Plant Density Conditions Research Articles

Yield and Oil Constituents of Chamomile (Matricaria chamomilla L.) Flowers Depending on Nitrogen Application, Plant Density and Climate Conditions

Although chamomile is found as a wild species throughout Iran, there is yet little information about cultivation of commercial cultivars of chamomile under various cultural practices in climatic conditions of Iran. In order to investigate the effects of different levels of nitrogen fertilization and plant densities on the yield and essential oil constituents of chamomile C.V. Bodegold flowers, this experiment was set up at the Ferdowsi University research field, Mashhad, Iran during 2006-2007. The experimental design was on the base of two-factor randomized complete blocks design (RCBD) with three replications. The first factor was plant density at four levels including D1 = 20, D2 = 25, D3 = 40 and D4 = 50 pl.m−2 and the second factor was nitrogen in the form of urea (% 46 nitrogen) at three levels, including N0 = control (absence of fertilization), N1 = 10 and N2 = 20 g.m−2. Observations were recorded on plant height, flower and disc florets diameter, dry flower yield, content (%) and yield of essential oil and main compounds of the oil. The crop responded significantly to different plant density. Plant height increased with increasing plant density from 20 pl.m−2 up to 50 pl.m−2, whereas the diameter of disc florets followed the reverse trend. Yield of dry flower and essential oil increased with plant density. Application of urea affected all observation of this study significantly. The maximum yields of dry flower and essential oil were observed at 50 pl.m−2 with 20 g.m−2 urea fertilization. The main oil compounds oil was including: α-bisabolol oxide A (53.45 ± 5.94 %), α-bisabolol oxide B (9.90 ± 3.03 %), α-bisabolone oxide A (5.24 ± 1.60 %), chamazulene (4.29 ± 2.78 %), (Z)-β-farnesene (2.75 ± 1.06 %) and spathulenol (0.81 ± 0.44 %).

Effects of planting density and pattern on physiological growth indices in maize (Zea mays L.) under nitrogenous fertilizer application

Growth indices are useful for interpreting plant reaction to environmental factors. To evaluate the beneficial impact of planting density and pattern on induced maize (Zea mays L. cul. Single-cross 704) by nitrogenous fertilizer, this research was conducted at Iran and the experimental design was a split factorial on the basis of completely randomized block design with four replications. The combination of nitrogenous fertilizer including 520, 400 and 280 kg urea ha-1 were assigned to the main plots and the planting density (70000 and 90000 plant ha-1) and the planting pattern treatment (one row and two rows planting) were factorially assigned to the subplots. Treatments significantly affected the total dry weight (TDW), leaf area index (LAI), relative growth rate (RGR) and crop growth rate (CGR). In this study, results showed that physiological growth indices were increased by high density, application of 520 kg urea ha-1 and two rows planting. Consequently, our finding may give applicable advice to farmers and agricultural researchers for management and proper use of nitrogenous fertilizer in farming of maize under different planting density conditions. Key words: Planting density, nitrogenous fertilizer, planting pattern, physiological growth indices, Zea mays L.

Efecto del sistema y densidad de la almaciguera en el cultivo de cebolla (Allium cepa)

C. Gomez, and C. Oberpaur. 2007. Effect of density and seedbed system in onion (Allium ( cepa) production. Cien. Inv. Agr. 34(3):205-214. Production of onion (Allium cepa) seedlings for transplants is done directly in fl at soil conditions or in trays using reduced cell volumes and high plant density conditions, without consideration of the possible effect that reduced cell volume can have on crop growth. Therefore, the objective of this study was to evaluate the production of onion seedlings in two seedbed systems and their subsequent behavior in the fi eld. Seedling production and transplant establishment were determined with a long-day type of onion (cv. Grano de Oro) in the Metropolitan Region of Chile (33°-34° south latitude) from 2004 to 2005. The production of covered root transplants was performed in trays with 286 (18 cm 3 ), 432 (10 cm 3 ) and 814 (5 cm 3 ) cells each, equivalent to plant densities of 1144 (low), 1728 (medium) and 3256 (high) plants·m -2 , respectively. The production of bare root transplants was done in boxes with equal plant densities as in the tray system. Next, plants obtained from each seedbed system and plant density were fi eld transplanted. Based on the results obtained, neither plant density nor transplant production system affected the pseudo stem diameter 25 days after emergency (DAE). At 77 DAE, the pseudo stem diameters were 3.8 and 5.2 mm, the root dry weights (DW) were 4.8 and 6.2 g·plant -1 produced in high and low plant density, respectively. This suggests that the tray system had a minor effect on plant development. At 23 days after transplanting (DAT) differences in the pseudo stem diameter between the three densities were obtained, although differences between the bare and covered root systems were not statistically signifi cant. Plants obtained from high-density seedbeds showed a smaller pseudo stem diameter and lower canopy DW than plants produced in low-density seedbeds until 84 DAT. At harvest, no differences were observed in formation or among the quality categories of the onion. Therefore, it is feasible to produce onion seedlings to be transplanted with bare roots or covered roots, produced in high-density boxes or in 5 cm 3 cells, without affecting the fi nal quality of harvested onion bulbs.

