ArticlePDF Available

Abstract and Figures

Cover crops provide a wide range of ecological benefits, so to be defined as Ecological Service providing Crops (ESCs). Accordingly, different ESCs could influence both weed density and biomass due to: (i) allelopathic effects, (ii) increased cash crop-weed competitiveness. In order to test this hypothesis, a field experiment was carried out in Central Italy, comparing different autumn-winter cereal ESCs (wheat, barley, spelt, rye, and their mixture), preceding melon crop, with a control (no ESC). Weed performances were evaluated during both the ESC and melon cropping cycles. At flowering stage, the ESCs were flattened by a roller crimper, obtaining a mulch layer in which the melon was transplanted. The competitive weed-crop relationship was assessed by means of indices of competition. Bioassay tests were performed to evaluate the allelopathic potential of the ESCs on target weed. The results obtained from both the open field and the laboratory tests demonstrated that the different ESC species significantly affected weed density before and after flattening, although no difference on ESC biomasses was recorded at termination. At melon harvest, weed biomass was significantly lower in ESC treatments than in control one, and crop biomasses did not show any difference among all treatments. Nevertheless, the melon competitive ability was significantly higher in the rye and barley mulch compared to control. The bioassay test showed lower root germination and growth in the tested ESC extracts with respect to the control. By this, the ESC species showed a role in weed management both during their cycle and after termination, giving a competitive advantage to the cash crop, probably due also to active allelopathic compounds released by the ESCs.
Content may be subject to copyright.
A preview of the PDF is not available
... short-and long-term. In organic vegetable systems managed under rotation schemes, the use of agroecological service crops (ASCs; i.e., cover crops, catch crops, break crops, living mulch) is one of the main agroecological practices used to manage soil fertility and improve biodiversity in time and space, providing ecological services to the agroecosystem [5][6][7]. The ASCs can alter the weed community through direct species-specific interference (competition and allelopathy), as well as affecting resources availability (e.g., nutrients, light, water indirectly). ...
... Moreover, tillage practice changes weed seed depth in the soil, which plays a role in weed species shifts [16]. As an alternative to termination of ASCs by green manure, the conservation tillage strategy named in-line/roller crimper (RC) has been identified as a feasible option to terminate ASCs and simultaneously prepare the transplanting bed for the following vegetable cultivation [6,17,18]. The RC allows to flatten the ASC, leaving the soil undisturbed and obtaining a natural mulch generally able to contrast seedling emergence and delay the development of spontaneous plants. ...
... Particularly, the choice of cash crop cultivar suitable for no-till soil management is fundamental to ensure yield maintenance [19]. For what concerns weed control, the literature reports strong evidence of the suppressive ability of RC against weeds, particularly when high ASC biomass is produced [6,17,20,21]. Besides these effects, several features of the no-till RC technique can also potentially have an impact on weed community composition. ...
Article
Full-text available
Weeds can cooperate with the agroecosystem’s functioning by providing ecosystem services. Effective weed management should mitigate negative weed–crop interference, while maintaining a functional and balanced weed community. In a two-year trial, the in-line/roller crimper (RC) was used to terminate an agroecological service crop (ASC; here barley, Hordeum vulgare L.) before organic zucchini (Cucurbita pepo, L.) and compared with green manure (GM) ASC and tilled no-ASC with Mater-Bi mulch on the rows (No_ASC). Zucchini yield, soil N availability, weed density/cover, biomass, and community composition were assessed. Analysis of variance, exploratory statistical analysis, and non-parametric inferential approaches were run, respectively, on agronomic data, species-specific weed frequencies, and Shannon diversity. Zucchini yield was the highest in No_ASC, due to soil N immobilization under high C:N barley residues in GM and RC. Multivariate analysis discriminated RC from tilled systems, outlining a specific ensemble of weed species correlated to Shannon diversity. From zucchini fruit set, RC selectively favored Polygonum aviculare L. and Helminthotheca echioides (L.), reasonably because of their oligotrophy and creeping habit. Their dominance finally caused low RC weed control. Results highlight strong weed selective pressure by the mulch-based no-tillage. Understanding the mechanisms underpinning the impact of soil management practices on weed community can drive towards a tailor-made and more effective weed management.
