Aboveground Weed Research Articles

Responses of soil seedbank and aboveground weed communities to globe artichoke–cropping systems: an on-farm analysis

AbstractGlobe artichoke [Cynara cardunculus L. var. scolymus (L.) Fiori] is one of the most important crops across the Mediterranean basin, where weeds are an important biotic constraint limiting crop yields. However, the effects of globe artichoke–cropping systems on weeds have been rarely tested. Following the demand for eco-friendly weed management practices, a multi-location trial (13 farms) was carried out, measuring weed seedbanks and aboveground communities within four globe artichoke–cropping systems: globe artichoke monoculture (ART), past cultivation of globe artichoke (8 to 10 yr ago) (past-ART), a globe artichoke–durum wheat (Triticum durum Desf.) rotation (ART-WHEAT), and a control where globe artichoke was never grown. Both below- and aboveground weed communities were dominated by annual therophytes, but a low correspondence was found between both types of communities. Averaged over farms, ART highly reduced both the weed soil seedbank (1,600 seeds m−2 on average) and the aboveground weed biomass (only 3.4 g dry weight m−2) compared with the control, with a decrease of 72% in the soil seedbank and 99% in the aboveground flora. Moreover, on the farms where globe artichoke was previously grown, a very low aboveground weed biomass (77% less than control) was found. In addition, ART contributed to the preservation of high levels of weed diversity (except for aboveground communities) and therefore avoided the creation of a specialized weed flora. In conclusion, we suggest the inclusion of globe artichoke into crop rotation schemes in Mediterranean agroecosystems as a sustainable tool for reducing both the soil weed seedbank and aboveground weeds, thus reducing the requirement of direct weed control methods and preserving the environment.

Differentiated Weed-Suppressive Ability of Modern and Old Durum Wheat Cultivars after Long-Term Cultivation under Semi-Arid Climate.

Durum wheat (Triticum turgidum spp. durum) is one of the most important grain crops cultivated across the Mediterranean Basin, where a strong return to local landraces cultivation is occurring to meet the market demand for high-quality food and low-input cropping systems. A characterisation of the long-term effect (10 years) of durum wheat landraces and modern cultivars on the potential and real weed flora is still lacking. Hence, a multilocation trial over 10 farms in Central-Eastern Sicily was carried out to investigate the repeated cultivation of several old landraces (OLD) and modern cultivars (MOD) on the abundance and diversity of weed flora. Overall, OLD was associated with a 47% reduction of the soil seedbank size and to -64% of the aboveground weed biomass compared to MOD. In addition, diversity indices pointed out a high similarity between MOD and OLD farm groups for the soil seedbank, while a lower diversity was found in OLD for aboveground weed communities. From the principal component analysis emerged that the species compositions of MOD and OLD were quite separated for both soil seedbank and real flora, with the latter showing few specific associations with major weeds. These findings demonstrated the indirect effect of durum wheat landraces in sustainably reducing weed pressure without the adoption of chemical weed control.

Effects of semi-decomposed weeds as substrate on plant growth, antioxidant capacity, and leaf nutrition of plum trees

Sustainable practices are inevitable requirements for modern agriculture. Incorporating weed waste into an organic substrate is one of such sustainable agricultural practice. We aimed to investigate whether semi-decomposed, aboveground weed biomass can be used as a substrate for plums. “Qingcui” plums were planted in boxes with semi-composted weeds, and garden soil without composted weeds was used as a control. Plant branch characteristics, leaf antioxidant capacity, leaf nutrition, and numbers of opening flowers and bearing fruits were analyzed. The results showed that treatment with semi-composted weed treatment significantly increased the stem diameter, effective branch number, and effective branch angle. The contents of the reduced glutathione, oxidized glutathione, and the levels of total antioxidant capacity and catalase were significantly higher in semi-composted weeds than in the control group. The macroelement content in the semi-composted weed group was higher than that of the control group, but the microelement contents did not show any significant differences. However, the trace elements and heavy metals showed heterogeneous changes. The Σ DOP of macroelements, microelements, and trace elements in the weed-compost treatment were larger than that in the control. The chlorophyll content in the weed-compost group was significantly higher than that in the control during the leaf abscission period. The leaf weight per area was significantly higher than that of the control, but the growth time was longer. The numbers of total opening flowers and fruit were higher in the semi-composted weed group than in the control group. We demonstrated that semi-composted weeds as substrates have beneficial effects on plum branch characteristics, leaf antioxidant capacity, and generative growth. However, it increases the degree of nutritional imbalance and extends growth time.

