Variation in yield loss of oilseed rape due to grazing by mute swans Cygnus olor

Yield loss due to grazing by mute swans was measured on nine fields of autumn-sown oilseed rape located in five regions of England. Using a paired-plot design, a significant reduction in yield (total dry weight of seed) was observed on three of the fields: 18%, 23% and 24%, respectively. On the first of these fields yield reduction was not simply due to fewer seeds being produced, as the weight of individual seeds was also significantly lower on grazed plots, with a reduction in thousand seed weight of 13%. Between fields (n=9), yield loss was positively correlated with the number of swans per ha, and the number of days of swan grazing per ha. Significant levels of yield loss occurred only on fields grazed by >5 swans per ha. The density of swans grazing per ha can thus be used to predict potentially significant yield loss and provides an indicator of the level of swan grazing activity at which growers should consider deploying measures to reduce grazing.     

苗期渍水对直播冬油菜产量和农学利用率的影响及油菜在不同氮肥施用下的响应

在轻简化施肥背景下,为减少渍害损失,解决长江流域冬油菜产区生产面临的重要问题,开展氮肥施用 对油菜渍害的缓解作用研究。设置三因素田间试验,分别为不同氮肥用量（0、60、120、180、240和300 kg N/hm2）、氮 肥类型（油菜专用控释尿素和普通尿素）和水分处理（苗期渍水和正常排水）,测定各处理产量和氮肥农学利用率, 明确苗期渍水对不同氮素供应水平油菜的影响,并比较油菜专用控释尿素一次性施用和普通尿素分次施用下油菜 对苗期渍水的响应。结果表明,直播冬油菜产量随氮肥施用量增加而提高,至240 kg N/hm2时不再增加。油菜专用 控释尿素一次性施用,在氮肥用量为60～180 kg N/hm2时产量高于普通尿素分次施用;在氮肥用量为240～300 kg N/hm2时,两种氮肥类型产量基本相当。氮肥施用通过增加收获密度、单株角果数和每角粒数提高产量。苗期渍水 导致直播冬油菜产量损失1.1%～41.9%,随氮肥用量增加,渍水引起的产量损失率呈先增加后降低趋势。0～60 kg N/hm2处理时,渍水使收获密度显著降低（降幅达29.4%~45.0%）,单株角果数增加;施氮量为120~180 kg N/hm2时, 渍水导致收获密度和单株角果数分别降低19.5%~33.7%和1.4%~17.7%;施氮高于180 kg N/hm2时,收获密度和单 株角果数降幅减小（降幅分别为5%~30.9%和3.6%~9.5%）。普通尿素分次施用和油菜专用控释尿素一次性施用, 分别在施氮量为120和180 kg N/hm2时产量损失率最高,分别达29.8%和41.9%。相同氮肥用量下油菜专用控释尿 素一次性施用的产量损失率大于普通尿素分次施用。渍水显著降低氮肥农学利用率,降幅为8.4%～51.9%,施氮充 足（240～300 kg N/hm2）时氮肥农学利用率降幅低于氮素用量较低处理（120～180 kg N/hm2）,油菜专用控释尿素一 次施用处理的农学利用率平均降幅（36.5%）高于普通尿素分次施用（17.3%）。综上可知,苗期渍水时,油菜专用控 释尿素一次施用,会加重油菜受渍影响;土壤氮素供应能力较低时,渍害逆境解除后,适量追施速效氮肥可有效缓 解产量损失,实现油菜稳产。     

Crop loss of pepper plants artificially infected with Xanthomonas campestris pv. vesicatoria in relation to symptom expression

Crop losses in peppers artificially infected with Xanthomonas campestris pv. vesicatoria (XCV) were determined during 3 years of field experiments in three areas of Israel. Direct losses of 23–44% in fruit yield were recorded when severe leaf infection occurred or was induced at an early stage of plant growth. Yield losses and disease index were markedly lower in plants inoculated at later stages and near maturation. Indirect losses in severely infected fields were mainly due to shedding of leaves and exposure of fruits to sun. In this case, up to 95% of the fruits lost their commercial value. In artificially infected symptomless plants with massive endogenous populations of XCV in the leaves, a loss of 24% in yield was measured, compared with plants free from an endogenous pathogen population.     