... The presence of mulch has physical and chemical effects, which can limit weed germination and seedling emergence. It has been shown that the extracts of some ASC species residues inhibit weed germination both in bioassays and open-field conditions (Ciaccia et al. 2015). The physical effect of the mulch might reduce weed density both by modifying the environmental conditions of the soil surface and by acting as a physical barrier that obstructs the development of the seedlings (Altieri et al. 2011). ...
... Since its development, the research has mainly focused on analyzing the effect of cold rainy season ASCs managed with ILRC on weed abundance in zucchini and melon cash crops, and all these experiments have been carried out in the longterm MOVE trial located in Italy (Canali et al. 2013;Ciaccia et al. 2015Ciaccia et al. , 2016. Moreover, most of the research focused on flattening the ASCs has been mainly focused on optimizing the RC design, selecting the best cold rainy season ASC composition, identifying changes in the abundance of perennial species, and analyzing the effect on cash crop development and production (Mirsky et al. 2012;Carr et al. 2012;Canali et al. 2013;Frasconi et al. 2019). ...
Article
Agroecological 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.
... This eco-social approach could be profitably applied to diversified, organic cropping systems, where agroecological service crops (i.e., living mulch, cover crops [CC]) are used for managing weeds by exploiting allelopathic and competitive interactions among coexisting plant species (Flash, 1990). The mechanisms of interaction underlying the ability of winter cereal CCs to contain weed were deeply investigated: some cereals, such as rice (Oryza sativa L.), barley (Hordeum vulgaris L.), spelt (Triticum dicoccum L.), and rye (Secale cereale L.) can reduce weed growth through competition and allelopathic interactions (Barnes, Putnam, Burke, & Aasen, 1987;Chung et al., 2002;Ciaccia et al., 2015;Creamer, Bennett Regnier, 1996;Jung, Kim, Ahn, Hahn, & Chung, 2004;Petersen, Belz, Walker, & Hurle, 2001). It was also found that the introduction of minimum tillage and CCs in conservative agroecosystems increases the diversity and the abundance of AMF in soil (van der Heijden, Boller, Weimken, & Sanders, 1998;Jordan, Zhang, & Huerd, 2000). ...
... Rye has been able to reduce weeds by homogeneously covering the soil, as confirmed by the highest D CC , probably exploiting also its recognized allelopathic properties (Barnes et al., 1987;Belz, 2007;Ciaccia et al., 2015;De Albuquerque et al., 2010). However, the lowest D WEED-TOT and RA% suggest that the rye was strongly active, but not selective in containing weed (Cheng & Cheng, 2015;Tabaglio, Marocco, & Schulz, 2013). ...
Article
Full-text available
The mycorrhizal fungi are symbiotic organisms able to provide many benefits to crop production by supplying a set of ecosystem functions. A recent ecological approach based on the ability of the fungi community to influence plant–plant interactions by extraradical mycelium development may be applied to diversified, herbaceous agroecosystems. Our hypothesis is that the introduction of a winter cereal cover crop (CC) as arbuscular mycorrhizal fungi (AMF)–host plant in an organic rotation can boosts the AMF colonization of the other plants, influencing crop–weed interference. In a 4‐years organic rotation, the effect of two winter cereal CC, rye and spelt, on weed density and AMF colonization was evaluated. The AMF extraradical mycelium on CC and weeds roots was observed by scanning electron microscopy analysis. By joining data of plant density and mycorrhization, we built the mycorrhizal colonization intensity of the Agroecosystem indicator (MA%). Both the CC were colonized by soil AMF, being the mycorrhizal colonization intensity (M%) affected by environmental conditions. Under CC, the weed density was reduced, due to the increase of the reciprocal competition in favor of CC, which benefited from mycorrhizal colonization and promoted the development of AMF extraradical mycelium. Even though non‐host plants, some weed species showed an increased mycorrhizal colonization in presence of CC respect to the control. Under intense rainfall, the MA% was less sensitive to the CC introduction. On the opposite, under highly competitive conditions, both the CC boosted significantly the mycorrhization of coexistent plants in the agroecosystem. The proposed indicator measured the agroecological service provided by the considered CCs in promoting or inhibiting the overall AMF colonization of the studied agroecosystems, as affected by weed selection and growth: It informs about agroecosystem resilience and may be profitably applied to indicate the extent of the linkage of specific crop traits to agroecosystem services, contributing to further develop the functional biodiversity theory.
