稻作区灌溉水流传播的杂草种子与稻田土壤杂草种子库的关系

选择典型稻作区,对灌溉水流传播的杂草种子的种类和数量进行取样调查,并与田埂、灌溉水渠周围生境、下茬麦田的杂草群落及稻田土壤杂草种子库进行比较分析,以研究自然条件下灌溉水流传播的杂草种子与土壤杂草种子库及其他生境杂草群落间的相互关系。 有14科21种杂草种子随灌溉水流输入稻田,这些杂草种子主要隶属禾本科、报春花科、藜科、蓼科等。土壤杂草种子库中共检出19科41种杂草种子,含有所有其他生境中杂草的种子。灌溉水流传播的杂草种子与田埂上、灌溉水渠周围生境、下茬麦田杂草群落及稻田土壤种子库的杂草群落间相似性较高,Sorensen指数均在0.5以上。     

江苏中部轻型栽培稻田杂草群落特征及草害综合评价

 利用“七级目测法”结合定量分析和综合评价对江苏中部的扬州、泰州和南通3个地区6种不同栽培模式稻田的杂草群落进行了调查研究,以期揭示经多年轻型栽培的稻田杂草群落结构及杂草危害特点。在轻型栽培稻田中共发现杂草36种,隶属于18个科33个属。其中,杂草种类较多的科依次为禾本科、莎草科、菊科、玄参科、泽泻科、千屈菜科等。在3个地区皆表现出较高的优势度和发生频率的杂草有4种：稗、水苋菜、鳢肠和千金子,其发生频率都达到或接近100%。然而,地区间草害水平存在差异,扬州地区的杂草危害最重,泰州地区次之,南通地区相对最轻。不同的稻作模式皆对应着不同的优势杂草。机插秧模式中优势度值与发生频率皆较高的杂草为鸭舌草、水苋菜;麦套稻模式中,主要的优势杂草包括水苋菜、马唐、鸭舌草、半边莲等;抛秧稻田中为稗、鸭舌草、水苋菜等;水直播稻作模式下是稗、水苋菜、鸭舌草等;旱直播模式中为稗、水苋菜、千金子等。与传统的手工插秧相比,轻型栽培稻作模式下的杂草群落中,不仅物种丰富度高,而且优势度也高。6种稻作模式杂草危害程度由低到高的顺序为：传统手工插秧＜机插秧＜抛秧＜水直播＜旱直播＜麦套稻。     

云南红河流域热带作物园区杂草组成及群落特征分析

采用相对优势度、物种丰富度指数、Shannon-Wiener指数、Simpson指数、Pielou指数、群落相似性指数等生态学指标及聚类分析的方法,对4种作物地杂草进行分析。结果表明：该地区农田杂草共有116种,隶属于37个科,其中禾本科和菊科种数较多,分别占总数的21.55%和19.83%;鬼针草（Bidens pilosa）和牛筋草（Eleusine indica）在各作物园区普遍为害,为常年优势恶性杂草,应重点防控;各作物地杂草的多样性,橡胶地最高,其次为香蕉地,菠萝地和油梨地多样性较低;多样性指数的季相变化规律,4种作物地均表现为夏秋季高于冬春季;杂草群落相似性和聚类分析结果一致表明：菠萝蜜地与油梨地杂草群落相似度最高,其次为香蕉地与菠萝蜜地,再次为香蕉地与油梨地,橡胶地与其他3种作物地相似度均较低。     

湖北省油菜主产区杂草群落的数量分析

采用七级目测法定量调查了湖北省油菜主产区28个样点的杂草发生情况,应用主成分分析法对杂草群落进行了数量分析。结果表明,28个样点可以分为4个聚类群,即江汉平原鄂北旱茬油菜田、鄂东南旱茬油菜田、江汉平原稻茬油菜田和鄂东南稻茬油菜田。轮作制度与地理因素决定了湖北省油菜主产区杂草群落的分布。根据综合草害指数和发生频率明确了各聚类群相应的优势杂草,并就该地区油菜田杂草发生的特点提出了治理策略。     

