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Cover crops (CC) are biological tools with a great potential for weed control, but the suppression level depends on the CC species and management. A 2-year study was performed in the eighth year of a long-term experiment located in Central Spain to study the effect of replacing winter fallow by barley (Hordeum vulgare L.) or vetch (Vicia sativa L.), on the weed control. Moreover, two CC termination dates were evaluated. Weed biomass, density, diversity, population composition and the seed bank were assessed. Ground cover and CC biomass, soil inorganic N and topsoil water content were determined throughout the season. Barley achieved a greater weed control compared to vetch in winter and early spring. Later in May, both CC residues decreased weed density compared to fallow (63% in 2015, 55% in 2016), and reduced the density of some broadleaf species (i.e. Xanthium spinosum L. reduced >50%). The weed seedbank density was not affected by CC but the effect on specific species confirmed the control over Xanthium spp. (78% reduction), and also warned of the incomplete weed control by CC. The year in which the biomass and ground cover increased between termination dates, delaying the CC termination reduced weed density >75%. Therefore, delaying the termination date was a mean to increase weed control but should be performed with caution to avoid pre-emptive competition with the cash crop. Results underline the relevance of CC species and the termination date as management tools for weed control, and must be considered to plan specific management strategies in different scenarios.
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... Cover crops can produce large amounts of biomass, thus improving carbon sequestration and soil organic matter (OM) content [10]. They can also compete directly with weeds and limit their growth during the fallow period and, as a consequence, reduce seedbank deposits [11][12][13][14]. When flowering cover crops are included in the cropping system, they can also attract more beneficial insects and reduce plant diseases [5]. ...
... The six cover crop species produced large amounts of biomass, especially the clover species (6-10 ton/ha). All the species of legumes tested were able to adapt to local conditions, leading to biomass production higher than the 4-6 ton/ha reported elsewhere [11,13,14]. ...
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Grain corn is the main cereal produced in Portugal. It is grown in intensive monoculture cropping systems that may have negative effects on soil quality, affecting long-term fertility and productivity, and, therefore, the sustainability of the production. A promising management practice to mitigate soil degradation is to grow winter cover crops used as green manure. This study examined the effectiveness of six legume cover crops (LCCs) species in providing agro-ecological services for grain corn systems in the Mediterranean region, specifically in terms of nutrient leaching, nutrient recycling, weed control, and soil fertility. The study was performed in Central Portugal during 2 years, and it assessed legumes/weeds dry biomass yield, their nutrients content, and soil organic matter evolution. Results show that, in general, LCC are well adapted to Mediterranean conditions, yielding large amounts of biomass (up to 8 ton/ha for some clover species). In terms of nutrient leaching mitigation, the overall N–P–K nutrient uptake was 176–20–172 kg/ha. Green manure services enabled a reduction of 35% of N, 50% of P, and 100% of mineral fertilizers for a grain corn production of 12 ton/ha. Weed control by LCC was effective only in the second year of the study and for three clover species (crimson, balansa, and arrowleaf) due to their early establishment and/or high biomass production competing with weeds. Soil fertility was not improved in the short term, LCC incorporation into the soil to a slight depletion of the soil organic matter content.
... Conventionally managed farmland fields are bare every year after the harvest of the summer crop. Planting cover crops reduces or eliminates this fallow period and provides aerial biomass during winter and spring to compete directly with weeds (Alonso-Ayuso et al., 2018;Brust et al., 2014;Teasdale & Mohler, 2000). But at the same time, the presence of a cover crop alters the thermal environment perceived by seeds located in the first centimetres of the soil, decreasing the thermal amplitude, and consequently preventing seed dormancy termination in a population requiring this stimulus (Benech-Arnold et al., 1988). ...