... The use of NT-RC for ASC management originated in Brazil (Kornecki et al., 2009), and this approach has been studied and developed mainly in Latin America, Canada and the United States (Altieri et al., 2011;Carr et al., 2013;Delate et al., 2012;Shirtliffe & Johnson, 2012). The few studies performed in European organic vegetable systems have concluded that NT-RC reduces weed abundance dramatically and requires less fossil fuel than the T-GM approach (Canali et al., 2013;Ciaccia, Testani, et al., 2015;Diacono et al., 2017). Nevertheless, both positive and negative effects have been observed on cash crop yields when NT-RC is implemented under Mediterranean conditions (Canali et al., 2013;Ciaccia et al., 2016;Diacono et al., 2017). ...
Article
Although organic farming was originally promoted as an alternative farming system to address agronomic, environmental and ecological issues, its conventionalisation has led to an intensification and specialisation of production. In the light of this, several studies have questioned the environmental benefits of organic farming as well as its agronomic viability. Thus, there is a need to improve organic vegetable systems to reduce their environmental impact without affecting their productivity. To tackle this challenge, European farmers and researchers have recently started to focus on agroecological service crops (ASCs). However, few studies have simultaneously evaluated the agronomic, environmental and ecological aspects of ASC management under different European pedo‐climatic conditions. We evaluated effects of the ASC management strategies—no‐till roller crimping (NT‐RC) and green manuring (T‐GM) on cropping system performance using agronomic, environmental and ecological indicators—to exemplify the need for multidimensional analysis to understand management implications for addressing environmental and agronomic challenges. We combined the results from 11 organic vegetable field trials conducted in seven European countries over a period of 2 years to test for general trends. Our results provide solid evidence that NT‐RC management across different pedo‐climatic conditions in Europe enhances the activity density of ground and rove beetles and improves both the potential energy recycling within the system and weed control. However, in NT‐RC plots, lower cash crop yield and quality, energetic efficiency of production and activity density of spiders were observed compared to T‐GM. Synthesis and applications. Multidimensional analyses using agronomic, environmental and ecological indicators are required to understand the implications of agricultural management in agroecosystem functioning. Introducing agroecological service crops combined with the use of no‐till roller crimping is a promising strategy for improving agronomic performance (e.g. fewer weeds) and reducing environmental (e.g. increasing the potentially recyclable energy) and ecological (e.g. enhancing the activity density of beneficial taxa such as ground and rove beetles) impacts. However, our study also indicates a need for agronomic and environmental improvements while promoting a wider acceptance of this strategy. Multidimensional analyses using agronomic, environmental and ecological indicators are required to understand the implications of agricultural management in agroecosystem functioning. Introducing agroecological service crops combined with the use of no‐till roller crimping is a promising strategy for improving agronomic performance (e.g. fewer weeds) and reducing environmental (e.g. increasing the potentially recyclable energy) and ecological (e.g. enhancing the activity density of beneficial taxa such as ground and rove beetles) impacts. However, our study also indicates a need for agronomic and environmental improvements while promoting a wider acceptance of this strategy.
... This suggested the absence of such competition between the main and the service crop and the positive effect of the flattening technique in controlling weeds. This positive effect was already observed in vegetable crops [54,55]. In August, when the flattened crop was disrupted and the soil cracking caused a rapid water depletion ( Figure 5, 163 DAFB), S Ψ , ΣPn and ΣTr values in F were the lowest of the four treatments. ...
... Fungi are particularly affected by soil tillage more than bacteria, since their large hyphal networks are disrupted by tillage, thus depressing plant-fungi symbioses [17]. Thus, in no-till organic crop rotations, the use of agroecological service crops (ASCs, i.e., all the plant species in a system which are grown not for yield purposes but to provide ecosystem services to the agroecosystem) intercropped, or as cover crops to form a green mulch after termination, is a profitable agronomic strategy to contain weed emergences, avoiding disturbance of microorganisms living in the upper soil layer, including mycorrhizal fungi [18][19][20][21][22]. ...