Long-term impact of zero-till residue management in post-rainy seasons after puddled rice and cropping intensification on weed seedbank, above-ground weed flora and crop productivity

Regulation in weed seed recruitment to soil and its emergence is an ecological approach of weed management for sustainable cropping intensification and land restoration. Intensive tillage operations in rice (Oryza sativa L.) - wheat (Triticum aestivum L.) system is a predominant practice in the South East Asian countries. This practice has emerged as an unsustainable crop management options. Consequently, zero tillage (ZT) in post–rainy seasons after conventional tilled (CT) puddled transplanted rice is being adopted to minimize tillage intensity in system in these regions. However, long–term impact of continuous CT in all seasons versus seasonal ZT (in post–rainy seasons) after puddled transplanted rice with crop residues in cropping system mode on above– and below– ground weed density and diversity is not adequately studied. Hence, we examined four tillage based residue management: (i) conventional tillage in each crop of rotation without residue (CT–CT), (ii) conventional tillage in each crop with incorporated residue (CT–CT + R), (iii) conventional tilled puddled transplanted rice – zero tillage in post–rainy season crops without residue (CT–ZT), (iv) conventional tilled puddled transplanted rice – zero tillage in post–rainy season crops with surface residue mulch (CT–ZT + R) each with three levels of crop rotation: (i) rice – wheat (R–W), (ii) rice – chickpea (Cicer arietinum L.) (R–C), (iii) rice – chickpea – mungbean (Vigna radiata (L.) (R–C–Mb) in split–plot design in Kanpur, India. Zero tillage in post–rainy seasons after conventional tilled rice resulted in 11%, 23%, and 13% lower (P < 0.05) weed seed density than CT–CT at 0–7.5, 7.5–15, and 0–15 cm depth, respectively. However, zero-tilled residue management had 15–19% and 10–14% (P < 0.05) higher above–ground weed density compared with CT–CT. Rice-chickpea-mungbean rotation reduced weed seed density by 6–11%, 4–11%, and 6–8% (P < 0.05) than those of rice-wheat and rice-chickpea across depth. In contrast, rice-chickpea-mungbean had 30–38% higher total above–ground weed density than rest of the crop rotations. Post–rainy seasons zero tillage with and without residues attributed higher weed diversity indices (Shannon and Simpson) compared with conventional tillage in seedbank. Importantly, CT–ZT + R with R–C–Mb (interaction) reduced 24% total viable seed density at 0–15 cm depth than CT–CT with R–W. Further, this system brought about 15% and 62% higher rice seed yield and system productivity over CT–CT with R–W, respectively. Conventional tilled puddled transplanted rice – zero tillage with added residues increased 16% and 33% seed yield of wheat and chickpea compared with CT–CT (P < 0.05), respectively. Thus, it can be concluded that zero tillage in post-rainy seasons after puddled transplanted rice and intensive pulse based cropping (rice-chickpea-mungbean) can minimize viable weed seeds in soil vis–a–vis above–ground weed density over time than conventional tillage and rice-wheat system. The reduced weed density could reduce soil fertility degradation, enhance crop/system productivity, restore soil health and provides opportunity for sustainable cropping intensification in rice ecologies of the Indo-Gangetic plains.

