Prospects and limitations of soil amendment and irrigation techniques for the water-saving public urban greenery and ephemeral weed management in the sandy soils of the United Arab Emirates

Public urban greenery greatly contributes to the residential and tourist value of cities in the Gulf Region,but due to the hyper-arid climatic conditions,the cost of irrigation and plant maintenance is very high.Existing strategies to reduce the monetary and ecological costs involve the cultivation of native xerophytic plantations,and/or the use of soil improvers to increase water-and nutrient-holding capacity of the sandy soils.Various soil improvers based on mineral,organic,or synthetic materials have entered the United Arab Emirates(UAE)market in recent years,but there is considerable uncertainty about how they should best be used in combination with ornamental plant stands involving xerophytic native plants.The present study investigated the effect of soil amendment and deep pipe irrigation on perennial ornamental plant stands involving native plants(Tephrosia appolinea(Gel.)Link in combination with Aerva javanica(Burm.f.)Juss.ex Schult.)and native-exotic plants(T.appolinea in combination with Ruelia simplex C.Wright)either or not topsoil and subsoil amendment with bentonite and hydrophobic sand under the irrigation water supply of less than 50%of reference evapotranspiration(ET0).After one year of cultivation,T.appolinea and A.javanica(native vs.native)produced high biomass and exhibited high water use efficiency(WUE)as compared with T.appolinea and R.simplex(native vs.exotic)combination given that no significant differences were found under the soil amendment treatments.All stands thrived under irrigation water supply far below what is usually supplied to exotic ornamental stands in public parks of the Al Ain City,the UAE.However,subsoil amendment in combination with deep pipe irrigation reduced the occurrence of weeds and increased the overall plant rooting depth.Our results suggest that subsoil amendment and irrigation up to 60-80 cm depth can potentially control ephemeral weed infestation,which is a great challenge in various plant production systems of the Gulf Region.The results of the present study suggest that the impact of soil amendment on the WUE of exotic plants is marginal and might not be economically justified.Replacing exotic with native ornamental plant species seems to have a far greater water-saving potential than the amendment of the soil,while weeds can be suppressed in the absence of topsoil moisture.

Artificial Intelligence for Maximizing Agricultural Input Use Efficiency: Exploring Nutrient, Water and Weed Management Strategies

Agriculture plays a crucial role in the economy,and there is an increasing global emphasis on automating agri-cultural processes.With the tremendous increase in population,the demand for food and employment has also increased significantly.Agricultural methods traditionally used to meet these requirements are no longer ade-quate,requiring solutions to issues such as excessive herbicide use and the use of chemical fertilizers.Integration of technologies such as the Internet of Things,wireless communication,machine learning,artificial intelligence(AI),and deep learning shows promise in addressing these challenges.However,there is a lack of comprehensive documentation on the application and potential of AI in improving agricultural input efficiency.To address this gap,a desk research approach was used by utilizing peer-reviewed electronic databases like PubMed,Scopus,Goo-gle Scholar,Web of Science,and Science Direct for relevant articles.Out of 327 initially identified articles,180 were deemed pertinent,focusing primarily on AI’s potential in enhancing yield through better management of nutrients,water,and weeds.Taking into account researchfindings worldwide,we found that AI technologies could assist farmers by providing recommendations on the optimal nutrients to enhance soil quality and deter-mine the best time for irrigation or herbicide application.The present status of AI-driven automation in agricul-ture holds significant promise for optimizing agricultural input utilization and reducing resource waste,particularly in the context of three pillars of crop management,i.e.,nutrient,irrigation,and weed management.

A Proposed Method for Evaluating Management Feasibility When Determining Weed Control Priorities after Major Fires and Floods

Major fires and floods have enormous impacts on natural ecosystems and are predicted to increase in frequency with global warming.Land managers need to make decisions on the prioritisation of weeds for control in post-disturbance landscapes,but little is available in the way of guidance to support timely decision making.Semi-quantitative models(e.g.,scoring systems)have been employed routinely in weed risk assessment,which considers the potential impacts posed by weeds,as well as the likelihood of these impacts being realised.Some progress has been made in the development of similar models addressing the topic of weed risk management.Under conditions prevailing after major disturbances,changes(both positive and negative)can be expected in the multiple factors that determine weed management feasibility,relative to pre-disturbance conditions.A semi-quantitative model is proposed that is based on the key factors that contribute to weed management feasibility in post-disturbance environments,along with annotated modules that could be used by land managers in both post-fire and post-flood situations.The fundamental challenge for weed management in these scenarios lies in the identification of differences between weeds and native species in relation to(1)patterns of seedling emergence;and(2)detectability relative to the growth stage.These two factors will determine the timing of control actions that are designed to address the trade-off between weed control and off-target damage during the period when both types of plants are recovering from a major disturbance event.The model is intuitively sound,but field testing is required to determine both its practical value and any necessary improvement.