The Ecological Characteristics of the Endangered Species Paeonia suffruticosa var. spontanea in China

Abstract Paeonia suffruticosa var. spontanea, distributed in a very small area in Shanxi and Shaanxi provinces of China, is an endemic, endangered, and nationally protected species. To assist the protection of this species, the biological and ecological characteristics of its populations were investigated and analyzed. There are eight communities (TWINSPAN result) in which this species is found. It prefers forest communities dominated by Quercus liaotungensis in the warm-temperate climate zone. Its spatial distribution pattern is clumped in all communities. Its populations are expanding in all study areas. Biomass and productivity are closely related to plant age, density, and environmental conditions. The level of sexual reproduction is low, and the main method of reproduction of this species is vegetative propagation. Canopy gaps may be important for the establishment, growth, and reproduction of this species. Based on these characteristics, some suggestions for the conservation management of Paeonia su...

MAIZE (ZEA MAYS L.) GROWTH AND YIELD RESPONSE TO ETHEPHON APPLICATION UNDER WATER STRESS CONDITIONS

The aim of the present investigation was to study the growth, yield and yield components of maize (Zea mays L.) single cross 704 under different levels of irrigation, plant density, and ethephon in southern Iran where this particular crop has not yet been studied in detail. A field experiment was performed in the 2004 5 growing season at the experimental farm of the College of Agriculture, Shiraz University, Shiraz, Iran, located at Badjgah. The experimental design was a randomized complete block with four replicates where the treatments had a split split plot arrangement. Irrigation level (low and high) was the main plot, plant density (53,333 and 80,000 plants/ha) the subplot, and ethephon level (0, 0.56, 0.84 kg/ha a.i., applied at the 6 leaf stage) the sub subplot. The results showed that the rates of foliar application of ethephon could play an important role in maize growth indices, and attribute to grain yield components. Application of ethephon was associated with a decrease in Leaf Area Index (LAI), Leaf Area Index Duration (LAID) and Crop Growth Rate (CGR). Furthermore, ethephon reduced plant and ear height. Increasing the application rates of ethephon showed a significant reduction in early season plant height and LAI, LAID. The control plants had lower grain yield than those treated with different rates of ethephon. Indeed, this research showed that under conditions of water stress, the maize plant is able to make better use of available water if vegetative growth is partially restricted early in the season. The results also indicated that the yield response of maize to ethephon application would vary with plant density and available water conditions. Ethephon treatment was found to be more beneficial for grain yield with higher plant densities and under water stress conditions.