Evaluation of Autonomous Mowers Weed Control Effect in Globe Artichoke Field

The development of a fully automated robotic weeder is currently hindered by the lack of a reliable technique for weed-crop detection. Autonomous mowers moving with random trajectories rely on simplified computational resources and have shown potential when applied for agricultural purposes. This study aimed to evaluate the applicability of these autonomous mowers for weed control in globe artichoke. A first trial consisting of the comparison of the performances of three different autonomous mowers (AM1, AM2 and AM3) was carried out evaluating percentage of area mowed and primary energy consumption. The most suitable autonomous mower was tested for its weed control effect and compared with a conventional weed management system. Average weeds height, weed cover percentage, above-ground weed biomass, artichoke yield, primary energy consumption and cost were assessed. All the autonomous mowers achieved a percentage of area mowed around the 80% after 180 min. AM2 was chosen as the best compromise for weed control in the artichoke field (83.83% of area mowed after 180 min of mowing, and a consumption of 430.50 kWh⋅ha−1⋅year−1). The autonomous mower weed management achieved a higher weed control effect (weed biomass of 71.76 vs. 143.67 g d.m.⋅m−2), a lower energy consumption (430.5 vs. 1135.13 kWh⋅ha−1⋅year−1), and a lower cost (EUR 2601.84 vs. EUR 3661.80 ha−1·year−1) compared to the conventional system.

Cover crops as a weed seed bank management tool: A soil down review

This review explores ways that cover crops alter soil environmental conditions that can be used to decrease seed survival, maintain weed seed dormancy, and reduce germination cues, thus reducing above-ground weed pressures. Cover crops are grown between cash crops in rotation, and their residues persist into subsequent crops, impacting weed seeds both during and after cover crops’ growth. Compared to no cover crop, cover crops may reduce weed seedling recruitment and density via: i) reducing soil temperature and fluctuations thereof; ii) reducing light availability and altering light quality; and iii) trapping nitrogen in the cover crop, thus making it less soil-available to weeds. In addition, cover crops may provide habitat for above- and below-ground fauna, resulting in increased weed seed predation. The allelopathic nature of some cover crops can also suppress weeds. However, not all effects of cover crops discourage weeds, such as potentially increasing soil oxygen. Furthermore, cover crops can reduce soil moisture while actively growing but conserve soil moisture after termination, resulting in time-dependent effects. Similarly, decaying legume cover crops can release nitrogen into the soil, potentially aiding weeds. The multiplicity of cover crop species and mixtures, differing responses between weed species, environmental conditions, and other factors hampers uniform recommendations and complicates management for producers. But, cover crops that are managed to maximize biomass, do not increase soil nitrogen, and are terminated at or after cash crop planting will have the greatest potential to attenuate the weed seed bank. There are still many questions to be answered, such as if targeting management efforts at the weed seed bank level is agronomically worthwhile. Future research on cover crops and weed management should include measurements of soil seed banks, including dormancy status, predation levels, and germination. Highlights - Cover crops alter the weed seed bank environment, influencing survival, dormancy, and germination. - Weed seed germination may be reduced by decreased temperature and fluctuations thereof, light, and soil nitrogen. - Weed seed germination may be increased by greater soil moisture, soil nitrogen, and oxygen. - Management should maximize cover crop biomass, decrease soil nitrogen, and delay termination for the greatest potential. - Future research should include measurements of weed seed banks, including dormancy status, predation, and germination.

Impact of Tillage and Crop Residue Management on the Weed Community and Wheat Yield in a Wheat–Maize Double Cropping System

Weeds are often harmful to crop growth due to the competition for space and resources. A field experiment containing four treatments with three replications in a complete randomized design was conducted at Yucheng Comprehensive Experiment Station, Chinese Academy of Sciences since 2008 to assess the impact of shifting from conventional tillage to no-till with crop residue management on weeds and wheat production at the North China Plain. We found that both aboveground weed density and species richness were higher under continuous no-till (NT) than conventional tillage (CT) in the regrowth and stem elongation stage of wheat growth. On the other hand, aboveground weed density in the stage of flowering and filling decreased with crop residue mulching. The density of the soil seed bank in crop residue removal treatments was significantly higher than that of crop residue retention. Besides, either crop residue mulching or incorporating into the soil significantly increased the wheat yield compared with crop residue removal regardless of tillage management. In conclusion, crop residue retention could decrease the weed density and species richness both aboveground and in the soil seed bank and inhibit the growth of broadleaf weeds by the residue layer. Moreover, crop residue retention could improve the wheat yield.