Weed growth, herbicide efficacy, and rice productivity in dry seeded paddy field under different wheat stubble management methods

To ascertain the influence of wheat stubble management options and chemical weed control methods on weed growth and productivity of dry direct-seeded fine rice, a two years' field study was undertaken at the Agronomic Research Farm, University of Agriculture, Faisalabad, Pakistan in 2013 and 2014. Different wheat stubble management methods, viz., incorporation, burning and retention were executed during seed-bed preparation. While, herbicide treatments comprised of a weed check, weed free, pendimethalin followed by tank mixture of fenoxaprop p-ethyl+ethoxysulfuron ethyl, and bispyribac sodium followed by tank mixture of fenoxaprop p-ethyl+ethoxysulfuron ethyl. Results revealed that weed control efficacy of both herbicide treatments ranged from 84 to 94%. Herbicide treatments significantly reduced weed density(88–90%) and dry weight(86–88%), while improved the rice growth attributes compared with weed check. Application of bispyribac sodium followed by tank mixture of fenoxaprop p-ethyl+ethoxysulfuron ethyl in stubble retention recorded 226 and 273% increase in kernel yield over weedy check in 2013 and 2014, respectively. In stubble incorporation, pendimethalin followed by tank mixture of fenoxaprop p-ethyl+ethoxysulfuron ethyl was more effective in increasing(256–293%) rice yields over weedy check. Among different treatment combinations, the maximum net benefits(1 397.49^(–1) 472.22 USD ha^(–1)), net returns(636–700 USD ha^(–1)), benefit cost ratio(1.77^(–1).83) and marginal rate of return(2 187–2 330%) were recorded with the application of bispyribac sodium followed by fenoxaprop p-ethyl+ethoxysulfuron ethyl in stubble retention. In crux, application of bispyribac sodium followed by tank mixture of fenoxaprop p-ethyl+ethoxysulfuron ethyl in stubble retention is efficient approach to control weeds, and get maximum rice productivity and net economic returns under dry seeded system.

Influence of Rice Residue Management Techniques and Weed Control Treatments on Soil Available Plant Nutrients in Rice-Wheat Cropping System

Rice-wheat is the predominant cropping system of fertile soils of Indian, Pakistan, Bangladesh and Nepal falling in the alluvial Indo-Gangetic Plains (IGP). Management of rice residues produced after the harvest of rice crop and before sowing of the next wheat crop is a big challenge in that area. Mostly farmers burn rice residues assuming it low profile fodder and of little use. Burning of rice residues deprives the fields from many plant nutrients as they are lost during burning along with environmental pollutions and other issues. A field study was conducted for two consecutive years at the experimental area of the Department of Agronomy, Punjab Agricultural University, Ludhiana (India) to assess the impact of different rice residue management techniques and weed control treatments in wheat on soil available plant nutrients in rice-wheat cropping system. The experiment was laid out in split plot design with three replications. In main plots, five rice residue management treatments viz., no rice residue, rice residue 5 t·ha-1 (surface), rice residue 6 t·ha-1 (surface), rice residue 7 t·ha-1 (surface) and rice residue 5 t·ha-1 (incorporation) were settled and in sub plots, four weed control treatments i.e. clodinafop 60 t·ha-1, sulfosulfuron 25 t·ha-1, mesosulfuron + iodosulfuron 12 t·ha-1 and control (unweeded) were arranged. Results of the study revealed that surface application as well as incorporation of rice residues improved the organic carbon and NPK status than no rice residues. Among the residue management practices, incorporation of rice residues 5 t·ha-1 significantly improved the soil organic carbon, available nitrogen, phosphorus and potassium than no rice residue treatment in the 0 - 15 soil layer during both the years. Same trend was observed for 15 - 30 cm soil layer but differences were less wide than 0 - 15 cm soil layer. Among the weed control treatments, organic carbon was not significantly influenced. Herbicide treated plots registered significantly higher available nitrogen, phosphorus and potassium than control (unweeded) treatment in the 0 - 15 cm soil layer during both the years.

