Correlation between the soil seed bank and weed populations in maize fields

Annual weed populations establish every year from persistent seed banks in the soil. This 3 year study investigated the relationship between the number of weed seeds in the soil seed bank and the resultant populations of major broadleaf and grass weeds in 30 maize fields. After planting the crop, 1 m² areas were protected from the pre-emergence herbicide application. Soil samples were collected soon after spraying to a depth of 100 mm and the weed seeds therein were enumerated. The emerged weed seedlings in the field sampling areas were counted over the following 8 weeks. Up to 67 broadleaf species and five grass weeds were identified, although not all were found at every site and some were specific to a region or soil type. For the most abundant weeds in the field plots, on average 2.1–8.2% of the seeds of the broadleaf species and 6.2–11.9% of the seeds of the grass weeds in the soil seed bank emerged in any one year, depending on the species. Overall, the results showed a strong linear relationship between the seed numbers in the soil and the seedling numbers in the field for all the grasses and for most broadleaf weeds. For some species, like Trifolium repens , only a weak relationship was observed. In the case of Chenopodium album , which had the largest seed bank, there was evidence of asymptotic behavior, with seedling emergence leveling off at high seed numbers. An estimate of the soil seed bank combined with knowledge of the germination and behavior of specific weed species would thus have good potential for predicting future weed infestations in maize fields.     

Effects of rye cover crop residue and herbicides on weed control in narrow and wide row soybean planting systems

Α three‐year, non‐irrigated field study was conducted in 1998, 1999, and 2000 at the Southern Weed Science Research Unit farm, Stoneville, MS to study the effects of rye cover crop residue, soybean planting systems, and herbicide application programs on the control, density and biomass of several weed species and soybean yield. The soybean planting systems comprised 19 cm rows with high plant density, 57 cm rows with medium plant density, and 95 cm rows with low plant density. The herbicide programs evaluated were pre‐emergence, postemergence, pre‐emergence followed by postemergence, and no herbicide. Flumetsulam and metolachlor were applied pre‐emergence, and acifluorfen, bentazon, and clethodim were applied postemergence. The presence or absence of rye cover crop residue and a soybean planting system did not affect weed control of the species evaluated (browntop millet, barnyard grass, broadleaf signal grass, pitted morningglory, yellow nutsedge, Palmer amaranth and hyssop spurge), when herbicides were applied, regardless of the application program. In addition, rye cover crop residue was not an effective weed management tool when no herbicide was applied, because density and biomass of most weeds evaluated were higher than a no cover crop residue system. Among soybean planting systems, narrow with high plant density soybeans reduced density of grasses, broadleaf weeds and yellow nutsedge by 24–83% and total weed biomass by 38%, compared to wide with low plant density soybeans. Although weed pressure was reduced by narrow with high plant density soybeans, herbicide applications had the most impact on weed control, weed density and biomass. All herbicide programs controlled all weed species 81–100% at two weeks after postemergence herbicide applications, in comparison to no‐herbicide. Density of grasses and all broadleaf weeds as well as total weed biomass was lower with the pre‐emergence followed by postemergence program than these programs alone. Soybean yields were higher in the pre‐emergence followed by postemergence, and postemergence only programs than the pre‐emergence alone program. Planting crops in narrow rows is one cultural method of reducing weed pressure. However, even with the use of this cultural practice, prevalent weed pressure often requires management with herbicides.     

几种除草剂组合对蒜田杂草的防除效果

为明确不同除草剂对蒜田杂草防除效果和对大蒜的安全性影响,进行了禾本科杂草与阔叶杂草混生的常规草相蒜田和阔叶杂草占据优势种群的蒜田除草剂防效试验,结果表明：对于常规草相蒜田,以综合防治禾本科杂草和阔叶杂草为目的,可以选择7％草酮·16％乙草胺·12％乙氧氟草醚复配剂或30％二甲戊乐灵·10％乙草胺·4％乙氧氟草醚复配剂;对于以荠菜为优势杂草种群的蒜田,可选择24％乙氧氟草醚;对于以猪殃殃及其他阔叶杂草为优势种群的蒜田,可选择12％草酮。     