COTTON IRRIGATION SCHEDULING USING REMOTELY SENSED AND FAO-56 BASAL CROP COEFFICIENTS

Multispectral vegetation indices calculated from canopy reflectance measurements have been used to simulate real-time basal crop coefficients (Kcb), which have been validated to improve evapotranspiration (ETc) estimation for several crops. In this article, an application of the approach was evaluated for cotton using remote sensing observations of the normalized difference vegetation index (NDVI) to estimate Kcb as a function of NDVI. The dual crop coefficient procedures of FAO Paper 56 (FAO-56) were used to calculate ETc and determine irrigation scheduling using Kcb estimates from remote sensing (NDVI treatment) as well as from time-based Kcb curves (FAO treatment), which were developed locally for standard crop conditions using FAO-56 procedures. Two cotton experiments, conducted in 2002 and 2003 in central Arizona, included sub-treatments of three levels of plant density and two levels of nitrogen management to impose a wide range of crop development and water use. The NDVI-Kcb relationships used for 2002, developed from previous data for a different cotton cultivar, row orientation, and soil type, substantially underestimated ETc, resulting in significantly less irrigation water applied and lower lint yields for NDVI compared to the FAO treatment. The 2002 data were used to recalibrate the NDVI-Kcb relationships, which were then used for the NDVI treatments in 2003. The FAO Kcb curve used in 2002 described ETc and irrigation scheduling reasonably well for sparse plots, but consistently underestimated water use and soil water depletion for the higher plant densities during the first half of the season. Consequently, an adjusted FAO Kcb curve, based on 2002 results, was employed for the FAO treatment in 2003. For the 2003 experiment, estimated cotton ETc for the NDVI treatment resulted in a mean absolute error of 9% compared to 10% for the FAO treatment, where the difference was not significant between treatments. However, the NDVI-Kcb relations used in 2003 greatly improved estimates for ETc compared to the previous year, where the mean absolute error for the NDVI treatment in 2002 was 22%. Predicted ETc using the FAO Kcb curve of 2003 for typical planting density and high nitrogen conditions resulted in a mean absolute error of 10% compared to 15% in 2002. Final lint yields for 2003 were not significantly different between the two Kcb methods. Although additional research is needed to validate remote sensing Kcb estimation for other conditions than those in these experiments, this study did not show significant advantages for the NDVI approach over a carefully derived single FAO Kcb application. However, the NDVI approach has the potential to further extend our present crop coefficient estimation capabilities when weather, plant density, or other factors cause cotton canopy development and water use patterns to depart from typical conditions.

Grain Sorghum Response to Row Spacing, Plant Density, and Planter Skips

Adverse weather and soil conditions may prevent grain sorghum (Sorghum bicolor L. Moench) growers from achieving an evenly spaced, optimum plant density. In these situations, growers must decide whether to replant or manage a grain sorghum crop with uneven and/or lower stands. Research indicated that grain sorghum grain yield response to row spacing was variable and dependent upon environment. In uniform stands, grain sorghum was able to partially compensate for densities below 60,000 plants per acre by producing additional grain heads per plant. Results also indicated that in uniform grain sorghum stands, N at 100 to 150 lb/acre produced the highest grain yield under both high and low plant density conditions. In non-uniform stands with frequent 6- to 9-ft skips, sorghum had significantly reduced grain yield when compared to a uniform stand or 3-ft skips. These results do not support reduced N rates in either uniform or uneven grain sorghum stands with less than optimal plant densities.

Dispersal patterns and chromatic response of Scaphoideus titanus Ball (Homoptera Cicadellidae), vector of the phytoplasma agent of grapevine flavescence dorée

Abstract 1 Scaphoideus titanus Ball, a nearctic leafhopper introduced into Europe in the 1950s, is known to be the vector of the phytoplasma agent of flavescence dorée (FD), a persistent disease of grapevine. Knowledge of its dispersal patterns is thus very important to prevent disease outbreaks.2 Yellow sticky traps were used to study the seasonal flight activity of S. titanus, its vertical flight, its movement outside the vineyard and the influence of plant density. Sticky traps of different colours (yellow, red, blue, and white) were also compared. The behaviour of males and females was tested for all those conditions.3 Abundance was greater in normal than in low plant density conditions, and a positive relationship was found between number of plants per square metre and presence of S. titanus. Leafhoppers did not appear capable of spreading significantly outside a vineyard. Few individuals were trapped above the canopy. Red sticky traps caught more individuals than white, yellow or blue, with the latter showing a poor attractiveness. Sex ratio was almost always male biased.4 Scaphoideus titanus is monophagous and appears incapable of great dispersal away from its host plant, and females are less likely to fly than males. Further studies on the influence of different factors on the behaviour of this leafhopper are suggested.

