Weed Management Strategies Research Articles

A survey of problem weeds of sorghum and their management in two sorghum-producing districts of Zimbabwe

Sorghum is an important staple food crop in dry areas of Zimbabwe but yields are reduced due to inefficient weed management strategies that largely rely on hand weeding. A study to establish weeds ...

Weed management in greengram: A review

Greengram [Vigna radiata (L.) Wilczek], also known as mungbean, is extensively cultivated in India and other Asian countries. Being rich in protein, its grains are an important daily dietary component. Weeds are a major limiting factor in production of greengram that lead to a drastic reduction in yield. The presence of hardy weeds and slow initial crop growth compound this problem. Different strategies incorporating non-chemical and chemical methods have been practiced for efficient weed control in greengram. Non-chemical control methods include straw mulch (12–63% reduction in weed biomass), narrow row spacing (60–92% reduction in weed biomass), method of sowing (1–20% reduction in weed biomass), tillage practices (58% reduction in weed biomass), the frequency and rate of irrigation and fertilizer application (13–23% reduction in weed biomass), timing of hand weeding and selection of cropping system. Chemical control methods include the many herbicides with different selectivity and efficiency available for use in greengram. For efficient weed control, herbicides should be applied at the recommended rate and time in order to avoid inhibiting growth, symbiotic properties (number of nodules, dry weight of nodules, leghaemoglobin content in nodules) and grain yield in greengram crop. In this review, different weed management strategies including nonchemical and chemical weed control methods have been reviewed for their ability to control weeds in greengram. Furthermore, their influence on growth, symbiosis, yield and nutrient uptake of greengram, soil microflora and residual effect on succeeding crops have also been reviewed.

Comparative efficacy of herbicides and hand weeding to control weeds in onion

Effective and efficient weed management strategies are essential to raise a successful onion crop. Therefore, to find out the economically feasible weed management practice, a field experiment was conducted at Sher-e-Kashmir University of Agricultural Sciences and Technology, Jammu, during 2015–16 and 2016–17. Five herbicides namely pendimethalin1.0 kg/ha, oxyfluorfen 0.15 kg/ha, alachlor 1.0 kg/ha, butachlor 1.0 kg/ha and quizalofop-ethyl 0.05 kg/ha were applied alone or in different combinations replicated thrice in randomized block design. Data was recorded on weed density, dry matter accumulation of weeds, weed control efficiency, weed index, herbicide efficiency index and yield parameters. Pre-emergence application of oxyfluorfen 0.15 kg/ha fb one hand weeding at 40–60 days after transplanting recorded the highest weed control efficiency and the lowest values of weed density, dry matter accumulation of weeds and weed index. The pre-emergence application of oxyfluorfen 0.15 kg/ha fb post-emergence application of quizalofop-ethyl 0.05 kg/ha at 40 DAT was also found to be equally effective in controlling the weeds in onion. The yield attributing traits such as average bulb weight and total bulb yield also exhibited the same pattern. However, the highest B: C ratio was recorded with preemergence application of oxyfluorfen 0.15 kg/ha fb post-emergence application of quizalofop-ethyl 0.05 kg/ha applied 40 DAT. Hence, this treatment can be used for controlling the prevalent weed flora in onion crop under Jammu condition.

Effects of Field and Greenhouse Solarization on Soil Microbiota and Weed Seeds in the Northeast USA