Effects of no-tillage sowing on soil properties and forage wheat and Italian ryegrass yields in winter fallow paddy fields.

In South China, it is common practice for the late rice (Oryza sativa) that is planted during the summer in the paddy fields after harvest to be used for fallowing or to plant winter forage crops. The land is ploughed before early rice planting. Both forage wheat (Triticum aestivum) and Italian ryegrass (Lolium multiflorum) have relatively high nutritional value, and planting them in winter fallow paddy fields could potentially address food shortages and provide quality forage for livestock. In this study, we examined the effects of no-tillage sowing 5 days before rice harvest (NB5), no-tillage sowing 1 day after rice harvest (NA1), and conventional tillage sowing (CK) 1 day after rice harvest on forage wheat and Italian ryegrass soil properties, dry matter (DM), and crude protein (CP) yields. Soil and plant samples were collected after three months of crop growth. The results showed that the NB5 and NA1 soil bulk density (0-20 cm soil layer) tended to increase when compared to that of the CK field. The NA1 treatment increased the total soil nitrogen and organic matter content. The enzyme activities and total soil porosity in the no-tillage forage wheat and Italian ryegrass fields tended to decrease, while the no-tillage water content and soil capillary porosity tended to increase when compared to that of the CK field. Overall, planting year significantly influenced soil chemical properties (except for total nitrogen) and enzyme activity, but crop type had no significant effect on soil physical-chemical properties (except for capillary moisture capacity) and enzyme activity. Sowing methods had no significant effects on the crop DM and CP yields. The DM yield was affected by the interaction between planting year and sowing methods, or between sowing methods and crop type. No-tillage also increased the number of species and aboveground weed biomass. We concluded that the best sowing method for forage wheat and Italian ryegrass in winter fallow paddy fields was no-tillage sowing following rice harvest.

Soil Nitrogen and Weed Biodiversity: An Assessment under Two Orchard Floor Management Practices in a Nitrogen Vulnerable Zone in Italy

Nowadays, understory vegetation along the tree row is considered a vital source of agroecosystem services and functional biodiversity improvement in the fruit orchard. Hence, current orchard floor management systems encourage practicing a more sustainable approach that supports vegetation cover rather than keeping bare soil herbicide use, or tillage. A two-year field trial was conducted using two different ground management techniques; integrated mowing (mower and brush or disc) and herbicide (glyphosate) in two commercial apple and peach orchards in a nitrogen vulnerable zone (NVZ) of the Marche region, Italy. This study aimed to evaluate the effects of these practices on soil N status, weed abundance, percent of soil cover, and dry weed biomass production. Weed management systems had no significant effect on soil organic matter and N availability; however, an improvement was noticed under integrated mowing when compared to the one treated with herbicides. Integrated mowing had a significant effect on species richness, soil coverage, and weed biomass production, which was approximately 2-times higher than in the herbicide-treated plots. The overall results showed that integrated mowing maintained a balance in the soil N status of both orchards, while supporting above-ground weed biodiversity and soil protection.

Viable weed seed density and diversity in soil and crop productivity under conservation agriculture practices in rice-based cropping systems