Article
Full-text available
Mycorrhizal symbiosis represents a valuable tool for increasing plant nutrient uptake, affecting system biodiversity, ecosystem services and productivity. Introduction of agroecological service crops (ASCs) in cropping systems may determine changes in weed community, that can affect the development of the mycorrhizal mycelial network in the rhizosphere, favoring or depressing the cash crop mycorrhization. Two no-till Mediterranean organic horticultural systems were considered: one located in central Italy, where organic melon was transplanted on four winter-cereals mulches (rye, spelt, barley, wheat), one located in southern Italy (Sicily), where barley (as catch crop) was intercropped in an organic young orange orchard, with the no tilled, unweeded systems taken as controls. Weed "Supporting Arbuscular Mycorrhiza" (SAM) trait, weed density and biodiversity indexes, mycorrhization of coexistent plants in the field, the external mycelial network on roots were analyzed by scanning electron microscopy, crop P uptake, yield and quality were evaluated. We verified that cereals, used as green mulches or intercropped, may drive the weed selection in favor of the SAM species, and promote the mycelial network, thus significantly increasing the mycorrhization, the P uptake, the yield and quality traits of the cash crop. This is a relevant economic factor when introducing sustainable cropping practices and assessing the overall functionality of the agroecosystem.
... This suggested the absence of such competition between the main and the service crop and the positive effect of the flattening technique in controlling weeds. This positive effect was already observed in vegetable crops [54,55]. In August, when the flattened crop was disrupted and the soil cracking caused a rapid water depletion ( Figure 5, 163 DAFB), S Ψ , ΣPn and ΣTr values in F were the lowest of the four treatments. ...
Article
Full-text available
Semi-arid conditions are favorable for the cultivation of late ripening peach cultivars; however, seasonal water scarcity and reduction in soil biological fertility, heightened by improper soil management, are jeopardizing this important sector. In the present two-year study, four soil managements were compared on a late ripening peach orchard: (i) completely tilled (control); (ii) mulched with reusable reflective plastic film; (iii) mulching with a Leguminosae cover-crop flattened after peach fruit set; (iv) completely tilled, supplying the water volumes of the plastic mulched treatment, supposed to be lower than the control. Comparison was performed for soil features, water use, tree functionality, fruit growth, fruit quality, yield and water productivity. Even receiving about 50% of the regular irrigation, reusable reflective mulching reduced water loss and soil carbon over mineralization, not affecting (sometimes increasing) net carbon assimilation, yield, and fruit size and increasing water productivity. The flattening technique should be refined in the last part of the season as in hot and dry areas with clay soils and low organic matter, soil cracking increased water evaporation predisposing the orchard at water stress. The development and implementation of appropriate soil management strategies could be pivotal for making peach production economically and environmentally sustainable.
... This result confirms the role of grass species as ASC in weed management, due to the slow decay of the residues and, consequently, of the mulch, in the first critical phases of the vegetable crop cycles. However, rye shows a general trend of total weed density reduction, probably due to its acknowledged allelopathic activity [36][37][38]. The role of the ASC species is more evident after termination, when the mulches differently influence weed communities' structural parameters, thus partially confirming our final hypothesis. ...
Article
Full-text available
This paper explores the effect of agroecological service crops (ASCs), i.e., crops included in the crop rotation for their ecosystem services, terminated with an in-line tillage roller crimper (ILRC) on weed community composition and their functional traits in comparison to a tilled control without ASC. A two-year study was performed in a long-term experiment with vegetables under organic management. Four different cereal crops were introduced as ASCs. Weed abundance and richness and the functional traits were assessed at three different stages, i.e., before and after ASC termination and before harvest of the following crop, melon. All the ASCs showed strong weed suppression, with few differences between the cereals tested. Weed communities with ASCs had later flowering onset and wider flowering span compared to the control, which positively affects weed dispersal and attraction of beneficial insects. However, weed communities with ASCs had higher values for traits related to competition (specific leaf area, seed weight and more perennials). A trade-off between weed suppression and selection of more competitive weed communities by the introduction of ASCs managed with the ILRC should be evaluated in the long-run. The use of the ILRC alternating with other soil management practices seems the more effective strategy to benefit from the minimal soil tillage while avoiding the selection of disservice-related traits in the weed community.
... In a ASC mixture, in accordance to the relative ratio of one genotype in respect to the others a specific ecological service can be promoted. Brassicaceae are known for their biocide and nematicidal effects by releasing glucosinolate compounds (Lazzeri et al. 2009); Poaceae for their ability as catch crops, to prevent leaching during winter time and/or for their smoother effect against weeds(Barberi 2002;Ciaccia et al. 2015a, b); Fabaceae for their soil N building capacity. Poligonaceae, Borraginaceae and Asteraceae can act as trap plant for nematodes and other pests. ...