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Seed dormancy is a common attribute of many weed species in temperate habitats that controls the seasonality of weed emergence from soil seedbanks. For some weed species, it is not enough to reduce seed dormancy, as germination can only proceed after exposure to dormancy termination factors (i.e. light and alternating temperatures). Sensitivity to alternating temperatures in Polygonum aviculare seeds increases during dormancy release. However, it is not known whether this sensitivity is lost during dormancy induction. The aim of this study was to investigate and quantify the changes in dormancy level of P. aviculare seeds during secondary dormancy induction, as measured by changes in sensitivity to alternating temperatures driven by the soil temperature. To achieve these objectives, seeds were stratified at 5°C until obtaining a minimum dormancy level. The seeds were then buried in pots and induced into secondary dormancy by storing them at 10, 15, 20 and 25°C for different time periods. During storage, seeds were exhumed periodically and exposed to different cycle‐doses of 10/24°C (12 h/12 h) (0, 1, 3, 5 and 15 cycles) to test germination. Our results showed that the high sensitivity to alternating temperatures achieved during primary dormancy release, decreased during secondary dormancy induction with a rate that is temperature dependent. These changes in sensitivity to alternating temperatures were quantified as a function of the accumulation of thermal time, which was calculated over a base temperature of 7.9°C. Coupling the present model with a previous one to assess changes in sensitivity to alternating temperatures during dormancy release, allowed us to develop a model for the prediction of cyclic changes in sensitivity to alternating temperature in relation to the thermal environment experienced by the seeds during burial. We present this model as a valuable tool for managing the weed seedbank through different agronomic practices.
... Inclusion of green manuring may help in decaying of the weed seeds, whereas cover crop favours the build-up of predators (Shearin et al., 2014). Furthermore, under CA, cover crop species and termination duration would be potential weed management strategies (Alonso-Ayuso et al., 2018). Moreover, seed predation should be integrated with other management practices to reduce the weed emergence and their competitive ability. ...
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The large-scale benefits of conservation agriculture (CA) have resulted in shift from conventional tillage to conservation tillage. This shift in tillage practice has also resulted in the shift in weed flora as well as weed management strategies for sustainable crop production. The weed shift in CA is being realized mainly due to adoption of no tillage, crop residue retention and crop rotation. Adoption of no-tillage practices increases the infestation of small seeded and perennial weeds and concentrates weed seeds in upper soil layers. The adoption of no-till wheat under rice-wheat system increases the infestation of broad-leaved weeds (Rumex dentatus, Medicago denticulata, Sonchus oleraceous) but decreases the infestation of Phalaris minor. Similarly, the adoption of no-till direct seeded or transplanted rice has shown abundance of water logging sensitive weeds such as Trianthemaportul acastrum, Dactyloctenium aegyptium, Digitaria sanguinalis, Cyperus rotundus and Digera arvensis and, which are virtually not observed in transplanted puddled rice. Weed management is really a challenge during the transition phase of CA in crops having restricted post-emergence herbicide options. The success of CA system depends on the efficient weed management with usage of herbicides as pre-planting (non-selective) and post-emergence (selective) options. The pre-plant non-selective herbicides such as glyphosate, glufosinate and paraquat will remain the key weed control tool in CA. The efficacy of pre-emergence herbicides in CA can be reduced due to their interception with crop residue mulch. Proper selection of herbicide, time and method of application as well as spray volume can improve the efficacy of pre-emergence herbicide in CA. However, the over reliance on herbicides alone is not desirable and will lead to shift in weed flora towards the tolerant and resistant ones, hence removal of escaped weeds has been advocated to avoid such situations. In CA system, the absence of tillage, which is otherwise utilized for weed control, presents challenges of designing suitable alternative weed management strategies involving crop plants competitiveness against weeds. Several cultural practices which can be useful are adjustment in crop row spacing, orientation, seeding density and sowing time, and use of competitive crop cultivars, residue mulching, diversified crop rotation, weed seed harvest, allelopathy and cover cropping. The integration of non-chemical and chemical weed management tools has to be utilized as the potential strategy for sustainable weed management in CA.
