Plant Population Density Research Articles

Mikroskopijne grzyby pasożytnicze w zbiorowiskach roślinnych Wyżyny Częstochowskiej [Phytoparasitic micromycetes in plant communities of the Wyżyna Częstochowska Upland

Mycosociological studies on microfungi parasitising vascular plants were carried out on 21 permanent observation plots in 5 phytocoenoses representing beech forests (<em>Luzulo pilosae-Fagetum</em>, <em>Melico-Fagetum</em>, <em>Dentario enneaphyllidis-Fagetum</em>, <em>Carici-Fagetum</em>) and xerothermic grassland (<em>Origano-Brachypodietum pinnati</em>) as well as using route method in other plant communities. The frequency of host plants and fungi occurring on permanent plots was estimated using 5-degree scale. The observations yielded in 478 fungal species belonging to <em>Peronosporales </em>(<em>Oomycota</em>), <em>Dothideales</em>, <em>Erysiphales</em>, <em>Helotiales</em>, <em>Hypocreales</em>, <em>Mycosphaerellales</em>, <em>Phyllachorales</em>, <em>Pleosporales</em>, <em>Xylariales </em>(<em>Ascomycota</em>), <em>Uredinales</em>, <em>Microbotryales</em>, <em>Urocystales </em>(<em>Basidiomycota</em>) and <em>Hyphomycetes </em>and <em>Coelomycetes </em>(anamorphic fungi), which were hosted by 301 species of vascular plants as well as by 19 taxa of <em>Erysiphales </em>and <em>Uredinales</em>. The predominanting group was anamorphic fungi (65% of species), especially members of <em>Sphaeropsidales </em>(39%). This group was however less dispersed on the study area than <em>Uredinales </em>and <em>Erysiphales</em>, which were represented by relatively small number of species. The results provided data on diversi- fied occurrence of fungi depending on abiotic (humidity, temperature, insolation) and biotic factors (e.g. density of host plant population) provided by plant communities. The differences concern species composition and richness of fungi, their distribution as well as frequency of hosts and parasites. In the case of members of <em>Erysiphales</em>, <em>Moniliales </em>and <em>Peronosporales </em>differences in phenology were also noted. The greatest species richness and distribution of the micromycetes was observed in <em>Origano-Brachypodietum </em>and the poorest were plots of <em>Luzulo pilosae-Fagetum</em>. Most frequently the parasites infected small percentage of the individuals in the population of the hosts (about 1%), which occurred with the lowest coverage (below 10%). This type of relationship between frequency of fungi and density of plants dominated in all of the studied phytocenoses. Sixty two species of fungi observed on Wyżyna Częstochowska Upland are new for Polish biota. They belong to anamorphic fungi, mainly to <em>Phyllosticta </em>(32 species) and <em>Ascochyta </em>(15).

Some remarks on the methods of assessing the population density of higher plants in cases of aggregated spatial structure

This paper presents a comparative analysis of the methods used for. assessing the density of higher plants. The analysis was carried out on natural population (<i>Vaccinium myrtillus</i> L.) characterized by aggregated spatial structure. Attention has been paid to the surface methods with high (0.25 m<sup>2</sup>) and low <0.01 m<sup>2</sup>) basal unit, as also to the non-surface methods: the closest individual, the nearest neighbour, and the wandering quarter. Studies have shown that these 'methods do not give comparable results. The discussion points out' which methods can be used for the assessment of the density of aggregated populations, and what conditions must be fulfilled in order to obtain reliable results.