Viable weed seed density and diversity in soil were assessed in an experiment that comprised two types of crop rotation [rice-wheat and rice-maize], two crop residue management (without residue and with residue), and four tillage techniques: conventional tillage (CT) transplanted puddled rice (TPR) – CT wheat/maize (CTTPR-CT), unpuddled transplanted rice – zero tillage (ZT) wheat/maize (UPTPR-ZT), ZT transplanted rice (ZTTPR) – ZT wheat/maize (ZTTPR-ZT), and ZT dry seeded rice (ZTDSR) - ZT wheat/maize (ZTDSR-ZT). The aim was to investigate the density and community composition of viable weed seed in soil in UPTPR-ZT, ZTTPR-ZT, and ZTDSR-ZT systems with and without crop residue, using the seedling germination method. The soil seed density was assessed in 2013-14 and 2014-15 after 4th and 5th year crop cycles established on a sandy loam soil of Patna, India. Total viable seed density was the highest for Cyperus iria L. irrespective of the treatment in both years. Rice-wheat system recorded 4% higher (mean of two years) seed density over the rice-maize system. Residue management practices did not differ for total viable seed density in both years. The ZTDSR-ZT, UPTPR-ZT, and ZTDSR-ZT systems resulted in significantly higher Shannon-Wiener, Simpson, and evenness indices compared to the CTTPR-CT system. Total viable seed density was the lowest for ZTDSR-ZT compared to the remaining tillage practices in both years. The sequence for Leptochloa chinensis (L.) Nees emergence was ZTTPR-ZT > ZTDSR-ZT > UPTPR-ZT > CTTPR-CT in 2014-15 (P < 0.05), signifying the more dominance of monocotyledons in ZT systems. The density of total aboveground weed density (no. m−2) was higher in ZTDSR-ZT in 2013-14 and lower in 2014-15 compared with remaining tillage techniques at 65 days after sowing. Thus, higher aboveground weed density in ZTDSR-ZT system minimized the soil seed density over time. Complete ZT-based practices (ZTDSR–ZT, ZTTPR–ZT) with crop residue significantly enhanced the grain yield of component crops over the CTTPR–CT. Thus, it implies that exhaustion of soil seedbank in ZTDSR-ZT system after 5 years can reduce the aboveground weed infestation and attain the higher grain yield compared to the CTTPR-CT system.

Suzbijanje korova u združenoj setvi useva pasulja i kukuruza tolerantnog na cikloksidim

Due to the narrow range of available herbicides, weeds are one of the limiting factors for intercropping of dry bean and maize. Various benefits of this production method have been confirmed by the results of many authors. The aim of this study was to investigate the possibility of using a cycloxydim-tolerant maize hybrid to expand the ability of weed control in intercroping systems with bean. Three-year field trials were conducted from 2015 to 2017, at the Institute of Field and Vegetable Crops in the vicinity of Novi Sad. Cycloxydim-tolerant maize and dry bean were sown mechanically in alternating strips, with one strip consisting of 4 rows of maize and the other strip containing 6 rows of bean. Combinations of herbicides based on dimethenamid-P, linuron, bentazone and cycloxydim were studied. The effect of herbicides on the number of weeds, fresh weed mass and grain yield of bean and maize was evaluated. No phytotoxicity of the herbicides was observed on the crops, indicating the safety of their use in this production system. The most common weeds were Chenopodium album, Datura stramonium and Sorghum halepense developed from rhizomes. Herbicides had a significant effect in reducing the abundance and fresh mass of the above-ground weed parts. A special contribution of the results obtained is the unique ability to control S. halepense using the cycloxydim-based product. Owing to the above-mentioned possibility, a significant reduction in the number and mass of S. halepense shoots developed from rhizomes was achieved (100% in 2015 and 2016, and &gt;90% in 2017). The results of our trials confirm the contribution of the extension of the choice of herbicides with cycloxydim in this system of intercropping with dry bean and cycloxydim-tolerant maize.

Agronomic and economic tradeoffs between alternative cover crop and organic soybean sequences

AbstractOrganic grain producers are interested in reducing tillage to conserve soil and decrease labor and fuel costs. We examined agronomic and economic tradeoffs associated with alternative strategies for reducing tillage frequency and intensity in a cover crop–soybean (Glycine max L. Merr.) sequence within a corn (Zea mays L.)–soybean–spelt (Triticum spelta L.) organic cropping system experiment in Pennsylvania. Tillage-based soybean production preceded by a cover crop mixture of annual ryegrass (Lolium perenne L. ssp. multiflorum), orchardgrass (Dactylis glomerata L.) and forage radish (Raphanus sativus L.) interseeded into corn grain (Z. mays L.) was compared with reduced-tillage soybean production preceded by roller-crimped cereal rye (Secale cereale L.) that was sown after corn silage. Total aboveground weed biomass did not differ between soybean production strategies. Each strategy, however, was characterized by high inter-annual variability in weed abundance. Tillage-based soybean production marginally increased grain yield by 0.28 Mg ha−1 compared with reduced-tillage soybean. A path model of soybean yield indicated that soybean stand establishment and weed biomass were primary drivers of yield, but soybean production strategy had a measurable effect on yields due to factors other than within-season weed–crop competition. Cumulative tillage frequency and intensity were quantified for each cover crop—sequence using the Soil Tillage Intensity Rating (STIR) index. The reduced-tillage soybean sequence resulted in 50% less soil disturbance compared to tillage-based soybean sequence across study years. Finally, enterprise budget comparisons showed that the reduced-tillage soybean sequence resulted in lower input costs than the tillage-based soybean sequence but was approximately $114 ha−1 less profitable because of lower average yields.

