Effects of winter barley as a cover crop on the weed vegetation in a no-tillage soybean

The present study clarified the effects of winter barley as a cover crop on the weed vegetation, expressed as a multiplied dominance ratio (MDR), and emergence of summer annual weeds in a no-tillage soybean system. A 3 year field study with treatments consisting of six systems was conducted: no-tillage single cropping, no-tillage cropping following winter barley and tillage single cropping, respectively with and without herbicide application. The MDR of perennial weeds increased annually in the no-tillage fields in spring, but summer annual weeds were abundant in all fields, including the no-tillage fields in summer. Grasses, for example Digitaria ciliaris (Retz.) Koeler, were especially abundant in the no-tillage fields. The MDR of summer annual weeds, especially grasses in the barley and soybean fields, were much lower than for the no-tillage single soybean fields. Densities of D. ciliaris and Echinochloa crus-galli (L.) Beauv. var. crus-galli in the no-tillage single soybean fields were much greater than in the tilled fields, with few exceptions. In contrast, broad-leaved weeds emerged more in tilled fields than in the no-tillage fields. Winter barley suppressed emergence of summer annual weeds, especially during the first 3 years. The MDR for grasses in summer showed a good correlation with the frequency of emergence for grasses every year. These results showed that the increase in the volume of grasses in summer resulted mainly from an increase in the frequency of emergence, and that the suppression of grasses by winter barley resulted mainly from suppression of the emergence frequency. Soybean yields were higher in the barley and soybean fields for the first 2 years.     

Impact of great gerbils(Rhombomys opimus) on desert plant communities

Great gerbil(Rhombomys opimus) colonies, with bare soil and herbaceous plants, are conspicuous to the background environment throughout their range area. In order to quantify the engineer role of great gerbils, we investigated the plant communities of 20 active colonies in the Junggar Basin, Xinjiang, China. In areas without disturbance, desert plant communities were dominated by the shrubs with low level species richness. In burrow areas and surrounding intermediate areas, which were disturbed by great gerbils, the shrubs were suppressed with the decrease of vegetation cover and aboveground biomass. As a result, "niche gaps" were created in disturbed areas and worked as a refuge for herbaceous annuals and perennials. So the existence of great gerbils increased the overall species richness of the desert. Furthermore, herbaceous annuals and perennials are the major food source for great gerbils in spring, indicating that great gerbils have a mutually beneficial relationship with herbaceous plants.     

放牧与刈割对科尔沁草甸植被演替的影响

本文研究了放牧与刈割两种草地利用方式对科尔沁草甸植被演替的影响。结果表明:1)在自由放牧干扰下,优势度最大的前五个种为虎尾草(27.8)、蒲公英(3.52)、狼毒(3.42)、野韭菜(3.03)、鹅绒委陵菜(2.67);在秋季割草干扰下,优势度最大的前五个种为大油芒(9.57)、狗尾草(7.36)、野古草(6.36)、洽草(4.85)、芦苇(4.74)等五种禾本科植物;2)在自由放牧干扰下,一年生植物在群落中占据重要地位,其优势度为35.0,小于多年生植物的优势度55.9;在割草干扰下,多年生植物在群落中占据绝对优势,其优势度为82.9,大于一年生植物优势度10.6;3)在放牧扰动下,草地群落物种替代表现在不同植物生活型之间,主要是多年生草本为一年生草本和灌木所替代;表现在同一生活型不同物种之间,主要是多年生优质牧草为多年生劣质牧草或有毒有害杂草替代。     

Seasonal variation in the emergence of annual weeds — an introductory investigation in Sweden