黄土塬区玉米大豆不同间作方式（比例）对产量和经济收益的影响及其机制

PDF HTML阅读 XML下载 导出引用 引用提醒 黄土塬区玉米大豆不同间作方式对产量和经济收益的影响及其机制 DOI: 10.5846/stxb201309182308 作者: 作者单位: 中国科学院水利部水土保持研究所,西北农林科技大学,中国科学院水利部水土保持研究所,中国科学院水利部水土保持研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家高技术研究(863)发展计划项目(2011AA100504); 高等学校学科创新引智计划资助(B12007) The effect and mechanism of intercropping pattern on yield and economic benefit on the Loess Plateau Author: Affiliation: Institute of Soil and Water Conservation,Northwest A F University,,Institute of Soil and Water Conservation Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:利用不同玉米品种(郑单958和豫玉22)和大豆品种(中黄24和中黄13)在单作和两种(2:2和2:4)间作方式下,研究品种、间作方式对间作系统产量和经济效益的影响,探讨其潜在的作用过程和机制,以期为旱区农业高产高效服务。实验结果表明:(1)两种间作方式的土地当量比(LER),相对拥挤系数(K)都高于单作,表明玉米、大豆在两种间作方式下较单作具有显著的间作优势,玉米间作相比单作增产显著。K、实际产量损失(AYL)、侵占力(A)和竞争比率(CR)的变化规律均表明在间作栽培条件下,玉米相对于大豆为竞争优势物种;郑单958相对于豫玉22,中黄24相对于中黄13均占有一定竞争优势。郑单958与中黄24以2:4比例间作的间作优势(IA)及货币优势指数(MAI)值最高。(2)相比单作,间作种植模式下玉米的水分利用效率明显增加,而且玉米:大豆以2:4间作的水分利用效率显著高于2:2。郑单958与中黄24 在2:4间作方式下的产量和经济效益都最高,适合在当地应用和推广。 Abstract:One of the tasks of agricultural ecologist is to increase agricultural yield. How to improve agricultural practice is the biggest challenge in drought and barren environments on the Loess Plateau. Many studies have attempted to increase yield through the integration of plant population density, water and fertilizer use efficiency in this region. Intercropping, which is the simultaneous growing of two (or more) crop species in the same field, is a good solution to resolve this problem. Especially under low input conditions, the high yield attributes to resource complementarity in the intercropped system in which the component crops use the resources efficiently by dynamically balancing the different absorbing time, space-occupying or phenology. Maize (Zea mays L.) and soybean (Glycine max L.) are important crops in China selected as the inter-planted crops. A field experiment was conducted to investigate the yield and economic benefit in the intercrops of maize (Zhengdan 958 and Yuyu 22) with soybean (Zhonghuang 24 and Zhonghuang 13) in two planting patterns (2:2 and 2:4) respectively on the Loess Plateau, and the sole crops set as controls. Based on the interrelation between varied components and planting patterns as well as their relation to crop yield, competition indices, economic indices and water use efficiency under intercropped, we look forward to understanding potential regulation and mechanisms of maize/soybean intercropped system and serving for the agricultural production. The aboveground biomass, grain yield and water use efficiency were surveyed in each planting pattern. Several indices of competition and economic were calculated and used to evaluate the intercropped systems and analyze the competitive relationships between intercropped components. The results showed that the land equivalent ratio (LER) and relative crowding coefficient (K) were greater in maize-soybean intercropping than that in sole crop, indicating an advantage of intercropping. Yield of maize in maize-soybean intercropping was higher than that in single crop. The actual yield loss (AYL), aggressivity (A) and competitive ratio (CR) indicated that maize was the dominant species in maize/soybean intercropped system. Zhengdan 958 and Zhonghuang 24 showed more competitiveness on the water than the other two varieties in intercropping cultivation. The highest values of monetary advantage index (MAI) and intercropping advantage (IA) were recorded by the intercropping pattern of Zhengdan 958 and Zhonghuang 24 (with 2:4). The highest water use efficiency of maize was in intercropping pattern of 2:4, followed by intercropping pattern of 2:2, and sole crop was the lowest. As mentioned above, maize and soybean intercropped system had an obvious advantage in enhancing yield. The increases in biomass, yield and water use efficiency were caused by different varieties interaction and plant patterns significantly. Zhengdan 958 intercropped with soybean (Zhonghuang 24 and Zhonghuang 13) had advantage, indicating that Zhenggdan 958 is able to improve intercropping advantage. Zhengdan 958 and Zhonghuang 24 intercropped in patterns of 2:4 obtained the highest yield and water use efficiency among all treatments. Therefore, we suggest that Zhengdan 958 and Zhonghuang 24 intercropped in patterns of 2:4 had the highest economic benefit than the other patterns and thus may be adopted and popularized by farmers. 参考文献 相似文献 引证文献

