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Abstract
Plant invasion is a big challenge to weed management of agricultural lands. In order to reveal the list of common weed species among alien invasive plants, and reveal practical management strategies, we extracted the species lists of common alien agricultural weeds (CAAWs) of various arable lands and plantations, by comparing the lists of alien invasive plant species and common weed species published in China. Totally 88 species from 18 families were recognized as CAAWs, among which 43.0 % are native to North America, followed by South America (34.4 %), Europe (29.0 %), Asia (23.7 %) and Africa (17.2 %); 62.4 % were introduced into China from 1840 to 1949. CAAWs such as Aegilops tauschii Coss., Alopecurus myosuroides Huds., Lolium multiflorum Lamk, Avena fatua L., Phalaris minor Retz, Phalaris paradoxa L., Veronica persica Poir., Geranium carolinianum L., Ranunculus muricatus L., and Cerastium glomeratum Thuill. frequently infest highlands with summer-ripe crops such as wheat and oilseed rape; Alternanthera spp., Panicum repens L., Paspalum conjugatum Bergius, and Ageratum conyzoides L. frequently infest highlands with autumn-ripe crops; and Paspalum distichum L., Alternanthera philoxeroides, and Ammannia coccinea Rott. occasionally infest rice fields. Troublesome CAAWs in plantations in China mainly consist of tall herbs, and climbing or spiny plants, such as Mikania micrantha Kunth, Ipomoea spp., Solidago canadensis L., Erigeron spp. and Bidens spp. Management strategies against CAAWs in current China mainly rely on chemical control, tillage, soil mulching, and manual removing of weeds. Next, effective risk assessing models targeting to different sorts of arable lands or plantations are urgently needed; as well, effective, feasible and sustainable integrated management strategies against troublesome CAAWs should be developed and applied.
The restoration of native plants in invaded habitats is constrained with the presence of highly competitive exotic species. Aboveground removal, such as clipping or mowing, of invasive plants is required for successful restoration. The effects of clipping an invasive plant species, Solidago canadensis, grown at five densities (1–5 plants per pot), and planting two co-occurring and competitive species, Sesbania cannabina and Imperata cylindrica, on the growth of both the invasive species and the co-occurring species were investigated in a greenhouse experiment. The established S. canadensis suppressed the growth of planted seedlings with 47.8–94.4% reduction in biomass, with stronger effects at higher densities; clipping significantly reduced 97.5–97.4% of biomass of S. canadensis and ameliorated the suppression effects (with only 8.7–52.7% reduction in biomass of the co-occurring plants), irrespective of density. Both the aboveground and belowground part of S. canadensis contributed to its suppression effects on planted co-occurring species. Seed sowing of co-occurring species reduced the belowground growth, but not the underground growth of S. canadensis. S. cannabina appeared to be more effective at reducing the growth of S. canadensis than I. cylindrica. Therefore, clipping together with planting competitive species that can overcome the belowground priority effects of S. canadensis could be a promising strategy for controlling S. canadensis invasion and restoring native plant communities.
Taking the data of 30 provinces (excluding Hong Kong, Macao, and Taiwan regions and Tibet) at the provincial level from 2010 to 2019 as the research object, this paper analyzes the current situation and characteristics of China’s agricultural modernization and response to carbon emissions. Agricultural modernization is decomposed into production modernization, management modernization, and ecological modernization. This study uses the spatial Dobbin model to demonstrate the impact of agricultural modernization on carbon emissions and analyzes the impact of agricultural modernization on carbon emissions in the East. The direct effect and spatial spillover effect of the three western regions are to different degrees. The results show that agricultural carbon emissions are spatially dependent. The development of agricultural modernization and transportation of neighboring provinces and cities will have an impact on agricultural carbon emissions in this region. Therefore, under the background of rural revitalization and low-carbon agriculture, this paper further analyzes the impact of agricultural modernization on the spatial distribution of carbon emissions in the eastern, central, and western regions. Recommendations are proposed with a view to giving better play to the process of agricultural modernization.
Amaranthus retroflexus L. is a highly competitive broadleaf weed of corn–soybean rotation in northeastern China. In recent years, the herbicide(s) resistance evolution has been threatening its effective management in crop fields. One resistant A. retroflexus (HW-01) population that survived the protoporphyrinogen oxidase (PPO) inhibitor fomesafen and acetolactate synthase (ALS) inhibitor nicosulfuron applied at their field-recommended rate was collected from a soybean field in Wudalianchi City, Heilongjiang Province. This study aimed to investigate the resistance mechanisms of fomesafen and nicosulfuron and determine the resistance profile of HW-01 to other herbicides. Whole plant dose–response bioassays revealed that HW-01 had evolved resistance to fomesafen (50.7-fold) and nicosulfuron (5.2-fold). Gene sequencing showed that the HW-01 population has a mutation in PPX2 (Arg-128-Gly) and a rare mutation in ALS (Ala-205-Val, eight/twenty mutations/total plants). In vitro enzyme activity assays showed that ALS extracted from the HW-01 plants was less sensitive to nicosulfuron (3.2-fold) than ST-1 plants. Pre-treatment with the cytochrome P450 inhibitors malathion, piperonyl butoxide (PBO), 3-amino-1,2,4-triazole (amitrole), and the GSTs inhibitor 4-chloro-7-nitrobenzofurazan (NBD-Cl) significantly increased fomesafen and nicosulfuron sensitivity in the HW-01 population compared with that of the sensitive (S) population ST-1. Moreover, the rapid fomesafen and nicosulfuron metabolism in the HW-01 plants was also confirmed via HPLC-MS/MS analysis. Furthermore, the HW-01 population showed multiple resistance (MR) to PPO, ALS, and PSII inhibitors, with resistance index (RI) values ranging from 3.8 to 9.6. This study confirmed MR to PPO-, ALS-, and PSII-inhibiting herbicides in the A. retroflexus population HW-01, as well as confirming that the cytochrome P450- and GST-based herbicide metabolic along with TSR mechanisms contribute to their multiple resistance to fomesafen and nicosulfuron.
Grazing is the main way of utilizing understory vegetation in the tropics. However, the effects of grazing on vegetation diversity and soil functions in coconut plantations remain unclear. Therefore, this study was conducted in a young coconut plantation that was grazed by geese in Wenchang, China. We identified four grazing intensities according to the aboveground biomass, namely, no grazing (CK), light grazing (LG), moderate grazing (MG), and heavy grazing (HG). In April 2022, we used the quadrat method to investigate the composition and traits of vegetation, collected and analyzed 0–40-cm soil samples in each grazing intensity. The results showed that grazing changed the composition of understory species. The predominant species changed from Bidens pilosa to Praxelis clematidea + Paspalum thunbergii and then to P. clematidea with increasing grazing intensity. The richness, Shannon-Wiener index, evenness, modified functional attribute diversity (MFAD), functional divergence (Fdiv), and functional evenness (Feve) of CK were 4.5, 1.0, 0.29, 0.20, 0.84, and 0.80, respectively. Taxonomic diversity did not respond to LG, but responded significantly to MG and HG. Compared with CK, MG and HG increased richness by 96% and 200%, respectively, and Shannon-Wiener index increased by 40% and 98%, respectively. HG increased evenness by 95%. For functional diversity, MG and HG increased MFAD by 164% and 560%, respectively, but Fdiv and Feve did not respond to grazing intensity. The carbon (C) functioning, nitrogen (N) functioning, phosphorus (P) functioning, and multifunctionality in the 0–10-cm topsoil of CK were −0.03, 0.37, −0.06, 0.20, and 0.14, respectively. Grazing increased C functioning, P functioning, and multifunctionality in the 0–10-cm topsoil but decreased N functioning. Multiple linear regression showed that the taxonomic diversity and functional diversity could be used to estimate soil functions, but these vary among soil layers. In general, MG and HG can increase vegetation diversity and soil function. It may be possible to promote even distribution of geese by adding water sources or zoning grazing. Furthermore, quantitative grazing experiments are needed to determine the efficient use pattern of the understory in coconut plantations in tropics.