Estimativa do coeficiente de cultura do cafeeiro em função de variáveis climatológicas e fitotécnicas

Com base em pesquisa realizada no cafezal do Departamento de Produção Vegetal da ESALQ, Universidade de São Paulo, utilizando a cultivar Mundo Novo IAC 388-17, enxertada na cultivar Apoatã IAC 2258, plantada no espaçamento de 2,5 m x 1,0 m (4.000 plantas.ha-1), propôs-se um método para a estimativa do coeficiente de cultura (Kc) de café. O método fundamentou-se na estimativa da transpiração do cafeeiro em função de variáveis climatológicas e fitotécnicas (área foliar, densidade de plantas e manejo de plantas daninhas). Entre 15 e 40 meses após a implantação do cafezal, realizaram-se estimativas de Kc nas condições de densidade de plantio e da área foliar do cafeeiro, bem como simulações para diferentes densidades, na presença e na ausência de plantas daninhas. Os resultados evidenciaram a dinâmica do coeficiente de cultura (Kc) com a variação da área foliar e a densidade de plantio. O Kc estimado foi superior na presença de mato até 30 meses após o plantio, para o espaçamento adotado neste experimento. Em comparação com os dados de Kc para café indicados na literatura, o método proporcionou resultados consistentes, com a vantagem de permitir simulações para diferentes densidades de plantas. Em vista dos resultados, sugerem-se estudos adicionais da relação entre área foliar e densidade de plantas elevada, ou seja, que ultrapasse o limite adotado neste experimento, de 4.000 plantas.ha-1.

Ecophysiology of Niche Occupation by Two Giant Rosette Plants, Lobelia gibberoa Hemsl and Solanecio gigas(Vatke) C. Jeffrey, in an Afromontane Forest Valley

The niche occupation of two giant rosette plants, Lobelia gibberoa Hemsl and Solanecio gigas(Vatke) C. Jeffrey, was investigated in a small mountain valley in an afromontane forest, central Ethiopia. Plant distribution, density, life-form, morphology and microsite conditions were related to transpiration, chlorophyll a fluorescence and δ13C analysis to explain how ecophysiological traits and morphology determine the niche differentiation of plants of similar life-forms. L. gibberoa was more abundant at the humid northern flank of the valley while S. gigas was equally distributed in the northern and drier southern flanks; both species occurred in the valley bottom. Photosynthetic capacity, as determined by chlorophyll a fluorescence, was similar for both species. In dry locations, S. gigas transpired somewhat less and had lower leaf conductance for water vapour, g<$>_{{\\rm H}_{2}{\\rm O}}<$>, than in wet locations. Both species had the highest g<$>_{{\\rm H}_{2}{\\rm O}}<$>and δ13C-isotope discrimination in the wettest locations. Overall for the ecophysiological traits, site differences were larger than differences between the two species. L. gibberoa had a well developed vascular cylinder, maintained a large number of rosettes and had an average leaf area index (LAI) of 2.8, which may restrict it to the more humid locations. S. gigas, with a poorly developed vascular bundle, had many fewer rosettes, an average LAI of 1.5, and reacted more to the water status of its habitat. It was thus also capable of colonizing drier locations. The role of morphological and anatomical traits and ecophysiological features in niche occupation as revealed by assessment of vegetation is discussed.

Crescimento vegetativo e coeficiente de cultura do feijoeiro relacionados a graus-dia acumulados

Estudou-se o crescimento vegetativo e o coeficiente de cultura (k c) do feijoeiro (Phaseolus vulgaris L.), relacionando-os ao índice de grausdia acumulados (sigmaG). O delineamento experimental foi o inteiramente casualizado com três tratamentos e quatro repetições. Os tratamentos de densidade populacional de plantas foram: cultura semeada em evapotranspirômetros a uma densidade de 50 plantas m-2, com redução para 25 plantas m-2, quando alcançada a cobertura completa do solo; cultura semeada com densidades populacionais de 14 e 28 plantas m-2 em campo irrigado. Os parâmetros de crescimento da cultura, como a matéria seca total, a porcentagem de cobertura vegetal e o índice de área foliar mostraram uma relação altamente significativa com sigmaG, tendo sido afetada pelos tratamentos e pelas condições de suprimento de água. A relação entre o coeficiente de cultura basal (k cb) e sigmaG foi altamente significativa para a cultura semeada nos evapotranspirômetros. No campo, o molhamento da superfície do solo após a chuva ou irrigação e o déficit hídrico moderado afetaram as correlações (r²) entre k c e sigmaG. Os tratamentos não alteraram os estádios fenológicos da cultura, quando correlacionados com graus-dia acumulados.