Effect of herbicide application on weed flora under conservation agriculture in Zimbabwe

Increased challenges of weed control in the smallholder farming sector of southern Africa have often resulted in small yields. The objective of this study was to evaluate the effects of different weed control strategies on weed flora and composition under conservation agriculture (CA) systems in Zimbabwe. This study was conducted at three on-station trial sites namely Domboshawa Training Centre (DTC), University of Zimbabwe farm (UZ farm) and Henderson Research Station (HRS) in a maize–soybean rotation for four seasons from 2009–2010 to 2012–2013 seasons. Hand weeding was done whenever weeds were 10 cm tall or 10 cm in circumference for weeds with a stoloniferous growth habit. Weed identification was done up to the weed species level, and the Shannon–Weiner diversity and evenness index was used to determine the response of weed flora to herbicides. Results showed that there were more weeds in the early years which decreased gradually until the final season. Weed species diversity was not affected by herbicide application and the results indicated that weed species diversity was small in CA systems. Annual weed species constituted a greater proportion of species, and species richness decreased with the duration of the study. Richardia scabra L. and Galinsoga parviflora Cav. were the most common dominant weed species at all sites and in all seasons. Moreover, herbicide application had no effect on the evenness of weeds in the plots but site characteristics had a significant effect on the distribution of weed species (weed species evenness). The results presented in this study suggest that herbicide application facilitates a depletion of weed seed bank/number of weeds over time. Thus, herbicide application in CA has potential to reduce weed density, species richness and species diversity in the long term which may lead to more labour savings and larger yields.     

Evaluation of irrigation water requirements and crop yields with different irrigation schedules for paddy fields in ChiaNan irrigated area,Taiwan

Recent water shortages in reservoirs have caused such problems as insufficient water and fallow rice fields in Southern Taiwan; therefore, comparing irrigation water requirements and crop production of paddy fields using a technique that differs from the conventional flood irrigation method is important. Field experiments for the second paddy field with four irrigation schedules and two repeated treatments were conducted at the HsuehChia Experiment Station, ChiaNan Irrigation Association, Taiwan. Experimental results demonstrate that irrigation water requirements for the comparison method, and 7-, 10- and 15-day irrigation schedules were 1248, 993, 848, and 718 mm, respectively. Compared to the conventional method of flooding fields at a 7-day interval, the 10- and 15-day irrigation schedules reduced water requirements by 14.6 and 27.3 %, respectively; however, crop yields decreased by 7 and 15 %, respectively. Based on the results, it was recommended that the ChaiNan Irrigation Association could adopt 10 days irrigation schedule and plant drought-enduring paddy to save irrigation water requirements for the water resource scarcity in southern Taiwan. The CROPWAT model was utilized to simulate the on-farm water balance with a 10-day irrigation schedule for the second paddy field. A comparison of net irrigation water requirements with the 10-day irrigation schedule from model and field experiment were 818 and 848 mm, respectively, and the error was 3.54 %.     

绿肥对咖啡园杂草多样性及功能群的影响

为揭示绿肥对咖啡园杂草多样性及功能群的影响,调查了云南省保山市常规种植咖啡园（CK）、种植绿肥田菁咖啡园（SC）、种植绿肥硬皮豆咖啡园（MU）的杂草群落,探讨种植绿肥对咖啡园杂草群落的生态位、多样性、群落结构相似性及功能群的影响。结果表明：CK有杂草12科21种,SC有杂草10科16种,MU有杂草7科10种。3种类型咖啡园杂草生态位宽度大于0.600的杂草有10种,其中,CK有6种,SC有2种,MU有3种。种植绿肥的咖啡园杂草的物种丰富度、个体数、ACE估计值、Fisher α指数、Shannon-Wiene指数及生物量均低于常规种植咖啡园（CK）,其中,杂草物种丰富度、ACE估计值和鲜重具有显著性差异。常规种植咖啡园与种植绿肥咖啡园杂草群落结构不相似。3种类型咖啡园杂草单子叶一年生或越年生植物功能群占据最大优势,但种植绿肥咖啡园的占比更高。种植绿肥改变了咖啡园杂草群落的生态位、群落结构及功能群,降低了咖啡园杂草群落多样性,对咖啡园杂草群落产生了影响。     