Integrating Cultural Practices with Herbicides Augments Weed Management in Flax

Core Ideas Current weed management strategies in flax are limited.A multi‐factor weed management system is needed to control herbicide‐resistant weeds.Combining several factors has a greater impact on crop‐weed competition than any factor alone.The best combination is a competitive cultivar, seed early, high seeding rate, and use an in‐crop herbicide. Flax (Linum usitatissimum L.) is an important crop with value in both food and industrial markets. However, flax competes poorly with weeds and as a result, flax yield can be severely inhibited by weed competition. Factors that favor crop competitive ability will have great value in improving weed management in flax. This research sought to identify different combinations of seeding date (early vs. late May), seeding rate (400 vs. 800 seeds m−2), cultivar height (short vs. tall), and herbicide (present vs. absent) that could improve the competitive ability of flax. Field studies were conducted across western Canada over 3 yr from 2014 to 2016. Results showed that seeding a tall cultivar at a high seeding rate in early May combined with an in‐crop herbicide application increased crop establishment by 210 plants m−2. This in turn increased aboveground crop biomass and seed yield by as much as 549 and 617 kg ha−1, respectively. This combination of factors significantly reduced aboveground weed biomass by 50 kg ha−1, although no single factor or combination of factors affected weed seed fecundity. By seeding competitive flax cultivars at higher rates earlier in the growing season, and by combining this with an in‐crop herbicide, producers can develop sound cropping systems that provide more competitive flax crops and another profitable cropping option.

Integrated Rice-Duck Farming Decreases Soil Seed Bank and Weed Density in a Paddy Field

Coupled cropping-breeding modes have been highly recommended due to their ecological and sustainable nature. Integrated rice-duck farming is a typical ecological planting system in rice paddy fields and has been widely popularized in Asia where a considerable area of cropland has been planting rice. In this study, two experimental treatments of turbid water or rice-duck treatment were established to compare with the control and a conventional treatment in absence of ducks. The turbid water treatment imitated the muddying effect by duck activities with the trampling and foraging effects excluded, while the rice-duck treatment included all of the mentioned effects by raising ducks in rice paddy field. Results showed that the rice-duck treatment significantly reduced soil seed bank density by more than 40% and the figures under the turbid water treatment were 18.2% and 30.5%, accordingly, in the early and late rice growing seasons. Moreover, the rice-duck treatment significantly altered the vertical distribution of soil seed bank by substantially declining the seed density in the topsoil (0–5 cm). Changes in soil seed bank density considerably contributed to the declines in above-ground weed density because a significant correlation was detected between the soil seed bank density in the early season and the weed density in the late season. Our results of declined soil seed bank and weed density in integrated rice-duck farming imply that this system is highly efficient as a biological pathway for controlling weeds.

An investigation of weed seed banks reveals similar potential weed community diversity among three different farmland types in Anhui Province, China