不同稻田综合种养模式下杂草长期控制效果的调查

为明确稻田综合种养模式是否可以长期有效控制杂草危害,通过对江苏省48个样点共6种综合种养模式(稻鸭、稻蟹、稻虾、稻鱼、稻鳖和稻鳅/鳝共作)农田的杂草群落和土壤种子库进行调查,比较分析杂草群落综合草情优势度、物种多样性以及杂草群落和土壤种子库的组成和变化。结果表明,在综合种养模式实施1~3年,杂草群落综合草情优势度和土壤种子库密度均明显下降,其中稻鸭共作模式下两者均下降最多,其次是稻虾共作模式下杂草群落综合草情优势度下降较多,而稻鱼共作模式下土壤种子库密度下降较多。实施4~5年,各种养模式下杂草群落综合草情优势度和土壤种子库密度均上升,草害加剧,杂草防控效果下降;其中稻鳅/鳝共作模式下杂草群落综合草情优势度和土壤种子库密度与常规稻田相比升幅最大,分别上升28.8%和25.3%;由于稻鳖、稻鳅/鳝共作模式实施均未超过5年,在实施4~5年时整体上杂草危害最为严重,禾本科杂草、阔叶杂草以及莎草科杂草的综合草情优势度较常规稻田分别上升42.4%、12.3%、0.7%和31.5%、27.7%、38.1%。实施5年以上,稻鸭共作模式下阔叶杂草的综合草情优势度较常规稻田下降65.0%,但禾本科杂草的综合草情优势度和土壤种子库密度较常规稻田分别上升80.5%和66.6%,成为杂草群落和土壤种子库的优势种群;稻虾共作模式下莎草科杂草和阔叶杂草的综合草情优势度较常规稻田分别上升17.8%和45.0%;稻蟹共作模式下莎草科杂草、阔叶杂草和禾本科杂草的综合草情优势度较常规稻田分别上升22.7%、35.3%和29.0%。表明当长期实施同种稻田综合种养模式时,杂草群落在单一的选择压力下会加快演替,杂草危害均呈先降后升的变化趋势,不利于田间杂草的长效防控,建议实施针对耗竭土壤种子库的综合技术措施。     

小麦田不同杂草群落及防除时间对小麦产量的影响

为明确小麦田不同杂草群落及防除时间对小麦产量的影响,于2013—2015连续两年在山东省聊城市高唐县小麦田中设无草对照区、禾本科杂草区、阔叶杂草区以及混合杂草自然发生区4种不同杂草群落以及不同的杂草防除时间,测定在不同条件下小麦产量及各项产量构成指标的情况。结果表明,阔叶杂草对小麦产量的影响大于禾本科杂草,冬小麦田杂草的最佳防除时间为4月1日之前,在此期间除草对小麦产量影响均不大,但之后防除或不除草会造成小麦严重减产甚至绝产,2014年4月15日除草可造成在阔叶杂草区和杂草混合生长区的小麦减产30.5%和32.6%,不除草可造成在禾本科杂草区、阔叶杂草区和杂草混生区的小麦减产8.6%、91.4%和94.3%,2015年趋势和2014年一致。从构成小麦产量的3个指标来看,杂草危害主要影响小麦的总穗数,其次为穗粒数,对千粒重影响最小。     

Response of leaf acetolactate synthase from different leaf positions and seedling ages to sulfonylurea herbicide