English

Seed is the basic unit for any agricultural production system. Without quality seed, no one can even think of good harvest and green been (Phaseolus vulgaris L.) production. Seed producers have to meet farmers seed demand by adopting appropriate plant population and arrangement pattern which would give them satisfactory seed yield of good quality. Previous researches on the same subject indicate that square arrangement results in high yield while others found no clear differences yet others advocate the use of higher plant densities during production. Several plant population densities (125,000 plants/ha, 163,265 plants/ha, 222,222 plants/ha and 320,000plants/ha) and three planting arrangement patterns (square, R50 and R40) were investigated in this study. Comparison of bush bean seed yield was highest (0.50t/ha) at population of 222,222 plants/ha and when planted in square arrangement pattern and least (0.13t/ha) at population of 360,000 plants/ha. Seed size was only influenced by plant population and not affected by plant arrangement pattern. Plant population density strongly influenced the percent of good seeds developed with populations of 125,000 and 163,265 plants/ha producing 97.01% and 96.15%, respectively. Germination of the harvested seeds was insignificant at all plant densities. The highest speed of germination (77.62%) of seeds was observed from a population density of 320,000 plants/ha. Therefore, green bean seed producers can adjust their planting density to 222,222 plants/ha in square arrangement to maximize seed yield

Factors influencing the population density of the weevil Microplontus millefolii Schze. (Coleoptera, Curculionidae: Ceutorhynchinae) in the environs of St. Petersburg

Environmental factors determining the population density of the weevil Microplontus millefolii, a stem miner of the common tansy, Tanacetum vulgare, were investigated in the suburbs and environs of St. Petersburg, Russia. Larvae or empty mines of M. millefolii were found in 39 out of 43 inspected sites; in total, 620 out of 2283 T. vulgare stems were infested. The percentage of infested stems per site ranged from 0 up to almost 90%, the density of infestation (the mean number of larvae and empty mines per stem) ranged up to 2.3 with the mean of 0.51 for all inspected sites. The surrounding vegetation was the single environmental factor significantly correlated with the percentage of infested stems (30 and 20% in sites with domination of grasses and of forbs, correspondingly). The mechanisms of this dependence are not clear. Probably, the domination of grasses (that is a relatively advanced stage of the vegetation succession) is correlated with the longer period of time for accumulation of phytophagous insects associated with tansy. The analysis of data for individual stems (within-site distribution) showed that the mean number of the weevil larvae almost linearly increased with the diameter of the stem. The dependence on the host plant population density was also strong but not linear: both in dense patches (percent cover of more than 50%) and in sparse plants (percent cover of 1% and less) the density of infestation was higher than at a medium abundance of the host plant. In addition, in the patches with only a short time shadow from trees or tall herbs the density of infestation was higher than in those where the shadow stayed for longer or was absent at all. The mean density of T. vulgare infestation by M. millefolii was independent of the type of habitat (meadows, old fields, roadsides, ruderal sites), the size of the site, the average cover of T. vulgare, the total cover of green plants, the degree of anthropogenic disturbance, soil composition, and humidity. This ability to infest T. vulgare in very different habitats allows considering M. millefolii as a potentially effective agent for biological control of the common tansy in the invasion areas.

The relationship between host lifespan and pathogen reservoir potential: an analysis in the system Arabidopsis thaliana--cucumber mosaic virus.