Yield loss prediction models based on early estimation of weed pressure

Weed control thresholds have been used to reduce costs and avoid unacceptable yield loss. Estimation of weed infestation has often been based on counts of weed plants per unit area or measurement of their relative leaf area index. Various linear, hyperbolic, and sigmoidal regression models have been proposed to predict yield loss, relative to yield in weed free environment from early measurements of weed infestation. The models are integrated in some weed management advisory systems. Generally, the recommendations from the advisory systems are applied to the whole field, but weed control thresholds are more relevant for site-specific weed management, because weeds are unevenly distributed in fields. Precision of prediction of yield loss is influenced by various factors such as locations, yield potential at the site, variation in competitive ability of mix stands of weed species and emergence time of weeds relative to crop. The aim of the review is to analyze various approaches to estimate infestation of weeds and the literature about yield loss prediction for multispecies. We discuss limitations of regression models and possible modifications to include the influential factors related to locations and species composition in context of their implementation in real time patch spraying.     

稻田土壤杂草种子库研究

对江苏省仪征市连年稻麦两熟轮作稻田土壤杂草种子库中杂草种类进行了考查。结果表明, 有11 科22 种杂草的种子主要分布在0～10 cm 土层内。同时, 阐述了土壤种子库杂草种子的来源, 因水分、湿度、光照等自然因素和耕作、人工除草等人为因素, 杂草种子本身的完熟度等综合因素造成了土壤杂草种子库中杂草种子活力的损失与累积, 以及杂草种子萌发与土层深度、水分等的关系, 初步探明了水旱轮作对稻田土壤杂草种子库的影响, 提出了减少杂草种子库种源的对策。     

云南保山喀斯特石漠化地区农田杂草种群组成与多样性特征

为了解云南保山喀斯特石漠化地区农田杂草种群组成及多样性特征,为当地的农田杂草的科学防治提供依据。在保山石漠化地区选择主要作物皇竹草（Pennisetum sinese Roxb）、核桃（Juglans regia L.）、烟草（Nicotiana tabacum L.）、玉米（Zea mays L.）进行农田杂草多样性调查。结果表明,该地区共有30科49种杂草,其中菊科（Compositae）和禾本科（Gramineae）杂草种类最多,发生频度最高的前10种杂草分别是：白花鬼针草（Bidens pilosa L. var. radiata Sch.-Bip.）、牛膝菊（Galinsoga parviflora Cav.）、马唐[Digitaria sanguinalis (L.) Scop.]、鸭跖草（Commelina communis）、金荞麦[Fagopyrum dibotrys (D. Don) Hara]、尼泊尔蓼（Polygonum nepalense Meisn.）、豨莶（Siegesbeckia orientalis L.）、牛筋草[Eleusine indica (L.) Gaertn.]、荷莲豆草（Drymaria diandra）、铁苋菜（Acalypha australis L.）;生态位宽度值前10的杂草与发生频度最高的杂草种类一致。核桃地的杂草物种数最多,烟草地最少,样地Shannon（H）指数、均匀度平均数分别为2.83、0.64,农田两两间的Jaccard相异系数、Baray-Curtis距离系数最大的为核桃与烟草,烟草与玉米的Jaccard相异系数最小,距离系数最小的为核桃与玉米,其平均数分别是0.67、0.74,说明保山喀斯特石漠化地区农田杂草多样性高,应结合土壤气候、农事操作等科学防治杂草。     

Numerical simulation on effect of irrigation conditions on water temperature distribution in a paddy field