Soil solarization using clear plastic is a promising weed management strategy for organic farms in the Northeast USA. Based on grower concerns that the practice might negatively affect beneficial soil microbiota, we conducted experiments to measure the effects of 2 and 4 weeks of solarization in a field and a closed greenhouse. Soil microbial communities were assayed by dilution plating on semi-selective agar media. Populations of general bacteria, general fungi, bacilli, and florescent pseudomonads were unaffected by field solarization, but fluorescent pseudomonads were reduced following greenhouse solarization. At plastic removal, soil biological activity was reduced non-significantly in the field and by 45% in the green- house. Soil biological activity fluctuated following field solarization, being significantly suppressed at 5 but not 14 days after plastic removal. In the greenhouse, biological activity remained suppressed up to 28 days after plastic removal. Solarization increased available nitrogen in the field and greenhouse. Four weeks of solarization reduced viability of buried weed seeds by 64% in the field and 98% in the greenhouse, indicating that the practice can cause substantial weed seed mortality. Maximum soil temperatures, measured at 10 cm depth under solarization, were 44◦ C in the field and 50◦ C in the greenhouse; temperatures were theoretically sufficient for the reduction of some soil borne pathogens. A subsequent experiment measured the effects of solarization and tarping (black plastic) on soil biological activity. During mulching, biological activity was unaffected by treatment, but 14 days after plastic removal, biological activity was reduced in the solarized treatment as compared with the control. Overall, these results suggest that solarization can deplete the weed seedbank. Although soil biological activity was reduced by solarization, it may bounce back after a period. Greenhouse solarization achieved higher temperatures and was more lethal to weed seeds and some microbiota than field solarization.

Crop rotation effects on weed communities of soybean (Glycine max L. Merr.) agricultural fields of the Flat Inland Pampa

Extensive grain crop production systems in the Flat inland Pampas mainly include soybean, double-crop wheat-soybean and maize in rotation. Due to difficult-to-control weed problems, farmers are tending to intensify the rotations in their fields by increasing the number of double crops or by including cover crops before the main crop. Land use intensification may be characterized using the intensification sequence index (ISI), which is the number of crops per year considering all crops sown in a particular period; i.e. the average number of crops sown in a time unit. To determine how agricultural intensification and crop sequences may modify weed communities, 31 soybean fields of commercial farms located in the Flat Pampa of Argentina were surveyed from 2012 to 2014. Frequency of individual weeds within the fields was determined and various statistical methods were used to evaluate changes in weed community composition or function due to intensification (ISI level). A total of fifty-three species, mostly therophytes (28 species), were recorded in soybean crop fields at harvest. Three weed communities were identified, which were related to the ISI level of the fields, and also to the number of years continuously sown with grain crops (i.e. number of years since the last pasture). Weed community under intensified fields was characterized by low species richness (p < 0.05); i.e. the number of weed species was reduced when more crops were sown per year. However, weed frequency (weed abundance) and weed functional groups were not significantly reduced by field intensification. Since weed problems in grain crops of the Pampas are increasing, mainly due to herbicide resistant weeds, the use of ISI as part of an integrated weed management strategy is discussed.

English

Weed is a very significant enemy of crop production. Its density, diversity and the interaction complexes on the yield and yield component of maize cv &ldquo;Quality protein&rdquo; were investigated in the present study. The experiment was laid out in randomized complete block design (RCBD) containing five weed management strategies and a weedy check as treatments in 2015 and 2016. Data were collected on weed density, yield and yield components of maize for the two years. For the years and the treatments, a mixed model factorial in RCBD was employed for the analysis of variance of the data. Significant (P&le;0.05) variation exists among the two years; the six treatments and their interaction for the grain yield and its components. The use of Pendimenthalin (330 EC) at 3.0 kg a.i.ha-1 supported the highest grain yield (2.4 tons ha-1); hoe weeding and mulching was next with significantly (P&le;0.05) lower grain yield of 2.2 tons ha-1. The weedy check had the lowest grain yield of 1.2 tons/ha. An average yield loss of 42% was obtained by comparing the weed control methods with each of the weedy check. By Shukla variance estimate, maize-soybean intercrop gave the most stable grain yield for the two years. Year 2016 significantly (P&le;0.05) favoured grain yield, its components and weed density. The proportion of weed categories in the study was: Broadleaves (52.38%), grasses (33.33%) and sedges (14.28%). Broad leaves and grasses density measured at interval displayed a significant linear trend. The sixth week after planting was most critical for grain yield determination in the tested maize cultivar. Key words: Weed management strategies, maize, grain yield, interaction complexes.&nbsp; &nbsp

