Summer Weeds Research Articles

Spring sown camelina (Camelina sativa) contributes to the management of three summer weeds

Camelina (Camelina sativa (L.) Crantz) is an attractive drought-tolerant crop for Mediterranean regions due to its rapid growth and ability to out-compete many dicotyledonous winter annual weeds. In this experiment the weed suppression capacity of spring sown camelina against Chenopodium album L. (common lambsquarters), Polygonum aviculare L. (prostrate knotweed), and Xanthium spinosum L. (spiny cocklebur) was studied. The trial was conducted in Lleida (Spain) between 2019 and 2021. Camelina was sown in March each year. Experimental plots contained quadrats with each weed species as well as weed-free and crop-free quadrats. Height and aboveground biomass of weeds in competition with camelina decreased by over 50 % compared to the controls. However, crop and weed growth had seasonal differences depending on the weather conditions: (1) a moderately dry spring promoted crop production (1573 kg ha−1); (2) a rainy spring benefited weed development, negatively affecting crop growth and yield (739 kg ha−1); and (3) a severe dry spring affected growth of both crop and weeds, reducing crop production by up to 80 % (298 kg ha−1). The summer weed suppression capacity of camelina is enhanced by drought conditions, which makes camelina useful for managing these weeds.

Allelopathic potentiality of Trianthema portulacastrum L. shoot extract and mulch on germination and growth of two summer weeds

Allelopathic potentiality of Trianthema portulacastrum L. shoot extract and mulch on germination and growth of two summer weeds

The Influence of Sugar Beet Cultivation Technologies on the Intensity and Species Biodiversity of Weeds

Sugar beet production is highly affected by weeds. The structure of crop rotation, the use of intercrops and different tillage techniques bring several benefits to sugar beet cultivation and create different living conditions for weeds. The response of weed communities in sugar beet stands has not been studied. The experimental plot is in the cadastral area of Ivanovice na Hané (Czech Republic). During an eight-year monitoring period (2013–2020), 46 weed species were identified. The dominant species was Chenopodium album. There were also summer and winter weeds. A more varied crop rotation increased the intensity of weed infestation, with winter weeds being the most common. On the contrary, a higher proportion of cereals in the crop structure favors the presence of summer weeds. The tillage technology and the inclusion of catch crops did not significantly affect the intensity of weed infestation in sugar beet stands or the spectrum of weed species. Current cropping technologies have driven the evolution of weeds. Due to their short life cycles and relatively simple genomes, weeds can respond very quickly to technological measures and, thus, change their harmfulness.

Cover crops terminated with roller-crimper to manage Cynodon dactylon and other weeds in vineyards.

Using cover crops in organic vineyards can provide many advantages, including weed suppression. However, their effectiveness may depend on the weed community, the cover crop species and the termination method. The most common practice for cover crop termination is shredding, but rapid residue decomposition can allow noxious species like Cynodon dactylon to proliferate during summer and compete with the vines. The use of roller-crimpers as an alternative method can be effective in some cropping systems, but no studies have focused on their use in the inter-row of vineyards. The objective of this study was to evaluate the effectiveness of seven cover crops (spontaneous, Avena strigosa, Hordeum vulgare, Lolium multiflorum, Phacelia tanacetifolia, Sinapis alba and X Triticosecale) and two termination methods (shredding or roller-crimper) in managing C. dactylon during summer. In 2020, rolled A. strigosa, P. tanacetifolia and the spontaneous flora limited the coverage of C. dactylon more than shredding (increases of 3% and 18% in C. dactylon cover from July to September in rolled and shredded cover crops, respectively), while in 2021, rolling was better than shredding for all cover crop species in September (5% and 18% increases, respectively). Roller-crimping cover crops was an effective method to control C. dactylon in vineyard inter-rows but it did not consistently work for all cover crops in both years. Our study is one of the first to test the efficacy of roller-crimpers to manage summer weeds in vineyards. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Channel Attention GAN-Based Synthetic Weed Generation for Precise Weed Identification.

