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Factors contributing to changes in weed population dynamics following conversion to organic farming systems.
Source publication
Organic agriculture is growing in importance worldwide. In the United States, the rate of increase of organic growers was estimated at 12% in 2000. However, many producers are reluctant to undertake the organic transition because of uncertainty of how organic production will affect weed population dynamics and management. The organic transition has...
Citations
... This might be due to the high weed cover above the ground. Organic field shows greater weed species richness and higher species diversity" [19], [20], [21]. Most of the weed species observed were annual herbs and grasses which are about 75 % of the total weed species. ...
... The highest weed control efficiency in the field experiment was found in 19.49 % and 18.75 %, respectively) at all intervals. ...
Aim: In order to compare the weed seed bank and population dynamics under organic, biodynamic, Bt-conventional, and non-Bt conventional management systems of cotton (Gossypium hirsutum), a field experiment was carried out.
Study Design: Randomized Block Design (RBD)
Place and Duration of Study: bioRe-FiBL research trails, bioRe Association, Kasrawad, Khurgone, Madhya Pradesh during the kharif season of 2020-21.
Methodology: Five distinct crop management techniques were used in the field experiment, each duplicated four times, and the experiment was set up using a randomized block design. The treatments were distributed at random to different plots. The five management treatments were Absolute Control (no fertilizers), Conventional management of non-Bt cotton, Conventional management of Bt cotton, Bio-dynamic and Organic management of cotton. For the duration of the experiment, four 1 m × 1 m (1 m 2) quadrats were randomly placed on each experimental plot's four sides, and different biometric observations were recorded from each quadrant according to its treatment. For the purpose of collecting the necessary observations, two of these quadrants were regularly weeded every 20 days, while the other two were left unweeded for the duration of the experiment.
Results: The dominant weed species includes Panicum dichotomiflorum, Cyperus rotundus, Paspalum dilatatum, Euphorbia hirta, Acalypha indica and Digeria arvensis. Poaceae was the dominant family in terms of composition. There was very less variation in the weed flora between the treatments. Significantly higher weed seed bank, weed species, weed density and weed dry weight were observed in Organic and Biodynamic cotton than in the Conventional cotton. Weed control efficiency was found to be maximum in the Conventional cotton compared to the Organic and Biodynamic cotton.
Conclusion: From the experiment, it can be concluded that the Conventional cotton especially Conventional management Bt Cotton was found to be most efficient among all the treatments. However, the Organic cotton was observed with high number of overall plant species and best in conserving the plant species biodiversity.
... Weed suppression by cover crops due to modifications in the soil microclimate has also been reported [74]. Similarly, a study attributed weed suppression in the form of the colonization of weed seeds by bacteria and fungi brought about by soil microbial changes by cover crops [75]. ...
Cover crops are an important component of integrated weed management programs in annual and perennial cropping systems because of their weed suppressive abilities. They influence weed populations using different mechanisms of plant interaction which can be facilitative or suppressive. However, the question often arises if cover crops can be solely relied upon for weed management or not. In this review we have tried to provide examples to answer this question. The most common methods of weed suppression by an actively growing cover crop include competition for limited plant growth resources that result in reduced weed biomass, seed production, and hence reductions in the addition of seeds to the soil seedbank. Cover crop mulches suppress weeds by reducing weed seedling emergence through allelopathic effects or physical effects of shading. However, there is a great degree of variability in the success or failure of cover crops in suppressing weeds that are influenced by the cover crop species, time of planting, cover crop densities and biomass, time of cover crop termination, the cash crop following in the rotation, and the season associated with several climatic variables. Several studies demonstrated that planting date was important to achieve maximum cover crop biomass, and a mixture of cover crop species was better than single cover crop species to achieve good weed suppression. Most of the studies that have demonstrated success in weed suppression have only shown partial success and not total success in weed suppression. Therefore, cover crops as a sole tool may not be sufficient to reduce weeds and need to be supplemented with other weed management tools. Nevertheless, cover crops are an important component of the toolbox for integrated weed management.
