relative salt-injury rate, radicle length and hypocotyl length. Results showed that seeds of G. soja can germinate well and rapidly at lower level of salt (< 200 mmol L(-1)), 50 mmol L(-1) salt concentrations is better to S. sudanense, suitable salt concentrations was beneficial to germinate of S. sudanense seeds. Seeds of L. sinense and S. sudanense can germinate at higher level of salt (400 mmol L(-1)). Three plant seeds had different physiological mechanism for germination under salt stress, radicle hypocotyl ratio of L. sinense and S. sudanense increased with increasing salt suggested that they had the higher tolerance in shoot growth under NaCl stress, which is perhaps the reason for their wide utilisation for saline soil rehabilitation.     

Influence of sward condition on leaf tissue turnover in tall fescue and tall wheatgrass swards under continuous grazing

Two experiments were carried out on a tall fescue sward in two periods of spring 1994 and on a tall wheatgrass sward in autumn 2001 and spring 2003 to analyse the effect of sward surface height on herbage mass, leaf area index and leaf tissue flows under continuous grazing. The experiment on tall fescue was conducted without the application of fertilizer and the experiment with tall wheatgrass received 20 kg P ha^?1 and a total of 100 kg N ha^?1 in two equal dressings applied in March (autumn) and end of July (mid‐winter). Growth and senescence rates per unit area increased with increasing sward surface height of swards of both species. Maximum estimated lamina growth rates were 28 and 23 kg DM ha^?1 d^?1 for the tall fescue in early and late spring, respectively, and 25 and 36 kg DM ha^?1 d^?1 for tall wheatgrass in autumn and spring respectively. In the tall fescue sward, predicted average proportions of the current growth that were lost to senescence in early and late spring were around 0·40 for the sward surface heights of 30–80 mm, and increased to around 0·60 for sward surface heights over 130 mm. In the tall wheatgrass sward the corresponding values during spring increased from around 0·40 to 0·70 for sward surface heights between 80 and 130 mm. During autumn, senescence losses exceeded growth at sward surface heights above 90 mm. These results show the low efficiency of extensively managed grazing systems when compared with the high‐input systems based on perennial ryegrass.     

外源海藻糖浸种对低温胁迫油菜种子萌发及幼苗生长的影响

为提高抗寒性,促进油菜种子发芽及幼苗生长,以甘蓝型油菜品种中油杂19为材料,研究外源海藻糖浸种对低温胁迫下油菜种子萌发及幼苗生长的影响,阐明外源海藻糖浸种的寒害缓解作用.结果表明,在低温处理下(10℃),油菜种子萌发受到抑制,发芽势、发芽率、发芽指数及活力指数均显著下降,平均发芽时间显著延长;种子萌发过程中异柠檬酸裂解...     

硅对盐胁迫下麻疯树种子萌发及幼苗生长的影响

添加外源硅溶液后,研究盐胁迫下麻疯树种子萌发和幼苗生长,测定种子发芽率、发芽指数、活力指数、丙二醛(MDA)含量和酶活性(包括SOD、POD和CAT)等指标,调查硅对盐胁迫下麻疯树的生理影响。结果表明,盐胁迫下外源硅处理可显著提高麻疯树种子发芽率、发芽指数和活力指数。水培营养液中施加外源硅可降低盐胁迫下幼苗叶片的MDA含量,显著提高了SOD和POD活性,部分提高CAT活性(但不显著)。外源硅缓解了盐胁迫的生长抑制作用。外源硅的缓解效应存在浓度差异,终浓度3mmol/L硅的生长缓解作用最好。     

Use of a biophysical simulation model (DairyMod) to represent tall fescue pasture growth in Argentina

Tall fescue pastures have an increasing potential to be used worldwide. The purpose of this study was to test the ability and flexibility of the model DairyMod to represent herbage mass accumulation (HMA) of tall fescue pastures from Argentina under several environmental conditions, including different seasons, fertilizer nitrogen levels and irrigation. Species‐specific responses were obtained by customizing particular parameters (i.e. number of living leaves per tiller, leaf appearance interval, optimum plant N concentration and the response of leaf gross photosynthesis to temperature). Additionally, a simulation experiment to compare the model assumption that optimum N concentration stays constant through HMA with the application of a reference critical N dilution curve verified for temperate forage grasses (N% = 4·8 HMA^?0·32) was conducted. Application of DairyMod simulated with reasonable accuracy the HMA of tall fescue pastures under a wide range of climatic and management conditions; however, the model tended to underestimate HMA where pastures grew under high N availability. The use of a reference critical N curve substantially improved this bias, indicating that a further analysis on the N issue of the model is necessary. Results from this study provide support for further evaluations of the model under other scenarios and conditions. An upgrade of the model to improve simulation of N nutrition is suggested to enhance its performance to predict growth dynamics at high N availabilities as well as its value to address the effectiveness of N‐management practices.