Identification of the determinants of pathogen reservoir potential is central to understand disease emergence. It has been proposed that host lifespan is one such determinant: short-lived hosts will invest less in costly defenses against pathogens, so that they will be more susceptible to infection, more competent as sources of infection and/or will sustain larger vector populations, thus being effective reservoirs for the infection of long-lived hosts. This hypothesis is sustained by analyses of different hosts of multihost pathogens, but not of different genotypes of the same host species. Here we examined this hypothesis by comparing two genotypes of the plant Arabidopsis thaliana that differ largely both in life-span and in tolerance to its natural pathogen Cucumber mosaic virus (CMV). Experiments with the aphid vector Myzus persicae showed that both genotypes were similarly competent as sources for virus transmission, but the short-lived genotype was more susceptible to infection and was able to sustain larger vector populations. To explore how differences in defense against CMV and its vector relate to reservoir potential, we developed a model that was run for a set of experimentally-determined parameters, and for a realistic range of host plant and vector population densities. Model simulations showed that the less efficient defenses of the short-lived genotype resulted in higher reservoir potential, which in heterogeneous host populations may be balanced by the longer infectious period of the long-lived genotype. This balance was modulated by the demography of both host and vector populations, and by the genetic composition of the host population. Thus, within-species genetic diversity for lifespan and defenses against pathogens will result in polymorphisms for pathogen reservoir potential, which will condition within-population infection dynamics. These results are relevant for a better understanding of host-pathogen co-evolution, and of the dynamics of pathogen emergence.

EFFECT OF PLANT POPULATION AND DISTRIBUTION ON YIELD AND YIELD COMPONENTS OF FIVE FABA BEAN GENOTYPES

Plant population density plays an important role on crop growth and yield as response to light penetration and photosynthesis rate. A field experiment was carried out at Sids Research Station, Agricultural Research Center (ARC), during two successive winter seasons, of 2012/13 and 2013/14. The objectives of this investigation was aimed to evaluate five faba bean genotypes namely Nubaria 1(large seeded cultivar), Giza 429, line 43130, E.19 (medium seeded types) in addition to the small seeded type Camolina. Plant densities were; a) 8 plants/m2 planted in single seeded hills spaced 20 cm on one side of 60 cm wide ridges, b) 17 plants/m2 planted in double seeded hills spaced 20 cm on one side of the ridges, c) 17 plants/m2 planted in single seeded hills spaced 20 cm on both sides of the ridges and d) 33 plants/m2 planted in double seeded hills spaced 20 cm on both sides of the ridges. Results indicated that, faba bean genotypes were significantly different in all studied characters. Nubaria 1 and E.19 genotypes had the tallest plants, respectively. The highest seed yield per feddan was obtained from Nubaria 1 cultivar, while the medium seeded line L-43130 produced the lowest seed yield per feddan over both seasons. Giza 429 (medium seeded cultivar) followed by Nubaria 1. Plant population of 17 plants/m2 in single seeded hills on both sides of the ridges produced highest seed yield per feddan over all genotypes. Concerning to the interaction between plant populations and faba bean genotypes, highest seed yield per feddan was obtained from the large seeded cultivar Nubaria 1 under the low plant population (8 plants/m2), while the medium seeded types i.e. Giza 429, L-43130 and E19 were more yielding under the third plant population (17 plants/m2 on both sides of the ridge). On the other hand, the small seed type Camolina produced highest seed yield per feddan under the high plant population (33 plants/m2). The interaction between faba bean genotypes and plant population had significant effects on all studied characters except number of days to flowering.

The effect of bacterial-based biofertilisers and cytokinin on the emergence of sunflower at non-limiting and supra-optimal temperatures

Subsurface sunflower (Helianthus annuus L.) seedling growth often deteriorates on sandy-textured soils due to supra-optimal temperature levels on the Highveld area of South Africa leading to poor emergence and suboptimum plant population densities. It has been shown that seedling growth is enhanced by the application of plant growth promoting rhizobacteria and cytokinin. The possibility therefore exists that the poor emergence problem might be remedied through the use of these applicants. The objective of this investigation was to determine if commercially available bacterial-based biofertilisers and cytokinin can enhance the seedling vigour of subsurface sunflower seedlings in controlled ambient temperatures ranging from non-limiting to supra-optimal and in unregulated field conditions. The results suggest that there are conditions where bacterial-based biofertiliser and cytokinin can alleviate the damaging effect of supra-optimal temperatures on the emergence of sunflower. However, the effect of these applicants on various cultivars and soil conditions require further investigation.