Weed Management in Rainfed Upland Rice Fields under Varied Agro-Ecologies in Nigeria

The demand for rice to meet the dietary need in low-income countries is expected to witness an exponential rise as the population increases.Meeting the rice demand domestically has remained challenging due to significant yield loss caused by several biotic and abiotic factors.Among these factors,one of the most important is the high weed pressure that ravages the upland rice ecology.In Nigeria,several independent weed control techniques,such as physical,chemical and cultural methods,have been recommended and adopted for weed control across varying rice upland ecologies.However,outcomes of these approaches when used independently have not consistently led to an increase in yield.There remains an outstanding deficit between the actual yield and the potential rice yield.This review aimed to identify potential research gaps,and quest effective and sustainable weed management strategies in smallholder upland rice farming systems in Nigeria.A critical analysis of studies suggests the potential of sustainable weed management practices if adopted and adapted smartly in different upland ecologies in Nigeria.Competitiveness of upland rice against weeds can be enhanced through strategic integration of weed competitive cultivars,optimum nitrogen application timings(within weed-free periods),uniform plant spacing,and high seeding rates,with conventional herbicide/manual weed control practices.However,such management practices can only be engaged where inputs are supplied on time and the technical know-how is extended to farmers.The review equally highlights potential research gaps for further studies.

Allelopathy of Medicinal Plants: Current Status and Future Prospects in Weed Management

An attempt has been made in this article to accumulate and elucidate the literatures about the allelopathic potentiality of medicinal plants, and its role on the development of bio-herbicides for eco-friendly weed management strategies to conserve bio-diversity and ecological balance. This review paper has been prepared by comprehensive studies of various published research articles, books and proceedings available in the world literature. The farmers of different countries use several weed management techniques in order to minimize the deleterious effect of weeds. Among them most commonly used practice is application of herbicides due to its high efficacy and cost effectiveness, less time-consuming nature, flexibility and easy accessibility, and more rapid out return. Although use of synthetic herbicides in the crop fields has increased the crop production as well as the productivity by reducing the weed infestation, over time it causes a number of environmental hazards. Hence, to avoid these detrimental effects of synthetic herbicide, a lot of efforts have been dedicated by the researchers to search the novel natural plant products mainly allelochemicals and try to apply them as a tool for the development of bio-degradable natural herbicides. This paper intended to reflect the current state of allelopathic medicinal plants and their potentiality to develop eco-friendly and natural product-based herbicides for sustainable agriculture, and to invite further debate on this issue.

Development of Weed Management Strategies for Cashew Cultivation in Ghana

Three field trials, one for establishment and two for mature phases respectively, were conducted to develop weed management strategies for cashew cultivation in Ghana. The treatments for the establishment phase consisted of hoe weeding of whole plot, hoe weeding of cashew lines and slashing of inter-rows, herbicide application with glyphosate of whole plot or cashew lines with slashing of inter-rows, relay cropping of the cashew plot with sorghum and a legume and intercropping with a legume. In one trial of the mature phase, the treatments were hoe weeding of whole plot two or three times a year, high slashing of whole plot three times a year, herbicide application （glyphosate） of whole plot and ring application of herbicide （glyphosate） plus high slashing of inter-rows twice a year. In the other trial, which was carried out on farmers＇ fields, glyphosate （Roundup） at 2.0 l/ha was tested against manual slashing. In the study of the establishment phase, neither the girth nor height of the cashew seedlings was significantly affected by the treatments. The first year and four year cumulative cashew yields were significantly affected by treatments with the intercrops giving higher yields than the glyphosate-treated plots. Intercropping as a weed control measure was generally more costly than glyphosate application or manual weeding. In the mature trials, chemical weed control slightly improved cashew nut yield and was cheaper to apply. It is recommended to adopt chemical weed control in cashew cultivation in Ghana.