... Cover crops have long been used in citrus for weed management and are especially important for organic citrus production, where agrochemical use is discouraged [1]. Besides weed suppression, additional benefits from planting cover crops include increased microbial diversity and reduced weed seed vigor from unremoved residues [2], increased soil C and N content, as well as suppressed activity from parasitic nematodes [3], and soil pathogens via allelochemicals [4]. The additional abundance and diversity from ground cover vegetation are positively correlated with the presence of insects [5], which can benefit or, in some cases, encumber pest management. ...
... Cover crops have been reported to improve soil properties in Florida citrus groves by the addition of soil organic matter, improved infiltration, moisture retention, and addition of soil N [37,38]. In addition, they aid in weed suppression, increase soil microbial diversity [2], and benefit ecosystem services such as the biological control of insect pests and pollination [23,39]. The selection of optimal cover crop species or mixtures of species to achieve both weed and pest management would benefit citrus management in Florida, where citrus greening has decimated yields and more than doubled production costs [40]. ...
Asian citrus psyllid, Diaphorina citri, transmits Candidatus Liberibacter asiaticus (CLas), the bacterial pathogen responsible for citrus greening disease. To explore the possibility that cover crops in citrus groves may serve as refuges for this pathogen vector during unfavorable host conditions, psyllid feeding was investigated on six common cover crop species and citrus using electrical penetration graph (EPG) recordings and behavioral bioassays. EPG recordings showed that the proportion of time spent by D. citri feeding on xylem was similar or higher on all tested cover crops (17%–32%) compared to the positive control (12%), the preferred host, Citrus macrophylla. Very little to no phloem feeding was observed on cover crops by the adults. In the choice assays, more D. citri adults settled on buckwheat (Fagopyrum esculentum) and cowpea (Vigna unguiculata) than on the host, C. macrophylla, 24 h after release. No-choice assays showed that the citrus cover crop species evaluated extend the survival of D. citri up to 8 d because of xylem feeding. Our results indicate that some cover crop species may be less suitable refuge sites for D. citri than others, but none served as breeding sites or supported more than 8 d of survival.
... This may be due to the higher weed diversity observed in the field. Organic field shows greater weed species richness and higher species diversity (Ngouajio and McGiffen 2002;Albrecht, 2005; Adam and Beata 2018). The soil was found to be having weed seed bank containing all the three categories of weeds, which included grasses, sedges and broad leaved weeds. ...
Cotton is a long duration, widely spaced, and relatively slow-growing crop that faces a serious weed threat in its early growth stages. The weeds growing in a crop can be considered as merely the vehicle by which seeds in the soil produce further seeds for incorporation into the soil seed bank. Due to the complexity of characterizing the soil seed bank, it is difficult to predict the abundance of weed species and communities. One way of describing weed soil seed bank is that they are primarily an assemblage of seeds that will occasionally germinate, emerge, and grow into adult plants. A pot culture experiment was conducted in the greenhouse located at Agronomy farm, Centre of Organic Agricultural Research and Training (COART), Department of Agronomy, Dr. PDKV, Akola during kharif season of the year 2020-21, to compare the weed seed bank and weed flora in the soil under organic, bio-dynamic, conventional management systems of Bt and non-Bt cotton (Gossypium hirsutum). The present investigation was carried out in completely randomized design with the soil collected from five different crop management practices done in the field, each replicated four times. The treatments were allotted randomly to various pots. The five treatments consist of Organic management soil of cotton, Bio-dynamic management soil of cotton, Conventional management soil of non-Bt cotton, Conventional management soil of Bt cotton, Absolute Control soil (without fertilizers). Panicum dichotomiflorum, Cyperus rotundus, Paspalum dilatatum, Euphorbia hirta, Acalypha indica and Digeria ravensis were the dominant weed species observed. Poaceae was the dominant family in terms of composition. Weed flora between the treatments was found to be having very minor differences. The weed seed bank, weed species, weed count and weed dry matter were found to be statistically non-significant, but numerically highest in the Organic and Biodynamic than in the Conventional treatments.