Meat Goats in Hillside Pastures: Control of Undesirable Plant Species and GPS Collar Determination of Activity Patterns

ABSTRACT Pasture weed control is complicated by the steep hill side topography found in many areas of Kentucky. Meat goats (Capra hircus) are a possible alternative to mechanical or chemical weed control in these pasture situations. A study using 120 boer-cross female goats averaging 44 kg, was conducted in Carter County (2010–2012) to determine the impact of meat goats on undesirable plant species. Additionally, 15 goats chosen at random were fitted with GPS collars for 5 days to determine animal activity. Plant population and canopy density measurements were recorded at the start, middle, and end of the grazing season for two or three years. Goat periodic preference for particular plant species resulted in an increase in growth of other species for the same period or year. Bramble density in the upper canopy (90 cm and above) decreased during the study, particularly in the first year of grazing, but increased in the second year, as goat preference changed (P < 0.05). Overall, grass availability in the m...

English

The study aimed at identifying the influence of different plant population density and fertilizer rates on three different maize varieties, it was carried out in two cropping seasons (2007/2008 and 2008/2009) at Ibadan and Ikenne in South-western Nigeria. The experiment was a split-split-plot design with three replications. Maize variety (Swan 1-SR an open-pollinated, Obasuper a hybrid and Quality Protein Maize, an improved) was used as the main plot, the sub-plot comprised three plant population densities determined from spacing combinations which are 53,320 plants ha-1 (75 x 50cm), 88,880 plants ha-1 (90 x 25cm) and 106,640 plants ha-1 (75 x 25cm) while&nbsp; the sub-sub-plot was NPK 20:10:10 fertilizer (applied at 120, 150 and 180 kg N ha-1). The results showed that there were significant differences (P&le;0.05) for plant height, stalk diameter, stalk lodging, maize cob weight, cob diameter, cob length and grain yield due to influence of different rates of fertilizer and plant population density at both locations. Irrespective of the rates of fertilizer applied, there were no significant differences for stalk diameter at Ibadan and Ikenne. Also, maize variety did not significantly affect (P&le;0.05) maize growth performances. However, the results indicated that, the application of 180 kg N ha-1 gave the highest grain yield of 3.8 and 3.5 ha-1at Ibadan and Ikenne, respectively, which was not significantly different from the application of 150 kg N ha-1. Thus, the plant population density of 88,880 plants ha-1 gave the highest maize grain yield while the lowest yields were recorded for plant population density of 106,670 plants ha-1 at both locations. The hybrid maize (Obasuper) variety gave the highest maize grain yield. &nbsp; Key words: Plant population density, fertilizer rates, maize varieties, NPK fertilizer, south west.

&lt;b&gt;Optimizing row spacing and plant population arrangement for a new short-height castor genotype in fall-winter

Plant population and arrangement should be properly designed to maximize the seed yield of short-height genotypes of castor ( Ricinus communis L.) in each cropping season. Experiments were performed in the in the fall-winter cropping season of 2008 and 2009 in Botucatu, State of Sao Paulo, Brazil, to evaluate the effects of row spacing (0.45, 0.60, 0.75, and 0.90 m) and plant population (25,000, 40,000, 55,000, and 70,000 plants ha -1 ) on agronomical traits, yield components, seed yield, and oil yield of the genotype FCA-PB. A high plant density caused a reduction in plant survival and increased the first raceme insertion height, particularly in the year with the higher rainfall. The basal stem diameter, number of racemes per plant, and seeds per raceme were reduced by increasing the plant density. However, the seed and oil yields were minimally influenced by plant population density and row spacing because the castor plant compensated for a low plant population with a high number of racemes and seeds. The maximum seed yield was achieved with an estimated 0.64 m of row spacing and 50,107 plants ha -1 (i.e., 3.2 plants m -1 ).