Responses of acetolactate synthase (ALS) from grass and broadleaf weed to sulfonylurea (SU) herbicide were compared in relation to the leaf position in a seedling and seedling age. The responses of Echinochloa crus-galli (L.) P. Beauv. and Eclipta prostrata L., dominant grass and broadleaf weed in paddy fields in Korea, respectively, to azimsulfuron were examined. In this study, in vivo ALS assay was used to verify the responsibility of selected weed species at different leaf stages to SU-herbicides. The data from in vivo ALS assay could be used for discriminating the degree of tolerance between weeds showed different susceptibility. In E. crus-galli and E. prostrata there was no apparent relationship between the chlorophyll concentrations and herbicide concentrations treated on leaves. Both in E. crus-galli and E. prostrata, the free amino acid concentrations, however, were increased as herbicide concentration increased in the younger leaves. The free amino acid concentrations were generally higher in older leaves than young leaves and were significantly increased concomitantly with increasing herbicide concentration. The ALS activity was decreased rapidly with higher azimsulfuron rates in old but not senescent leaves compared to juvenile leaves. Generally, ALS activity was less sensitive at the early leaf stage than late leaf stage. The activity of ALS in E. prostrata was highly responsive to application time and more susceptible to the herbicide as compared to E. crus-galli. The highest levels of acetoin were observed in the uppermost and youngest leaf in all species tested.     

春播紫花苜蓿生长期（刈割后）的杂草防除研究

选用7种不同的除草处理,探究不同茬次刈割后的单、混用除草技术对紫花苜蓿的安全性、产量及杂草防除效果的影响.结果表明：一茬刈割后施药,杂草鲜重防效最好的是烯草酮＋2,4-DB,最差的是2,4-DB;禾草鲜防最好的是烯草酮,其次分别是精稳杀得和精喹禾灵,效果一般;喷施精稳杀得＋2,4-DB和精稳杀得＋苯达松可显著提高二茬的产量.然而,二茬刈割后施药,杂草鲜重防效最好的却是精稳杀得＋苯达松;喷施烯草酮、精稳杀得和精喹禾灵防除禾草的效果非常好,防效在86.18％ ～ 100.00％.喷施2,4-DB的单、混用处理三茬产量显著减少.此外,喷施2,4-DB和苯达松的单、混用处理对阔叶草的鲜重防效和株防效都超过66.70％.     

Precision farming for weed management: techniques

Site-specific weed control techniques have gained interest in the precision farming community over the last years. Managing weeds on a subfield level requires measuring the varying density of weeds within a field. Decision models aid in the selection and adjustment of the treatments, depending on the weed infestation. The weed control can be done either with herbicides or mechanically. A site-specific herbicide application technology can save large amounts of herbicides. Mechanical weed control techniques adapting to the weed situation in the field are applicable to a wide spectrum of crops. Site-specific techniques for the detection and management of weeds are presented. A system for the discrimination of different weed species and crops from images is described, which generates weed maps automatically. Models for the yield effect of weeds are developed and applied in on-farm-research experimental setups. Economic weed thresholds are derived and used for a herbicide application with a patch sprayer.     

Real-time weed detection, decision making and patch spraying in maize, sugarbeet, winter wheat and winter barley

Information on temporal and spatial variation in weed seedling populations within agricultural fields is very important for weed population assessment and management. Most of all, it allows a potential reduction in herbicide use, when post‐emergence herbicides are only applied to field sections with weed infestation levels higher than the economic weed threshold; a review of such work is provided. This paper presents a system for site‐specific weed control in sugarbeet (Beta vulgaris L.), maize (Zea mays L.), winter wheat (Triticum aestivum L.) and winter barley (Hordeum vulgare L.), including online weed detection using digital image analysis, computer‐based decision making and global positioning systems (GPS)‐controlled patch spraying. In a 4‐year study, herbicide use with this map‐based approach was reduced in winter cereals by 60% for herbicides against broad‐leaved weeds and 90% for grass weed herbicides. In sugarbeet and maize, average savings for grass weed herbicides were 78% in maize and 36% in sugarbeet. For herbicides against broad‐leaved weeds, 11% were saved in maize and 41% in sugarbeet.     