Chapter
Biodiversity is intended as the whole of living organisms within an ecosystem, whereby the ecosystem functioning strictly depends on the complex interaction among its biotic and abiotic components. Ecosystem services, as the set of benefits provided by the ecosystems to humans, are related to biodiversity conservation and promotion. Similarly, the agrobiodiversity, as the whole of cropped/bred and associated wild biodiversity under agricultural management, can foster agroecological services provided by agroecosystems. Understanding the linkages between agrobiodiversity and services should drive on the agricultural management strategies. By this, the agroecosystems should be designed through biodiversification in space and time, and managed in order to promote those agrobiodiversity traits connected to ecological services (functional biodiversity). However, since successfully diversification implies changes at field production as well as in downstream, the entire food system—and not only the primary production phase—should be considered to proceed towards the ultimate goal of sustainability. In this context, the adoption of agroecology principles, intended as the ecology of the entire food system, can drive towards biodiversified agroecosystems, which are the sustainable from an environmental, economical and social perspective. In this chapter, the actual food system is described, underlining the negative externalities associated to modern agriculture. Agroecology is described as a possible approach to change production paradigm, from the cropped field to the landscape scale, achieving new models for food provisioning in a globalized context. In the meanwhile, the central role of agrobiodiversity in this redesign approach is clarified, focusing on its definition, measurement and management practices aimed to foster the ecological services provided.
Article
In un contesto di cambiamento climatico, da qualche anno il CREA (Consiglio per la ricerca in agricoltura e l’analisi dell'economia agraria) ha iniziato a studiare e tentare di mettere a punto un sistema di coltivazione, rivolto ad aziende orticole biologiche, che permetta agli agricoltori di fronteggiare al meglio questi cambiamenti. Tale sistema consiste in un insieme di tecniche agro-ecologiche (sistemazioni idrauliche, rotazioni colturali, uso di colture di servizio agro-ecologico e utilizzo di fertilizzanti organici) combinate tra loro in un dispositivo di lungo termine denominato Mitiorg. In questa nota si riportano i principi generali del dispositivo sperimentale e a titolo di esempio i risultati di una annualità di coltivazione del cavolfiore.
Article
Full-text available
The difficulty of distinguishing allelopathy from resource competition among plants has hindered investigations of the role of phytotoxic allelochemicals in plant communities. The effects of allelopathic substances on competitive outcome when two species differ in their sensitivity to an inhibitor were modelled by applying atrazine, a commonly used herbicide for broadleaf weeds, to corn-soybean mixtures. A target-neighbor design was used, in which differing densities of a neighbor species are planted around one individual of the target species. This design is particularly appropriate to investigations of allelopathy, due to the density-dependent nature of phytotoxic effects. Neighbor density greatly influenced the response to the toxin. At corn densities of 0, 3, 6, 9, and 12 plants per pot and atrazine treatment of 3.0 mg/kg, the dry mass of the soybean (target) plant increased from 0.2 g with no neighbors to 0.5 g with 9-12 neighboring corn plants. The increased growth of soybean at higher corn densities is contrary to the predicted effects of resource competition and is due to uptake of atrazine by the corn plants, which decreased the amount available to the soybean target. Detoxification of soil by neighbors may explain in part the conflicting assessments of some putatively allelopathic species, such as black walnut (Juglans nigra).