Adaptation of indeterminate faba beans to weather and management under a Mediterranean climate

The response and adaptation of faba bean to terminal drought was studied during two growing seasons differing in radiation, rainfall and vapour pressure deficit. Field experiments were carried out under irrigated and rainfed conditions, using highly productive, indeterminate cultivars sown at various densities. Water relations, crop evapotranspiration, dry matter production and partitioning, yield components and root development were monitored. During the first year, a strong water deficit developed, leaf midday and predawn water potentials decreased and stomatal resistance increased sharply during pod filling. Water deficit developed gradually during the second year and stomatal resistance increased progressively during the reproductive period. In both years, faba bean adopted water conservation mechanisms that delayed dehydration mainly through stomatal closure at relatively high water potential. No significant osmotic adjustment was observed. The two water stress patterns, plant densities and spatial distribution produced different water-use efficiencies. These differences disappeared when corrected for vapour pressure deficit. Maximum grain yield, over 6000 kg ha −1, was obtained with irrigation at plant densities of 20 and 33 plants m −2. In irrigated plots, where the density was increased to 33 plants m −2, greater biomass production was not associated with greater yield, because of low mobilisation (reflected by a decrease in harvest index). High yields were also obtained under rainfed conditions at a density of 25 plants m −2 when moist conditions prevailed in spring. A combination of dry spring and low plant density (20 plants m −2) produced the smallest yield (ca. 3900 kg ha −1). No differences due to nitrogen application or inoculation were found. Root length densities did not vary significantly among treatments, at most sampling dates and among the experiments, but indirect estimation of root/shoot ratio indicated an increase in rainfed treatments. Indeterminate cultivars proved to be suitable in this region of highly variable spring water supply. A density of 25 plants m −2 is appropriate for the area whereas higher plant density (33 plants m −2) and non-limiting water conditions can lead to excessive vegetative growth and smaller harvest indices in these cultivars.

Estimates of physiological determinants forAmaranthus retroflexus

Redroot pigweed is a troublesome weed in the sorghum-growing regions of North America. In 1994 and 1995, field studies were conducted at two locations near Manhattan, KS, to determine the influence of redroot pigweed density and environmental conditions on physiological determinants of redroot pigweed growth: duration of plant growth, light interception, radiation-use efficiency, and dry matter partitioning. In addition, specific leaf area was determined. Redroot pigweed was seeded at monoculture densities of 2, 4, and 12 plants m−1of row each year at each location. Duration of redroot pigweed growth was not influenced by plant density. Light interception was defined as a simple exponential function of leaf area index. Specific leaf area did not change over the season and averaged 135 cm2g−1. Partitioning of redroot pigweed dry matter was not influenced by plant density or environmental conditions but did not change within vegetative and reproductive stages. Radiation-use efficiency was not influenced by redroot pigweed density; the most reliable estimate was 1.74 g dry matter MJ−1of intercepted photosynthetically active radiation. Physiological determinants described were not affected by redroot pigweed density or environmental conditions and therefore provide a starting point for the development of a redroot pigweed growth module. The module could be coupled with available crop growth models (e.g., the sorghum growth model SORKAM) to simulate redroot pigweed–sorghum competition.

Exploring Cost Constraints on Stem Elongation in Plants Using Phenotypic Manipulation

Exploring Cost Constraints on Stem Elongation in Plants Using Phenotypic Manipulation

Relationships between Vascular Bundles of Panicle Neck Internode and Characters of Head under Different Planting Densities and Nitrogen Fertilizers Applied in Oryza sativa L..

異なる栽培条件下で生育した水稲品種シモキクの株を成熟期に採取して, 穂の諸形質を調査するとともに, 徒手およびパラフィン切片法により穂首節間の維管束数を観察して, その大・小両維管束数と一次・二次の各枝梗数, 一穂籾数および籾重との各相関関係, ならびに異なる栽植密度および窒素施肥量による大・小両維管束数の変化を調査した. 大・小両維管束数はともに正規型分布を示し, 平均値は各々9および16.5であった. これら維管束数の変動係数は, 下位伸長節間に比べて遥かに大きい値を示した. 大維管束数は一次枝梗数と相関係数0.894で, 小維管束数は二次枝梗数と相関係数0.764で, それぞれ有意な正の相関を示した. 大・小両維管束数は一穂籾数とも各々相関係数が0.855および0.850で,極めて高い正相関を示した. 両維管束数ともに窒素施肥量と正の回帰関係を示す一方, 栽植密度とは各々負の回帰性を示した.