... This is might be due to the high weed cover above the ground. Ngouajio et al. (2002), Albrecht (2005), Adam and Beata (2018) also reported that the organic field showed greater weed species richness and higher species diversity. ...
... fertilization and direct weed control) on crop-weed interactions usually manifest themselves more slowly. It follows that weed management should be tackled in an extended time domain and needs deep integration with the other cultural practices, aiming to optimize the whole cropping system rather than weed control per se.Ngouajio et al. (2002) conducted experiment on the effect of going organic on weed population dynamics and reported that the organic transition has a profound impact on the agro ecosystem. Changes in soil physical and chemical properties during the transition often impact indirectly insect, disease, and weed dynamics. ...
An experiment entitled "Weed Population Dynamics under Organic, Bio-Dynamic, Conventional Bt and Non-Bt Cotton" was conducted at bioRe-FiBL research trails, bioRe Association, Kasrawad, Khurgone, Madhya Pradesh during kharif season of 2020-21. The experiment was laid out in randomized block design with five different crop management practices for field experiment and in completely randomized design with same five crop management practices for greenhouse studies i.e., pot culture experiment, each replicated four times in both the experiments.The treatments were allotted randomly to various plots. The five treatments consists of T1-Organic management cotton, T2-Bio-dynamic management cotton, T3-Conventional management of non-Bt cotton, T4-Conventional management of Bt cotton, T5-Absolute Control (without fertilizers).
The dominant weed species includes Panicum dichotomiflorum, Cyperus rotundus, Paspalum dilatatum, Euphorbia hirta, Acalypha indica and Digeria arvensis. Poaceae was the dominant family in terms of composition. There was very less variation in the weed flora between the treatments. Significantly higher weed seed bank, weed species, weed count and weed dry matter were observed in the Organic and Biodynamic cotton than in the Conventional cotton. Weed control efficiency was found to be maximum in the Conventional cotton compared to the Organic and Biodynamic cotton. Highest weed seed bank and weed species richness were seen in the field experiment compared to pot culture experiment. However, similar trend of weed count and weed dry matter was observed in both the experiments. Significantly maximum growth attributes, yield attributes, available NPK in the soil and the nutrient uptake by plants were observed in the Conventional cotton compared to the Organic and Biodynamic cotton. The Conventional management Bt Cotton was found to be most efficient among all the treatments. However, the Organic cotton was observed with high number of overall plant species and best in conserving the plant species biodiversity.
... The results reported that spring barley grain yields inversely correlated with the weight of weeds (r = − 0.70, p < 0.05). The use of compost and manure amendment, cover crops, and other low-external-input management practices create a change in the physical, chemical and biological properties of soil [29]. Additionally, surface residues can affect seed germination via physical and chemical changes to the seed environment [31]. ...
Background
In organic crop farms, growing crop yields are limited by insufficient nitrogen supply to plants and crop weediness. In such farms, legume swards are proposed as a service crop to improve nitrogen cycling. However, a positive effect of nitrogen is not only on cereals but also on weeds. In crop rotation, legume swards can stimulate the competition of cereals using the above-ground mass of legume to control the spread of weeds.
The effects of the following methods for weeds control were analyzed: (i) forage legumes ( Trifolium pratense L. and T. repens ) undersown in cereals, (ii) forage legumes ( T. pratense L., Medicago sativa L . ) and their mixture with festulolium ( x Festuliolium ) and their above-ground mass management methods, and (iii) plant-based fertilizers (red clover above-ground mass fermented and composted).