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Pressure is mounting on the agricultural sector to reduce reliance on herbicides for weed control leading to increased interest in the potential of cover crops to control weeds in summer fallows. The weed suppression ability of three summer cover crop species, buckwheat, millet and teff, was evaluated in field trials at two sites near Camden, NSW in 2021. Buckwheat, millet and teff reduced weed biomass by 65%, 77% and 95%, respectively at Bringelly and by 94%, 92% and 90%, respectively at Lansdowne. Following cover crop desiccation, teff residues reduced weed emergence in subsequently planted wheat by 73% and 26% at Bringelly and Lansdowne, respectively. Overall cover crops were found to be effective in suppressing weed emergence, growth, and reproductive capacity. These studies identified teff grass as an important summer crop option for the northern grains region.
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The ability of adaptation of Rhizobia in diverse environment namely, soil, rhizosphere and grown within legume roots may lead to nitrogen fixation, in a complicated process which contain a coordinated exchange of signal between plants and the symbionts. Green manures, cash and cover crops have significant role in soil fertility. Green manuring techniques also can decrease biomass burning known as main source of air pollutant in the atmosphere. Catch crops have positive effects on both physical and chemical properties of soil, subsequent crop yield, decrease nitrogen leaching into the ground water, decrease soil erosion, and decrease nitrogen losses in cropping systems. Cover crops are those crops which cover the ground and protect loss of plant nutrients, the soil from erosion, decrease rate of soil moisture by evaporation, lower ground temperature and improve weed control and nutrient recycling. Rhizobia produce Nod factors during the early development of nodules upon perception of flavonoid molecules secreted by legume roots, and Nod factor’s structure dependens on species, chemical, substitutions added which may influence legume specificity. The benefial effects of rhizobia may depend on rhizobium strain, the genotype of the legume, management practices and bio-physical environment. Rhizobium can directly promote both plant growth and plant health, and modulating root architecture and growth via the release of plant phytohormones. In this manuscript, we want to review the most important advantages and benefits of green manures, catch and cover crops with considering the positive effects of rhizobium on soil fertility and sustainable agricultural production.
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Satriawan H, Fuady Z, Ernawita. 2021. The potential of Nephrolepis biserrata fern as ground cover vegetation in oil palm plantation. Biodiversitas 22: 4808-4817. Nuisance plants or weeds are commonly found in agricultural landscapes including in oil palm plantations. Despite being considered as weeds, several of them have the potential to be used as ground cover vegetation including Nephrolepis biserrata (Sw). Schott. This fern species exhibits beneficial characteristic as ground cover plant especially in terms of the contribution of organic matter and soil moisture through the prevention of evapotranspiration. The objective of this research is to explore the potential of N.biserrata as ground cover vegetation in oil palm plantations based on the assessment of its ecological characteristics regarding the growth and decomposition rate, tolerance to shade, organic contents and carbon accumulation. The split plot experimental design was used with the age of oil palm plants was used as main plot while in the sub-plots the spacing of N. biserrata was used at three varying distances 10x10cm, 20x20 cm, and 30x30 cm, each treatment had three replicates. Nine parameters observed were the percentage of growth, the percentage of ground cover, plant height, fronds number per plant, leaves number per plant, Leaf Area Index, dry weight (g), nutrient content in plant tissue, and potential carbon stock. Results showed that N. biserrata showed rapid growth in covering the ground surface (8-12 weeks after planting), had rapid decomposition rate (30-60 days), tolerant to shading which was characterized by the highest percentage of growth up to 81.16% and covering area up to 95.9%, accumulated organic contents of N (1.23-1.53%), P (0.18-0.22%), and K (1.4-1.67%), respectively. In addition, total dry weight biomass obtained was 27.1 ton/ha, accumulated carbon in plant of 0.9 tons C/ha/year, and amount of soil carbon stock 76.4-97.4 tonnes/ha/year. The results of this study suggest that Nephrolepis biserrata is a potential plant to be utilized as a ground cover plant in oil palm plantations.