山东省泰安市甘薯田杂草调查

山东省泰安市甘薯田杂草隶属12科35种,以禾本科杂草与阔叶杂草混生为主,常见一年生禾本科杂草以牛筋草、马唐、狗尾草为主,阔叶杂草以反枝苋、马齿苋、铁苋菜、饭包草为主,莎草科杂草以碎米莎草、异型莎草及香附子为主。甘薯扦插后生长前期主要以阔叶杂草反枝苋、藜、马齿苋、苘麻、碎米莎草占优势,甘薯生长后期(6～7月),以一年生禾本科杂草牛筋草、马唐、稗草及狗尾草为主。甘薯田杂草的防除重点是扦插后至封垄前,此阶段及时有效的除草对甘薯的优质高产至关重要。     

稻田除草剂选择智能决策系统APP的构建与思考

当前我国水稻田登记的除草剂活性成分组合共204种, 包括55种单剂和149种复配剂?在总结各种稻田除草剂应用技术要素的基础上, 提出稻田除草剂选用中具有普遍性的6个关键问题, 包括:水稻栽培方式?稻田除草剂施用时期?施用方法?稻田主要禾本科杂草种类?稻田非禾本科主要杂草类型?田间杂草生育期; 基于各种除草剂品种对应上述6个问题上的应用特点, 开发了“稻田除草剂选用参考系统”, 该手机软件共1.8 MB, 可以在安卓手机上安装使用?该软件可以根据用户在上述6个问题上的选项组合, 直接获得适用除草剂品种清单; 也可以根据用户输入除草剂名称所含字词, 检索相关的除草剂品种清单?此外, 软件中列出了每种除草剂的使用技术要点?     

Prevalence of herbicide‐resistant weed species in Malaysian rice fields: A review

The management of weeds in Malaysian rice fields is very much herbicide‐based. The heavy reliance on herbicide for weed control by many rice‐growers arguably eventually has led to the development and evolution of herbicide‐resistant biotypes in Malaysian rice fields over the years. The continuous use of synthetic auxin (phenoxy group) herbicides and acetohydroxyacid synthase‐inhibiting herbicides to control rice weeds was consequential in leading to the emergence and prevalence of resistant weed biotypes. This review discusses the history and confirmed cases and incidence of herbicide‐resistant weeds in Malaysian rice fields. It also reviews the Clearfield Production System and its impact on the evolution of herbicide resistance among rice weed species and biotypes. This review also emphasizes the strategies and management options for herbicide‐resistant rice field weeds within the framework of herbicide‐based integrated weed management. These include the use of optimum tillage practices, certified clean seeds, increased crop competition through high seeding rates, crop rotation, the application of multiple modes of action of herbicides in annual rotations, tank mixtures and sequential applications to enable a broad spectrum of weed control, increase the selective control of noxious weed species in a field and help to delay the resistance evolution by reducing the selection pressure that is forced on those weed populations by a specific herbicidal mode of action.     

Photosynthetic and growth responses of zea mays L and four weed species following post-emergence treatments with mesotrione and atrazinet

We compared photosynthesis and growth of Zea mays L (corn) and four weed species, Setaria viridis (L) Beauv (green foxtail), Echinochloa crus-galli (L) Beauv (barnyardgrass), Abutilon theophrasti Medic (velvetleaf), and Amaranthus retroflexus L (redroot pigweed), following foliar applications with atrazine, mesotrione, or a combination of atrazine and mesotrione in two greenhouse experiments. Plant responses to the three herbicide treatments were compared with responses of untreated plants (control). Photosynthesis on day 14 and dry mass of Z mays was not reduced by any of the herbicide treatments. Photosynthesis and dry mass of E crus-galli, A retroflexus and A theophrasti were significantly reduced by mesotrione and atrazine alone and in combination. Photosynthesis on day 14 and dry mass of large Sviridis plants were not suppressed by either herbicide applied alone. The mesotrione plus atrazine treatment was the most effective treatment for grass weed control because plants did not regain photosynthetic capacity and had significantly lower dry mass. Shoot dry mass of broadleaf weeds was significantly reduced by all three herbicide treatments, except for A retroflexus treated with mesotrione alone.     