Biochar has wide application prospects as a good soil conditioner, leguminous plants can fix nitrogen and improve soil available nutrients. However, it is not clear how adding biochar when planting leguminous plants affects soil bacterial community and soil available nutrients. This study investigates the effects of biochar addition on the content of ammonia nitrogen, Olsen-P, and available potassium in northeastern farmland soils under the plantation of Trifolium repens and then compared with the application of organic fertilizer. A 90-day incubation experiment was conducted to compare the changes in the structure and relative abundance of soil microflora under varied biochar additions. It was found that the addition of biochar could affect the structure of the microflora and the available nutrients in the soil. When compared with soil planted with T. repens without the addition of biochar, with the application of 3% biochar increased the content of ammonia nitrogen, Olsen-P, and available potassium in the soil by 31.71%, 21.40%, and 11.51%, respectively. High throughput sequencing revealed that the relative abundance of functional bacteria such as azotobacter, rhizobacteria, and phosphorus solubilizing bacteria in the soil increased with the addition of biochar. Furthermore, the effect was more obvious with the addition of organic fertilizers. The addition of biochar improved the microbial community structure and increased the relative abundance of functional bacteria and the content of available nutrients in the soil. This is expected to reduce the application of chemical fertilizers, thereby protecting the environment and conserving natural resources.
Fall panicum is a problematic weed in cropping systems including rice in southern Florida. There is limited information on growth and reproductive ability of fall panicum in water-stressed environments. The objective of this study was to determine the effect of 12.5%, 25%, 50%, 75%, and 100% pot soil water content (SWC) levels on fall panicum growth and panicle branch production under greenhouse conditions. Fall panicum height, number of leaves, and tillers decreased over time as SWC decreased. Fall panicum height decreased by 65% and 50% at 12.5% and 25% SWC, respectively, relative to height achieved at 100% SWC. Plants at 50% to 100% SWC were able to achieve 50% tiller production within 31 to 43 d compared with 28 d at 25% SWC. The 50% tiller production was not reached at 12.5% SWC during the duration of the study. Fall panicum shoot and root biomass, total leaf area, and number of panicle branches per plant at 56 d after SWC treatment initiation decreased as SWC decreased. Fall panicum biomass decreased 83% to 85% and 66% to 68% at 12.5% and 25% SWC, respectively, relative to 100% SWC. Leaf area declined 79% and 65% at 12.5% and 25% SWC levels, respectively, compared to the 100% SWC. Fall panicum was able to produce panicles at all SWC levels, although the plant produced significantly fewer panicle branches as SWC decreased. Plants at 12.5% and 25% SWC produced 82% and 59% fewer panicle branches, respectively, compared with plants at 100% SWC. This study shows that SWC influences the growth and reproductive capacity of fall panicum. Although fall panicum did not reach its full growth potential at low SWC levels, it was able to survive and develop panicles, showing its ability to adapt and reproduce under dry conditions.
•The latest 403 invasive alien plants in China are updated.•A summary of five volumes of 'Alien Invasive Flora of China' and recent invasive plants reports.•Compared with weeds, invasive plants emphasis on the destruction of biodiversity and native ecosystems.•Classical plant taxonomy is the basis of invasive plants research.
Italian ryegrass (Lolium multiflorum Lam.) was introduced into China as a kind of turfgrass and has invaded wheat fields of the Huang-Huai-Hai Plain, causing great losses to grain yield. The acetyl–CoA carboxylase (ACCase) inhibitor clodinafop-propargyl and the acetolactate synthase (ALS) inhibitor mesosulfuron-methyl are highly efficient herbicides that have been widely used for control of this species, which has also resulted in its resistance evolution. However, the resistance status of L. multiflorum in the Huang-Huai-Hai Plain of China remains unclear, which hinders the integrated management of this weed in winter wheat production systems. In the current study, a total of 37 L. multiflorum populations were collected from the wheat fields across the region, and their susceptibility to clodinafop-propargyl and mesosulfuron-methyl was assessed. Of these, 13 populations were resistant or evolving resistance to clodinafop-propargyl (R?, RR, and RRR) with resistance index (RI) ranging from 2.62 to 830.05, and 8 populations were resistant or evolving resistance to mesosulfuron-methyl (R? and RR) with RI ranging from 3.89 to 16.68. Seven populations showed multiple-resistance to both clodinafop-propargyl and mesosulfuron-methyl. Three ACCase (I1781L, I2041N, and D2078G) and four ALS (P197T, P197S, P197A, and W574L) resistance mutations were identified in the herbicide-resistant populations, and I1781L and P197T were predominant ACCase and ALS mutations, respectively. Real-time quantitative PCR assays showed that compared with the susceptible population, the ACCase expression was slightly upregulated in some of the clodinafop-propargyl-resistant populations (AH-01 and AH-05) following clodinafop-propargyl treatment, while the ALS expression in the mesosulfuron-methyl-resistant populations showed no significant change following mesosulfuron-methyl treatment. Whole-plant dose-response testing showed that the AH-01 population carrying an ACCase gene I2041N mutation exhibited cross-resistance to all the ACCase inhibitors tested and multiple-resistance to the ALS inhibitor bispyribac-sodium, the AH-05 population carrying an ACCase gene I1781L mutation and an ALS gene P197T mutation showed cross-resistance to all the ACCase and ALS inhibitors tested, and the HN-07 population carrying an ACCase gene D2078G mutation showed cross-resistance to all the ACCase inhibitors tested and multiple-resistance to some ALS inhibitors. All the resistant populations remained susceptible to the 5-enolpyruvylshikimate-3-phosphate inhibitor glyphosate and the photosystem II inhibitor isoproturon. This study has clarified the distributions of clodinafop-propargyl- and/or mesosulfuron-methyl-resistant L. multiflorum in the Huang-Huai-Hai Plain of China, and target gene mutation was one of the most common mechanisms responsible for the resistance.
Black-grass (Alopecurus myosuroides Huds.) is a common weed in Chinese wheat fields, and has become troublesome due to its evolution of herbicide resistance. One black-grass population (HN-14) collected from a wheat field where herbicides were applied was suspected to be resistant (R) to mesosulfuron-methyl. This study aims to establish a cross-resistance pattern and explore potential resistance mechanisms. The results of a whole-plant dose response assay showed that the resistant (R) population had a high of resistance to mesosulfuron-methyl (33-fold); meanwhile, no synergism of P450s activity inhibitor malathion was observed. The sequencing results revealed that ALS resistance mutation Trp-574-Leu occurred in R plants. The results of in vitro ALS enzyme activity assays also supported that the extractable ALS from R plants were 23.22-fold resistant to mesosulfuron-methyl. In the light of the “R” resistance rating system, HN-14 has evolved RRR and RR resistance to fenoxaprop-P-ethyl, clodinafop-propargyl, haloxyfop-methyl, and fluazifop-P-butyl and R? (resistance may be developing) to pinoxaden, however remains sensitive to imazethapyr, quizalofop-P-ethyl, tralkoxydim, and isoproturon. These results indicated that the mesosulfuron-methyl resistance in the black-grass population HN-14 was driven by a target-site mechanism rather than a nontarget (at least P450s-mediated) mechanism.