Water management methods regulate water temperature in paddy fields, which affects rice growth and the environment. To understand the effect of irrigation conditions on water temperature in a paddy field, water temperature distribution under 42 different irrigation models including the use of ICT water management, which enables remote and automatic irrigation, was simulated using a physical model of heat balance. The following results were obtained: (1) Irrigation water temperature had a more significant effect on paddy water temperature close to the inlet. As the distance from the inlet increased, the water temperature converged to an equilibrium, which was determined by meteorological conditions and changes in water depth. (2) Increasing the irrigation rate with higher irrigation water amount increased the extent and magnitude of the effects of the irrigation water temperature. (3) When total irrigation water amount was the same, increasing the irrigation rate decreased the time-averaged temperature gradient effect over time across the paddy field. (4) Irrigation during the lowest and highest paddy water temperatures effectively decreased and increased the equilibrium water temperature, respectively. The results indicate that irrigation management can be used to alter and control water temperature in paddy fields, and showed the potential of ICT water management in enhancing the effect of water management in paddy fields. Our results demonstrated that a numerical simulation using a physical model for water temperature distribution is useful for revealing effective water management techniques under various irrigation methods and meteorological conditions.

     

Effects of tillage and irrigation on the occurrence and establishment of native wetland plant species in fallow paddy fields

Traditional weed management, such as tillage and irrigation, has led to an enhanced maintenance of wetland plant species in fallow paddy fields. Recent herbicide usage and improvements in irrigation and drainage systems however have caused habitat loss of these species, especially in fields on open lowlands. We conducted experiments in three fallow paddy fields situated on the alluvial Echigo Plain in central Japan with an aim to restore the habitat of native wetland plant species. The three experimental fields were managed under different irrigation regimes, (1) perennially flooded with water, (2) intermittent irrigation, and (3) temporary irrigation. Half the area of each experimental field was tilled before irrigation. Detrended correspondence analysis revealed obvious floristic differences between experimental and control fields with no irrigation. The proportion of wetland plant species in the experimental fields increased corresponding to the irrigation period, ranging 60–86%, and was relatively greater than that in control fields. In the experimental fields, differences in both tillage and irrigation affected the occurrence of plant species. Tillage restricted the occurrence of many non-wetland plant species, and had a positive effect on the establishment of several annual wetland plant species. In addition, a longer duration of irrigation is not necessarily suitable for the occurrence of all wetland plant species. We concluded that fallow paddy fields provide a possible habitat for the restoration of native wetland plant species through appropriate tillage and irrigation.     

稻田环境植物多样性研究

 选择稻田灌溉水无工业废水污染的禹山坞和受工业废水污染的城北村两地进行稻田环境植物多样性调查。禹山坞稻田普遍使用化学除草剂,杂草种数明显少于城北村,水竹叶成为禹山坞稻田的优势种;城北村稻田未用除草剂及低洼积水环境保护了槐叶萍、满江红、轮藻和尖头丽藻等。禹山坞的畦畔植物种数显著高于城北村。城北村灌溉水质差有利于部分耐性植物蔓延形成优势种,如空心莲子草的强烈竞争,使部分竞争力弱的植物逐步消失,植物种数减少。两村的沟渠植物种类差异明显。     

Nitrous oxide emissions from paddy fields under different water managements in southeast China

Water management is recognized as one of the most important factors in regulating nitrous oxide (N₂O) emissions from paddy fields. In China, controlled irrigation (CI) is widely applied because it has been proved highly effective in saving water. During the rice-growing season, the soil in CI paddy fields remains dry 60–80% of the time compared with soil irrigated by traditional methods. This study aims to assess N₂O emissions from paddy fields under CI, with traditional irrigation (TI) as the control. The cumulative N₂O emission from CI paddy fields was 2.5 kg N ha⁻¹, which was significantly greater than that from TI paddy fields (1.0 kg N ha⁻¹) (P < 0.05). Soil drying caused substantial N₂O emissions. The majority (73.9%) of the cumulative N₂O emission from CI paddy fields was observed during the drying phase, whereas no substantial N₂O emissions were observed when the soil was re-wetted after the drying phase. More and significantly higher peaks of N₂O emissions from CI paddy fields (P < 0.05) were also detected. These peaks were observed ~8 days after fertilizer application at water-filled pore spaces (WFPS) ranging from 78.0 to 83.5%, soil temperature ranging from 29.1 to 29.4°C, and soil redox potential (Eh) values ranging from +207.5 to +256.7 mV. The highest N₂O emission was measured 8 days after the application of base fertilizer at a WFPS of 79.0%, soil temperature of 29.1°C, and soil Eh value of +207.5 mV. These results suggest that N₂O emissions may be reduced obviously by keeping the WFPS higher than 83.5% within 10 days after each fertilizer application, especially when the soil temperature is suitable.     