Cultivation of Perennial Herbaceous Legumes in Weed Management in Coffee Plantation on the Cerrado

The aim of this study was to evaluate the cultivation of perennial herbaceous legumes on weed control and yield of the coffee crop in the Cerrado. The experimental design was a randomized complete block with four replications. The 10 treatments tested in factorial 4 × 2 ＋ 2, were four legumes： forage peanut （Arachis pintoi）, hybrid Java （Macrotyloma axillare）, perennial soybean （Neonotonia wightii） and wild ground nut （Calopogonium mucunoides）; two forms in the interrows of coffee plants with two and three rows of legumes spaced by 0.50 m and 0.25 m, respectively; and two additional treatments consisted of hand weeding with hoe and chemical control with glyphosate. The hybrid Java and wild ground nut in the first year and the hybrid Java and perennial soybean in the second year, all followed by forage peanut, promoted lower density and biomass of the weeds. The wild ground nut in the first year and forage peanut in the second year showed higher soil cover. The hybrid Java had its highest biomass production in two years, and wild ground nut being higher in the first year. The cultivation of perennial herbaceous legumes promoted weed control without interfering in the productivity of the coffee crop.

Environmental and Management Factors That Influence Commelina Species in Selected Agro-Ecological Zones in Western Kenya

Commelina species are plant resources full of promise as future food and feed that thrive in diverse ecosystems. They are medicinal plants, leafy vegetables, forage for ruminants, feed for cricket insects, crop protection, and fuel. However, information regarding factors driving Commelina in agro-ecological zones in Western Kenya is lacking. Therefore, we investigated the diversity of Commelina species, the composition of associated weed species as well as environmental and management factors affecting their diversity and distribution based on 22 variables from 12 production sites. In the survey, 115 species belonging to 30 families were recorded of which 11 Commelina species were identified. Among Commelina species, Commelina diffusa and Commelina benghalensis var. benghalensis (non-hybrid variant) had higher relative density. Multiple linear regressions revealed that the environment (exchangeable sodium percentage, magnesium, soil pH, and total nitrogen) and management (agriculture system type) variables exert a stronger effect on the diversity of Commelina species. Detrended Correspondence Analysis detected different ecological conditions for Commelina species and the composition of associated weed species. The forward selection based on Canonical Correspondence Analysis indicated that the distribution of Commelina species responded significantly to soil pH, available phosphorous, total nitrogen, fertility, and crop spacing. Partitioning variation showed the great importance to the environment than management (10.57% versus 5.97%). The low shared variance (environment × management) was -0.4%, indicating that the two factors have a more individualistic than interactive nature. However, the 83.86% that remained unexplained was attributed to stochastic variation or unmeasured variables. This study suggests that the identified five important variables affecting the distribution of Commelina species will certainly contribute to the prioritization of ecological aspects leading to the growth condition of Commelina species.

Cultivation system influenced the critical period for weed control in cotton field

Background The critical period of weed control(CPWC) refers to the period of time during the crop growth cycle when weeds must be controlled to prevent yield losses.Ultra-narrow row(UNR) is a method of planting of cotton in rows that are 25 cm or less apart.Amongst cultural techniques for weed control,the use of narrow row spacing is considered to be a most promising approach that can effectively suppress weed growth and provide greater yields in cotton.This cultivation system can shorten the length of the critical weed-crop interference duration and results in greater yield.The current research aimed to determination of critical time of weed control in cotton(Gossypium hirsutum L.) under conventional and ultra-narrow row spacing conditions.Field experiments were arranged as factorial experiment in a randomized complete block design with three replications.Factors were cultivation system(conventional(50 cm row spacing) and ultra narrow row(25 cm row spacing and weed treatment including 30,45,60,and 75 days weeding after emergence during the growing season(weed free),and 30,45,60,and 75 without weeding(weed infested) in the growing season along with weedy and weed-free from sowing to harvesting.A four-parameter loglogistic model was fit to the two sets of relating relative crop yield to data obtained from increasing durations of weed interference and lengths of weed-free period.Results In both years and cultivation systems,the relative yield of cotton decreased with the increasing duration of weed-interference but increased with the increasing duration of weed-free period.Ultra-narrow row cultivation delayed the beginning of the CPWC in cotton.Under ultra-narrow row condition,the CPWC ranged from 21 to 99 days after germination in 2021 and 23 to 91 days in 2022 based on the 5% acceptable yield loss.Under conventional cultivation CPWC ranged from 17 to 102 days after emergence in 2021 and 18 to 95 days after emergence in 2022.Conclusions Under both conventional and Ultra-narrow row conditions,weed interference reduces seed yield.Under ultra-narrow row condition,weed interference until 21.1–23.5 days after cotton emergence and under conventional condition,weed interference until 16.9–18.5 days after cotton emergence had not significant reduction on cotton yield.