Seeds of thirteen annual weed species were collected in early autumn. Within a few weeks they were incorporated in soil. They were stored either in the field or in climate chambers where seasonal variations in field soil temperature were simulated. Seedling emergence under various conditions was determined at different times, within a period of 1 or 2 years after the incorporation of seeds in soil. Some material was transferred from the storage places at different times of year and placed in cabinets with standardized temperature regimes for 3-week emergence tests. These showed increased emergence during late autumn and winter and a maximum at some time in winter in both summer and winter annuals. Some winter annuals showed a second maximum in late summer. Counts of seedlings in the storage places, in unstirred soil, showed maximum emergence in spring for both winter and summer annuals — or in summer for Spergula arvensis and, possibly, Capsella bursa-pastoris. In certain treatments in the field, the soil was stirred once, on different dates, simulating tillage at different limes of year. The emergence following stirring of the soil was greatest in spring for the summer annuals, except for Spergula arvensis, which showed more emergence from early to mid summer. Several winter annuals showed an emergence peak after stirring in late summer or early autumn. Variations saisonnières dans la levèe des mauvaises herbes annuelles-étude préliminaire en Suède     

Digitaria ciliaris seed banks in untilled and tilled soybean fields

We gained an understanding of the vertical distribution and seasonal dynamics of Digitaria ciliaris (Retz.) Koeler seed banks in untilled and tilled soybean fields using studies on naturally established seed banks and on seeds stored in the field. In untilled fields, D. ciliaris seeds were highly concentrated on or near the soil surface from late autumn to spring, whereas only a few seeds were found on the soil surface in the following summer. One year after tillage, there was a high concentration of the seeds on the soil surface. In the tilled fields, seeds were distributed uniformly throughout the soil profile and were present all year long, with only a few seeds found in the following summer. A study of seeds that were artificially buried or stored on the soil surface verified that D. ciliaris seeds were extremely short-lived in the field and could not form a large, persistent seed bank, even when the seeds were buried by tillage. Tillage contributes to suppression of D. ciliaris seedling emergence by reducing the number of seeds that are on or near the soil surface. Furthermore, D. ciliaris seeds showed a greater need for light in order to germinate throughout the year, even when they were stored on the soil surface. Particularly, light was critical for germination during summer. The light requirement for germination should be one reason why viable D. ciliaris seeds on the soil surface are carried over into the next season in untilled fields.     

Weed suppression by soil steaming in combination with activating compounds

The aim of this study was to determine the weed suppression potential of soil steaming plus activating compounds (KOH or CaO) to boost soil temperature. Different combinations between the compounds and rates were tested in experiments carried out in the field and in a controlled environment. Treatment effects were assessed on field weed vegetation and on seedbank and seedling emergence of three winter ( Alopecurus myosuroides , Matricaria chamomilla and Raphanus raphanistrum ) and four spring annuals ( Amaranthus retroflexus , Echinochloa crus-galli , Fallopia convolvulus and Setaria viridis ), were assessed on field weed vegetation. Neither maximum soil temperature (from 72 to 85°C) nor duration of high temperature in the 3 h following application consistently affected weed suppression. In the field, no significant effects on total weed density were recorded, but there were some significant effects on individual species. The weed seedbank was clearly suppressed by activated steaming: total seedling emergence was inversely related to increasing KOH rates both in the 0–10 and 10–20 cm soil layers, while for CaO the relationship was significant only in the 0–10 cm layer. Winter annuals were more sensitive to KOH than CaO and spring annuals had a more pronounced species-specific response to treatments. There was a strong negative relationship between compound rate and seedling emergence for all species. Alopecurus myosuroides was the most sensitive to the steam-alone treatment (77% reduction), whereas M. chamomilla and E. crus-galli were the least sensitive. Results from this study indicate that the type and rates of activating compounds for soil steaming must be adjusted to the weed community composition.     

Interannual variation in weed biomass on arable land in Sweden

Data were analysed on weed biomass from untreated plots in 2672 field experiments conducted in spring- and autumn-sown cereal and oilseed crops in Sweden 1972–1992. The coefficient of variation (CV) among years in the biomass of annual weeds per square metre was 29% in autumn-sown crops. In spring-sown crops, which had less weed biomass, the corresponding value was 49%. The biomass of summer annuals varied most (105%). Low winter temperatures seemed to increase the biomass of weeds in autumn-sown crops. In spring-sown crops, weed biomass production was higher in years with high rainfall during late spring. Partial ordination (pCCA) of weed data indicated that the interannual variations in autumn-sown crops were mainly manifested by the occurrence of summer annuals. Results from similar ordination of data from spring-sown crops were partly explained by the occurrence of winter annuals.     