Black grass (Alopecurus myosuroides Huds.) is a highly competitive weed in winter wheat fields of China. Due to repeated use of acetolactate synthase (ALS) inhibitors, many A. myosuroides populations have evolved resistance to pyroxsulam in some wheat fields. Research was conducted to determine the molecular basis of herbicide resistance in the AH93 A. myosuroides population. Whole-plant dose-response assay confirmed that the AH93 population was resistant to pyroxsulam with a resistance index of 4.2. Cross- and multiple-resistance assays indicated that the AH93 population was cross-resistant to mesosulfuron-methyl and multiple-resistant to pinoxaden. Sequencing of the ALS and ACCase gene revealed that there was no target-site mutation in ALS, but Trp-2027-Cys and Cys-2088-Arg amino acid mutations in ACCase in the AH93 population. A malathion pretreatment study indicated that the AH93 population might have cytochrome P450-mediated herbicide metabolic resistance. This is the first report of pyroxsulam resistance in a multiple-resistant A. myosuroides population in China, and the Cys-2088-Arg mutation is the first reported case of an ACCase mutant conferring herbicide resistance in A. myosuroides.
The four alien farmland weeds of genus Veronica (i.e., V. arvensis, V. didyma, V. hederifolia, and V. persica) have successfully colonized in China, but caused different ecological consequences in the colonized habitats. However, the key biological traits conferring to bio-invasion differences under different light conditions among the four alien species of Veronica remain unknown. A comprehensive contrastive analysis experiment was conducted to assess the contribution intensity of photosynthetic and sexual and asexual reproductive traits of the four alien Veronica weeds to their invasion level in both field trial and laboratory. The field survey results showed that V. persica had the highest invasion level, V. didyma, V. hederifolia and V. arvensis in turn. Their invasiveness were mainly attributed to photosynthetic-related parameters (LMA) and asexual reproduction traits (the ratio of adventitious root) out of all the 22 tested indexes. The photosynthetic-related and some asexual reproduction indexes from separated determinations under both sun and shade conditions showed that V. persica was able to adapt strong illumination but more tolerant to the shade than the other species. This adaptive differentiation to illumination conferred the four alien Veronica weeds to different competitiveness to crops through allocating resource to the biomass of each organ in farmland. It may conclude that the adaptability to illumination conditions and the asexual reproduction traits may endow their successful invasion and become different important farmland weeds.
Using crops to control invasive weeds is an important approach for the long-term management of invasive species in agroecosystems. Nitrogen application can improve the yield and quality of crops, but may shift interactions of invasive weeds and crops, potentially affecting grass control ability. To explore the yield of a crop and its control efficacy of invasive weed under different nitrogen conditions, we studied the competitive effects of the high-value crop rapeseed (Brassica napus L.) on growth and photosynthetic characteristics of invasive species littleseed canarygrass in the field experiments. The results showed that the rapeseed yield and its control efficacy on littleseed canarygrass were significantly affected (p < 0.05) under different N regimes, and the control efficacy of littleseed canarygrass by rapeseed increased first and then decreased with the increase of basal nitrogen rates, while increasing topdressing N rates increased control efficacy of littleseed canarygrass by rapeseed. In fact, yield and weed control efficacy of rapeseed was most ideal when both basal and topdressing N was 90 kg·ha−1. We also found that N significantly impacted the competitive ability of rapeseed toward littleseed canarygrass, and rapeseed had the highest competitive ability when both basal and topdressing N was 90 kg·ha−1. With the increase of basal nitrogen rates, competitive balance index (CB) of rapeseed increased initially but decreased beyond an optimal level. CB continually increased with increasing topdressing N rates. Our research also showed level and period of N application had a significant effect (p < 0.01) on the photosynthetic rate (Pn) and chlorophyll content (Chl) of both rapeseed and littleseed canarygrass. Under the same N application regime, the Pn and Chl of littleseed canarygrass were higher than that of rapeseed in December, while the Pn and Chl of rapeseed was higher than that of littleseed canarygrass in February. Our study indicated that photosynthetic characteristics of rapeseed and littleseed canarygrass in different growth stages differ in their sensitivity to N regimes, creating a dynamic competitive relationship. Together, our results demonstrated that optimal application of fertilizer N could help rapeseed produce higher yields and greater weed control efficacy, suggesting that future modeling or experimental studies on utilizing crops to control invasive weeds should carefully consider both timing and placement of N.
The study of weed flora dynamics in agricultural crops is a complex and never-ending process which requires the continuous inventory and monitoring of problem weeds that cause the greatest damages on crops, according to which the most effective fighting strategies are established. The mapping action was carried out in fields cultivated with winter wheat in crop rotation and in monoculture crop from Ilfov, Giurgiu and Constanta counties. Weed files have been drawn up for each fields and they have shown the density, participation and constancy of each weed species. The analysis of the data shows that the dominant species in the fields where the wheat was cultivated in crop rotation system were: Veronica hederifolia, Veronica persica and Setaria pumila in Giurgiu county, V. hederifolia and V. persica in Ilfov county, V. hederifolia and Polygonum convolvulus in Constanta county. In monoculture system the number of weeds was higher and several species appeared, including weeds on the list of invasive species: Ambrosia artemisifolia and Coniza Canadensis. Regarding the distribution of weed species by botanical groups, the largest group was the one of the annual dicotyledonous and among the perennial dicotyledonous the most important species were Cirsium arvense and Convolvulus arvensis. From the group of annual monocotyledonous, the most important species were those of the genre Setaria and broad-leaved cockspur (Echinochloa crus-galli), species that invades all cultures in our country and is found in all areas and is also considered to be an invasive species. The dominant species in both crop rotation and monoculture system belong to the Veronica genre, exceeding an average density of 100 plants/m².
In desert habitats, sand burial is an important factor affecting germination of plant seeds and seedling growth. Xanthium spinosum has strong adaptability in arid desert areas, and is a common malignant invasive plant in Xinjiang, China. The effects of different sand burial depths on seed germination, seedling emergence, growth and biomass allocation were studied to provide a scientific basis for further control of X. spinosum . Six sand burial depths (1, 2, 3, 5, 7 and 9 cm) were established to explore the response of X. spinosum seed germination and seedling growth to sand burial. The first emergence time, peak emergence time, emergence rate, seedling growth height, biomass and biomass distribution of X. spinosum seeds was significantly different at sand burial depths ( P < 0.05). The X. spinosum seeds had the highest emergence rate (71.5%) at 1 cm sand burial and the maximum seedling height (7.1 cm). As sand burial depth increased, the emergence rate and seedling height gradually decreased. Emergence rate (12.25%) and seedling height (2.9 cm) were lowest at 9 cm sand burial. The root length at 9 cm depth (13.6 cm) was significantly higher than that at other sand depths ( P < 0.05). The sand burial depth affected the biomass accumulation and distribution of X. spinosum . As sand burial depth increased, the root biomass and rhizome ratio increased, and the most deeply buried seedlings allocated more biomass for root growth. The optimal sand burial depth for seed germination and seedling growth of X. spinosum was 1–3 cm, and high burial depth (5–9 cm) was not conducive to the germination and growth of X. spinosum seedlings. For prevention and control of X. spinosum , we suggest deeply ploughing crops before sowing to ensure X. spinosum seeds are ploughed into a deep soil layer.