Weed is a major biological factor causing declines in crop yield. However, widespread herbicide application and indiscriminate weeding with soil disturbance are of great concern because of their environmental impacts. Site-specific weed management (SSWM) refers to a weed management strategy for digital agriculture that results in low energy loss. Deep learning is crucial for developing SSWM, as it distinguishes crops from weeds and identifies weed species. However, this technique requires substantial annotated data, which necessitates expertise in weed science and agronomy. In this study, we present a channel attention mechanism-driven generative adversarial network (CA-GAN) that can generate realistic synthetic weed data. The performance of the model was evaluated using two datasets: the public segmented Plant Seedling Dataset (sPSD), featuring nine common broadleaf weeds from arable land, and the Institute for Sustainable Agro-ecosystem Services (ISAS) dataset, which includes five common summer weeds in Japan. Consequently, the synthetic dataset generated by the proposed CA-GAN obtained an 82.63% recognition accuracy on the sPSD and 93.46% on the ISAS dataset. The Fréchet inception distance (FID) score test measures the similarity between a synthetic and real dataset, and it has been shown to correlate well with human judgments of the quality of synthetic samples. The synthetic dataset achieved a low FID score (20.95 on the sPSD and 24.31 on the ISAS dataset). Overall, the experimental results demonstrated that the proposed method outperformed previous state-of-the-art GAN models in terms of image quality, diversity, and discriminability, making it a promising approach for synthetic agricultural data generation.

Impact of eco-physiological factors on the weed seed germination and emergence: A review on its role in weed management

Dormancy is a typical feature of many weed seed populations, which makes forecasting the time and magnitude of weed emergence difficult. The mean minimum temperatures required for undergoing germination of different weed seeds varies considerably depending on the place of their origin as well as the season on which the plants grow. For instance, the temperature requirement for the germination of summer weeds was observed to be 40% higher than for the winter weeds. Decreasing the water potential from 0 Mpa (mega pascal) to -1.0 Mpa tends to reduce the germination capacity of many weed seeds with some seeds totally failing to germinate at -1.0 Mpa (Chloris truncate, Retama raetam). The effects of planting depth on seed germination and seedling growth of Aframomum citratum on varied soil types indicated that sowing depth greatly influenced the plant's cumulative germination percentage and early growth. The seeds of Sysimbrium officinale (L.), a summer annual species, displayed greater sensitivity to nitrates and lost dormancy throughout the winter. The germination of Thlaspi arvense was also discovered to be stimulated by nitrate only in the presence of light. Tilling the surface of soil has a positive impact in the weed seed germination, however if the tillage depth increases more than 9cm, it tends to lower down the germination of several weed species. However, weed seeds of Bernard grass are among the exceptions in which they germinate better at a shallow depth (2cm). The nature and the thickness of the mulching component influence the germination of weed seeds. Thicker mulches and mulching materials like pearl millet resulted in a greater suppression of the weed seed germination due to an increased allelopathic effects.

Influence of environmental factors on seed germination and seedling emergence of Amaranthus blitoides S. Watson and A. hybridus L.

AbstractAmaranthus blitoides S. Watson and A. hybridus L. are common herbaceous annual summer weeds in different regions of Iran, which produce a large number of small seeds per plant. The goal of these experiments was to determine seed germination cardinal temperature and investigate the effect of constant temperature, osmotic and salt stresses, stratification, flooding duration, after‐ripening and seed planting depth on seed germination and seedling emergence. Two‐piece segmented, dent‐like and beta four‐parameter models were used to investigate the relationship between germination rate and constant temperature. The dent‐like model showed the best description of the effect of constant temperature on seed germination rate of both A. blitoides and A. hybridus. Optimal seed germination of A. blitoides occurred at 35°C, but in A. hybridus optimum germination was observed in a range of constant temperatures from 30 to 40°C. Osmotic and salt stresses and flooding adversely affected seed germination of both species. After ripening for 6 months increased germination percentage of both A. blitoides and A. hybridus. Maximum seedling emergence of A. blitoides (42.8%) and A. hybridus (44.9%) occurred at a planting depth of 3.3 cm, whereas further increased planting depth minimized seedling emergence of both weeds. Information obtained from this study will help us to develop effective techniques for management of A. blitoides and A. hybridus.