Digitaria sanguinalis seed dormancy release and seedling emergence are affected by crop canopy and stubble

SummaryDigitaria sanguinalis is a troublesome annual weed that causes important yield losses in different crops. Despite this, there is scarce information about different aspects of its biology under field conditions. New knowledge about the establishment process of this species will be of paramount importance in order to maximise the effectiveness of weed management. The aims of this paper were to evaluate the effect of stubble found on the surface on seed dormancy levels through the season, the effects of stubble and soyabean crop canopy on seedling emergence and to determine the field emergence pattern as a consequence of seed dormancy level at dispersal time. Seeds on the soil surface, which showed a high dormancy level at the beginning of autumn, were released from dormancy by low winter temperatures and germinated during spring as temperatures rose, showing a transient surface seedbank. Seeds covered by stubbles had delayed the emergence in the field due to lower alternating temperatures perceived by the surface seedbank. On the other hand, the presence of a soyabean crop and stubble together reduced the number of seedlings. Seeds with a high dormancy level at dispersal time showed a delayed emergence in the next season when compared with seeds with a lower dormancy level. However, the final number of seedlings was similar. Both stubble on surface and crop canopy are useful factors to lessen and delay the seedling emergence allowing the design of weed management strategies in order to diminish the population levels of this species.

Evaluation of bag-of-features (BoF) technique for weed management in sugarcane production

Weeds interfere in agricultural production, causing a reduction in crop yields and quality. The identification of weed species and the level of infestation is very important for the definition of appropriate management strategies. This is especially true for sugarcane, which is widely produced around the world. The present study has sought to develop and evaluate the performance of the Bag-of-Features (BoF) approach for use as a tool to aid decision-making in weed management in sugarcane production. The support vector machine to build a mathematical model of rank consisted of 30553 25x25-pixel images. Statistical analysis demonstrated the efficacy of the proposed method in the identification and classification of crops and weeds, with an accuracy of 71.6% and a Kappa index of 0.43. Moreover, even under conditions of high weed density and large numbers of overlapping and/or occluded leaves, weeds could be distinguished from crops This study clearly shows that the system can provide important subsidies for the formulation of strategies for weed management, especially in sugarcane, for which the timing of weed control is crucial.

Interference of Annual Sowthistle (Sonchus oleraceus) in Wheat

Abstract Annual sowthistle (Sonchus oleraceus L.) is a broadleaf weed that is increasing in prevalence in the northern cropping regions of Australia. Being a member of Asteraceae family, this weed possesses many biological attributes needed to thrive in varying environments and weed management pressure. Interference of this weed was examined in a wheat (Triticum aestivum L.) crop through field studies in 2016 and 2017. Different densities of S. oleraceus were evaluated for their potential to cause yield loss in wheat: 0.0 (weed free), low (9 to 15 plants m−2), medium (29 to 38 plants m−2), and high (62 to 63 plants m−2). Based on the exponential decay model, 43 and 52 plants m−2 caused a yield reduction of 50% in 2016 and 2017, respectively. Yield components such as panicles m−2 and grains per panicles were affected by weed density. At the high weed infestation level, S. oleraceus produced a maximum of 182,940 and 192,657 seeds m−2 in 2016 and 2017, respectively. Sonchus oleraceus exhibited poor seed retention at harvest as more than 95% of seeds were blown away by wind. Adverse effects on crop, high seed production and wind-blown dispersal may lead to an increased prevalence of this weed in the absence of an integrated weed management strategy utilizing both herbicides and non-chemical options.