Different weeding frequencies (WFs)―0WF, 2WF, 4WF, 6WF, and 8WF―were adopted in an organic rice field to investigate their influence on weed types, rice and weed biomass, rice tiller and weed number, N concentration, and N uptake. The study field was located in Tsuruoka, Yamagata, Japan. Rice (cv. Sasanishiki) was planted from May to September 2019, and all weeding events were carried out until 49 days after transplantation (DAT) using a rotary weeder. Rice and weed samples were collected at 60, 88, and 110 DAT. Echinochloa crus-galli (E. crus-galli), Schoenoplectus juncoides, and Monochoria vaginalis (Burm. f.) were the most commonly found weeds. High weed diversity was observed at both 6WF and 8WF, E. crus-galli was the dominant weed at 0WF. Compared to 0WF, 2WF displayed a significantly decreased weed biomass. However, at 8WF, the weed biomass was reduced by 79.0%, the rice biomass was increased by 277%, and the rice tiller number was almost three times higher than that at 0WF and 110 DAT. Compared to 0WF, a significantly increased rice N uptake was observed at 4WF, and rice N uptakes achieved at 6WF and 8WF were two and four times higher than those at 0WF, respectively. Higher weeding frequencies provide notable benefits in suppressing weeds and supporting rice growth, especially in N uptake competition with weeds.
An investigative weed flora survey was conducted in parthenium-infested maize fields in West Gojjam Zone in 2019/2020. The objective was to investigate the distribution and impact of parthenium on species diversity. A survey was conducted on 90 fields using 2 m × 2 m (4 m2) quadrats (totally 270). A total of 110 weed species belonging to 27 families were identified out of these families. Asteraceae with 26 species (23.36%) and Poaceae with 18 species (16.36%) were abundant. The highest importance value (IV) was recorded by Ageratum conyzoides, Amaranthus hybridus, and Bidens pilosa, with 28.05, 19.18, and 13.16%, respectively, in no parthenium infestation level. The highest IV of 27.08, 17.71, and 16.44%, respectively, was shown by Ageratum conyzoides, Bidens pilosa, and Galinsoga parviflora with 27.08, 17.71, and 16.44%, respectively, in very low parthenium infestation level. Ageratum conyzoides (29.38%), Bidens pilosa (24.10%), and Parthenium hysterophorus (22.68%) had the highest IV in low parthenium infestation level. Parthenium hysterophorus (91.32%), Ageratum conyzoides (17.19%), and Echinochloa colona (16.34%) had high IV in moderate parthenium infestation level. It is concluded that Ageratum conyzoides, Bidens pilosa, Echinochloa colona, and Galinsoga parviflora were competitive over parthenium based on importance value, and this indicates to suggest parthenium as a biological management option.
Aegilops tauschii Coss. is known as a noxious grass weed seriously affecting wheat quality and yield. To investigate its present occurrence in wheat fields and the potential genetic diversity of the grass weed in China, a filed survey covering major wheat production regions was conducted during 2017–2019. Seeds of different Ae. tauschii populations collected from the survey were analyzed with Simple Sequence Repeats (SSRs) technique. Results showed that Ae. tauschii was occurring in each of the provinces surveyed with varied occurrence frequency ranging from 0.91% in Sichuan Province to 92.85% in Henan Provinces. Eighty alleles with size ranging from 98 bp to 277 bp were detected from the 192 collected Ae. tauschii populations with 17 SSR markers. Ae. tauschii, in this study, exhibited a moderately high level of genetic diversity, high differentiation, deficient heterozygosity and limited gene flow. Compared with other provinces, Hubei populations possessed relatively low genetic diversity. Dendrogram analysis showed that genetic distance did not seem to be related to geographic distribution. Additionally, STRUCTURE analysis suggested that Ae. tauschii populations in wheat fields of China can be divided into three groups, which was further supported by cluster analysis. Among the three groups, solely 7% of the total variation was detected, whereas the majority variation (67%) occurred among different populations within same group. Undoubtedly, such information will help us to better understand population relationships and spread of Ae. tauschii in China and will provide a new perspective for its integrated management.
Forestry eco-engineering programs in China occupy 721.77 × 104 km2, among which plantations have a pivotal role in protecting the fragile ecological environment. Reforestation understory is often ignored because of the simple vertical structure. The importance of light in understory has been discovered. However, how other ecology factors (e.g., soil properties and geographical factors) influence understory composition and stratification remain unclear. In this study, we investigated the effects of understory composition and stratification on environmental factors in black locust plantations. We used systematic clustering analysis based on plant average height to describe understory stratification. The finding of this study was that black locust plantation understory consisted of three levels: (I) a low herbaceous layer (<80 cm), (II) a high herbaceous layer (80–130 cm), and (III) a shrub layer (>130 cm). Redundancy analysis indicated that soil moisture content and soil total phosphorus content were the largest contributors to the variation in understory vegetation composition. Soil moisture content, altitude, and soil organic carbon content were the largest contributors to the variation in understory stratification. Overall, by analyzing understory stratification and the relationship between soil and geographical factors, we gained a more comprehensive understanding of the interaction between understory and the microenvironment. This is especially important for reforestation management that maintains understory ecology function in the face of global climate change.
Chemical-dependent weed control has led to the evolution of herbicide-resistant weeds and pollution of arable land and water systems, posing a great threat to food security and environmental safety. For the first time, we developed a simple weed management regime to ecologically deplete the weed seed bank under a wheat-rice cropping system, which in turn allowed a reduction in the frequency of conventional herbicide applications while sustainably reducing weed infestation levels. The key ecological methods adopted here involve cleaning irrigation water by intercepting seeds at the water entrance and exit and removing floating weed seeds with a net during irrigation before rice planting, which significantly reduced the input of weed seeds into the seed bank. Quantitative analysis of the weed seed bank and population dynamics showed that implementation of this management regime consecutively for 6 years reduced the density of the total weed seed bank by 51% and the dominant grassy weed population density by 53% compared to those at the beginning. The effect of this ecologically sound weed control regime was comparable to that of conventional dual- or triple-application herbicide chemical control in each crop growing season. The results indicated that, compared with the conventional control method, the integrated weed management method could reduce the number of herbicide applications by half and reduce costs and labor by 30%. Furthermore, quantitative modeling analysis of the seed bank and population dynamics of the dominant weed species, Alopecurus japonicus, showed that continuous adoption of this ecological strategy could deplete the seed bank by more than 90%, thereby freeing the fields of the presence of this noxious weed.