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Accurate evaluation of weed density is crucial for effective utilization of herbicides, improvement of rice quality, and reduction of herbicide dosages. The application of visual methods is disadvantageous because intra-row weeds are blocked by the canopies of adjacent rice plants. Therefore, an innovative tactile sensing method is proposed. A flexible gasbag filled with special microstructures distributed over its surface was developed. The tactile data of weed density were generated through contact between the microstructures and weeds, and the data were measured using the voltage value of a barometric sensor mounted inside the gasbag. The tactile time series was processed using fractal theory and Hilbert–Huang transform (HHT), and the discriminating features of the weed density were acquired. The discriminating features were input into a neural network to train a weed density classifier to evaluate the weed density. The results of the feasibility experiment demonstrated that the evaluation accuracies for high-density, medium-density, and low-density weeds were 95.4%, 91.8%, and 87.9%, respectively, with an average accuracy of 91.7%. The field validation test demonstrated that the visual-based method had an average classification accuracy of 64.17%, whereas the proposed method had an average accuracy of 77.04%, experimentally demonstrating superior accuracy over the image-based method.
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ÖZET Turunçgil yetiştiriciliğinde, yabancı otların ürüne verdiği zararlar, hastalık etmenleri ve zararlı böcekler gibi gözle görülen bir simptom veya zararlanma oluşturmazlar. Yabancı otların verdiği zararlar, fidanlarda gelişmede gerilik, ağaçlarda çalılaşma, hasatta düşük verim ve kalite kayıpları olarak ortaya çıkmaktadır. Bu yüzden yabancı otlar ile mücadelede bilinçli bir takip ile zararlı yabancı ot türlerinin tanınması ve teşhisi çok önemli hale gelmektedir. Yabancı otlar, yetiştiricilikle ilgili tarımsal işlemlerin (gübreleme, sulama, hasat, vb.) hızlı ve sağlıklı yapılmasına engel olmaktadır. Yabancı otlar ile mücadelede herbisitlerin yoğun kullanımı sonucunda, direnç vb. problemlerin yanı sıra ekosistemde olumsuz etkilenmektedir. Bu çalışma ile turunçgil bahçelerinde kimyasal mücadeleye alternatif olabilecek, sahip oldukları toprak yüzeyini kaplama özellikleri sayesinde yabancı ot türlerinin gelişimini baskılayarak mücadelede kullanılabilecek ve aynı zamanda ekosisteme fayda sağlayabilecek örtücü bitki türlerinin belirlenmesi amaçlanmıştır. Bu amaçla planlanan çalışma, 2019 yılında, Adana ilinin Seyhan ilçesinde yeni tesis edilen bir Enterdonat limon bahçesinde, bölünmüş parseller deneme desenine göre dört tekerrürlü olarak kurulmuştur. Parselizasyon yapıldıktan sonra, sıra arasına, örtücü bitki olarak, adi fiğ (Vicia sativa L.), tüylü fiğ (Vicia villosa L.), arpa (Hordeum vulgare L.), çavdar (Seceale cereale L.), çayır düğmesi (Poterium sanguisorba L.), korunga (Onobrychis sativa Lam.) ve turp (Raphanus sativus L.) ekilmiştir. Her parselde dört adet ¼ m2 ‘lik çakılı alanlar oluşturularak bu alanlar içerisindeki örtücü bitki ve yabancı ot türlerinin sayısı ile kaplama alanları (%) belirlenmiştir. Örtücü bitkiler %10 çiçeklenme dönemine geldiğinde, çakılı alanlar içerisindeki örtücü bitki ve yabancı ot türleri ölçümler yapılmak üzere toprak yüzeyinden biçilerek hasat edilmiştir. Çalışmanın sonuçlarına göre, denemeye alınan tüm örtücü bitki türleri kontrole kıyasla yabancı ot tür sayısını azaltmıştır. Kontrol