发展化学除草重视综合治理

我国农田杂草有２５０多种，全国农田受草害面积４３００多万ｈｍ２，平均受草害减产１３．４％，每年减产粮食１７５０万ｔ，皮棉２５．５万ｔ和大豆５０万ｔ。传统农业生产采用机械作业及人力等除草。随着农村经济的发展，化学除草面积迅速扩大，全国农田化学除草面积从１９７５年的１７０万ｈｍ２增加到１９９５年的４１３３万ｈｍ２。但是，长期化学除草也带来了除草剂土壤残留对后茬作物药害、农田杂草种群更替和产生抗药性等新问题。必须重视农田杂草综合治理，通过采用各种有效的农业技术措施，为农作物保持良好的生态条件，结合化学除草才是最有效的防除杂草方法     

3种除草剂对水稻旱直播阔叶杂草防效及安全性研究

为明确不同除草剂茎叶处理对旱直播水稻田旱生阔叶杂草防除及安全性的影响,采用随机区组试验设计,选用30% 2,4-滴丁酸钠盐AS、84%氯酯磺草胺WG、480 g/L灭草松AS 3种除草剂在水稻4叶期、5叶期施用,施药后每间隔7 d测定杂草株防效、鲜重防效和水稻目测药害,同步测定水稻生长指标和抗逆酶活性。结果表明:30% 2,4-滴丁酸钠盐AS 900.0 g/hm2在水稻4叶期的杂草防效最佳,第28天杂草株防效及鲜重防效仍可达93.55%和96.42%,且对大龄鸭跖草防效显著,施药后水稻生长与人工除草相比无显著差异。叶片SOD、POD活性和MDA含量均先升后降,至施药后28 d恢复正常。30% 2,4-滴丁酸钠盐AS 900.0 g/hm2可高效防除阔叶杂草,该药剂在水稻4叶期和5叶期施用对旱直播水稻安全。     

Practical experiences with a system for site-specific weed control in arable crops using real-time image analysis and GPS-controlled patch spraying

Information on temporal and spatial variation in weed seedling populations within agricultural fields is very important for weed population assessment and management. Primarily, spatial information allows a potential reduction in herbicide use, when post‐emergent herbicides are only applied to field sections with high weed infestation levels. This paper presents a system for site‐specific weed control in sugar beet, maize, winter wheat, winter barley, winter rape and spring barley. The system includes on‐line weed detection using digital image analysis, computer‐based decision making and Global Positioning System‐controlled patch spraying. In a 2‐year study, herbicide use with this map‐based approach was reduced in winter cereals by 6–81% for herbicides against broad leaved weeds and 20–79% for grass weed herbicides. Highest savings were achieved in cereals followed by sugar beet, maize and winter rape. The efficacy of weed control varied from 85% to 98%, indicating that site‐specific weed management will not result in higher infestation levels in the following crops.     

Development of lowland weed management and weed succession in Japan

Since the introduction of rice production in Japan, lowland areas have been managed for rice production with the purpose of better rice growth, as well as lesser weed infestation. Rice is cropped every year in lowland fields by repeated cultivation of a single crop, with high yields and without soil sickness usually being observed in upland fields. This is probably because the irrigation water supplies various nutrients for healthy rice growth and the drainage washes out and removes harmful factors. However, until recently, the wet or flooded conditions of lowland fields in the Asian monsoon region never have allowed humans to cultivate useful summer crops, except rice or some aquatic plants. Therefore, the management of lowland areas in the Asian monsoon region has been significantly different from European field management, where crop rotation has been the traditional standard practice. Paddy weeds are aquatic plants or hygrophytes that have adapted to lowland fields. Traditionally, tillage and puddling were practiced seasonally in lowland fields on a regular schedule every year. Rice cultivation technology was developed and supported by regional irrigation systems that created stable environments for typical paddy weeds to complete their life cycle. After the introduction of chemical weed control, rice fields became very severe habitats for these paddy weeds, where they could not grow and reproduce without strategies for survival under herbicide exposure. Even so, many of the traditional paddy weeds survived because of their accumulated or uneradicated seed banks, although several aquatic plants were listed as endangered or threatened species. The important weed species changed, sometimes rapidly and sometimes slowly, depending both on their reproductive system and their biological response towards field management and weed control systems. Very recently, the level of perennial weeds, herbicide‐resistant weeds, and weedy rice has increased in paddy fields that are highly dependent on herbicide use. In addition, several hygrophyte species have invaded paddy fields. In order to address these issues, the improvement and application of integrated weed management methods are expected to be critical.     