Article
Full-text available
Novel technologies to reduce tillage in organic systems include a no-tillage roller/crimper for terminating cover crops prior to commercial crop planting. The objective of this experiment was to compare: (1) weed management and yield effects of organic tilled and no-tillage systems for corn (Zea mays L.), soybean [Glycine max (L.) Merr.] and irrigated tomato (Lycopersicon esculentum Mill.), using a roller/crimper and two cover crop combinations [hairy vetch/rye (Vicia villosa Roth/Secale cereale L.) and winter wheat/Austrian winter pea (Triticum vulgare L./Pisum sativum L. ssp. arvense (L.) Poir.)]; and (2) the economic performance of each system. Weed management ranged from fair to excellent in the organic no-tillage system for soybean and tomato crops, with the rye/hairy vetch mulch generally providing the most weed suppression. Corn suffered from low rainfall, competition from weeds and hairy vetch re-growth and, potentially, low soil nitrogen (N) from lack of supplemental fertilization and N immobilization during cover crop decomposition. No-tillage corn yields averaged 5618 and 634 kg ha−1 in 2006 and 2007, respectively, which was 42–92% lower than tilled corn. No-tillage soybeans in 2007 averaged 2793 kg ha−1 compared to 3170 kg ha−1 for tilled soybeans, although no-tillage yields were 48% of tilled yields in the dry year of 2006. Irrigated tomato yields averaged 40 t ha−1 in 2006 and 63 t ha−1 in 2007, with no statistical differences among tillage treatments. Economic analysis for the three crops revealed additional cover crop seed and management costs in the no-tillage system. Average organic corn returns to management were US$1028 and US$2466 ha−1 greater in the tilled system compared to the no-tillage system in 2006 and 2007, respectively, which resulted mainly from the dramatically lower no-tillage yields. No-tillage soybean returns to management were negative in 2006, averaging US$ −14 ha−1, compared to US$742 ha−1 for tilled soybeans. However, in 2007, no-tillage soybean returns averaged US$1096 ha−1. The 2007 no-tillage irrigated tomato returns to management averaged US$53,515 compared to US$55,515 in the tilled system. Overall, the organic no-tillage soybean and irrigated tomato system demonstrated some promise for reducing tillage in organic systems, but until economic benefits from soil carbon enhancement can be included for no-tillage systems, soil improvements probably cannot offset the economic losses in no-tillage systems. Irrigation could improve the performance of the no-tillage system in dry years, especially if grain crops are rotated with a high-value irrigated tomato crop.
Article
Full-text available
A two-year field experiment was carried out at the MOVE (MOnsampolo VEgetables) organic long-term experiment, Monsampolo del Tronto – Central Italy – growing transplanted zucchini (Cucurbita pepo L.) to compare the effect of different tillage strategies and cover crop management (no cover crop; green manured barley; in-line till/roller crimped barley) on zucchini yield, zucchini yield quality, weed control and N dynamic in the soil–plant system. Energy consumption for mechanical operations, soil temperature and water content was also evaluated. Zucchini cultivated by the in line tillage/roller crimper technique yielded 69% more than the zucchini preceded by the green manure and similarly to the control. Moreover, zucchini yield quality did not differ among the treatments. Weed above ground biomass was 22 and 91% lower than the control in the green manure and in the roller crimper treatments, respectively. The in line-tillage/roller crimper (ILRC) also increased the N system use efficiency (yield N ratio) of twofold respect to the control and of 29% respect to the green manure treatment. Despite the additional tillage needed to sow and manage the cover crop, the ILRC treatment allowed 10% of work hours and 24% of energy saving respect to the control (no cover crop). Moreover, the in-line tillage/roller crimper technology used 46% of work hours and 56% of energy less than the green manure treatment, which is – so far – the most widely used system by organic farmers to manage cover crops. Our results demonstrated that the adoption of the novel ILRC technology would considerably contribute to enhance the sustainability of the organically managed vegetable cropping systems.
Article
Full-text available
The importance, characteristics, positive and negative impacts, and future role of weeds as an integral part of the natural and agroecosystems are evaluated and discussed. Interference between plants in nature and the importance of differentiating between competition and allelopathy are interpreted. Allelopathy as one component of weed/crop interference, allelochemicals from weed species and their possible mechanism of action are listed and discussed. Weed species with inhibitory action against cultivated crops, other weed species, and plant pathogens, as well as self-inhibitory (autopathic) species are reviewed. Stimulatory or inhibitory allelopathic effects of different crop plants, trapping and catching species, and the potential of allelopathic weeds in inhibiting or stimulating certain parasitic weed species are discussed and evaluated. Allelopathy as a mechanism and future strategy for agricultural pest control and farm management and the potential use and development of some allelochemicals as natural pesticides or plant growth regulators are also considered and discussed.
Article
Disappearance of rye cover crop residue and allelochemicals from rye residue were evaluated in a field study at Clayton, NC, in 1992 and 1993. The aerial portion of rye biomass declined linearly over time with 50% of the residue disappearing by 105 d after clipping. Extrapolations indicated all residue would disappear approximately 200 d after rye clipping. Total content of DIBOA and two related compounds, DIBOA-glucoside and BOA, in the residue also was measured over time. Fifty percent of the 0-d content of the compounds disappeared from residue 10 and 12 d after kill for 1992 and 1993, respectively. Extrapolations indicated content reached 0121 and 168 d after kill for 1992 and 1993, respectively. Reported duration of weed suppression by rye cover crops more closely follows disappearance of allelochemicals from rye residue than disappearance of the residue.