Due to increasing globalization and human disturbance, plant invasion has become a worldwide concern. Soil characteristics associated with the vegetation of recipient communities affect plant invasion success to a great extent. However, the relative importance of soil biotic and abiotic factors of different recipient communities in resisting plant invasion is not fully understood. We hypothesized that natural forest soils can better resist plant invasion than can plantation soils, that the allelopathic legacy of resident trees in soil plays a role in resisting invasive plants, and that late-successional soils have a strong effect. We examined the effects of soil and litter collected from four natural forests at successional stages and one Robinia pseudoacacia Linn. plantation in eastern China on the growth of Phytolacca americana L., which is a highly invasive species across China, and explored the individual effects of soil nutrients, allelochemicals, and soil microbes. We found that allelopathic activity of natural forest soils can effectively resist P. americana invasion, and that low level of nutrients, especially of phosphorus, in the soils might be potential limiting factors for the plant growth. The profound conditioning of soil resources by exotic R. pseudoacacia based on tree traits (including allelopathy) facilitated further P. americana invasion. Allelochemicals from forest litter inhibited the germination of P. americana seeds, but pH played a major role in P. americana growth when these substances entered the soil. However, we have no evidence that late-successional forest soils exhibit strong allelopathy toward P. americana. The present study will help to further our understanding of the mechanism of community resistance to invasion.
Understory vegetation is crucial and necessary for the stability and biodiversity in plantation forests. However, the role of understory vegetation is easy to be neglected in traditionally intensity plantations. To date, the foliar functional traits of understory shrub in different plantation types are still in debate. Herein, a field–based restoration experiment with different plantation types was conducted to explore the variation of foliar functional traits of understory shrubs in two 13-year reforested plantations and assess which is the most suitable understory species for the plantation development and succession in subtropical China. The results showed that the foliar functional traits of the understory shrubs were species-specific. Both L. cubeba and I. asprella had higher specific leaf area (SLA) and photosynthetic pigments, suggesting that they can efficiently acquire and utilize light in the understory shade environment rather than M. candidum and R. tomentosa regardless of the plantation types. Also, the leaf N and P concentrations of L. cubeba and I. asprella were significantly larger than those of the other two species. Moreover, the SLA, leaf N and P concentrations were significantly positively related to the leaf photosynthetic pigments (chlorophyll and carotenoid) within the two plantations. These further supported that the L. cubeba and I. asprella can adapt well to the shade environment. Therefore, considering the higher SLA, leaf N and P concentrations, and photosynthetic pigments in L. cubeba and I. asprella, we strongly recommend that L. cubeba and I. asprella can be selective species for the understory management in the subtropical plantations of southern China.
Because cropping systems can greatly affect the establishment and spread of alien species populations, the design of cropping systems to control invasive weeds is an important approach for invasive species management in agro-ecosystems to avoid excessive increases in other control measures such as herbicides. The annual weed Phalaris minor Retz. (P. minor) is one of the most troublesome invasive weed species of winter crops in Yunnan Province, China, but the development of cropping systems for ecological control of this weed have received limited research attention. Here, we studied seed dormancy, germination characteristics and reproductive responses of P. minor to various cropping systems to show how cropping systems could be better designed to control P. minor in China. Our research showed that cropping systems significantly affected seed dormancy in submerged paddy fields. Phalaris minor seed remained dormant and the germination rates (less than 10%) were significantly lower (p < 0.05) than in maize fields and dry, bare soil conditions. Wheat, faba bean and rapeseed crops had no significant influence (p < 0.05) on the seed germination rate of P. minor, but increasing soil depth significantly decreased (p < 0.05) the germination rate and germination index of this weed. Total biomass, spike biomass, spike number and seed number of P. minor were significantly reduced (p < 0.05) with increasing proportions of the three crops (wheat, faba bean and rapeseed), with rapeseed having the strongest inhibition effects among the three crops. The reproductive allocation and reproductive investment of P. minor were also significantly reduced (p < 0.05) in mixed culture with wheat and rapeseed. With increasing proportions of wheat or rapeseed, the specific leaf area of P. minor significantly increased (p < 0.05), but the reverse was true for leaf area and specific leaf weight. Moreover, the net photosynthetic rate, stomatal conductance and transpiration rate for P. minor also decreased significantly (p < 0.05) when grown with wheat or rapeseed. These results suggest that optimal cropping systems design could involve planting rapeseed in conjunction with deep plowing and planting rice (continuous submergence underwater) in summer. Such a system could reduce the field populations and seed bank of P. minor, thus providing a sustainable and environmentally friendly means of suppressing P. minor.
The evolution of glyphosate-resistant and -tolerant weeds has caused changes in weed management around the world. Residual herbicides are crucial tools for weed management, but the rate of adoption by soybean growers remains very low in Brazil. In this research, we used glyphosate tolerant Ipomoea triloba as a model weed species to evaluate the advantages of using residual herbicides on soybeans in multiple years and locations of transition and Cerrado regions of Brazil, rather than relying only on post-emergence control. Most residual herbicides provided enough residual activity to allow a longer application window in post-emergence. Treatments with residual herbicides increased overall weed control, preventing weed interference and increasing soybean yield. When two residual herbicides were used as opposed to only one, a better I. triloba control was achieved, reflecting in higher crop yield, especially in conditions of high weed infestation. The use of pre-emergence herbicides allows growers to have a longer application window for the post-emergence treatment, which is particularly important in Brazilian Cerrado large fields when logistic could be an issue.
Weed control using herbicides with the same mechanism of action can encourage the emergence of resistant biotypes or tolerant plants. An example of this is the occurrence of morning-glory (Ipomoea sp.) in soybean crops in southern Brazil. In this sense, the aim of this study was to quantify the losses arising from two species of morning-glory weeding coexisting with soybean crop. A field study was conducted in the 2013/2014 season. The experimental design was a randomized block with four replications, with treatments being distributed in a factorial arrangement (2x2x5), which assessed the effect of competition on two soybean cultivars (TEC6029 and TEC7849) of morning-glory species (I. triloba and I. purpurea) in different population (0, 4, 8, 16 and 32 plants m-2). The interaction of soybean with different densities of morning-glory affects yield components. The first eight morning glory plants have a more intense competition, reducing productivity by 45% and 27% for TEC6029 and TEC7849 cultivars, respectively.
Knowledge about weed density and composition plays an important role in weed management
decision making. Surveys were carried out to study the weed flora composition in rice fields of Guilan
Province in Iran. 481 fields from 16 regions were selected for survey. Weed samples were taken with a
W-shaped sampling pattern. Weed species were identified and the plant density, percentage frequency,
uniformity, and abundance indices were determined. Biodiversity was calculated using Shannon -Weiner
(H′) and Simpson (D) diversity indices. A total of 66 species, belonging to 43 genera and 29 families
were identified. The highest number of weeds belonged to the two families Cyperaceae and Poaceae with
15 and 8 species, respectively. The most frequent weed species were Echinochloa crus-galli (89.8%), and
Paspalum distichum (79.4%), Echinochloa oryzoides (60.3%), Cyperus difformis (56.5%), Ecliptal
prostrate (49.5%), Cyperus serotinus (34.7%), Azolla filiculoides (34.5%), Sagittaria trifolia (31.6%),
Cyperus esculentus (31.6%) and Alisma plantago-aquatica (28.7%). Relative abundance index indicated
that the annual weed species were more dominant than the perennial ones. Based on Shannon-Weiner and
Simpson’s diversity indices Talesh area had the highest weed diversity (H′ = 2.85; D = 0.916) and Rudbar
showed the lowest diversity values (H′ = 1.97; D = 0.749).