Different cover crops have a limited impact on marketable yields and biogeochemical cycling but secondary effects on pollinators and plant-parasitic nematodes in Florida organic vegetable systems

Cover crops are typically grown during the summer in Florida’s organic vegetable systems, where they can affect nutrient cycling, soil health, and pests/pollinators. We compared the effects of five summer cover crops and a weedy fallow on marketable yields and the cycling of phosphorus, potassium, and carbon. Weed, nematode, and insect pollinator abundance were also monitored to measure any secondary impacts of cover cropping. Cover crops included monocultures of sunn hemp or sorghum sudangrass, a sunn hemp and sorghum sudangrass biculture, a three species mixture (biculture plus buckwheat), and a five species mixture (three species mixture plus cowpea and sunflower). In both 2018 and 2019, cover crops were planted in June and terminated in August, and bell peppers were grown from August until December. Marketable yields were greater with the tree and five species mixtures relative to the biculture in 2018, with no effects of cover crops on yields in 2019. Phosphorus and potassium accumulation was typically greater with cover crops than in the weedy fallow, but cover crops did not affect pepper nutrient accumulation or soil concentrations. Similarly, differences in carbon accumulation (lowest in sorghum sudangrass monoculture and weedy fallow) did not affect soil organic matter, soil total carbon or permanganate-oxidizable carbon. When analyzed as part of a radar plot analysis, cover crops helped manage summer weeds and root-knot nematodes in 2019, but the sorghum sudangrass monoculture increased sting nematodes; only the three and five species mixtures benefitted pollinators as buckwheat was the only cover crop that flowered in this study. Overall, cover crops had a limited effect on marketable yields and biogeochemical cycling but had more important secondary effects on pests and pollinators.

Herbicide Resistance in Summer Annual Weeds of Australia’s Northern Grains Region

For more than two decades, glyphosate has been relied on to control summer annual weeds in fallow systems in Australia’s northern grains region. With numerous cases of glyphosate resistance reported in weed species collected from this region, there are concerns about the future viability of this herbicide. A random seed collection survey of summer weeds was conducted between 2016 and 2018 with the aim of determining the frequency and distribution of resistance to glyphosate and other herbicides commonly used for summer weed control. Glyphosate resistance was ubiquitous in fleabane, with all collected populations resistant to this herbicide. Glyphosate resistance was also prevalent in feathertop Rhodes grass, windmill grass, and awnless barnyard grass, with resistance detected in 68%, 58%, and 36% of populations, respectively. Only 14% of sowthistle populations collected between 2013 and 2108 were resistant to glyphosate. Resistance to haloxyfop was detected in feathertop Rhodes grass, albeit at a low frequency (2%). Other herbicides, such as 2,4-D amine, propaquizafop, and clethodim, provided good control of the broadleaf and grass weeds tested. The results from these surveys conducted between 2013 and 2017 provide a first glimpse of the state of herbicide resistance in key crop weeds for Queensland and the northern region of New South Wales. It is clear that farmers and agronomists need to consider incorporating non-chemical weed management tactics to promote the sustainability of current herbicides.

EVALUATION OF THE EFFECTS OF HERBICIDES ON THE WEEDS AND THE PRODUCTIVITY OF HYBRIDS MAIZE

In the early stages of maize (Zea mays L.) development, it is important to limit weeds that compete with maize for nutrients, moisture, light. Weed control has various methods, for example, agrotechnical, chemical. The aim of the study is to evaluate of the Effects of Weeds and Hybrids on the Productivity of Maize grain in Ukraine. The research was conducted in field conditions in 2019-2021 at the Mykolayiv National Agrarian University, which is located in the southern steppe of Ukraine. The results of the study show that weeds significantly (P0.05) reduced the maize grain yield. During the grain harvesting period, the number of weeds in GS 89 decreased to 137 and 121 weeds m-2. In the experiment, the predominance of early summer weeds (more than 66%) over late summer weeds (about 49%) was found. Effective weed reduction requires the use of several agrotechnical elements. Grain yield of maize hybrids increased significantly in areas where herbicides were applied. The corn hybrid 'Gran 6' was more productive. Maize hybrid Gran 6 is 1.3 times more productive than maize hybrid Odesskii 385 МВ in all test variants, which was also influenced by the hybrids' biological differences: maize hybrid Gran 6 has a shorter vegetation period and is taller (on average 209.1 cm) than maize hybrid Odesskii 385 МВ, which is 198.0 cm tall on average. Moisture consumption differed in vegetation years (2019-2021), the highest was in 2021 (70.6%), when a higher corn grain yield was also established.