Growth and Yield Performance of Cassava/Maize Intercrop Under Different Plant Population Density of Maize

Field experiments involving cassava/maize intercrops under different plant population densities of maize were conducted during 2002 and 2003 cropping seasons on the research farm of the Institute of Agricultural Research and Training situated at Ilora, Nigeria (7o 22? N, 3o 52? E). Results obtained in 2002 and 2003 consistently showed that increases in plant population density of maize in maize/cassava intercrop directly increased maize plant height at tasselling, plant height at harvest and plant lodging percentage, but reduced stalk diameter, average cob weight, dry matter yield and grain yield. Significantly least values (2.03 and 2.11 t/ha) were obtained from maize grain yield in 2002 and 2003 under 20,000 plants/ha while the highest values (3.28 and 3.55 t/ha) were obtained in 2002 and 2003 under 40,000 plants/ha. Results obtained in 2002 and 2003 showed that increased in plant population density of maize in cassava/maize intercropping system significantly affected the cassava plant height at 2 and 4 month after planting (MAP) and fresh tuber yield. Increased in plant population density of maize in cassava/maize intercrop did not significantly affect cassava plant height at 7 and 12 MAP. The highest values (25.9 and 25.3 t/ha) cassava fresh tuber were obtained in 2002 and 2003 under 20,000 plants/ha maize component. The least values (17.6 and 18.2 t/ha) were obtained in 2002 and 2003 under 80,000 plants/ha maize component.

Effect of varying plant population density on aphid infestation level and yield of faba bean

Effect of varying plant population density on aphid infestation level and yield of faba bean

Towards modelling the flexible timing of shoot development: simulation of maize organogenesis based on coordination within and between phytomers.

Experimental evidence challenges the approximation, central in crop models, that developmental events follow a fixed thermal time schedule, and indicates that leaf emergence events play a role in the timing of development. The objective of this study was to build a structural development model of maize (Zea mays) based on a set of coordination rules at organ level that regulate duration of elongation, and to show how the distribution of leaf sizes emerges from this. A model of maize development was constructed based on three coordination rules between leaf emergence events and the dynamics of organ extension. The model was parameterized with data from maize grown at a low plant population density and tested using data from maize grown at high population density. The model gave a good account of the timing and duration of organ extension. By using initial conditions associated with high population density, the model reproduced well the increase in blade elongation duration and the delay in sheath extension in high-density populations compared with low-density populations. Predictions of the sizes of sheaths at high density were accurate, whereas predictions of the dynamics of blade length were accurate up to rank 9; moderate overestimation of blade length occurred at higher ranks. A set of simple rules for coordinated growth of organs is sufficient to simulate the development of maize plant structure without taking into account any regulation by assimilates. In this model, whole-plant architecture is shaped through initial conditions that feed a cascade of coordination events.

When Is the Best Time to Emerge: Reproductive Phenology and Success of Natural Common Waterhemp (Amaranthus rudis) Cohorts in the Midwest United States?