Exploration of unconventional fodder for arid land rehabilitation

Exploring new wild plant species of economic importance with tolerance to harsh environmental conditions in arid countries may be a viable option to improve forage yield. The present study was conducted during two consecutive years and aimed to investigate the nutritional values of eleven selected wild fodder species, six annuals, and five perennials. Detailed analyses of the nutritional values during two different seasons for perennials and two different growth stages for annuals are presented. The results showed that most studied plants have high nutritional values compared to earlier studies on taxonomically related species growing in different arid areas. The mean content of dry matter, ash, crude protein and lipids was 27, 13, 14, and 3.5%, respectively. Neutral detergent fiber, acid detergent fiber, lignin, cellulose and hemicellulose were 44, 26.5, 6.2, 20.2, and 13.7%, respectively. The studied species showed means of 43 and 49% for in vitro dry matter disappearance (IVDMD) for perennials and annuals, respectively. In general, there were slight differences between the 2 years for both perennials and annual species and significant differences among different seasons for perennials and between growth stages for annuals. The study strongly recommends further detailed experimental studies on A. graecizans, Boerhavia diffusa and Cymbopogon schoenanthus, which showed more crude protein, a low fiber content and high IVDMD, as unconventional forage crops in arid lands.     

山西省二点委夜蛾发生规律

二点委夜蛾[Athetis lepigone(Mschler)]是中国黄淮海夏玉米区一种新的重要苗期害虫,为摸清二点委夜蛾在山西省的发生规律及动态,在山西设置了4个试验点,通过田间定点调查与随机普查、性诱和灯诱等方法对二点委夜蛾的越冬、发生世代和分布等进行了研究。结果表明:二点委夜蛾可在本地越冬;在山西南部冬小麦-夏玉米复播区1年发生4代,越冬代成虫在4月中下旬至5月上旬羽化出土,第1代成虫高峰出现在6月中下旬,第2代成虫高峰出现在7月下旬,第3代成虫高峰出现在9月中旬;根据调查和诱虫结果,绘制了二点委夜蛾在山西临汾的年生活史;二点委夜蛾的分布范围不仅在山西南部夏玉米区,在山西中北部忻州市的春玉米区也有发生,但种群数量很少,不造成危害。     

Plant growth regulators

Abstract

A preliminary survey of weeds of cocoa, kola, coffee and cashew was made to identify problem weeds in order to understand their distribution and later formulate appropriate methods for their control. The survey was conducted in experimental plots, plantations and small farms. Whereas certain weeds are common to all the four tree crops, some appear to be associated with a particular crop. Many of the weeds are annuals which complete two or more life cycles a year and have a tremendous capacity for seed production. Others are short-lived perennials and perennials which are very difficult to control or eradicate. Rapid and vigorous growth of early-season weeds starts annually with rains in February or March and their mode of regeneration varies in the different species. Tree crops planted under clear-felled conditions are subjected to serious weed competition and frequent weeding is necessary to ensure the successful establishment of young seedlings.     