Ecological importance and sociological characters of fourteen widespread weeds and their contribution to the observed (dis)similarity between weed communities

Widespread weeds are a serious nuisance to farmers in any country whether they are growing agricultural or horticultural crops for the great damage they cause to the economy, human health and environment loss. Thus, it is important to measure their ecological importance, sociological characters, their contribution to the observed (dis)similarity between weed communities associated with agronomic and horticulture crops, as well as performing time series analysis and forecasting for their cumulative records. Hopefully with the aforementioned information available, it will be possible to determine the most detrimental which deserve resistance priority within a successful weed control plan, which is the aim of the current study. Depending on species records 2018–2020, fourteen weeds assigned widespread out of the 537-species recorded. Their values in the Importance Value Index (IVI) suggested that Sonchus oleraceus had the highest ecological importance among winter weeds (IVI = 50.5), whereas Bassia indica had the highest IVI among summer weeds (IVI = 42.7) and Cynodon dactylon showed the highest value in the observed competition throughout the year (IVI = 46.2). Analysis of Similarities (ANOSIM) indicates that the weed community structure is significantly affected by widespread weeds and the mean of ranked dissimilarities in floristic composition between groups (weed communities associated with crop categories) is greater than within groups. Similarity Percentage analysis (SIMPER) based on Bray-Curtis as a distance dissimilarity measure, revealed that Cyperus rotundus, Melilotus indicus and Beta vulgaris were the most discriminant species in creating the observed pattern of (dis)similarity between the weed community structure associated with agronomic and horticultural crops during the winter half of the year, while Aster squamatus and Echinochloa colona were the most discriminant during the summer half. It is prominent from the results of the current study and the implemented time-series analysis and forecasting that no-decline is expected in the cumulative records of the 14-widespread weeds when the same current weed management strategy is applied.

Dose–Response Curves of Pelargonic Acid against Summer and Winter Weeds in Central Italy

Pelargonic acid is a non-selective post-emergence contact bio-herbicide which is registered both for cropping and non-cropping uses in several countries. Dose–response curves on the efficacy of pelargonic acid against common weeds in Mediterranean areas are not available. Dose–response curves of pelargonic acid efficacy against summer and winter annual weeds were evaluated in two field experiments (winter exp. in 2019 and summer exp. in 2020) in central Italy. Pelargonic acid was applied at five doses (1.4, 2.7, 5.4, 10.9 and 21.8 kg a.i. ha−1). Data on weed density, weed dry weight, and weed ground cover were used to calculate the efficacy of pelargonic acid against winter and summer weeds. Data were subjected to a non-linear regression analysis using the logistic dose–response model. Dose of pelargonic acid required to obtain 50%, 70%, 90% and 95% weed control against each weed species (ED50, ED70, ED90 and ED95) were estimated. ED values allowed us to classify winter and summer weeds with respect to their susceptibility to pelargonic acid (ED50 values in kg ha−1 are reported in parenthesis): Kickxia spuria (2.6) (more susceptible) > Heliotropium europaeum (3.0) > Echinochloa crus-galli (3.4) > Solanum nigrum (3.6) > Stachys annua (5.3) > Papaver rhoeas (6.5) > Veronica hederifolia (10.3) > Amaranthus retroflexus (11.4) > Matricaria chamomilla (11.6) > Portulaca oleracea (18.7) > Lolium multiflorum (>21.8) (less susceptible). These findings will allow for the optimization of weed control by pelargonic acid and its use in weed management strategies, both in organic and sustainable cropping systems, under different environmental conditions.