Keywords: abundance index, density, dominance, rice fields, sustainable agriculture
When in competition with cotton, Amaranthus retroflexus can cause high yield losses. Due to the limited availability of selective herbicides registered for post emergence control of this weed, the same herbicides have been used repeated times over the last few years, which may have selected resistant biotypes. Biotypes of A. retroflexus collected from the main areas of cotton cultivation in Brazil were submitted to dose-response trials, by applying the herbicides trifloxysulfuron-sodium and pyrithiobac-sodium in doses equivalent to 0, ¼, ½, 1, 2 and 4 times the recommended rates. Resistance to ALS inhibitors was confirmed in biotypes of A. retroflexus. Biotype MS 2 from Mato Grosso do Sul, was cross-resistant to both trifloxysulfuron-sodium and pyrithiobac-sodium, while biotype MS 1 was resistant to trifloxysulfuron-sodium only. Likewise, singular and cross resistance was also confirmed in biotypes from Goiás (GO 3, GO 4 and GO 6), in relation to trifloxysulfuronsodium and pyrithiobac-sodium. One biotype from Mato Grosso (MT 13) was not resistant to any of the ALS inhibitors evaluated in this work.
Core Ideas
Weed seedbanks were compared in three rice planting systems: machine‐transplanted rice, water direct‐seeded rice, and dry direct‐seeded rice.
Weed seedbanks were mainly distributed in soil within a depth of 10 cm.
Dry direct‐seeded rice tended to maintain larger seedbanks of sedges, grasses, and some upland weeds.
Water direct‐seeded rice contained the smallest weed seedbank overall.
Machine‐transplanted rice had larger seedbanks of broadleaf weeds and some traditional rice weeds.
Machine‐transplanted rice ( Oryza sativa L.) (MTR), water direct‐seeded rice (WDSR), and dry direct‐seeded rice (DDSR) are three important alternatives to traditional manual transplantation of rice. Weed infestation is a pervasive problem in all rice planting systems. The weed seedbanks under different rice planting systems have seldom been compared. Thus, we sampled weed seeds in fields employing MTR, WDSR, and DDSR consecutively for at least 5 yr in Wujin County, eastern China. Seeds of 26 companion weed species of rice, comprising 16 families, were observed. Most weed seeds, 82.5% in MTR, 75.3% in WDSR, and 81.7% in DDSR, were distributed in soil 0‐ to 10‐cm deep. As soil depth increased, the seedbanks of total weeds, broadleaf weeds, grasses, and sedges all significantly decreased under the different rice planting systems, except for sedges under WDSR. The DDSR tended to maintain larger seedbanks of sedges and grasses, as well as some upland weeds, such as Digitaria sanguinalis (L.) Scop. and Eleusine indica Gaertn. The WDSR system contained the smallest weed seedbank overall but tended to have larger seedbanks of several weeds, such as Ammannia arenaria H. B. K. and Lindernia procumbens (Krock.) Philcox. Weedy rice and Cyperus difformis L. tended to maintain larger seedbanks in DSR fields. The MTR fields tended to have larger seedbanks of broadleaf weeds and some traditional rice weeds, with significantly lower richness of weed species in the seedbank. Therefore, to downsize the weed seedbank, WDSR or MTR should be employed rather than DDSR when possible. Moreover, the influences rotation of different rice planting systems on the weed seedbank merit more studies.
Global environmental changes and biological invasions are important environmental problems. A better understanding of their interactions will help us improve management for plant invasion control under global change context. Mikania
micrantha and Chromolaena
odorata are two of the most notorious invasive weeds in southern China. They have caused serious damage to semi-natural forests, pastures, crops and plantations. In this study, they were grown under elevated and ambient CO2 (700 ± 50 and 380 ± 50 μmol mol−1, respectively) in open-top chambers in south China botanical garden and treated with fertilizers in the form of soluble nitrogen (N), phosphorus (P), N + P (NP), and with tap water as control. Elevated CO2 had significant positive effects on most variables for M. micrantha, and N addition had positive effects on most variables for C. odorata. Elevated CO2 and N or NP addition increased Rubisco content, photosynthetic rates and photosynthetic N use efficiency of both weeds, which improved their resource capture ability and resource utilization efficiency, and improved their growth capacity. SDS-insoluble protein decreased in response to elevated CO2 in both weeds indicating a decrease in their mechanical defense when CO2 elevated. P addition decreased the quantity of N invested in the photosynthetic apparatus under ambient CO2 in both weeds, but this effect was reduced under elevated CO2, suggesting that high soil P will not benefit for the growth of the two weeds under current CO2 levels but less so if CO2 levels continue to rise. From the results we predict that the invasion potential of both weeds will decrease in the high P and low N area at present CO2 concentration, but increase in the high N deposition area, especially with elevated CO2.
Leaf functional traits strongly influence plant growth, reproduction, and survival, which are also associated with ecosystem functions. Understory plants are important components of plantation biodiversity. How plantation type affects the performance of different understory shrubs is still poorly understood. In the present study, to address suitable shrub species for the understory management of mature plantations, three common understory species, including Psychotria rubra , Ilex asprella , and Evodia lepta , were selected to investigate the responses of leaf traits to four plantation types ( Acacia auriculiformis , Eucalyptus urophylla , Schima superba , and Pinus massoniana ). The results showed that the leaf functional traits of understory shrubs were species‐specific among different plantations. The plantation types significantly influenced the specific leaf area (SLA), leaf N:P ratios, chlorophyll, and starch concentrations of these studied shrubs, which may have contributed to the microclimate rather than the soil nitrogen availability originating from different plantations in P‐limited ecosystems. For individual shrubs, I. asprella had higher SLA and chlorophyll contents, indicating that it adapted to shade environment to increase light capture and maintain high light use efficiency. This can help to increase carbon assimilation to cope with the shaded environment. However, the higher starch and nonstructural carbohydrates (NSCs) in the leaves of I. asprella also suggested that it had greater carbon assimilation and storage. Additionally, the similar performance of the three shrubs was also found in four mature plantations, suggesting that the nature of the understory plants also, to some extent, determined their growth and survival rate in the shade environment. Therefore, I. asprella can adapt well to the shaded environment of restored mature plantations. Thus, we recommend that I. asprella is a suitable and alternative species for understory regeneration in the reforested mature plantations of southern China.
Recently, the herbicide fomesafen has frequently failed to control the troublesome weed Ipomoea nil in soybean fields in Liaoning Province, China. Hence, we collected 10 suspected resistant populations and evaluated their sensitivity to fomesafen. The results revealed various degrees of Ipomoea nil resistance to fomesafen, with a resistance index of 2.88 to 22.43; the highest value occurred in the LN3 population. Therefore, the mechanisms of the resistance in LN3 to fomesafen were explored. After fomesafen treatment, the expression levels of InPPX1 and InPPX2 genes were 4.19- and 9.29-fold higher, respectively, in LN3 than those in the susceptible (LN1) population. However, mutations and copy number variations were not detected between the two populations. Additionally, malathion pretreatment reduced the dose necessary to halve the growth rate of LN3 by 58%. Liquid chromatography with tandem mass spectrometry demonstrated that metabolism of fomesafen was significantly suppressed by malathion. Moreover, LN3 displayed increased reactive oxygen species scavenging capacity, which was represented by higher superoxide dismutase and peroxidase activities after fomesafen application than those in LN1. An orthogonal partial least squares-discriminant analysis revealed that the high resistance in LN3 could be attributed mainly to enhanced metabolism. Fortunately, the fomesafen-resistant I. nil remained sensitive to 2,4-D-ethylhexylester and bentazon, providing methods for its control.