Results
Oat with red clover undersown reduced weediness more than red clover monocrops, pea, and their mixture with oats. Incorporated undersown white clover mass increased spring barley competitiveness with weeds. When growing legume swards for a longer period of time (green fallow), red clover and their mixture with festulolium are the most suitable for this purpose. The lowest weed dry weight (average 34%, compared with the removal from the field) was obtained while using the mixed management. The cultivation of cereals after forage legumes and their mixtures with festulolium (as a preceding crop) increases its grain yield and competitive ability against weeds. Fermented red clover and fermented pea and spring wheat mixture mass, as a manure, did not increase weediness.
Conclusions
It was concluded that the effectiveness of the perennial forage legumes is determined by the uses of the above-ground mass: soil cover, mulching, application of green manure, and intensity of mass mineralization. Type of activity of forage legumes on weeds were competition for environmental resources, disruption/promotion of germination, destruction of above-ground mass, reduction of the amount of matured seeds, creation of a physical barrier (mulch), and increase of competitiveness of cereals. Growing forage legumes in pure crops usually leads to a loss of marketable production.
Graphic abstract
... In the present study, photinia plants were found to be much more competitive in weed suppression than camellia and cupressus. The reasons may lie in many different aspects, which include different ability of competition for nutrients and water in the root zone, different leaf area index that can limit radiation interception by weeds, different canopy structures that may interact with weed seed deposition in the pot, and emission of exudates and other allelopathic substances in the root zone (Amoroso et al., 2010;Benvenuti and Pardossi, 2017;Bond and Grundy, 2001;Ngouajio and McGiffen, 2002;Parish, 1990;Reberg-Horton et al., 2005;Saha et al., 2018). Among the other possible characteristics, indeed photinia showed the highest values for leaf area and total dry weight compared with the other two tested species, which may lead to higher rates of leaf gaseous exchange (Miyazawa and Kikuzawa, 2005) and exigencies in terms of water and utrients in the root zone. ...
... These approaches allowed for more intensification and also encouraged diversification of crop rotations with pulses, oilseed crops, legume green manure crops and perennial forages (Peterson et al., 1993;Zentner et al., 2001Zentner et al., , 2002Entz et al., 2002;Entz et al., 2014). Organic farming is also gaining popularity in Canada, in response to concerns regarding the environmental impact of agro-chemicals, the costs of inputs in conventional farming, and the growing demand for organic products (Ngouajio and McGiffen, 2000;Entz et al., 2001). ...
... Cowpea (Vigna unguiculata L. Walp.) is often used a rotational crop/cover crop because it is a legume crop with the potential to add soil nitrogen (Cherr et al., 2006;Creamer & Baldwin, 2000;Dabney et al., 2001), increase soil health and tilth (Abdul-Baki et al., 2005;Harrison et al., 2006;Teasdale, 1998;Teasdale & Abdul-Baki, 1997;Teasdale & Shirley, 1998), and suppress weeds (Herrero et al., 2001;Hill et al., 2006;Hutchinson & McGiffen, 2000;McGiffen et al., 2000;Ngouajio & McGiffen, 2002;Ngouajio et al., 2003;Unamma et al., 1986). As with kenaf, research has also shown that cowpea has exhibited allelopathic activity (Adler & Chase, 2007;Hill et al., 2007). ...