李园杂草管理方式对土壤细菌群落和生态功能的影响

【目的】分析不同杂草管理方式对位于国家重点生态功能县的李园细菌群落结构和生态功能的影响,为李园土壤健康管理提供参考。【方法】以自然生草、人工生草、除草剂除草的李园和邻近天然槲栎次生林土壤为研究对象,提取土壤细菌DNA,对其ITS基因进行扩增,采用高通量测序和功能预测的方法研究细菌的多样性、群落结构及生态功能。【结果】不同处理OTU数量为2012~3522,细菌种类33门、108纲、242目、383科、667属。绿弯菌门、放线菌门、变形菌门和酸杆菌门为主要门类,在各处理中4个门的总丰度达到80%以上。多样性分析显示,天然林Ace和Chao指数显著低于李园的3个处理。群落组成和差异分析显示,天然林土壤酸杆菌优势比较大,病害细菌少,并有少量的有益细菌蛭弧菌;李园的鞘脂单胞菌相关病害的风险大,生草可在一定程度上提高芽孢杆菌等有益细菌的丰度,尤其自然生草比较明显。人工生草还有利于提高李园细菌的多样性,尤其是芽单胞菌的富集比较明显。使用除草剂的李园则主要富集了绿弯菌门的种类,而降低了苔藓杆菌的丰度。功能预测分析显示,土壤细菌新陈代谢最活跃,主要包括碳水化合物代谢和氨基酸代谢等,涉及化能异养、纤维素分解、固氮作用等功能。与其他处理比较,人工生草李园土壤硝酸还原功能较强、天然林土壤的木质素分解功能较强、除草剂处理的李园土壤甲基营养功能较强。【结论】天然林Ace和Chao指数显著低于李园,表现为土壤酸杆菌优势明显。不同杂草管理方式对李园土壤细菌群落结构和功能的影响较大,生草有利于李园有益细菌群落的建立。

果园除草技术的研究现状及发展趋势

随着我国发展特色林果业相关政策的出台,林果种植面积逐渐增多,同时果园管理问题也日益凸显。在果园种植生产管理过程中,杂草影响了果树的正常生长,降低了果品的产量和质量。目前国内外在果园除草方面开发了多种技术与方式,通过对不同的除草方式进行分析总结,指出不同除草方式的优点和存在的问题,并从化学除草、机械除草2个主要方面总结梳理了当下研究现状及技术应用,提出合理的除草方式,并指出了果园田间管理未来研究的发展趋势。

肥密措施对水直播稻苗期杂草发生及产量的影响

为明确水分管理方式、施氮量和用种量对水直播稻生长发育特性、产量和苗期稻田杂草发生的影响,于2021年以卓两优1126为试验材料,采用再裂区试验设计,在湖南省浏阳市开展大田试验。以水分管理方式为主区,施氮量为副区,播种量为再副区。水分管理(播种至3叶1心期)设淹水(W1)和湿润(W2)2个处理;施氮量设0 kg/hm^(2)(N0)、150 kg/hm^(2)(N1)和195 kg/hm^(2)(N2)3个处理;播种量设15.0 kg/hm^(2)(D1)、22.5 kg/hm^(2)(D2)和30.0 kg/hm^(2)(D3)3个处理。结果表明,不同水分管理方式间苗期稻田杂草总数差异极显著,而不同施氮量和用种量处理间杂草总数差异不显著。W1处理水稻平均产量为8.5 t/hm^(2),显著高于W2处理;N1和N2处理间水稻平均产量差异不显著,但均显著高于N0处理;水稻产量随着用种量的增加而增加,但不同用种量处理间差异不显著。综上,水稻淹水直播条件下,施氮量为150 kg/hm^(2),播种量为15.0 kg/hm^(2),并于3叶1心期除草1次,可在减少除草剂用量的同时实现水稻增产。