Plant community dynamics in arid lands: the role of desert ants

Ants (Formicidae, Hymenoptera) play an important role in seed bank, seedling establishment andplant composition of arid ecosystems. Thus, knowing plant-ant interaction provides useful information formanagers to design restoration and conservation plans. In this study, the roles of desert harvester ants (Messorintermedius and Messor melancholicus) and scavenger ants (Cataglyphis nodus and Lepisiota semenovi) on plantcommunities were investigated in arid ecosystems of southeastern Iran. Two vegetation types weredistinguished in the study area and the nest density of ant species was determined. Furthermore, plantcomposition and soil seed bank were estimated at different distances from the ant nests. Results showed thatthe density of M. intermedius and M. melancholicus nests was higher in dwarf shrub-shrub vegetation type and thedensity of C. nodus and L. semenovi nests was higher in dwarf shrub vegetation type. The harvester and scavengerants had enhanced the seed bank to 55% and 70%, respectively. Therefore, the role of scavenger ants on theplant communities' seed bank was greater than that of harvester ants. Although the scavenger ants were moreinfluential on the annuals and the invasive plant species, the radius impact of the harvester ants on theperennials was greater, i.e., a positive interaction existed between the perennial plants and the harvester ants. C.nodus and L. semenovi played an important role in enhancing the ecosystem's potential for restoration throughestablishment of pioneer species in early stage of succession. The activity of M. intermedius is crucial for thedevelopment and maintenance of climax plant communities in arid ecosystems through assisting the plantspecies' establishment in late stage of succession. It is essential to preserve the diversity of these key ant speciesfor the maintenance and sustainability of shrubs in arid ecosystems.     

北京地区褐足角胸肖叶甲发生规律的初步研究

通过普查、系统调查、室内饲养和田间笼罩观察等方法,对褐足角胸肖叶甲在北京地区的发生为害规律开展了研究。结果表明,褐足角胸肖叶甲在全市均有分布,北部山区的虫口密度显著低于南部潮土区。在春夏玉米交错分布区,未发现褐足角胸肖叶甲取食春玉米。北京地区有红棕型和铜绿鞘型2种色型,其中红棕型占93.32%,为绝对优势色型。普查中发现该虫可取食多种植物,其中马齿苋、野艾蒿、茵陈蒿等3种杂草是寄主植物新记录。系统调查表明,北京1年仅见1代成虫,7中下旬是该虫在北京为害的关键期。调查分析显示北京地区褐足角胸肖叶甲在夏玉米田符合聚集分布特征。行为观察发现褐足角胸肖叶甲为害玉米时,喜欢从正面啃食。室内饲养和田间笼罩观察发现成虫平均寿命约为20d。通过调查,首次证实在北京地区,褐足角胸肖叶甲以幼虫在玉米根部5~10cm土层中越冬。本研究初步明确了褐足角胸肖叶甲在北京地区的发生规律,可促进相关预测预报技术的提升,为综合防控提供决策依据。     

Factors affecting the distribution and associated species of Malva parviflora in the Nile Delta,Egypt

Malva parviflora (little mallow) is a wild herb with agricultural importance in Egypt, where it is cultivated as a food crop. The main objective of the present work was to study the distribution and common associated species of the arable weed, M. parviflora, in the Nile Delta, Egypt. In addition, the diversity and behavior of the common species along the prevailing environmental conditions were assessed. Fifty stands, representing five common habitats (crop fields, orchards, canals, drains and roadsides), were selected. Eighty‐five species and one variety (50 annuals and 36 perennials) were recorded. Therophytes dominated the other life forms and biregional taxa contributed the highest chorological elements. Malva parviflora is a therophytic plant that has a Mediterranean distribution intermingled with Irano‐Turanian elements. Moreover, the highest coverage percentage of M. parviflora was recorded in the canal banks. Four vegetation groups that represented the distinct habitats were produced by the application of a two‐way indicator species analysis and a detrended correspondence analysis as a classification and ordination technique, respectively. Vegetation group C, which inhabited the crop fields, was the most diverse. A canonical correspondence analysis indicated that calcium carbonate, organic carbon, carbonate, potassium and the potassium adsorption ratio and electrical conductivity are the most effective soil variables on the distribution of M. parviflora and its associated species in the different habitats. It was found that M. parviflora was affected greatly by calcium carbonate, sand and magnesium. In addition, it was significantly associated with soil bicarbonate. Such a study could help in managing this important agricultural weed.     