uygulamasında 16 farklı yabancı ot türüne rastlanmış iken; Arpa ve korungada 10, adi fiğ içerisinde 8, çayır düğmesinde 7, tüylü fiğde 6, çavdarda 3, turpta 1 yabancı ot türü belirlenmiştir. Çalışmada, en çok karşılaşılan yabancı ot türü Ebe Gümeci (Malva sylvestris L.), kontrol parselinde 18.00 adet/m2 iken, tüylü fiğ, çavdar ve turp uygulamalarında sırasıyla 6.75 adet/m2, 6.50 adet/m2 ve 4.00 adet/m2 olarak tespit edilmiştir. Diğer yabancı ot türü olan Sarı Taş Yoncası [Melilotus officinalis(L.) Pall.] ise, kontrol parselinde 5.00 adet/m2 iken, çavdar ve tüylü fiğ uygulamalarında sırasıyla 4.50 adet/m2 ve 2.00 adet/m2 olarak hesaplanmıştır. Turp uygulamasında ise Ebe Gümeci dışında farklı bir yabancı ot türüne rastlanılmamıştır. ABSTRACT In citrus production, damages caused by weeds in the crop do not cause any visible damage like diseases and insects. But appear as an insufficient or, bushy-type growth in trees and yield and quality losses at the harvest. Damages caused by weeds appear as low yield and quality losses in seedlings, undergrowth on trees and harvest. Therefore, in the management against weeds, the recognition and diagnosis of harmful weed species with a conscious follow-up becomes very important. Weeds cause the fast and right application of agricultural practices (fertilization, irrigation, harvesting, etc.) related to cultivation. As a result of intensive use of herbicides in management against weeds, the ecosystem is adversely affected as well as problems such as resistance etc. In this study, it’s aimed to determine the types of cover crops that can be an alternative to chemical management in citrus orchards, can be used in the manage by suppressing the development of weed species through their soil coverage properties, and at the same time can benefit the ecosystem. The study, planned for this purpose, was established in a newly established Enterdonat lemon orchard in the Seyhan district of Adana province in 2019 according to split plots experimental design with four replications. After designing the experiment, cover crops common vetch (Vicia sativa L.), hairy vetch (Vicia villosa L.), barley (Hordeum vulgare L.), rye (Seceale cereale L.), common burnet (Poterium sanguisorba L.), sainfoin (Onobrychis sativa Lam), and radish (Raphanus sativus L.) were sowed between rows. Four ¼ m2 permanent squares were established in the each plot, coverage (%) and the number of cover crops and weed species was determined. When cover crops reached up to 10% flowering, cover crops and weed species in the squares were harvested from the soil surface for measurements. The results show that, all cover crop species included in the trial decreased the number of weed species compared to the control. According to this; 10 weed species were determined in barley and sainfoin, 8 in common burnet, 7 in meadow button, 6 in hairy vetch, 3 in rye and 1 in radish while 16 different weed species were found in the control application. In the study, the most common weed species are Common mallow (Malva sylvestris L.), was founded 18.00 weed/m2 in control plot, while it was recorded as 4.00 weed/m2, 6.50 weed/m2 and 6.75 weed/m2 in radish, rye and hairy vetch applications, respectively. The other main harmful weed species is Yellow sweet clover [Melilotus officinalis (L.) Pall.] was 5.00 weed/m2 in the control plot, while it was calculated as 4.50 weed/m2 and 2.00 weed/m2 in rye and hairy vetch applications, respectively. Cover crop which is radish, application, there were no different weed species found except for Common mallow.