卷积神经网络及其在田间杂草管理中应用的研究进展

杂草是影响作物产量的主要生物因素之一,可阻碍作物的生长,进而影响作物的产量和品质,传统的人工除草、机械除草、化学药剂除草方式已不能满足精准除草的需求,而近年来基于卷积神经网络(CNN)的深度学习技术发展迅速,成为图像识别的重要工具,并且在杂草检测、害虫识别、植物或果实计数及其成熟度分级等农业领域取得了显著成果。为了使田间杂草管理更高效,促进农业生产智能化,基于卷积神经网络研究情况,从目标检测、图像分割、图像分类、基于无人机图像应用等方面概述了卷积神经网络在田间杂草管理中应用的研究进展,并从数据采集、杂草检测的精度、模型的泛化能力3个方面进行了展望。总之,基于CNN的杂草管理应用研究已经取得了一定的成果,但仍存在许多挑战和问题需要解决。未来研究应关注提高数据数量和质量、提高杂草识别的准确性和可靠性、提高深度学习模型的泛化能力和鲁棒性,并引导无人机自主进行制图,实现无人机与地面设备的协同作业;同时,加强CNN等深度学习技术在实际生产中多方面的应用研究,为农业生产提供更高效、智能的解决方案。

使用高光谱成像技术对田间杂草进行表征和识别

进行杂草表征和分类对于智慧农业杂草清除与田间管理而言至关重要,然而杂草识别精度较低的问题尚未得到深入探究。本研究以田间杂草为研究对象,建立了农业地区7种杂草物种的高光谱数据库。首先,使用地面高光谱相机采集了高光谱图像,提取并分析了每个物种的代表性光谱曲线、光谱剖面特征,并对各物种进行主成分分析,揭示了不同杂草物种的差异性。采用多元散射校正、归一化、一阶和二阶差分求导对原始光谱数据进行预处理。最后通过建立支持向量机与一维卷积神经网络分类模型,用于高光谱图像中识别杂草。结果表明,MSC-1DCNN模型的分类效果最佳,不同物种的用户准确性为95.71%~100%。该研究不仅为了解杂草物种的高光谱特征以及杂草管理提供了有力的保障,而且也有助于自动化除草机器人的研制与无人农场的实施。

南方红壤区茶果园杂草管理与水土保持技术研究进展

南方红壤区的茶果园因其独特的地理和气候条件而成为重要的农业资源,但同时也面临着杂草问题和水土流失的挑战。本文综合分析了国内外关于茶果园杂草管理和水土保持的研究进展,提出了一系列针对性的管理策略。在杂草管理方面,建议采用综合杂草管理技术,结合化学、物理和生物控制方法,以提高茶果园的生产效率并减少环境影响。在水土保持方面,强调了梯田建设、植被覆盖和土壤改良技术的重要性,这些措施能有效减少水土流失并提升土壤保水保肥能力。文章还指出,未来研究应关注生态友好的杂草管理技术的开发,探索成本效益更高的水土保持技术,并建立完善的长期监测和评估体系。通过跨学科合作,本文旨在为南方红壤区茶果园的可持续发展提供科学指导和实践支持。

Integrated Use of Herbicide and Crop Mulch in Suppressing Weed Growth in a Dry-Seeded Rice System

Dry-seeded rice production systems are increasing in many Asian countries because of labor and water scarcities. However, weeds are the main biological constraints in these systems. Herbicides are widely used to manage weeds but they do not provide effective weed control. The use of crop residue as mulch can suppress weed emergence and weed biomass but mulch alone does not provide effective weed control. The integrated use of herbicide and mulch, however, could provide more effective and sustainable weed control in dry-seeded rice systems. A study was conducted in two consecutive rice growing seasons to evaluate the combined effect of herbicide (treated and nontreated) and rice straw mulch (0, 2, and 4 t.ha-1) on weed growth and rice yield in a dry-seeded rice system. In the nontreated plots, weed biomass decreased with increases in mulch amounts, whereas weed biomass in the herbicide-treated plots was similar at different mulch amounts. Overall, herbicide treatments provided better weed control than the mulch treatments. In the nontreated plots, grain yield was similar at different mulch amounts, whereas grain yield in the herbicide-treated plots was greater when the field was mulched with 4 t.ha-1 of rice straw than with no mulch or mulched with only 2 t.ha-1 of rice straw. The results suggest that integrated use of mulch and herbicides can help weed control and increase crop yield in dry-seeded rice.