Allelopathic potential of summer weeds on germination and growth performance of wheat and chickpea

The biochemical interference between weed-crop for the available resources is one of the most crucial and burning issues for this modern and technologically blessed farming community. Because-of, the early adaptative nature, rapid growth, and fast distribution of weed make it able to inhibit the desired crop growth and reduce the final estimated yields. Thus, our interest was raised in examining the bio-efficacy of some winter weeds against two main agronomic crop germination and seedling growth, and weeds were collected from two different districts D.I. Khan and Peshawar. Wheat variety (Atta Habib) and Chickpea variety (Karak-1) varieties were used in the trial. The experiment was conducted in (2020) in a Completely Randomized Design (CRD) with a factorial arrangement having three replications. We used the following weeds extracts; Trianthema portulacastrum L., Cyperus rotundus L., Plantago lenceolata L., Xanthium strumarium L., Oxalis corniculata L., Eleusine indica L. and distilled water as a control in this study, and introduced them to chickpea and wheat seeds. Our results show that weeds collected from district Dera Ismail Khan were more phytotoxic as compared to Peshawar and greatly inhibited the overall seed germination of wheat and chickpea respectively i.e., 44.53%, and 37.97%. In the case of weeds extract inhibitory effect, the T. portulacastrum was declared more repressive for both crops in terms of germination inhibition and seedling growth retardation. Taken together, the T. portulacastrum weed extract of D.I Khan was highly phytotoxic to inhibit the germination and germination of both crops, therefore, eco-friendly and proper weed management tactics require from the farming community in the early stages or before crop sowing.

Effects of dryland summer cover crops and a weedy fallow on soil water, disease levels, wheat growth and grain yield in a Mediterranean-type environment

Numerous studies have reported wide-ranging benefits of cultivating cover crops during the typical fallow period in temperate cropping systems. However, data on the impacts of summer cover crops in water-limited, Mediterranean-type climates, is lacking. A 3-year field experiment was conducted near the town of Northam in the wheat-belt of Western Australia to test the hypothesis that inclusion of summer cover crops would increase ground cover, water storage and grain yield in subsequent wheat crops. White French millet ( Panicum miliaceum ) and cowpea ( Vigna unguiculata ) cover crops and a weedy fallow were compared to a typical chemical fallow over the summer period. Autumn groundcover was 10–30% higher when summer weeds were left uncontrolled compared to the chemical fallow treatment. Dry-sown and late established (February) millet failed to increase groundcover, whereas cowpea demonstrated a small increase (~9–10%) in one season, when cowpea biomass approached 1 t ha −1 . Cover crops and weeds growing over summer had no significant effect on total plant available water (0–50 cm depth) prior to sowing wheat in any season. However, there was less readily available soil N in the cover crop (less 10–30 kg N ha −1 ) and weedy fallow (less 50 kg N ha −1 ) treatments prior to the second wheat crop. Despite some significant effects of weedy fallow and cowpeas on Gaeumannomyces graminis var tritici (take-all) and Didymella pinodes (causing black pea spot), disease levels were low and thought to pose little risk to following winter crops. Wheat grain yields were not significantly different between treatments, other than a low yield after cowpeas in 2015 due to a low wheat emergence count. Grain protein and screenings were not generally affected by summer fallow treatment in any year, except for higher screenings after the weedy fallow in one year. Given the limited impacts of cover crops and weeds on soil water and disease, it is possible that summer cover crops may be able to be integrated with cereal winter rotations in Western Australia without yield reductions in wheat crops. In light of current chemical usage, issues around herbicide residues in soil and herbicide-resistant weeds, it would be worthwhile revisiting the need for chemical fallow, particularly in the higher rainfall areas.

Improving weed control in sustainable agro-ecosystems: Role of cultivar and termination timing of rye cover crop