Article
Effects of competition were measured by; 1) the competitive balance (relative competitive ability) of the components of the mixture using the competitive balance index; 2) intensity of competition (as determined by plant size) using the competitive intensity index; 3) the efficiency of resource use by the mixture using the relative yield total, relative yield of the mixture and overyield. Root competition usually affected the balance between components more than shoot competition, and root competition was usually more intense than than shoot competition. However, in crop-weed experiments, shoot competition was often more intense than root competition; crop usually had a greater competitive ability than weeds. The only firm evidence suggests that the relative importance of root competition increases with time, though in some situations the reverse may be true. Increased yield of a mixture can indicate niche separation, which is of potential agricultural significance as a means of obtaining higher yields than with monocultures. Increased yield of mixtures tended to occur in experiments that allowed different species to root at different depths; root interaction was usually the more important cause. Although positive interaction between shoot and root competition has often been considered a basic feature of competition, such interactions occurred rarely; in the case of intensity of competition the interaction was usually negative. -from Author
Article
Many field vegetables such as leek are weak competitors against weeds, causing high costs for weed management practice. Using celery as a companion cash crop was suggested to improve the weed suppression of leek. Three field experiments were carried out to study the intra- and interspecific competition in a leek:celery intercrop with and without additional weed competition. Results from this experimental work show that intercropping of leek and celery in a row-by-row replacement design considerably shortened the critical period for weed control in the intercrop compared with the leek pure stand. The relative soil cover of weeds that emerged at the end of the critical period was reduced by 41% in the intercrop. In another experiment, the biomass of Senecio vulgaris, which was planted 20 days after crop establishment, was reduced by 58% in the intercrop and the number of seedlings which emerged as offspring was reduced by 98%, all reductions compared with the pure stand of leek. The relative yield total of the intercrop exceeded that of the pure stand by 10%, probably as a result of an optimized exploitation of the resources. The quality of the leek, however, was reduced. Advantages and bottlenecks of the intercrop system of leek and celery and implications for the weed control are discussed and used to identify future research needs.
Article
1 There is evidence that plants in natural communities form transitive competitive hierarchies, but the pervasiveness and malleability of hierarchies remain controversial. We constructed three competitive rankings among 20 wetland plant species in conditions known to be important in wetlands: a mesic, fertile environment, an infertile environment and a flooded environment. 2 Rankings were constructed using plants grown from seed in pairwise combinations for one growing season in an outdoor compound. The indicator species used to construct the rankings were Carex crinita, Gnaphalium uliginosum and Lycopus americanus. The others represented a wide array of morphologies, habitats and abundances and ranged from the large cosmopolitan Typha angustifolia to the small and rare Sabatia kennedyana. 3 Competitive rankings formed in all three environments. Competitive effect rankings based upon the results for all three indicator species were significantly concordant across the three environments $(W = 0.59; P < 0.05)$, i.e. competitive effect did not change across environment. When calculated separately for each indicator species, rankings across the three environments were significantly concordant for two of the three indicator species. Within any environment the ranking varied among the indicator species. 4 Ranking based upon the mean competitive response to all three phytometer species were not concordant across the three environments $(W = 0.35; P > 0.3)$ and were not concordant when calculated separately for each indicator species. Within any environment, response rankings were significantly concordant for two out of the three indicator species. 5 Competitive effect rankings tended to be constant across environments and were sensitive to the kind of neighbour. Competitive response rankings varied across environments and were insensitive to the kind of neighbour.
Article
(1) Replacement and additive designs are compared for their ability to provide valid and interpretable measures of (a) resource complementarity, i.e. relative yield total (RYT), (b) competitive ability, and (c) severity of competition in binary mixtures. (2) In replacement designs, the density of one component of the mixture is confounded with that of the other, so that competition between plants of one component is confounded with competition between plants of different components; the design is therefore statistically invalid. Because of this confounding, values of the relative yield total (RYT), competitive ability and severity of competition in replacement designs are affected by: (a) the density of each component to density in its pure-stand; (b) the pattern of response of each to density; and (c) the proportions of the components in mixtures; interpretation of these indices is therefore difficult or impossible. (3) By contrast, additive designs give valid and interpretable values of each of the indices of competition, regardless of density or proportions. Various misconceptions about additive designs are considered. (4) The value of binary factorial designs in competition studies is explored, and methods of analysing the resulting data are briefly considered.