Aegilops tauschii Coss. is a malignant weed in wheat fields in China, its herbicide resistance has been threatening crop production. This study identified one mesosulfuron-methyl-resistant(R) population, JJMHN2018-05 (R), without target resistance mutations. To fully understand the resistance mechanism, non-target site resistance was investigated by using transcriptome sequencing combined with a reference genome. Results showed that the cytochrome P450 monooxygenase (P450) inhibitor malathion significantly increased the mesosulfuron-methyl sensitivity in R plants, and greater herbicide-induced glutathione S-transferase (GST) activity was also confirmed. Liquid chromatography with tandem mass spectrometry analysis further supported the enhanced mesosulfuron-methyl metabolism in R plants. Gene expression data analysis and qRT-PCR validation indicated that eight P450s, six GSTs, two glycosyltransferases (GTs), four peroxidases, and one aldo-keto reductase (AKRs) stably upregulated in R plants. This research demonstrates that the P450s and GSTs involved in enhanced mesosulfuron-methyl metabolism contribute to mesosulfuron-methyl resistance in A. tauschii and identifies potential contributors from metabolic enzyme families.
Effective accumulated temperature (EAT) is a basic index to predict plant growing and development, while EATs for key stages during Echinochloa crus‐galli seed‐setting are still unclear. We collected three E. crus‐galli populations (Nanling [NL], Feidong [FD], and Sihong [SH]) from different rice fields in eastern China and conducted four sets of pot experiments in a greenhouse. Plants of the three populations sown on May 9–12, averagely reproduced 484–671 mature seeds per plant; showed a duration of 67–76 days from sowing to heading, with an average EAT of 1,156–1,274°C; showed a duration of 90–94 days from sowing to seeds starting maturation in plant individuals with average EATs about 1,571–1,647°C; and showed a maturation stage lasting for 14–36 days. Significant negative correlations (p < .01) were found between the period of collecting day after seed maturation and the number or 1,000‐seed weight of mature seeds collected on the day, in each set of experiment. Compared with NL individuals sown on May 9, NL individuals sown on April 10 needed significantly higher EATs for periods from sowing to seed maturation, and from heading to seed maturation. According to logistic regressions, duration days needed for 50% of seeds to mature were 93–122 days after sowing, with EATs of 1,625–1893°C for these E. crus‐galli populations. This study revealed EATs for E. crus‐galli seed‐setting, which suggested time windows for panicle‐removing control of E. crus‐galli in rice fields.
Physalis angulata L. (Solanaceae) an invasive alien weed displayed a great spreading and invasion in Egypt, thus the growth traits and functional strategies within the invaded lads and crops were analyzed. Seedling, juvenile, flowering, fruiting, and dispersion stages were distinguished with a short time and life cycle with an average from 70 to 90 days during the year. Specific leaf area was gradually increased until the final stage and vice versa in root mass and stem mass fractions. The accumulation coefficient of dry weight was increased significantly (P > 0.001) and ranged from 0.844 to 0.99 in response to the habitat conditions. The higher plasticity of P. angulata referred to the substantial adaptability to variable environmental conditions and to invade a new community. The demographic surveys of 60 invaded fields were found about 28 weed species within 25 genera in 10 families in examined crops. Physalis angulata have a high relative growth rate, massive fruits and subsequently seeds production, as well as a higher coefficient of similarity in the recipient communities. While their interaction with the native community was reflexed in their low richness, diversity, and evenness. The most susceptible crop to P. angulate invasion was Citrullus lanatus var. Colocynthoide followed by Sesamum indicum and in contrast Zea mays and Solanum melongena crops that can be considered as competitive crops to this weed. Finally, this information is important for the prediction of P. angulate impacts and future behavior.
Land use change and extreme precipitation are the main challenges for tropical forests, and numerous studies have indicated that these changes could affect soil ecology. However, it is not yet known whether the soil legacy effect of ongoing changes could influence the invasiveness of alien plants. Two mixtures of invader and native species (Chromolaena odorata-Artemisia leucophylla and C. odorata-Desmodium sequax) were transplanted to 18 soil treatments (3 forest types × 3 pre-water supply levels × 2 microorganism treatments). The results showed that the biomass of the invader was greater while its biomass fraction was lower in secondary forest soil than in primary and rubber forest soil; the soil legacy effect of drought was positive on both the biomass and biomass fraction of C. odorata. In rubber plantation soil, the biomass and biomass fraction of C. odorata were enhanced by the pre-increased water supply level. In primary and rubber forests, compared with normal precipitation, the sterilization treatment increased the biomass of the invader under drought and increased precipitation. The nutrient cycle and microorganisms both played a crucial role in this process. Overall, our study demonstrated the pronounced soil legacy effect of land use change, extreme precipitation and their interactions on the invasion success of C. odorata.
The effect of degradable mulching film on dry direct-seeded rice remains largely unknown. Then the aim of this research is to investigate the effects of degradable mulching film on dry direct-seeded rice. A field investigation of four treatments (CK: non-mulching; MF1: a degradable film (Shanghai Hongrui Biotech, Shanghai, China); MF2: a degradable film (Xifeng Plastic Corp. Ltd., Baishan, China); MF3: common agricultural mulching film (Jialiming New Material Corp Ltd., Hinggan League, China)) was conducted to evaluate the effects of degradable mulching film on the rice seed germination, seedling growth, soil temperature, and grain yield of dry direct-seeded rice. The results showed that compared to CK, mulching film treatments increased soil temperature, especially at night time, improved seed germination rate, plant height, leaf area of seedlings, and grain yield. MF1 showed good degradation performances and had the highest soil temperature at the night time of 13.65 ℃-14.08 ℃, grain yield at 7.938t ha⁻¹, and seedling growth with shoot dry mass at 46.73 mg plant⁻¹ and root dry mass at 31.34 mg plant⁻¹. The germination rate significantly increased by 6.99%-755.60% at MF1 as compared to CK. Overall, mulching films resulted in high yield due to the increasing soil temperature, seedling germination, and improving seedling growth, amongst MF1 performance the best.
Giant chickweed [ Myosoton aquaticum (L.) Moench], a troublesome broadleaf weed species, is widespread in winter wheat ( Triticum aestivum L.) fields in China. However, limited information is available on its seed germination and seedling emergence ecology. Thus, three M. aquaticum populations (JS, HN and AH) from different geographic regions were studied under laboratory conditions to determine the effects of different environmental factors on seed germination or seedling emergence. The seeds germinated at a relatively wide constant temperature range of 5-25 C; however, the optimal temperature for germination varied among the populations. Compared with constant temperatures, fluctuating temperatures with the same mean significantly improved the final germination of all populations. Light was not required for seed germination. The seeds germinated under a wide pH range of 3-10, and the optimum pH was 6-7, with a final germination percentage of 81-95%. The seeds of all populations showed similar sensitivities to osmotic potential and similar high tolerances of saline conditions. The seedling emergence of all populations decreased with increasing burial depth, and no emergence was observed when the seeds were buried more than 3 cm, but the AH population showed higher sensitivity to burial depth than the others. The results generated from this study will contribute to the development of integrated M. aquaticum management strategies for winter wheat fields in China, and deep plowing and late sowing of autumn-sown wheat are suggested for managing M. aquaticum , as it showed lower germination at a low temperature and under relatively deep burial.