Alternative strategies to control weeds are required at the field level to reduce herbicides and derived pollution. As cover crop, rye (Secale cereale L.) is adopted mainly because of its allelopathic weed control, which takes place through a strong inhibition of germination and seedling growth in several types of grass and broad-leaved weeds. The present study consisted of: i) a field trial, focused on the evaluation of biomass production and allelochemical concentration in the biomass, and in situ weed control at 30 days after termination (with two termination timings: T1 - heading phase and T2 - 10 days later) of 8 rye varieties; ii) a pot experiment, focused on the inhibition effect of mulches derived by those 8 rye varieties on four summer weeds: velvetleaf (Abutilon theophrasti Med.), lambsquarters (Chenopodium album L.), redroot pigweed (Amaranthus retroflexus L.), and common purslane (Portulaca oleracea L). Results showed that biomass production was the highest with Protector, closely followed by Primizia, Sito 70, Hellvus, Forestal, and Hymonta. In any case, rye mulching always reduced the weed biomass, especially with Fasto and Forestal. The allelochemical concentration in the biomass was the highest with Fasto and Forestal and decreased on average from T1 to T2 (–38% for total benzoxazinoids and –57% for isovitexin). Conversely, the rye biomass production increased (on average +77%), passing from T1 to T2. We also found that the reduction of weed biomass, compared with the control, is highly correlated with the allelochemical content in rye biomass in the case of T1 termination, while with the biomass production in the case of T2. In pots, a strong inhibitory effect on seedling growth due to rye mulching was observed for C. album (–76%), A. retroflexus (–56%), and P. olearcea (–84%), while not for A. theophrasti. We concluded that, regardless of the variety, adopting rye as a cover crop may be considered as a suitable practice to reduce weed pressure at the field level. Among all the varieties tested, Forestal and Protector showed the most significant weed suppression potential, due to the high amount of allelochemicals production for Forestal and high biomass production for Protector. Highlights - One month after rye termination, the weed biomass under mulching is reduced by 4 times, compared with the control. - When rye is terminated early, the allelochemical content in rye tissues reduces the weed biomass production. - When rye is terminated late, the weed biomass production is reduced by the amount of rye biomass. - Lambsquarters, redroot pigweed and purslane growth is inhibited by rye mulching, while velvetleaf is not affected.

Emergence patterns of winter and summer annual weeds in Ethiopian mustard (Brassica carinata) cropping system

Abstract Ethiopian mustard (Brassica carinata A. Braun) is a biofuel crop recently introduced in the southeastern United States. For this crop to be successful, integrated weed management strategies that complement its rotation with summer cash crops must be developed. The objectives of this research were to evaluate the effect of previous season summer crops on winter weed emergence patterns during Ethiopian mustard growing season and to assess the impact of planting Ethiopian mustard on the emergence patterns of summer weed species. Gompertz models were fit to winter and summer weed emergence patterns. All models represented more than 80% of the variation, with root mean-square error values less than 0.20. The emergence pattern for winter weed species was best described using growing degree-day accumulation, and this model can be utilized for implementing weed control strategies at the critical Ethiopian mustard growth stages. The results also showed that summer weeds can emerge during the winter in northern Florida but do not survive frost damage, which might create off-season seedbank reductions before the summer crop growing season.

Germination Parameters of Selected Summer Weeds: Transferring of the AlertInf Model to Other Geographical Regions

Effective weed management depends on correct control timing, which depends on seedling emergence dynamics. Since soil temperature and soil moisture are the two main factors that determine weed germination, the hydrothermal time model can be used to predict their emergence. The aim of this study was to estimate the base temperature (Tb) and base water potential (Ψb) for the germination of Chenopodium album, Amaranthus retroflexus, Setaria pumila, and Panicum capillare collected from fields in continental Croatia and then to compare these values with those of Italian populations embedded in the AlertInf model. Germination tests were performed at seven constant temperatures (ranging from 4 to 27 °C) and eight water potentials (0.00–1.00 MPa). The estimated Tb and Ψb were 3.4 °C and −1.38 MPa for C. album, 13.9 °C and −0.36 MPa for A. retroflexus, 6.6 °C and −0.71 MPa for S. pumila, and 11.0 °C and −0.87 MPa for P. capillare, respectively. According to the criterion of overlap of the 95% confidence intervals, only the Tb of C. album and the Ψb of A. retroflexus of the Croatian and Italian populations were similar. Further field experiments should be conducted to monitor the weed emergence patterns of C. album and calibrate the AlerInf equation parameters.