稻蟹共作模式生态效应研究进展

主要从土壤、水环境和杂草防控三个方面,对目前我国稻蟹共作模式下田间生态的研究现状进行了总结与分析.提出了几种目前比较常见的稻蟹共作模式,即有机稻蟹和常规稻蟹两种普遍模式.分析了稻蟹共作对土壤理化性质、土壤酶活性和根际微生物区系的影响.养蟹稻田可以显著降低土壤容重,而总孔隙度及全氮、全磷、碱解氮、有效磷、速效钾和土壤有机质含量都显著增加;显著提高0~10 cm土壤脲酶、蛋白酶、脱氢酶以及过氧化氢酶的活性;土壤根际微生物以细菌为主要菌群,氨化细菌、反硝化细菌、嫌气性纤维素分解菌、好气性自生固氮菌、亚硝酸细菌数量显著高于单作水稻;与常规稻蟹相比,有机稻蟹的土壤性状表现更好.稻蟹模式下浮游动植物的多样性和生物量显著低于单作水稻,而水体中溶解氧(DO)明显偏低,硝酸盐、磷酸盐含量显著高于不养蟹稻田.稻田养蟹能够显著抑制稻田4种优势杂草的密度,对于稻田杂草的防控效果明显.     

不同氮肥施用量对东北玉米田杂草发生的影响

利用吉林省梨树县黑土区氮肥长期定位试验田(施氮水平为0、60、120、180、240、300 kg/hm2),2019～2020两年调查玉米田杂草种类、密度和生物量及其与玉米生物量和产量的关系.结果表明,试验条件下玉米田杂草主要是禾本科杂草,尤其是水稗草Echinochloa oryzoides.与不施肥相比,60 k...     

Weed management in aerobic rice systems

Aerobic rice systems can substitute the conventional rice cultivation system in the wake of water shortage and energy crises. The major constraint in the success of aerobic rice is high weed infestation. Hence, we have discussed the weed flora, yield losses, herbicide-resistant weeds, need for integrated weed management, and approaches to manage weeds in aerobic rice systems. A review of several studies indicated that 90 weed species were competing with rice under aerobic systems, causing 23–100% reductions in grain yield. Weed control in aerobic rice gets difficult due to shifts in weed flora and herbicide resistance development in weeds. A wide increase in grain yield (15–307%) by implementing different weed control practices elaborates the scope of weed management in aerobic rice. Practices, such as soil solarization, sowing of competitive crop cultivars, stale seedbed preparation, mulch application, correct fertilization, and intercropping, were found to have particular significance for managing weeds in aerobic rice systems. Moreover, hand weeding and mechanical control were more effective when combined with other weed control methods. Herbicides, such as pendimethalin, 2,4-D, penoxsulam, ethoxysulfuron, bispyribac-sodium, triclopyr, imazosulfuron, bensulfuron, pretilachlor, and metsulfuron, were found most effective in aerobic rice systems. Keeping in view the severity of weed infestation in these systems and the evolution of herbicide resistance, reliance on a single control method is out of question. Hence, the approach of integrated weed management is the most appropriate for proper weed management and the subsequent success of rice cultivation using aerobic systems.     