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Crop residues on the soil surface protect the soil against erosion, increase water infiltration and reduce agrochemicals in runoff water. Crop residues and soils are spectrally different in the absorption features associated with cellulose and lignin. Our objectives were to: (1) assess the impact of water on the spectral indices for estimating crop residue cover (fR); (2) evaluate spectral water indices for estimating the relative water content (RWC) of crop residues and soils; and (3) propose methods that mitigate the uncertainty caused by variable moisture conditions on estimates of fR. Reflectance spectra of diverse crops and soils were acquired in the laboratory over the 400–2400-nm wavelength region. Using the laboratory data, a linear mixture model simulated the reflectance of scenes with various fR and levels of RWC. Additional reflectance spectra were acquired over agricultural fields with a wide range of crop residue covers and scene moisture conditions. Spectral indices for estimating crop residue cover that were evaluated in this study included the Normalized Difference Tillage Index (NDTI), the Shortwave Infrared Normalized Difference Residue Index (SINDRI) and the Cellulose Absorption Index (CAI). Multivariate linear models that used pairs of spectral indices—one for RWC and one for fR—significantly improved estimates of fR using CAI and SINDRI. For NDTI to reliably assess fR, scene RWC should be relatively dry (RWC < 0.25). These techniques provide the tools needed to monitor the spatial and temporal changes in crop residue cover and help determine where additional conservation practices may be required.
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Overwintered cover crops mechanically terminated into mulch can be a weed management tool for reduced-tillage organic agriculture. However, the impacts of management options for cover cropping are not well understood, including cover crop variety, termination timing and termination method. In a field experiment, conducted in 2012 and 2013 in Western Washington, we examined three grains, four vetches and one barley–vetch mix terminated with two mechanical methods and at two different times. We determined the influence of cover crop variety and termination time on cover crop biomass production and tissue nitrogen (N), effectiveness of cover crop termination, soil nitrate–N and percent weed cover. We also determined the influence of termination method on percent weed cover. Cover crop biomass ranged between 3 and 9 Mg ha −1 and was not influenced by termination time; the greatest production was from three varieties of grain. Rye varieties were more effectively terminated with a roller–crimper than barley. Mean soil nitrate–N levels ranged from 1.9 to 18 mg kg −1 and were the greatest with vetches. Post-termination weed cover was greater in 2013 than in 2012 and the cover crop variety influenced weed cover at the Late termination time only. Neither plant N concentration in the cover crop mulch nor soil nitrate influenced weed cover. The results of this study indicate that cover crop biomass and termination timing are important factors influencing weed cover and termination effectiveness in cover crop mulch.
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Integrating cover crops (CC) in rotations provides multiple ecological services, but it must be ensured that management does not increase pre-emptive competition with the subsequent crop. This experiment was conducted to study the effect of kill date on: (i) CC growth and N content; (ii) the chemical composition of residues; (iii) soil inorganic N and potentially mineralizable N; and (iv) soil water content. Treatments were fallow and a CC mixture of barley (Hordeum vulgare L.) and vetch (Vicia sativa L.) sown in October and killed on two different dates in spring. Above-ground biomass and chemical composition of CC were determined at harvest, and ground cover was monitored based on digital image analysis. Soil mineral N was determined before sowing and after killing the CC, and potentially mineralizable N was measured by aerobic incubation at the end of the experiment. Soil water content was monitored daily to a depth of 1.1 m using capacitance sensors. Under the present conditions of high N availability, delaying kill date increased barley above-ground biomass and N uptake from deep soil layers; little differences were observed in vetch. Postponing kill date increased the C/N ratio and the fiber content of plant residues. Ground cover reached >80% by the first kill date (∼1250°C days). Kill date was a means to control soil inorganic N by balancing the N retained in the residue and soil, and showed promise for mitigating N losses. The early kill date decreased the risk of water and N pre-emptive competition by reducing soil depletion, preserving rain harvested between kill dates and allowing more time for N release in spring. The soil potentially mineralizable N was enhanced by the CC and kill date delay. Therefore kill date is a crucial management variable for maximizing the CC benefits in agricultural systems.