Crop residue retention suppresses seedling emergence and biomass of winter and summer Australian weed species

AbstractCrop residue retention could affect the emergence and biomass of weeds in different ways. A summer and winter pot study was conducted to evaluate the effect of different amounts of sorghum and wheat residue on the emergence and biomass of 12 summer and winter Australian weeds. The equivalent amount of sorghum residue to 0, 1, 2, 4 and 6 t/ha was used in the summer study and winter weed seeds were covered with wheat residue equivalent to the amount of 0, 1, 2, 4 and 8 t/ha in the winter study. The emergence and biomass of Amaranthus retroflexus and Echinochloa colona was not affected by sorghum residue treatment. For other summer weeds, the use of the 6 t/ha sorghum residue treatment resulted in 59–94% reductions in biomass compared to no‐sorghum residue retention. Similarly, the application of 8 t/ha wheat residue in the winter study resulted in a reduced biomass of 15–100% compared to no‐crop residue treatment. The results demonstrated the high potential of using crop residues in eco‐friendly weed management strategies, such as harvest weed seed control tactics.

Incorporation of winter grasses suppresses summer weed germination and affects inorganic nitrogen in flooded paddy soil

ABSTRACT Laboratory experiments were conducted to investigate how incorporation of the winter grasses foxtail (Alopecurus aequalis) and milk vetch (Astragalus sinicus) into flooded paddy soil affects the germination of summer weeds and soil inorganic nitrogen (N) levels. Polyethylene terephthalate (PET) vessels (10.0 × 8.0 × 15.0 cm) were filled with 0.7 kg air-dried soil that had been collected from organic paddy fields located in Tochigi, Japan. Foxtail and milk vetch were then independently incorporated into the soil at rates of 0% (untreated control), 0.25%, 0.5%, 1%, and 1.5%, with four repetitions per treatment. The PET vessels were placed in a growth chamber (Biotron) set to day/night temperatures and humidities of 27/18°C and 70%/65%, respectively, and with an illuminance of 40,000 lx (12 h) for 28 days, and the total number of weeds and changes in the electrical conductivity (EC) of the surface water were investigated throughout this period, while changes in soil inorganic N were determined at the ends of the experiments. The incorporation of both foxtail and milk vetch significantly suppressed the germination of summer weeds by 56% and 50%, respectively, at incorporation rates of 1% and by 78% and 77%, respectively, at incorporation rates of 1.5% compared with their respective controls. There was a high and significant positive correlation between both the rate of winter grass incorporation and the degree of growth suppression and EC. Incorporation of foxtail at rates of 0.25% and 0.5% significantly increased the inorganic N contents of the sub-layer by an average of 68% compared with the control but had no significant effect in the top layer, whereas the incorporation of milk vetch at a rate of 1% significantly increased the inorganic N contents of both the top layer and sub-layer by 200% and 316%, respectively, compared with the control. Furthermore, the effect of milk vetch on inorganic N significantly increased with an increase in the rate of incorporation. These findings demonstrate that incorporation of the winter grasses foxtail and milk vetch into flooded organic paddy soil can suppress weed growth and act as a source of inorganic N.

Mechanical characterization of blends containing recycled paper pulp and other lignocellulosic materials to develop hydromulches for weed control

Spreading of hydromulch as a crop management technique might show important advantages over plastic films for weed control, because it can be applied anywhere in a field, even in orchard and vineyard rows. In the present work, 24 blends were prepared by mixing paper pulp, from recovered paper and cardboard coming from paper mills, with different additives: (a) wheat straw, rice hulls, and substrate used for mushroom cultivation on the one hand as fillers, and (b) rice bran, white glue, sodium silicate, and powered gypsum on the other hand as agglomerating agents. The blends were tested with a texture analyser to evaluate their mechanical properties, testing the puncture resistance (24 blends) and the tensile strength (15 blends). Scanning electron photomicrographs of some blends were obtained in order to explore the relationship between their components and the mechanical properties. The results indicate that a blend prepared with paper pulp, wheat straw sieved at 2.5 mm and gypsum attained the highest stress resistance and tensile strength. An environmentally controlled experiment was performed on this and another hydromulch in which rice husk substituted wheat straw to evaluate their efficiency for reducing weed seedling emergence, using propagules of four common summer weeds. Compared with the control treatment performed, the hydromulches reduced seedling emergence from 64.6% to 95.9%. In general, the percentage of dead seedlings underneath was greater than that which passed through the barrier, making the hydromulches promising tools for preventing seedling emergence and for managing the weed seed bank in field conditions.