Effects of summer fallow management on take-all of winter wheat caused by <Emphasis Type="Italic">Gaeumannomyces graminis</Emphasis> var. <Emphasis Type="Italic">tritici</Emphasis>

Crop rotation is the oldest, and perhaps the best cultural practice for reducing the risk of take-all. The effects of crops sown before wheat in a rotation are known in detail, but we know little about the opportunities for reducing take-all risk by planting certain crops in the summer period between wheat harvest and the planting of a subsequent winter wheat crop. We investigated the effects on take-all of five summer fallow crops, two soil tillage treatments and a fungicide seed treatment, in a five site-year experiment. We tested the effects of oats, oilseed rape, mustard, ryegrass and volunteer wheat crops. Bare-soil plots were also included. Take-all epidemics varied with year and site. Summer fallow crops had a greater effect on tilled plots. The incidence and severity of take-all were significantly higher in the wheat volunteer plots, whereas maintaining bare soil provided the lowest level of disease. Oilseed rape had no significant effect on take-all incidence in our experiment. The best candidates for reducing take-all risk appeared to be oats, mustard and ryegrass. These summer fallow crops decreased disease levels only when associated with conventional tillage. Summer fallow crops did not alter take-all decline in the same way as a break crop after a wheat monoculture.     

Seasonal differences in climatic controls of vegetation growth in the Beijing-Tianjin Sand Source Region of China

Launched in 2002, the Beiing-Tianjin Sand Source Control Project (BTSSCP) is an ecological restoration project intended to prevent desertification in China. Evidence from multiple sources has confirmed increases in vegetation growth in the BTSSCP region since the initiation of this project. Precipitation and essential climate variable-soil moisture (ECV-SM) conditions are typically considered to be the main drivers of vegetation growth in this region. Although many studies have investigated the inter-annual variations of vegetation growth, few concerns have been focused on the annual and seasonal variations of vegetation growth and their climatic drivers, which are crucial for understanding the relationships among the climate, vegetation, and human activities at the regional scale. Based on the normalized difference vegetation index (NDVI) derived from MODIS and the corresponding climatic data, we explored the responses of vegetation growth to climatic factors at annual and seasonal scales in the BTSSCP region during the period 2000-2014. Over the study region as a whole, NDVI generally increased from 2000 to 2014, at a rate of 0.002/a. Vegetation growth is stimulated mainly by the elevated temperature in spring, whereas precipitation is the leading driver of summer greening. In autumn, positive effects of both temperature and precipitation on vegetation growth were observed. The warming in spring promotes vegetation growth but reduces ECV-SM. Summer greening has a strong cooling effect on land surface temperature. These results indicate that the ecological and environmental consequences of ecological restoration projects should be comprehensively evaluated.     

新疆麦棉间作布局及麦棉比例与棉田捕食性天敌发生的关系

2008年在新疆莎车县分别比较研究了棉田与麦田间作不同条件下棉田几种主要捕食性天敌发生数量和益害比情况。结果表明：在麦收后前期（6月17日）,麦 棉、麦 棉 麦、麦 棉 麦 棉3种布局方式棉田和3种麦棉比例棉田的增益作用要强于全棉棉田,控害效果明显。3种布局方式棉田和3种麦棉比例棉田与全棉棉田的天敌总数、瓢虫类天敌数量和两种益害比差异显著;3种麦棉布局棉田天敌总数分别高出全棉棉田104%、109.4%和113.8%;瓢虫类天敌数量分别高出全棉棉田137.4%、135.3%和173.4%。麦棉布局棉田中,麦 棉 麦 棉镶嵌式布局增益效果最好。麦棉比例1∶5以上、1∶1~1∶5及1∶1以下棉田的天敌总数分别高出全棉棉田79.1%、128.4%和121.2%;瓢虫类天敌数量分别高出全棉棉田108.7%、165.7%和176.2%;3种麦棉比棉田中,1∶1~1∶5的麦棉比例的增益效果最好。麦收后期（7月16日）,麦田增益效果减弱,各类棉田天敌害虫发生趋于一致,差异不显著。     

Infection prevalence,seasonality and host specificity of actinosporean types (Myxozoa) in an Atlantic salmon fish farm located in Northern Scotland