间作对油菜和紫云英生长及产量的影响

为使用地与养地相结合,在保持油菜不减产的同时,建立合理的油菜/紫云英间作技术体系。采用大田试验,研究了紫云英(Astragalus sinicus L.)与不同密度油菜(Brassica napus L.)间作对二者生长和产量的影响。结果表明：紫云英与密度为20~40万株/hm2油菜按2:1带型间作(即1m宽带内播种两行油菜,1行紫云英),间作油菜各处理不同生育期氮磷钾和碳的养分累积量均有高于或接近于油菜单作(MR)的趋势,间作油菜株高、根长、根颈粗、单株鲜重和产量接近于或显著高于密度为30万株/hm2的单作油菜。在保持油菜产量不显著降低的同时,间作模式可以收获3 592~5 724kg/hm2的紫云英绿肥。紫云英与不同密度油菜间作均表现土地资源利用优势(LER>1)。     

Variation in forage yield and quality of three cruciferous catch crops grown in southern England

Cruciferous catch crops are an important source of forage, particularly in sheep systems, but due to their late sowing date, commonly July or early August, soil moisture is often a limiting factor in crop establishment and subsequent growth, causing wide variations in yield from year to year. Crops of stubble turnip ( Brassica campestris ssp. rapifera ), forage rape ( B. napus ssp. biennis ) and fodder radish ( Raphanus sativus ) were grown at Hurley between 1969 and 1977. Fodder radish was the most variable in dry matter (DM) yield, while stubble turnip was the most stable. Both DM yields and in vitro digestibilities rose during the autumn, reaching a maximum in mid-December for stubble turnip and forage rape, and in mid to late November for fodder radish. Yield and digestibility subsequently declined. The N concentrations of the forages exhibited a contrary trend, reaching minimum values at about the time of the highest DM yields. The gradual changes in crop quality suggest that the crops are well suited to grazing utilization, in which management is simplified if crop quality shows little variation.     

大豆根潜蝇发生为害及防治的研究

1983～1989年研究大豆根潜蝇的发生为害及防治规律,取得以下结果:①大豆根潜蝇主要在大豆苗期为害,使地下根长度、支根数及根瘤数降低,地上叶片内叶绿素含量减少,植株干重降低14.47～28.57％。受害株荚数、豆粒数和百粒重降低,单株产量降低23.48％,使大豆减产15.82％。②大豆与玉米轮作被害率较连作低48.73％。于根潜蝇化蛹期(大豆始花期)追肥能加速虫伤愈合、发根并能挽回受害损失40—50％。③应用辛硫磷、3911 0.1％(种子量)的量拌种防效均达100％,较对照有明显的增产作用,增产达10—15％。     

密度和氮肥用量对油菜产量及氮肥利用率的影响?

 为机械化种植油菜,研究不同施氮水平下密度对直播油菜生长发育和氮肥利用效率的影响。以甘蓝型油菜品种中双11号为材料,在低密（15万株/hm2）和高密（45万株/hm2）两种密度下,设施氮0、90、180和270kg/hm2处理,分析施氮量与密度对油菜农学性状、产量、氮肥利用效率的影响,并对比分析了密度与油菜需氮量之间的关系。结果表明,增密后油菜的株高、分枝数、单株角果数和每角粒数显著降低,分枝高度和千粒重显著增加。高密油菜群体株型结构整齐均一,更能满足机械化收获需要。高密处理油菜籽粒产量高于低密处理。施氮0～180kg/hm2时,两个密度下的籽粒产量均随施氮量增加而显著提高,但在270kg/hm2时两密度下油菜产量均有所下降。油菜氮肥表观利用率随着施氮量的增加而下降,但是又随种植密度的增加而增加。说明增加密度能促进氮素向油菜籽粒转移,降低每生产100kg籽粒油菜需氮量,提高氮肥表观利用率。在相同的目标产量（低密下的经济产量、湖北省油菜平均单产和全国油菜平均单产）下,油菜增密后可以节约氮肥用量22.9%~30.6%,增密减氮效果明显。       

Yield and quality losses caused by common rust (Puccinia sorghi Schw.) in sweet corn (Zea mays) hybrids

Yield and quality of fresh ears were measured in field plots of selected hybrids of sweet corn (Zea mays L.) that were affected by rust (Puccinia sorghi Schw.) or were nearly rust-free (mancozeb-sprayed). In 1978, 28 hybrids were tested. Losses in total yield ranged from zero in the more resistant entries to nearly 50% in more susceptible entries. In 1979, three cultivars were planted. Yield losses of these cultivars were similar in ranking order to those in 1978, although the loss was greater in late-planted plots because of the greater final severity of the disease. Losses in total yield in late-planted sweet corn were 18%, 26% and 49% for cv. Sugarloaf (most resistant), cv. Jubilee (intermediate) and cv. Style Pak (most susceptible), respectively.     