Crop type is one of main factors influencing weed community structure. However, the identity of weed communities associated with the cultivation of different crops in farmlands remains largely unclear. A field survey of weed seed banks was conducted in 2280 fields at 228 sites of 62 locations representing three different types of farmland (95 paddy, 73 summer-ripe, and 60 autumn-ripe farmlands) along the bank of the Yangtze River in Anhui Province, China. A total of 43 families and 174 species of weeds were found in these weed seed banks. A comparison of the composition of weed groups in the seed banks showed that the species number and density percentage of grass, sedge and broadleaf weed groups were similar among the different types of farmland. The seed banks of all three farmland types shared 71 common weed species, accounting for 40.80% of the total number of species. These common weeds, which were both associated and not associated with crops, accounted for 91.71% of the total dominance degree among all farmland types. The crop-associated weed species were distributed in all soil layers of each farmland type. The Shannon-Wiener index H' (description of species diversity which is more sensitive to dense species) and Pielou's evenness index J (description of species evenness) in summer-ripe farmland were similar to those in autumn-ripe farmland but differed from those in paddy farmland. However, the Simpson's index D (description of species diversity which is more sensitive to sparse species) was similar among all three farmland types. The results of similarity comparison indicated that although the aboveground weed community differed among the different cropping patterns, the weed species composition in the soil seed bank was still similar. Consequently, our results demonstrate that after the implementation of long-term monoculture patterns, weed species compositions in the soil seed bank in different farmlands become homogenized regardless of the crop type.

Effects of Reduced and Conventional Tillage on Weed Communities: Results of a Long-Term Experiment in Southwestern Spain

ABSTRACT: An important drawback in adopting minimum tillage (MT) and no-tillage (NT) techniques is the frequently observed weed shift promoting adapted species and achieving poorer weed control. These changes can be detected best with long-term experiments, and results might differ depending on soil characteristics and the local flora. The objectives of this work were to evaluate the effect of reduced tillage on weed seed distribution in the soil profile and to identify possible consequences on weed diversity on a long-term experiment maintained during 24 years in Seville (Spain) with three tillage systems: NT, MT and conventional tillage (CT) including moldboard plow on a vertisol. For this purpose, soil seedbanks at 0-8 cm and 8-16 cm depths were enumerated in autumn 2005 and in-field emerged plants in autumn 2005 and winter 2006. Shannon diversity index (H) and evenness (J’) were calculated for seedbank and aboveground weed communities. Total weed seed density was highest for NT and lowest for CT. Some big-seeded species, such as Chrozophora tinctorea L., showed highest seed density in CT. NT increased the relative density of Amaranthus blitoides S. Watson seeds in the seedbank and the abundance of emerged plants of Malva parviflora L., Anagallis arvensis L. and Picris echioides L. Overall, MT led to a less diverse seedbank in the 0-8 cm depth of soil than CT. The frequent drought-induced deep fractures in the expandable clay soil caused natural tillage, which probably resulted in fewer differences in weed seed and seedling densities among tillage treatments compared to what might be expected in other soil types.

Seedbank and Field Emergence of Weeds in Glyphosate-Resistant Cropping Systems in the United States

A segment of the debate surrounding the commercialization and use of glyphosate-resistant (GR) crops focuses on the theory that the implementation of these traits is an extension of the intensification of agriculture that will further erode the biodiversity of agricultural landscapes. A large field-scale study was initiated in 2006 in the United States on 156 different field sites with a minimum 3-yr history of GR-corn, -cotton or -soybean in the cropping system. The impact of cropping system, crop rotation, frequency of using the GR crop trait, and several categorical variables on seedbank weed population density and diversity was analyzed. The parameters of total weed population density of all species in the seedbank, species richness, Shannon's H′ and evenness were not affected by any management treatment. The similarity between the seedbank and aboveground weed community was more strongly related to location than management; previous year's crops and cropping systems were also important while GR trait rotation was not. The composition of the weed flora was more strongly related to location (geography) than any other parameter. The diversity of weed flora in agricultural sites with a history of GR crop production can be influenced by several factors relating to the specific method in which the GR trait is integrated (cropping system, crop rotation, GR trait rotation), the specific weed species, and the geographical location. Continuous GR crop, compared to fields with other cropping systems, only had greater species diversity (species richness) of some life forms, i.e., biennials, winter annuals, and prostrate weeds. Overall diversity was related to geography and not cropping system. These results justify further research to clarify the complexities of crops grown with herbicide-resistance traits to provide a more complete characterization of their culture and local adaptation to the weed seedbank.