Competitiveness of Winter Rice Varieties against Weed under Dry Direct Seeded Conditions

Aerobic rice or dry direct seeded rice is highly vulnerable to weeds because of lack of “head start” over weeds and standing water layer to suppress weeds. The risks of chemical control and the huge cost involvement in mechanical control demand an eco-friendly and cost-effective integrated weed management. Weed competitive rice cultivar may be considered as a viable tool for integrated weed management. In these circumstances, an experiment was designed to evaluate weed competitiveness of some selected winter rice varieties under aerobic soil conditions. The study was conducted during dry season (February to June) 2016 at the Agronomy Field Laboratory and Weed Management Laboratory, Bangladesh Agricultural University, Mymensingh. Fourteen rice varieties namely, BRRI dhan28, BRRI dhan29, BRRI dhan47, BRRI dhan50, BRRI dhan55, BRRI dhan58, BRRI dhan59, BRRI dhan67, Binadhan-5, Binadhan-6, Binadhan-8, Binadhan-10, BRRI hybrid dhan3 and Agrodhan-14 were grown under weedy and weed-free conditions. Plots with no rice were also maintained to observe the natural growth of weed in absence of rice. The experiment was conducted with split-plot design with three replications. Weeding regime was allocated in main plot and rice variety was allocated in sub-plot. Results showed that rice varieties varied widely in their yield performances and weed competitiveness. Among rice varieties, BRRI dhan59 allowed the minimum weed growth (19.2 g m-2) while Binadhan-5 allowed the maximum weed growth (62.8 g m-2). Grain yield ranged from 1.85 t ha-1 (BRRI dhan55) to 3.92 t ha-1 (Binadhan-5) under weed-free condition and between 0.41 t ha-1 (BRRI dhan55) and 2.06 t ha-1 (BRRI dhan59) under weedy condition. Weed inflicted relative yield loss ranged from 43.4% to 82.1% among the varieties. BRRI dhan59 allowed the least yield penalty (43.4%) while Binadhan-5 had the maximum yield penalty (82.1%) due to weed competition. Although Binadhan-5 is the most productive variety (3.92 t ha-1) for aerobic culture but its weed inflicted relative yield loss is higher (82.1%) than many other varieties with low yield potential. On the other hand, BRRI dhan59 appeared as the most weed competitive variety (only 43.4% relative yield loss) with productivity of 3.84 t ha-1. Therefore, weed competitive variety should be considered as a vital tool while designing integrated weed management system for aerobic rice.

Phenotyping of Weedy Rice to Assess Root Characteristics Associated with Allelopathy

Weedy rice is a species of Oryza, and is a wild relative of cultivated rice. The weed possesses unique hardiness that allows them to thrive in dynamic and stressful environments. These characteristics suggest that weedy rice is a stored source of novel genes for competitive traits. One such trait is allelopathy, where a species releases secondary metabolites that suppress the growth and development of neighboring species. Weed competition is a limiting factor in rice production systems;therefore, it is critical to identify specific allelopathic weedy rice accessions to determine the genetic pathways and mechanisms associated with allelopathy to be used in breeding programs. Due to the complex nature of allelochemical production and the lack of knowledge of allelopathy mechanisms in weedy rice, phenotypic traits, particularly root traits, can be used to overcome this limitation and serve as target characteristics for breeding weed suppressive rice varieties. Five weedy rice accessions were chosen from preliminary screenings of larger sample sizes with the ability to suppress barnyardgrass weed seedling growth. Another five weedy rice with low barnyardgrass suppression was selected for the current root phenotypic study. Five cultivated rice lines were used as a comparison. All plants were propagated in a transparent germination pouch for four weeks. Roots were scanned and analyzed for root length and area covered. No differences were found in the seedling root area among weedy rice and rice accessions;however, allelopathic weedy rice plants exhibited a 14% increase in root length than non-allelopathic weedy rice plants. The allelopathic weedy rice accession B2 possessed the most extended root system (22.4 cm root length). The highly allelopathic weedy rice accessions (including B2) screened and phenotyped in this study are ideal candidates for identifying the genetic controls of early root length, a possible trait contributing to underground allelopathic production and competitive advantage.