GRAZING MANAGEMENT FOR SEED PRODUCTION IN LEAFY STRAINS OF GRASSES

Leafy strains of five grasses were grown for seed and subjected to various cattle grazing treatments between October and April for three harvest years. The grasses were: S.143 cocksfoot, S.215 meadow fescue, S.170 tall fescue, S.59 red fescue and S.23 perennial ryegrass. All but S.59 red fescue (row crop) were studied as row and broadcast crops. The plots were sown under an arable silage crop and received top dressings of nitrogenous fertiliser every year. Yield of seed, and also quantity of herbage in winter, were measured.
October grazing in the seeding year reduced the first crop of seed in all species except ryegrass. Grazing in December improved the yield of meadow fescue throughout the experiment, and of cocksfoot, tall fescue and red fescue after the first year. Several factors might operate to bring about this effect; suggestions are made for further investigation. Repeated grazing from December to March tended to reduce vigour, and so to offset the advantage of removing autumn-grown herbage. Grazing at intervals from December to late April seriously reduced yield in all species. Tall fescue and red fescue, early flowering species, were most seriously affected, meadow fescue and perennial ryegrass least. Cocksfoot and tall fescue yielded more seed when grown in 2-ft. rows than when broadcast. Meadow fescue and perennial ryegrass did not. The yield of meadow fescue was less affected by adverse conditions than cocksfoot.     

Impact of oilseed rape crop management systems on the spatial distribution of Brassicogethes aeneus (Fabricius 1775): Implications for integrated pest management

The pollen beetle is one of the most important oilseed rape pests wherever the crop is grown. If no control measures are applied, it can cause a greater than 50% reduction in yield. The over-use of insecticides (especially pyrethroids) to control the pollen beetle has led to the development of resistance. Thus, alternative control strategies are required. A field trial with three experimental fields with different contributions of turnip rape as a trap crop was established during the growth season of 2013–2014. A grid of GPS points was established on each field. Pollen beetle abundance was recorded at each GPS point by beating into trays, and damage was assessed by dissection of buds from terminal racemes. Data analysis was performed by two-way analysis of variance and the appearance of pollen beetle adults was processed in a geographic information system (GIS). Statistically significant differences were found in terms of the density of the pollen beetle population between trap crop plants and oilseed rape plants. Control thresholds on each oilseed rape field were not exceeded, whereas the density of the pollen beetle population on trap crop plants was greater by up to 40 fold, regardless of the contribution of trap crop plants. The data indicate that support systems should use sampling strategies that incorporate spatial information to model crop loss more accurately and that there may be the potential for spatially targeted applications of insecticides to optimize the influence of natural enemies in oilseed rape.     

Potato yield losses due to early blight in Minnesota fields, 1981 and 1982

In both 1981 and 1982, 51 potato fields were surveyed every 7–10 days for early blight severity and fungicide use. Early blight severity data from each field were used as input to a regression model to estimate yield loss in that field. The model for early maturing potato cultivars was Percent Yield Loss=0.8183+0.6441* (% blight increment between days 56 and 66)+0.6102* (% blight increment between days 66 and 76)+1.3480* (% blight increment between days 76 and 86). The model for late maturing cultivars was Percent Yield Loss=2.1846-4.7734* (% blight on day 56)+0.7440* (% blight on day 76)+ 0.5676* (% blight on day 96). In both 1981 and 1982, early blight was found to be present in all fields of the survey. In 1981, early blight was estimated to have caused mean losses of 6.5% (Red River Valley), 3.7% (Central sands) and 2.3% (Southern muck). In 1982, losses from the same areas were 5.4%, 3.7% and 2.6% respectively. In 1981, individual county losses ranged from 2.3% for Freeborn to 12.9% for Marshall while in 1982 losses were from 2.0% for Freeborn to 6.7% for Clay. Although fungicide use data were incomplete, the county with lowest yield loss had the most fungicide applications.     