A total of 28,387 oligochaetes belonging to the families Tubificidae, Lumbriculidae, Naididae and Enchytraeidae were examined at regular intervals for actinosporean infections from October 1996 to August 1998 from a freshwater salmon farm in Northern Scotland. A total of 21 types of actinosporeans belonging to seven collective groups synactinomyxon (three types), aurantiactinomyxon (four types), echinactinomyxon (five types), raabeia (six types), triactinomyxon (one type), neoactinomyxum (one type) and siedleckiella (one type) were found. Synactinomyxon type 1, echinactinomyxon type 1 and raabeia type 4 were most abundant. The overall infection prevalence of oligochaetes was 2.9%. Aurantiactinomyxon, synactinomyxon and neoactinomyxum were most common in summer and autumn. Raabeia was most common in spring and summer and echinactinomyxon in winter and spring. Siedleckiella was found only in spring and triactinomyxon in all seasons except winter. A positive relationship between water temperature and the number of actinosporean types released was observed. Most actinosporean types were found in only one host species.     

半干旱区夏闲期不同耕作方式对土壤水分及小麦水分利用效率的影响

在宁南旱平地进行了夏闲期深松、免耕及传统翻耕(对照)对土壤水分及后作冬小麦水分利用效率影响的研究结果表明,夏闲期深松和传统翻耕能有效地蓄雨保墒,提高旱平地冬小麦播前的土壤贮水量,深松和翻耕土壤蓄墒率极显著高于免耕处理,深松处理较翻耕高0.79%;夏闲期末深松处理0～200 cm土壤贮水量(310.78 mm)分别较免耕、传统翻耕高8.23 mm、1.61 mm.深松和免耕较传统翻耕显著改善了冬小麦苗期的土壤水分状况,对越冬期0～60 cm耕层土壤水分状况的改善有利于冬小麦的越冬.苗期0～200 cm土壤贮水量深松、免耕分别较传统翻耕(351.05 mm)高35.9 mm、28.8mm,不同的耕作处理对后作冬小麦苗期的土壤水分影响差异主要在80 cm以上土层.冬小麦返青期降雨主要使0～80 cm土层土壤贮水量有所增加,处理间的差异减小.夏闲期深松处理能有效地增加对降雨的蓄保能力,提高旱地冬小麦播前及整个生长阶段0～200 cm的土壤贮水量.不同耕作方式的冬小麦产量以夏闲期翻耕处理最高(3 475.9 kg/hm2),与深松处理(3 322.0 kg/hm2)无显著差异,免耕显著低于其它2种耕作处理;水分利用效率以翻耕最高[14.12 kg/(hm2·mm)],深松次之[13.62 kg/(hm2·mm)],免耕处理显著低于前二者[10.64 kg/(hm2·mm)].     

Suppression of weeds and weed seeds in the soil by stubbles and no-tillage in an arid maize-winter wheat-common vetch rotation on the Loess Plateau of China

Reduced tillage provides ecological and economic benefits to arable land on the Loess Plateau of China, where soil erosion has long been a serious problem and soil water availability is largely restricted. However, high abundances of weeds in reduced tillage systems cause significant yield losses. In this study, we explored the effects of no-tillage and stubble retention on the number and density of weeds and weed seeds in a 12-year maize-winter wheat-common vetch rotation on the Loess Plateau. Four treatments including conventional tillage, no-tillage, conventional tillage+stubble retention and no-tillage+stubble retention were designed and applied. We found that no-tillage increased the number of weed species and weed density in most of the crops, while stubble retention decreased weed density in maize and tended to suppress weeds in both no-tillage treatments(no-tillage and no-tillage+stubble retention). No-tillage led to an increase in the number of weed species in the weed seedbank and tended to increase seed density during the spring growth of winter wheat, but it decreased seed density during post-vetch fallow. Stubble retention tended to reduce seed density during the spring growth of winter wheat and post-vetch fallow. We concluded that no-tillage can promote weeds in the experimental crop rotation, while stubble retention suppresses weeds in untilled fields. The combined effects of stubble retention and no-tillage on weed suppression varied among the three crops. Based on these results, we recommend stubble retention in untilled legume-crop rotations on the Loess Plateau to improve the control of weeds.