Agroecological service crops managed with roller crimper reduce weed density and weed species richness in organic vegetable systems across Europe

AbstractAgroecological service crops are introduced into the vegetable crop rotation to provide agroecosystem services, and are a key strategy for weed management in organic systems. Organic farmers across Europe usually terminate these crops before cultivation of the subsequent cash crop, using them as green manure. Recently, the in-line tillage-roller crimper has attracted interest across Europe. It allows flattening the agroecological service crops and creates a narrow furrow that facilitates the fertilization and transplantation of organic vegetables. In Europe, most of the research on this technology has been carried out in Italy, and no studies are available analyzing its effect on weed density, weed species richness, and community composition in different vegetable crops, soils, and climatic conditions across Europe. We compared the effects of the usage of in-line tillage-roller crimper versus green manure on the weed abundance, species richness, and community composition in fourteen original datasets from five countries over 2 years. The support for a common effect of in-line tillage-roller crimper across trials was tested by means of a meta-analytic approach based on a weighted version of Stouffer’s method. Our results indicate that in-line tillage-roller crimper management reduced weed density by 35.1% on average in comparison with green manure, and this trend was significant across trials. Moreover, we document a significant reduction of weed species richness under this technique and significant but, in general, minor changes in the weed community composition across the trials. Therefore, this study provides for the first time a solid evidence of the effectiveness of this management technique to reduce weed density at the early stages of crop growth across a wide range of vegetable systems and production conditions in Europe. Nonetheless, it is important to note that the effect of this technology can be strongly affected by variations in cropping conditions.

Weed regulation by crop and grassland competition: critical biomass level and persistence rate

Abstract It is widely agreed that competition is an important factor that regulates plant populations and shapes communities in agricultural landscapes. Many studies have suggested that crop and grassland competition can be used for cost-effective sustainable weed control. However, effective weed management requires a precise knowledge of the effects of agronomic practices and there is a lack of quantitative indicators to compare and predict the success of weed control by competition. Here, we studied weed abundance dynamics over a 12-year period in crop-grassland rotations (rotation treatments consisted of maize, wheat and barley crops, alternating with temporary grassland maintained for three or six years in the rotation and fertilised with ∼30 or ∼230 kg ha−1 year−1 of nitrogen). In addition to classical statistical analysis of the different rotation treatments, we modelled weed abundance as a function of the crop and grassland competition, expressed here by biomasses harvested in the preceding years. We show that weed abundance decreases over the years in grassland and subsequent crops only if the grassland receives sufficient nitrogen fertiliser. Our model had a greater explanatory power than the rotation treatments. This model estimates a critical biomass level above which weeds are suppressed in subsequent years, and below which they tend to thrive. This critical biomass level was 24.3 and 4.7 tonnes ha−1 of dry matter for crops and grassland, respectively, highlighting the greater competitiveness of grasslands than of crops. Several clear differences between weed functional groups emerged. This new modelling approach directly links the interannual dynamics of weed populations to current and previous biomass production levels. This approach facilitates the development of environment-friendly weed management strategies and paves the way for comparisons of the competitiveness against weeds of crops and grassland under various pedoclimatic conditions and agronomic practices.

Nutrient Cycling in Organic Field Crops in Canada and the United States

Organic farmers have identified soil fertility and weed management as the two highest research priority areas. No review exists of research on soil nutrient management in organic field crop systems. We conducted a comprehensive review to identify the principles and factors governing nutrient management, knowledge gaps, and future research needs in organic grain and other field crop systems in Canada and the United States. We compared results from research conducted in different climates, soils, and crop rotational sequences. Results indicate that (i) dual‐use cover/green manure crops and/or animal manure are the most common sources of plant available N and other nutrients in organic field crop systems; (ii) soil nutrient deficiencies can develop through sole reliance on cover/green manure crops; (iii) dependence on animal manure can lead to N and P excesses; (iv) conventional soil testing procedures may not accurately predict crop nutrient needs; (v) greater knowledge of microbial processes governing nutrient cycling is needed; and (vi) better understanding of the impact of weeds on soil fertility may create weed and nutrient management synergies. Knowledge gaps include a lack in understanding of how the soil and plant biomes influence nutrient‐use efficiency and how crop diversity and rotations impact soil fertility, sustainability, and resilience in organic field crop systems. Likewise, interactions between weeds, crops, soil fertility, and weed management strategies are poorly understood.Core Ideas Soil, climate, fertility sources, and land use impact organic nutrient management strategies. Cover/green manure crops and animal manures are used to maintain soil fertility on organic farms. Conventional soil testing may not be ideally suited to organic systems. Tracking soil nutrient temporal changes can improve comprehensive nutrient management plans. More research of how weeds and soil microbial community structure/function impact nutrient cycling and crop production is needed.