Maximizing oilseed rape's yield by glyphosate under Mediterranean conditions

Adverse hot and dry environmental conditions prevailing during the period of oilseed rape ripening can be blamed for considerable yield losses during the crop's mechanized harvesting in the Mediterranean area. In this paper, the effect of chemical dessication of oilseed rape with glyphosate applied 35 days after anthesis for reducing seed yield loss was studied. The experiment was conducted in four fields at two locations in central Greece and for two growth periods following a completely randomized plot design with 8 treatments in three replications. Treatments include all possible combinations of two crop varieties and four levels of glyphosate (as dessicant) application. A significant positive effect of dessicant application level on crop yield for both studied varieties was found. The application dose of 200 g a.i. of glyphosate per hectare had the best results. The highest dry weight was found among the plants sprayed with 200 g. a.i. of glyphosate per hectare. The highest seed yield and oil yield were found among the plants sprayed with 200 g a.i. per hectare, which makes clear the positive effect of this spraying minimizing pod shattering and yield losses. The greatest 1000-seed weight was found among the plants sprayed with 200 g a.i. ha⁻¹, due to the greater size of seeds that remained on the plants until harvesting.     

THE USE OF CUTTING TREATMENTS DESIGNED TO SIMULATE DEFOLIATION BY SHEEP

A series of cutting treatments was designed to simulate the defoliation process under sheep grazing, in order to obtain more accurate measures of the production processes in the sward than can be obtained in the presence of the grazing animal. Two rotational grazing managements were simulated, together with three continuous grazing managements involving the maintenance of a roughly constant LAI within a sward, as described earlier (10). Harvested yield was measured, and the dry weight of material which died without heing harvested was estimated. From these, gross aerial growth, i.e., the amount of new living material produced in the sward, was calculated. The maximum harvested yield was obtained by rotational defoliation to 3 cm every 4 weeks, hut this was derived from the minimum gross aerial growth. Maximum gross aerial growth occurred under the simulated continuous grazing treatments at the higher levels of LAI. This difference was due largely to the death and subsequent decay of leaves. Up to 50% of the material which grew was lost in this way. The need to distinguish between growth and harvested yield when evaluating grazing managements was stressed.     

Assessing yield losses caused by the harvester ant Messor barbarus (L.) in winter cereals

Harvester ants from the species Messor barbarus (L.) are important seed predators in semi-arid cereal fields of NE Spain, and can contribute substantially to weed control. However, occasionally they harvest newly sown crop seeds at sowing in autumn, or ripe cereal grains close to harvest in summer, causing yield losses.A preliminary study was conducted in 34 commercial winter cereal fields to measure yield loss, and to identify factors that influence it. The area affected by ants was measured ten days prior to the anticipated harvest date. Ant colony size, nest density, crop height, weed densities and temperatures at sowing were assessed.At sowing, harvester ants did not cause yield losses (0.2% of potential yield on average). At harvest, yield losses were generally low as well (0.6%) although occasionally higher losses were recorded (max. 9.2%). Yield losses significantly increased with increasing nest density, nest size and with number of years of no-till. The results of this study show that in 2009 yield losses caused by M. barbarus were insignificant and more than offset by the benefits provided by the destruction of weed seeds.     

Factors that modify early and late reproductive phases in oilseed rape (Brassica napus L.): Its impact on seed yield and oil content

Oilseed rape yield potential could be improved lengthening the duration of the late reproductive phase by increasing the number of grains per unit area. Photoperiod sensitivity could be used as a tool to manipulate the reproductive phase and thereby the number of grains. The aim of this study was to assess (i) the effects of different combinations of photoperiod on the duration of different phases and (ii) analyze how the changes in that duration affect yield (and its components) as well as oil seed content in oilseed rape. Field experiments were conducted in a factorial combination of three cultivars and three photoperiod regimes: natural photoperiod (NP) which represents the control and extended photoperiod of 6 h over NP (NP + 6) during emergence (E)-flower buds visible (FBV) and FBV-maturity (M) arranged in a randomized complete block design with three replicates, during two years representing three environments. Results showed that oilseed rape evidenced photoperiod responses during vegetative and early reproductive phases. Due to the lack of correlation between the duration of the vegetative and reproductive phases, it is possible to speculate the vegetative period may be altered independently of the modification of the rest of the phases. The positive relationship between grain number per m² and the duration of the late reproductive phase suggests that yield could be increased by lengthening the duration of that phase. Thus, regardless of the effect on the previous phase, the photoperiod sensitivity found in the early reproductive phase opens the possibility to manipulate the relative durations of vegetative and reproductive phases. Therefore, the length of the reproductive phase will be increased at the expense of a reduction in the duration of the vegetative phase, but without changing the whole duration of the crop cycle. This strategy could increase yield in oilseed rape in the future. Variations in yield were mostly explained by changes in the grain number per unit area without significant correlation with grain weight. However, a negative relationship between grain weight and grain number was found, showing a slight counterbalance in yield, by decreasing the grain weight. Since oil concentration appeared to be a more conservative attribute, increases in crop yield through a higher grain number per unit area would be a suitable strategy for improving oil yield as no reductions in oil concentration can be expected.     