Weed Seedbank Characterization in Long‐Term Cotton–Tomato Rotations in California

This article characterizes the weed seedbank after a 12‐yr rotation of cotton (Gossypium hirsutum L.)–tomato (Lycopersicon esculentum L.) under standard tillage (ST) and conservation tillage (CT) with and without cover crops in Five Points, CA, from 1999 to 2011. Treatment comparisons included standard tillage with no cover crop (STNO), standard tillage with cover crop (STCC), conservation tillage with no cover crop (CTNO), and conservation tillage with cover crop (CTCC). Weed density, by species, in each plot was assessed in 2003, 2006, and 2011. In 2011, soil cores were taken from each plot and seedlings that emerged from these cores were monitored in the greenhouse, counted by species, and the data were subjected to canonical discriminant analysis. Differences in weed densities were not consistent between CT and ST plots but they were generally greater in plots with cover crops than in those without, particularly in the CT system. The seedbank size was largest in the CTCC system. The weed seedbank community composition of this system was also distinctly different from the other systems. Shepherd's‐purse (Capsella bursa‐pastoris L. Medik.), black nightshade (Solanum nigrum L.), henbit (Lamium amplexicaule L.), and common chickweed (Stellaria media L. Vill.) were associated with the CTCC system. Barnyardgrass (Echinochloa crus‐galli L. Beauv.) and horseweed (Conyza canadensis L. Cronq.) were associated with the CTNO system. Although differences in the aboveground weed densities were inconsistent between the tillage systems, the weed seedbank size was greater in the CT system and having a cover crop further increased the seedbank size.

Weed growth and crop performance following hairy vetch, rye, and wheat cover crops in a cool semiarid region

Tillage is used to control weeds but can degrade soil quality. Our objective was to determine if tillage could be replaced by killed cover crop mulch for weed control when growing organic grain crops. An attempt was made to kill winter cereal and hairy vetch cover crops using a roller-crimper, wide-sweep blade plow, and disk (control) and then followed with warm-season buckwheat, dry bean, and maize grain crops during three growing seasons in southwestern North Dakota, USA. Aboveground weed production was greater in rolled-crimped hairy vetch than in rolled-crimped and disked rye plots. Maize failed to produce grain in any season, while buckwheat and dry bean produced harvestable grain following undercut or rolled-crimped cover crops in only one season. Even then, grain yield averaged only 37 kg ha−1 across cover crop and grain crop treatments in rolled-crimped plots, compared with 255 kg ha−1 in undercut plots and 487 kg ha−1 in disked plots. Yield likely would have been higher in tilled plots but tillage was imposed within 13 days of rolling-crimping, which required cover crops to reach advanced growth stages for effective termination. Rolled-crimped rye mulch can suppress weeds, but soil water deficits following cover crops and the delay needed for consistent termination may prevent timely seeding and successful grain crop production in single-season cover crop/grain crop relay systems in semiarid upper-latitude environments. Preliminary research indicates potential for use of rolled-crimped cover crop mulch for weed suppression in multi-year cover crop/grain crop relay systems in these regions, though additional research is needed which demonstrates commercial viability of this 2-year cropping strategy.

Changes in the weed seed bank over 9 consecutive years of rice–duck farming

Rice–duck farming (RDF), a form of organic farming, has been widely adopted in rice production in East Asia. In RDF, it is believed that ducks can control weeds effectively. Since the weed seed bank determines the weed community in the following crop, a better understanding of the seed bank could provide useful insights into the long-term effects of RDF adopted for weed control. Nine consecutive years' field experiments were conducted to study the characteristics of the weed seed bank under RDF and evaluate the weed control effect of RDF. After 9 years under RDF, the number of weed species in the weed seed bank declined from 38 to 21 and the density of both the weed seed bank and the above-ground weed decreased by more than 90%. RDF resulted in a more uniform vertical distribution of the weed seed bank both quantitatively and qualitatively. The ecological indices point to a gradual change towards fewer species, lower density, and lower diversity following continued RDF. The dominant species in the weed seed bank shifted from Lindernia procumbens, Mazus japonicus, Cardamine hirsuta, and Alopecurus aequalis at the beginning of this experiment in 1999 to A. aequalis, Rotala indica, M. japonicus, and Cyperus difformis in 2008. The results provide concrete evidence for the efficacy of RDF in depleting the weed seed bank and as a weed management approach without any herbicides.