Non-Target-Site Resistance to Herbicides: Recent Developments.

Non-target-site resistance (NTSR) to herbicides in weeds can be conferred as a result of the alteration of one or more physiological processes, including herbicide absorption, translocation, sequestration, and metabolism. The mechanisms of NTSR are generally more complex to decipher than target-site resistance (TSR) and can impart cross-resistance to herbicides with different modes of action. Metabolism-based NTSR has been reported in many agriculturally important weeds, although reduced translocation and sequestration of herbicides has also been found in some weeds. This review focuses on summarizing the recent advances in our understanding of the physiological, biochemical, and molecular basis of NTSR mechanisms found in weed species. Further, the importance of examining the co-existence of TSR and NTSR for the same herbicide in the same weed species and influence of environmental conditions in the altering and selection of NTSR is also discussed. Knowledge of the prevalence of NTSR mechanisms and co-existing TSR and NTSR in weeds is crucial for designing sustainable weed management strategies to discourage the further evolution and selection of herbicide resistance in weeds.

Effects of seed bed types and weed control methods on the vegetative parameters of long cayenne pepper (Capsicum frutesens L)

Effects of seed bed types and weed control methods on the vegetative parameters of long cayenne pepper (Capsicum frutesens L)

Floristic composition, phytosociology and weed diversity in chives (Allium schoenoprasum L.)

Assessment of floristic composition, phytosociology and diversity of weed communities are crucial for weed control in chives. A survey was conducted on two selected chives cropping fields in the state of Maranhão, northeastern Brazil to identify the weed flora and the most important weed species associated with chives. The weed survey was carried out by the quadrat method with 30 weed samples taken from each chives field. Phytosociological parameters assessed were absolute and relative densities, frequencies and abundances and the importance value of each species. Weed diversity was assessed by the Shannon Diversity Index (H’). We recorded a total of 3,689 individuals from 36 species and 16 families. The two families with the highest species richness were Poaceae (n = 7) and Cyperaceae (n = 5). The greater number of species (30) was recorded in the chives grown in Catucá. The most important species based on the importance value were Hediotys corimbosa, Schoenoplectus juncoides and Ludwigia octovalvis, in Areal and Eleusine indica, Trianthema portulacastrum and Cyperus iria in Catucá. Floristic diversity was higher in Areal (H’ = 5.21 nats. ind-1). These results could lead to improved weed management strategies in chives croppping in the state of Maranhão, northeastern Brazil.

Weeds as Reservoirs of Plant Pathogens Affecting Economically Important Crops

Weeds are a major contributor to yield loss and reduction in yield quality in an agricultural setting, competing with the crop for resources like light, water, and nutrients. This competition along with the cost of weed management strategies like tillage and herbicides, are responsible for the economic impact of weeds, which can reach into the billions. In addition to the damage caused by direct competition, weeds can also harm crop plants by acting as reservoirs for destructive plant pathogens, the insect vectors that move these pathogens from plant to plant, or both. The objective of this publication is to summarize previously published weed-pathogen associations to help growers scout and monitor pathogens in weeds near production areas.https://edis.ifas.ufl.edu/hs1335