Using geographic information systems to map the prevalent weeds at an early stage of the cotton crop in relation to abiotic factors

Cotton is still one of the most important crops in Greece despite the changes in the country’s socioeconomic status which have reduced the total cultivated area. In order to minimize yield losses, weed control is essential during the cultivation period. The aim of this study was to determine the distribution of the prevalent weeds that escape the usual herbicide application in the main cotton zone, located in the Karditsa prefecture. The weed densities and the irrigation methods used were recorded in 101 sampling sites of 25 m²; the cotton crop had been grown for the last 5 years using similar weed control techniques. Existing soil maps of the area were also used, through which soil data (texture and carbonates content) were accessed. Among the 14 weed species that have been recorded, four were perennial (Cyperus rotundus, Convolvulus arvensis, Cynodon dactylon, Sorhum halepense) and were ranked as first, second, fourth and fifth, respectively, according to the mean density, indicating the inefficient herbicidal control. In the fields irrigated by sprinklers, the weeds occurred in greater populations than those that occurred in fields irrigated by drippers, at values of 4.64 and 3 weeds m^-2, respectively. In terms of the studied soil properties, the distribution of C. arvensis was significantly correlated with carbonate content and soil texture in the surface soil layer. The autocorrelation analysis showed that only perennial weeds are spatially correlated whereas the interpolated maps showed this spatial trend of weed appearance.     

A stochastic simulation model for evaluating the concept of patch spraying

The long-term economic benefits of `patch' spraying are likely to be related to the initial spatial distribution of the target weeds, the demographic characteristics of the species and the weed control and crop husbandry practices to which they are subjected. This paper describes a stochastic simulation model developed to investigate the interaction between weed seed dispersal and patch spraying. Simulated weed plant and seed populations are generated and compared with data from field observations. Lloyd's Patchiness index is used to quantify the patchiness of the weed density distribution, and the parameter k of the negative binomial distribution is used as a measure of distribution shape. A method of assessing the spatial scale of weed aggregation is proposed, in which spatial weed density information is transformed into the frequency domain, using a discrete two-dimensional Fourier transform. In this paper, we simulate `on/off' patch spraying (full or zero herbicide application rate). A quantitative analysis of the effects of sprayer resolution and weed seed dispersal range on the herbicide reduction and yield benefits from patch spraying is performed for three initial spatial seedbank distributions. The model is parameterized for the grass weed Alopecurus myosuroides Huds. Herbicide is applied in square areas (whose size is defined by the spatial resolution of the sprayer) in which mean weed density is greater than or equal to one plant m^–2. For a system conforming to this specification we show that for the control of A. myosuroides , it is unlikely that patch spraying would be profitable in the long term if the control area is larger than 6 m × 6 m. In some circumstances higher resolution may be required.     

Performance of pyrazosulfuron-ethyl in non-puddled transplanted rainy season rice and its residual effect on growth of the succeeding crop in rice-wheat cropping pattern

Abstract

A study was carried out in sandy clay loam textured soil of Mymensingh, Bangladesh to evaluate weed control efficiency of pre-emergence herbicide pyrazosulfuron-ethyl either alone or in sequential application with post-emergence herbicide in transplanted rainy season rice under non-puddled strip-tilled (NPST) field condition and also to examine the residual effect of those herbicides on germination and growth of the subsequently grown wheat crop. Five treatment combinations of pyrazosulfuron-ethyl were tested against one weedy check and one weed-free check. The study revealed that NPST rice field was mostly infested by grass and sedge weeds and herbicide treatments offered a wide range of control (above 50% to 95%) on all types of weeds. Application of pyrazosulfuron-ethyl followed by (fb) orthosulfamuron fb butachlor plus propanil provided the most effective and economic weed control over two years of the study. Moreover, micro-plot bioassay study claimed germination and growth of subsequently grown wheat were not adversely affected by herbicides that were applied in rice. Therefore, application of pyrazosulfuron-ethyl followed by post-emergence herbicide could be effective and economic to control weeds in NPST rice under rice-wheat system, but proper rate and time of application should strictly be followed.