Although the prolonged emergence pattern of common waterhemp is well known, its effect on flowering phenology and success is less well understood. The ecological significance of later common waterhemp cohorts could have been underestimated. Ecological knowledge of common waterhemp, such as reproductive phenology and success, would help us better understand the invasiveness of this weed and thus facilitate the development of more targeted control methods. Field studies were conducted at Ames, IA, to evaluate temporal variation in flowering phenology (e.g., date of flower initiation, number of flowering plants per day) and reproductive success (e.g., seed production) of natural common waterhemp cohorts. Later-emerging common waterhemp cohorts flowered quicker and had a relatively shorter flowering period than early cohorts. Common waterhemp cohorts showed very large variations for the duration of their vegetative phases, indicating different photoperiod sensitivity among cohorts. Furthermore, common waterhemp cohorts exhibited a pulsed flowering pattern, which was probably influenced by temporal distribution of rain events; up to seven distinct flowering pulses within 40 d were observed in 2009, and about eight flowering pulses scattered over a 60 d period were observed in 2010. Common waterhemp maintained high seed production throughout the growing season. Seed production for the entire cohort was influenced more by emergence timing, whereas individual plant fecundity was more affected by plant population densities. Common waterhemp demonstrates strong phenological plasticity by evolving a pulsed flowering pattern, which rendered it plastic enough to tailor flowering to variable environmental conditions thus facilitating effective pollination. Common waterhemp later cohorts have a strong seed production potential, which may be ecologically significant with regard to herbicide resistance evolution.

Influence of genotype and sowing date on camelina growth and yield in the north central U.S.

Camelina (Camelina sativa L.) has gained considerable attention in North America as a potential oilseed feedstock for advanced biofuels and bioproducts. Progress has been made towards characterizing camelina's production potential for the western U.S. and Canada. However, little has been done to evaluate its potential for the north central region of the U.S. The objectives of the following study were to evaluate plant stand establishment, growth, and yield of 10 camelina cultivars and target the optimum sowing time for spring seeding in the northern Corn Belt. The study was conducted over three growing seasons between 2008 and 2010 in west central Minnesota, on a Barnes loam soil. Eight cultivars were evaluated in 2008, 10 cultivars in 2009, and four cultivars in 2010. Sowing dates ranged from 16 April to 15 June over the three-year study. Plant population density, time to 50% flowering, seed yield, and oil content were affected by sowing date, tending to decline with delayed sowing. Seed yield was significantly affected by cultivar only in 2009, whereas oil content was consistently affected by cultivar all three years. Across cultivars, seed yields were as high as 2300kgha−1 to as low as 743kgha−1 and were generally greatest for sowings between mid-April to mid-May. Across sowing dates and cultivars, oil content ranged from about 36 to 43% (wtwt−1) and declined with delayed sowing. Generally, seed yield and oil content differences tended to be small between most genotypes in the study. Results indicate that the best time to sow spring camelina in west central Minnesota is from about mid-April to mid-May. Further research is needed to optimize other agricultural inputs for camelina production in the northern Corn Belt.

Modelling the structural response of cotton plants to mepiquat chloride and population density.

Cotton (Gossypium hirsutum) has indeterminate growth. The growth regulator mepiquat chloride (MC) is used worldwide to restrict vegetative growth and promote boll formation and yield. The effects of MC are modulated by complex interactions with growing conditions (nutrients, weather) and plant population density, and as a result the effects on plant form are not fully understood and are difficult to predict. The use of MC is thus hard to optimize. To explore crop responses to plant density and MC, a functional-structural plant model (FSPM) for cotton (named CottonXL) was designed. The model was calibrated using 1 year's field data, and validated by using two additional years of detailed experimental data on the effects of MC and plant density in stands of pure cotton and in intercrops of cotton with wheat. CottonXL simulates development of leaf and fruits (square, flower and boll), plant height and branching. Crop development is driven by thermal time, population density, MC application, and topping of the main stem and branches. Validation of the model showed good correspondence between simulated and observed values for leaf area index with an overall root-mean-square error of 0·50 m(2) m(-2), and with an overall prediction error of less than 10% for number of bolls, plant height, number of fruit branches and number of phytomers. Canopy structure became more compact with the decrease of leaf area index and internode length due to the application of MC. Moreover, MC did not have a substantial effect on boll density but increased lint yield at higher densities. The model satisfactorily represents the effects of agronomic measures on cotton plant structure. It can be used to identify optimal agronomic management of cotton to achieve optimal plant structure for maximum yield under varying environmental conditions.