Using panicle dry weight to estimate seed production inEchinochloa crus‐galli

SummaryA better understanding of weed seed production is a key element for any long‐term management allowing some weeds to shed seeds. The challenge with measuring seed production in weeds is the large effort required in terms of time and labour. For the weed speciesEchinochloa crus‐galli,it was tested whether the number of seeds per panicle dry weight or per panicle length can be used to estimate seed production. Experiments were conducted in three maize fields in north‐eastern Germany. The effect of factors that could influence this relationship, such as the time of seedling emergence, the density ofE. crus‐galli, the control intensity of other weeds, seed predation and field, was included. A few days before maize harvest, all panicles were removed and weighed, panicle length was measured, and for a subsample of 178 panicles, the number of seeds was counted manually. Panicle dry weight predicted the number of seeds per panicle better (R2 = 0.92) than did panicle length (R2 = 0.69). The other factors except for ‘field’ and ‘seed predation’ had no effect on these relationships. The relationships between seed number and panicle dry weight found in this study closely resembled those reported in an earlier study. Based on our results, we conclude that both plant traits are appropriate for the estimatation of seed production, depending on required level of precision and availablilty of resources for the evaluation of sustainable weed management strategies.

Grasses as suitable targets for classical weed biological control

Grasses are amongst the most abundant and environmentally damaging invasive weeds worldwide. Biological control is frequently employed as a sustainable and cost-effective management strategy for many weeds. However, grasses have not been actively pursued as targets for classical weed biological control due to a perceived lack of sufficiently specialised and damaging natural enemies to use as biological control agents. There are also concerns that the risk posed to economically important crop/pasture species and closely-related native species is too great to consider implementing biological control for invasive grasses. In this paper, we review the literature and demonstrate that grasses can possess suitably host-specific and damaging natural enemies to warrant consideration as potential biological control agents. The risk of grass biological control is no greater than for other weedy taxa if practitioners follow appropriately rigorous risk assessments protocols.

The response of glyphosate-resistant and glyphosate-susceptible biotypes of annual sowthistle (Sonchus oleraceus) to mungbean density

AbstractAnnual sowthistle (Sonchus oleraceus L.) is a major weed of mungbean crops in Australia. Resistance in this weed to several herbicide groups is a challenging issue for its management. Hence, cultural weed management strategies, such as increasing the crop competitive ability through increased stand density, should be considered to reduce reliance on herbicides. It was hypothesized that a competitive crop stand may reduce the growth and seed production of S. oleraceus. Two pot studies were conducted, and each study was repeated once. The first study evaluated the effect of different mungbean [Vigna radiata (L.) R. Wilczek] densities (0, 82, 164, 246, and 328 plants m−2) on S. oleraceus growth and seed production, while the second study focused on glyphosate-resistant and glyphosate-susceptible biotypes of this weed in competition with densities of 0, 82, and 164 mungbean plants m−2. Although increasing mungbean density from 0 to 82 and 164 plants m−2 reduced S. oleraceus seed production by 55% and 78%, respectively, a large number of seeds were produced, even at the mungbean density of 328 plants m−2 (1,185 seeds plant−1). Both glyphosate-resistant and glyphosate-susceptible biotypes of S. oleraceus responded similarly to the increase in mungbean density. The results of the second study showed that height, leaves, number of inflorescence, and seed production per plant of both glyphosate-resistant and glyphosate-susceptible biotypes were reduced but not suppressed adequately. The glyphosate-resistant biotype produced fewer leaves and less biomass and, consequently, its seed production was 24% less compared with the glyphosate-susceptible biotype in the no-competition treatment. Both biotypes of S. oleraceus produced about 4,000 seeds plant−1 in competition with 164 mungbean plants m−2. The results suggest that crop competition alone cannot provide satisfactory control of S. oleraceus; therefore, for effective and adequate weed management, other practices such as PRE herbicides should be integrated with increased crop density.

Seasonal Hay Feeding for Cattle Production in the Fescue Belt

AbstractWe determined how pasture and grazing management practices affected the number of days hay was fed to cattle by season. Data were collected from a survey of Tennessee cattle producers. Days of cattle on hay varied across seasons because of variations in forage production and weather. The number of days hay was fed to cattle varied with pasture-animal management practices such as rotating pastures, forage mixtures, and weed management strategies. Having mixtures of cool- and warm-season grasses reduced the number of days on hay in the winter, spring, and summer months indicating benefits from diversified forages.