BENEFICIAL MICROORGANISMS IN THE ROOT REGION SOILS OF COCONUT PALM UNDER DIFFERENT CROPPING SYSTEMS A REVIEW

The coconut palm is amenable to intensive crop combinations at most periods of its life and great possibilities exist for increasing the agricultural production through intensive cropping in coconut areas. Coconut palms are grown under diverse soil conditions ranging from littoral sands to clayey soils (Menon and Pandalai, 1960). In pure stand of coconuts at normal planting (7.5 x 7.5 m) density and management conditions, about 75% of the area is not being effectively utilised to the fullest extent by coconut roots (Kushwah et al. 1973). The intensive cropping system involving coconuts are essentially crop combinations which envisage the cultivation of other compatible crops in the interspaces between the palms. Depending upon the duration of additional crops, so grown, the system shall be considered as inter, mixed, multi‑storeyed or multispecies cropping. The crops chosen vary from tract to tract (Nelliat and Shama Bhat, 1979).

Studies on competition between Macroptilium atropurpureum and Crotalaria goreensis

Summary:Experiments were conducted at Walkamin, Queensland, Australia on the competitive effects of Crotalaria goreensis Guill. &amp; Perr. on Macroptilium atropurpureum (DC.) Urb. cv. Siratro. In one experiment it was shown that varying C. goreensis densities of 10, 20, 40 and 200 plants/m2 produced successive reductions in M. atropurpureum yields and successive increases in C. goreensis yields. Varying the M. atropurpureum density from 2.3 to 6 plants/m2 did not significantly affect the yield of either species. Two hundred C. goreensis plants/m2 produced approximately 500 106 seeds/ha.In three time of emergence experiments it was shown that the competitive ability of one species relative to the other varied with environmental factors. In one of these experiments with equal numbers of each species C. goreensis lowered M. atropurpureum top dry matter yield only when the former species emerged 2 weeks prior to the M. atropurpureum. When there were many more plants of C. goreensis present, emergence of both species at the same time lowered M. atropurpureum top dry matter yield in one experiment and emergence of C. goreensis 2 weeks after the M. atropurpureum lowered the dry matter yield of the latter species in a third experiment.In a time of weeding experiment it was shown that under the particular environmental and plant density conditions prevailing removal of C. goreensis for 12 days after planting was sufficient to prevent a reduction in M. atropurpureum dry matter. In this experiment it was also shown that under these conditions the two species were not mutually exclusive. In mixtures the C. goreensis provided physical support to the M. atropurpureum, enabling the latter species to intercept more light energy than it could when growing in monoculture.

An ecological study of an attempt at biological control of Noogoora burr (Xanthium strumarium)

The recent introduction of two cerambycids, Mecas saturnina and Nupserha vexator, for the biological control of Noogoora burr, Xanthium strumarium, a weed of sheep pastures in subtropical eastern Australia, has led to the development of a verbal model of the effect of these introductions on the populations of the weed. The model takes into account the dependence of X. strumarium on late spring and summer rainfall, the overwinter survival and germinability of the burrs, and the effect of plant density and growth conditions oil the number of stems and burr production per plant. The fact that only one cerambycid survives in each rootstock, no matter how many stems are attacked, and the small estimated reduction in burrs per plant produced by an individual cerambycid larva (15 for N. vexator, 35 for M. saturnina), indicated that successful biocontrol depended on high cerambycid populations. On taking into account the egg production of each cerambycid, it was concluded that, although high beetle populations could develop in dense, strongly growing X. strumarium stands in coastal and subcoastal regions, they would cause only minor reductions in plant density. They would be more effective against poorly growing stands and at sites with low overwinter burr survival, provided that stands occur consistently each year. These conclusions are dependent on the adaptability of the cerambycids to the climates of the Noogoora burr-infested region. a factor not considered.