稻田田埂植物的生物多样性

 在浙江安吉两个村对利用不同污染程度水源进行灌溉的稻田田埂植物进行了调查。利用未受工业污染的水灌溉的禹山坞稻田田埂植物种数高于受工业废水污染的城北村。在相同类型植物群落中, 禹山坞稻田田埂的植物种总重要值Iv(t)显著高于城北村,两村的田埂植物生物多样性指数也存在类似的变化趋势。不同类型植物群落的生物多样性参数差异极为显著, 矮秆植物占优势群落的植物种数、植物种总重要值和生物多样性指数(H')显著高于高秆植物占优势群落和外来植物占优势群落。应重视防除外来植物空心莲子草, 控制高秆植物和保护矮秆植物。     

Spatial variability in the growth of direct-seeded rainfed lowland rice (Oryza sativa L.) in northeast Thailand

Large within-field variation in rice growth often causes production loss in broadcast-seeded (BC) rainfed lowland rice. The spatial variability of direct-seeded rainfed lowland rice was evaluated in 2004, 2005, and 2007 in on-station experiments at Ubon Ratchathani, northeast Thailand, in relation to soil water content and weed infestation, by adopting semivariogram and block kriging, including comparisons among BC with harrowing (BCH; no weeding), BC with no harrowing (BCNH; no weeding), and row-seeded (RS; interrow weeding once) fields. BCH and BCNH were also compared in 11 farmers’ fields in 2006 and 2007, to assess the effect of harrowing on rice growth and weed infestation. During most of the rice growing periods, flooded and non-flooded portions existed simultaneously in the fields, with different proportions among years and among seeding methods in the on-station experiment. BCH and BCNH rice had large within-field variation in seedling density, heading date, shoot dry matter, grain yield, harvest index, panicle density, and filled spikelet per panicle, as well as in weed infestation, measured by a quick visual estimation. Many of the measured variables (except mean soil water content in RS in 2007, seedling density in BCH in 2005 and 2007, shoot dry matter in BCH and BCNH in 2007, and panicle density in BCH in 2007) were spatially dependent (i.e., data from nearby locations were most similar) by geostatistical analysis. Analysis of correlations using the 420 data sets of BCH plots in 2005 and BCH, BCNH, and RS plots in 2007 revealed a positive correlation between soil water content and grain yield and negative correlations between weed infestation and soil water content and grain yield. Compared with BCH, in 2007 BCNH had much lower grain yield because of lower soil water content after establishment and more weed infestation. BCH had higher grain yield than BCNH in weedy fields in the farmers’ fields experiment. RS with interrow weeding resulted in a smaller coefficient of variation, smaller sill value, and higher grain yield than BCH, due to less weed infestation and a higher proportion of flooded water. These results indicated that reducing the spatial variability in rice growth requires careful field preparation, such as harrowing to level the soil surface and to reduce the uneven distribution of standing water and the variability in soil water content, combined with effective crop and weed management (i.e., harrowing and row-seeding). This is the first study that examined spatial variability in the growth of direct-seeded rice as a function of soil water content and weed infestation in a rainfed lowland environment.     

Can winter cover crops influence weed density and diversity in a reduced tillage vegetable system?

Weeds are a major constraint for organic crop production. Previous research has found that cover crops in reduced tillage systems can provide weed interference, subsequently reducing inputs and improving crop yield. However, questions remain about effects of cover crop species identity and cover crop biomass on weed suppression and crop yield. This four-year study investigated how winter cover crops grown alone or in mixture influenced weed presence and crop yield in a reduced tillage organic vegetable system. Treatments were barley (Hordeum vulgare L.), crimson clover (Trifolium incarnatum L.), mixed barley + crimson clover, and a no-cover crop control. Plots were flail-mowed and strip-tilled prior to planting main crops (2011 and 2012: broccoli Brassica oleracea L.; 2013 and 2014: crookneck squash Cucurbita pepo L.). We measured density, diversity, and community composition of weeds and viable weed seeds, changes in weed percent cover within growing seasons, and crop yield. We found that the presence of barley, crimson clover, or barley + crimson clover reduced weed density by 50% relative to the control. Cover crop biomass negatively influenced weed density and weed seed diversity, and positively influenced squash yield. Weed percent cover within growing seasons did not respond differentially to cover crop treatment. Cover crop treatment and cover crop biomass had no influence on weed or weed seed community composition. These results suggest that reduced tillage winter cover crops in mixture or monoculture can similarly suppress weeds and improve yield, primarily due to biomass effects.