苏皖两省油菜的气候—土壤生产力研究

运用经过改进的农业生态区域法,计算了江苏、安徽两省141个县(市)油菜的气候生产力及土壤条件对它们的定量影响。大面积油菜的每亩生产潜力因各地的自然资源条件而不同。通过对各地油菜增产潜力及主要自然限制因素的分析,可以为油菜的合理布局与因地制宜确定增产措施提供科学依据。     

Association of growth dynamics, yield components and seed quality in long-term trials covering rapeseed cultivation history at high latitudes

Brassica oilseed yield trend has declined in Finland by over 20% during the last 15 years. Improved genetic yield potential of turnip rape (B. rapa L.) and oilseed rape (B. napus L.) can be better realised with increased understanding of yield determining processes under northernmost growing conditions. This study aimed at (1) determining the genetic improvements in seed yield, yield components, quality traits and duration of the main growth phases and (2) comparing all these traits in turnip rape and oilseed rape. This work is based on the dataset from long-term Official Variety Trials (1976–2006), covering the entire historically relevant period of rapeseed cultivation in Finland. The results indicated that number of seeds per square metre dominated production of high yields, while single seed weight was not correlated with yield. Over the years, seed yields were produced with very different combinations of seed numbers and weights, differing markedly between the two crops. While high seed numbers were required for production of superior seed yields, single seed weights were not particularly high. Environmental variation markedly affected seed yield, seed number per square metre and duration of flowering compared with its effect on single seed weight. Duration of flowering was, however, negatively associated with seed number. Even though seed weight was largely determined by genotype, no marked plant breeding improvements were identified, contrary to those in number of seeds per square metre, seed yield, oil content and oil yield. For oilseed rape the increase in seed yield (41%) was far higher than for turnip rape (19%) without being associated with a longer seed-filling phase and later ripening, but rather the contrary.     

Assessing yield losses in deepwater rice due to yellow stem borer,Scirpophaga incertulas (Walker), in Bangladesh and Thailand

Yield loss from damage by yellow stem borer, Scirpophaga incertulas, was assessed in deep-water rice in Bangladesh and Thailand using five different methods. Because of the long stems and special growing conditions of the crop only three methods proved reliable: pot experiments in metal containers, potted plants exposed in the field, and floating exclusion cages in the field. Yields were reduced by 27–34%, and 1% yield loss was associated with 2% damaged stems at harvest. Yield loss was mainly due to a loss of bearing stems and lighter panicles borne by compensatory nodal tillers. A tentative damage threshold of 10% damaged stems at booting/flowering stage and 20% damaged stems at plant maturity is proposed.     

Lodging yield penalties as affected by breeding in Mediterranean wheats

Stem lodging, a permanent displacement of cereal stems which may reduce wheat yields significantly, affects wheat crops in both developed and developing countries, mainly under high-yielding conditions. Although breeding has decreased these losses by reducing the likelihood of the plant lodging through reduced height (mainly by the introgression of dwarfing genes), lodging continues to affect wheat yields. We aimed to quantify how wheat breeding has modified the sensitivity of yield to lodging, identifying physiological causes for yield reductions. Two field experiments were carried out in Mediterranean Spain during the 2006/07 and 2007/08 growing seasons. The first season two genotypes (Aragon 03 and ID-2151) and two lodging treatments (control and lodged near anthesis) were analysed. The second season four genotypes (Aragon 03, Estrella, Anza and ID-2151) and three lodging treatments (control, lodged from either jointing to maturity or anthesis to maturity) were imposed. In addition, in the 2007/08 experiment the source-sink ratios of five representative spikes of each plot were modified through hand trimming all spikelets from one side of each spike soon after anthesis. Yield losses due to early lodging were reduced by wheat breeding: yield penalties in the oldest and newest genotypes were 61% and 43% (mean values of both lodging treatments), respectively while it was 57% in intermediate cultivars (mean value of both lodging treatments and cultivars). Lodging decreased both the number of grains per m² and the average grain weight (AGW). The decrease of the number of grains per m² was associated with reductions in the crop growth, while the AGW loss seemed related to both a reduction of the availability of assimilates to fill grains and a direct effect on grain size potential. Lodged plants exhibited stronger source-limitation during grain filling than those un-lodged, while the response of the grain weight to sink-strength reductions in lodged plants was very similar to that in the un-trimmed controls, indicating that grain filling in un-lodged and in strongly lodged canopies was similarly balanced in terms of source-sink ratios.