p>A Louisiana sugarcane field is typically replanted every four years due to declining yields, and, although, it is a costly process, it is both necessary and an opportunity to maximize the financial return during the next four year cropping cycle. Fallow planting systems (FPS) during the fallow period prior to replanting sugarcane have the potential to influence not only the following sugarcane crop, but the economics of the production system as a whole. A 2 year experiment was conducted at the USDA, ARS, Sugarcane Research Unit at Houma, LA to determine the impact of unique FPS on sugarcane production. The experiment included seven treatments; two cover crops, kenaf ( Hibiscus cannabinus L.) and cowpeas ( Vigna unguiculata L. Walp.), three FPS harvest treatments for each FPS crop, and a control. The experiment had four replications. Kenaf was selected as a potential cover crop due to interest in its commercial by-products and cowpea was selected due to its potential to facilitate climate friendly soils. The kenaf and cowpeas were planted on 8 May 2013. The three FPS harvest treatments included the removal of the FPS crop at 50 days after planting (DAP), the removal of the harvested FPS crop at 100 DAP, and lastly, cutting the FPS crop at 100 DAP and incorporating the plant material into the soil prior to sugarcane planting. The control treatment did not have a cover crop. Unlike kenaf, the cowpea leaf, fresh and dry weight yields (50 DAP), 19.4 and 2.5 mt/ha, respectively, decreased to 17.0 and 2.4 mt/ha (100 DAP). Although the sugarcane total recoverable sucrose (TRS) (kg/mt) was greater with the kenaf cover-crop treatment 50 DAP (120 kg/mt) compared to the cowpea treatment 50 DAP (111 kg/mt) and the cowpea 100 DAP with the residue incorporated (112 kg/ha), none of the FPS crop treatments were significantly better or worse than the control (no cover crop). The average values for the sugarcane production factors across all treatments were 95,700 stalks/ha (millable stalks), 112 mt/ha (sugarcane yield), 114 kg/mt (sugar yield per metric ton of sugarcane), and 12,841 kg/ha (sugar yield per hectare). The results demonstrate the potential use of these alternative cover crops during the fallow period prior to planting sugarcane without adversely affecting the plant cane yields.</p
... (Sanguankeo and León 2011), although the richness values in the current study are similar to the lowest values observed in the herbicide treatment in that study and 3-fold lower than their highest values in their cover crop treatment. The lack of tillage's consistent effect on these indices is distinct from previous studies, in which more intensively managed annual agricultural systems typically demonstrate decreased diversity compared to low-input, no-till counterparts (Barberí and Mazzoncini 2001, Hyvönen and Salonen 2002, Mas and Verdù 2003, Ngouajio and McGiffen 2002. ...
Adoption of permanent cover crops and no-till systems is considered integral to achieving the California state air quality standards regulating airborne particulate matter, as indicated in Senate Bill 656. Imposition of such management techniques in a vineyard could create competition with vines for limited water resources. We evaluated the effects of cover crops that were either tilled or just mowed on vineyard floor composition, weed populations, vine water relations and growth, and fruit composition over three years within a mature commercial Merlot vineyard subjected to deficit irrigation in Lodi, San Joaquin Valley, California. The vineyard floor in this experiment supported resident vegetation that was tilled (standard grower practice), an oat cover crop, or a legume/oat cover crop. The two planted cover crops were either tilled or mowed (i.e., no-till). Biomass of cover crops, weeds, and legumes varied by year and treatment, but consistent effects among treatments were not observed. Weed species composition and cover segregated with the presence or absence of tillage rather than cover crop type and the weed species composition of the resident vegetation was distinct from those in the cover crop treatments. Some treatments, like ‘Oats/Legumes + NoTill’, ‘Oats + NoTill’, ‘Oats/Legumes + Till’, and ‘Resident Vegetation + Till’ reduced soil water content (Өv) in at least one of the three shallow soil layers spanning 0 to 30 cm, 30 to 60 cm, and 60 to 100 cm in 2008, and ‘Oats/Legumes + NoTill’ also dried the two upper layers in 2009, but these differences had no consistent influence on plant water status. Distinctions in Өv between years were attributed partly to the cessation of rainfall two months earlier in 2008 than in 2009, despite similar total annual quantities. Significant reductions in Өv imposed by the ‘Oats/Legumes + NoTill’ treatments reduced vine vegetative growth in two of three years, but these effects did not manifest in yield and fruit composition. Values for the Ravaz index for two of the three years indicate that the vineyard was overcropped for all treatments, but maximizing production in this region is a common practice. Weak competitive effects of the cover crops for water were likely associated with the use of a well-established mature vineyard and demonstrated that these management strategies could be employed to improve air quality to meet California air quality regulations with limited effects on vine water status and production. © 2016 by the American Society for Enology and Viticulture. All rights reserved.