Effects of Precision Seeding without Thinning Process on Yield and Yield Components of Cotton

Thinning is a considerably popular practice in cotton field management in the Yellow River Valley of China, but such a traditional practice is currently facing a big challenge because of labor costs and time consuming. The objective of the present study was to determine the effects of precision seeding on seed cotton yield and yield components so as to provide a new alternative technique to simplify cotton cultivation in the region. A three-year field experiment was conducted at four experimental sites(Linqing, Xiajin, Huimin, and Dongying) to comparatively investigate the effects of precision seeding without thinning on plant population density, seed cotton yield and yield components, with conventional seeding with thinning(seeding rate of 22.5 kg ha–1 and thinning seedlings two times after emergence) as the control. There existed significant interaction effects among planting years, experimental sites and planting patterns on plant density, seed cotton yield and number of bolls per unit area. In 2011–2013, the plant population reached 4.5–8.5 plants m–2 in precision seeding treatment at ten out of twelve sites, and number of bolls per unit area and seed cotton yield were equivalent to those of conventional seeding at these ten sites. However, the seed cotton yield of precision seeding treatment at Dongying in 2011 and at Huimin in 2012 was significantly reduced by 14.2% and 5.5% owing to the low density(3.53 and 3.63 plants m–2) and their boll number was reduced by 13.8% and 9.7% relative to that of conventional seeding treatment. There was no significant difference in single boll weight between the two seeding patterns. The yield reduction of precision seeding treatment at two experimental sites was mainly attributed to the decrease in number of bolls per unit area as a result of reduced plant density. Therefore, costs saving without yield reduction can be realized through precision seeding under the support of improved seeding quality and a relatively high plant density. Precision seeding without seedling thinning can be one ofthe simplified cultivation measures of cotton production in the Yellow River valley of China.

Optimization of plant population and nitrogen requirement for commercial cultivation of Kalmegh (Andrographis paniculata Nees) under Indo-Gangetic plains of north India

To optimize the plant population density and nitrogen requirement of Andrographics paniculata under indo-Gangetic plains, a field experiment was conducted in a sandy loam soil during rainy season (July-October) at the research farm of the Central Institute of Medicinal and Aromatic Pl ants, Lucknow. Sixteen treatments comprising of four plant population dens ities (66,666, 111,111,222,222 and 444,444 plants ha-1 by planting at 50 x 30cm, 30 x 30cm, 30 x 15cm and 15 x 15 cm spacing, respectively) and four nitrogen levels (0, 40, 80 and 120 kg ha-1) were tested in a factorial randomized block design with three replications. Yield contributing traits such as plant height, number of branches per plant, leaf area index (LAI), dry b iomas s and content of di terpenoid lactones (Andrographolide + neo-andrographolide) registered a significant increased at a plant population of 222,222 plants ha-1 and application of 80 kg ha1 nitrogen. The optimum dose of N was worked out to be 90.7 kg ha1 that gave a maximum dry biomass yield of 3833.7 kg ha1.

Comparing an empirical crop model with a functional structural plant model to account for individual variability

Individual variability generally exists in crop fields. It increases with an increase in plant population density, water or nutrient deficiency, or spatio-temporal irregularity, and often results in a reduction in yield. As individual variability exists in a community but is expressed through individuals, we studied it by applying two models, one at the stand level and the other at the individual level.The crop model PILOTE and the functional structural plant model (FSPM) GreenLab were applied to a field of maize (Zea mays L.) to provide a numerical description of the crop at different levels. The delay and slower increase in LAI and in total dry matter at stand level compared to individual level, led us to hypothesize that uneven emergence could have an effect on variability. We derived a theoretical distribution of germination dates, which supported this hypothesis. In parallel, we used GreenLab to analyze possible sources of variability in accumulated biomass within a dynamic system, and to estimate possible parameters from experimental data.Using PILOTE and GreenLab, we successfully identified two typical types of individual variability in the maize field: variability in development over time and variability in competition for space during growth. Our method could be used in future research on the cause and influence of individual variability on performance, and to identify the link between an FSPM based on individual plants and a crop model at stand level.