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Weeds are a major constraint for organic crop production. Previous research has found that cover crops in reduced tillage systems can provide weed interference, subsequently reducing inputs and improving crop yield. However, questions remain about effects of cover crop species identity and cover crop biomass on weed suppression and crop yield. This four-year study investigated how winter cover crops grown alone or in mixture influenced weed presence and crop yield in a reduced tillage organic vegetable system. Treatments were barley (Hordeum vulgare L.), crimson clover (Trifolium incarnatum L.), mixed barley + crimson clover, and a no-cover crop control. Plots were flail-mowed and strip-tilled prior to planting main crops (2011 and 2012: broccoli Brassica oleracea L.; 2013 and 2014: crookneck squash Cucurbita pepo L.). We measured density, diversity, and community composition of weeds and viable weed seeds, changes in weed percent cover within growing seasons, and crop yield. We found that the presence of barley, crimson clover, or barley + crimson clover reduced weed density by 50% relative to the control. Cover crop biomass negatively influenced weed density and weed seed diversity, and positively influenced squash yield. Weed percent cover within growing seasons did not respond differentially to cover crop treatment. Cover crop treatment and cover crop biomass had no influence on weed or weed seed community composition. These results suggest that reduced tillage winter cover crops in mixture or monoculture can similarly suppress weeds and improve yield, primarily due to biomass effects.
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The symbiosis between plants and arbuscular mycorrhizal fungi (AMF) benefits the health, nutrition and abiotic stress tolerance of the host plant. The maintenance of potential AMF inoculum in the winter is important because it will affect the colonization process in the subsequent crop. The objective of this study was to evaluate the effect of winter cover crops (CC) on AMF parameters (root colonization, length of hyphae and number of AMF spores), other variables indirectly related to AMF (the easily extractable glomalin-related soil protein (EE-GRSP) and the enzymatic activity of β-glucosaminidase), along with water-stable aggregates (WSA) as a soil quality indicator. In addition, the effect of two sampling dates on the variables in maize and the relationships among all of the variables were studied. The samples were obtained from a field experiment established in 2006 located in Aranjuez (Central Spain) under a Mediterranean semiarid climate. The treatments were winter cover crops of barley (Hordeum vulgare L.) or vetch (Vicia villosa L.) and fallow as a control. The study covered two seasons in 2011–12 and 2012–13 with sunflower (Helianthus annuus L.) and maize (Zea mays L.) as the main crop, respectively, with both sown in the spring. The main crops were irrigated according to the crop demand. Compared with the bare fallow conditions, cover crops improved most of the variables, maintaining the benefits of CC on AMF under the semiarid conditions of the Mediterranean climate. Barley as a cover crop gave the best results, whereas the performance of vetch was poorer. In sunflower, barley increased by 80% the hyphae length and β-glucosaminidase activity and by 30% other variables compared with the fallow; whereas in maize, 60–70% increments were found in AMF spores and the hyphae length and 2-fold in the enzyme activity. The sampling date affected all of the variables analyzed in the maize crop, except for the EE-GRSP and the WSA. Positive relationships were found between the variables directly related to AMF, EE-GRSP content and β-glucosaminidase activity. This suggests that the variables indirectly related to AMF, mainly the EE-GRSP, could be used as indicators of AMF. Finally, the enhancement of soil aggregate stability by the CC via AMF promotion was corroborated.
Article
Soil dispersion in an aqueous solution of sodium hexametaphosphate and sodium bicarbonate facilitates extraction of seeds by flotation with megnesium sulphate. The percentage viability of seeds collected in this manner subsequently can be determined with 2,3,5-triphenyl-tetrazolium chloride. Extraction of seeds usually is 100% efficient and enumeration of viable seeds via the tetrazolium test is accomplished much more rapidly than with conventional methods.