Farmer training is important to improve weed management practices in tea cultivation. To explore the group characteristics of tea growers, we interviewed 354 growers in Guizhou Province, China. Sixty-one percent of the respondents planted tea for companies or cooperative groups, and 56% managed tea gardens larger than 10 ha. Self-employed tea growers tended to be older and smallholders, and to apply herbicides and conduct weed control less frequently ( P < 0.05). Approximately 87% of the respondents conducted weed control two to four times yr ⁻¹ , 83% spent between 2,000 ha ⁻¹ yr ⁻¹ for weed control, and 42% thought weed control costs would decrease by 5 years from this study. Twenty-eight species were mentioned by the respondents as being the most serious. According to canonical correspondence analysis, latitude, altitude, being self-employed or a member of a cooperative, having training experience in tea-garden weed management, and frequency and cost of weed control in tea gardens had significant ( P < 0.05) influence on the composition of most troublesome weed species listed by respondents. Among the respondents, 60% had had farmer’s training on weed management in tea gardens. Of these, a significant number ( P < 0.05) tended to think weed control costs would decrease, and a nonsignificant number ( P > 0.05) tended to conduct weed control more frequently and have lower weed management costs in their tea gardens.
Amaranthus retroflexus L. is a troublesome broadleaf weed in autumn crop fields in China. Farmers complain that A. retroflexus cannot be controlled by nicosulfuron at the recommended field rate in maize fields in Heilongjiang Province. The aim of this study was to determine the molecular basis of nicosulfuron resistance in A. retroflexus. Whole-plant response assays revealed that two resistant populations (R1 and R2)exhibited resistance (14.50- and 44.24-fold)to nicosulfuron. In vitro acetolactate synthase (ALS)activity assays indicated that the nicosulfuron I 50 values for R1 and R2 populations were 8.12 and 22.32 times higher than that for the susceptible population (S), respectively. Sequence analysis of ALS showed amino acid mutations Ser-653-Asn in R1 and Trp-574-Leu in R2. These two target-site mutations seem to play a primary role in A. retroflexus resistance to nicosulfuron, and this is the first time that the Ser-653-Asn mutation has been reported in this species.
Weeds are among the major biotic factors that reduce rice productivity. Alternative weed control methods are required in the wake of problems, such as increasing number of herbicide-resistant weed species and environmental pollution. In this research work, we evaluated the weed-suppressive effects of water levels and rice cultivars against an important rice weed Echinochloa oryzoides (Ard.) Fritsch. The studies comprised three water levels [low (5 cm), medium (15 cm) and high (25 cm)], three medium-grain rice cultivars (Ronaldo, Nembo and, Cameo) and three weed levels [high weed density (>30 plants m−2), low weed density (<10 plants m−2), and weed-free]. Weed-free condition helped the rice plants achieve excellent growth and development, and resulted in the highest grain yield, while weedy condition hampered the growth and productivity of rice cultivars. Water levels had the greatest impact on weeds, rice growth, and paddy yield. A standing layer of water (high water level i.e., 25 cm in particular) not only had a highly suppressive effect against weeds, but it also helped to enhance the growth and yield of rice cultivars. Deep and shallow water levels respectively caused an increase in the leaf area, number of tillers, and dry weight of rice cultivars, particularly for Ronaldo. Ronaldo performed better than other cultivars in terms of growth and competitiveness either under weedy or weed-free conditions. This work concludes that maintaining a water layer (15–25 cm) in rice fields could produce multiple beneficial effects including improved rice growth and decreased weed growth, resulting in high rice productivity.
Tausch's goatgrass (Aegilops tauschii Coss.) is one of the most troublesome weeds in winter wheat-growing regions of China. In recent years, the recommended field rate of mesosulfuron-methyl failed to control the Tausch's goatgrass population in Shanxi province (SX), China. Experiments were conducted to characterize the herbicide resistance level and investigate the basis of mesosulfuron-methyl resistance in Tausch's goatgrass. Whole-plant dose–response tests showed that the SX population exhibited 11.42-fold resistance to mesosulfuron-methyl than the susceptible HN population, and the resistance level in the SX population could be significantly reduced by malathion, a cytochrome P450 inhibitor. The SX population also exhibited cross-resistance to imazethapyr, pyroxsulam and bispyribac‑sodium. Acetohydroxyacid synthase (AHAS) sequencing and enzyme activity assays demonstrated that the mesosulfuron-methyl resistance was not conferred by target-site substitution. A sensitive AHAS, together with the malathion revisable resistance, suggested that herbicide metabolism likely plays a main role in the mechanism of mesosulfuron-methyl resistance in the SX population. To our knowledge, this is the first report elucidating the mesosulfuron-methyl resistance in Tausch's goatgrass.
Alternative irrigation systems are viable options to reduce water footprint in rice; however, it could increase the difficulty of controlling weeds, as the water layer prevent weed emergence. Despite the environmental importance, there is no knowledge regarding effective chemical control of Echinochloa crus-galli (L.) P. Beauv. under contrasting field layouts and irrigation systems in dry-seeded rice. In this study, we quantified the efficacy of some pre-emergence (PRE) and post-emergence (POST) herbicide sequences and tank mixtures to control E. crus-galli under continuous and intermittent irrigation at two different field layouts. The experiment was conducted during three growing seasons between 2012 and 2014, in two edaphoclimatic regions of Uruguay. The rice yield was directly related to the efficacy of controlling of E. crus-galli at flowering (R²≈ 0.60). The efficacy of chemical options to control E. crus-galli was not affected by the irrigation or the field layout system. Clomazone PRE followed by penoxsulam was the most effective option (80% weed control). The results suggest that chemical options are available to control E. crus-galli when applying alternative field layout and irrigation systems that promote improved water efficacy in rice. We expect this new approach to control E. crus-galli be useful in reducing water needs, and hence making rice production more sustainable.
Understory management is evidently important for improving the ecological and economic effects of orchards, and grass maintenance in orchards is a potentially preferable floor management measure relative to clean tillage. It is widely accepted that grass maintenance increases soil organic carbon (SOC) content, but whether different SOC fractions respond consistently is less understood. To clarify the potential effects of grass maintenance on SOC fractions, three grass species, including a leguminous species (Stylosanthes guianensis cv. Reyan) and two gramineous species (Paspalum notatum Alain ex Flugge. and Pennisetum americanum x P. purpureum), were planted under young Litchi trees in a subtropical orchard of southern China for eight months using clean tillage as a control. The labile and non-labile SOC fractions and microbial C mineralization were investigated. Relative to the control, grass cultivation significantly increased or trended to increase the SOC content and this was mainly due to increases in the labile SOC fractions. The increased C lability and substrate supply support higher soil microbial biomass C, consequently accelerating the soil C mineralization process and resulting in a greater biologically mineralizable C pool. However, grass cultivation significantly decreased the non-readily oxidizable OC content, although it was relatively more chemically recalcitrant. Our results suggest that grass cultivation may favorably accelerate nutrient cycling in orchards due to higher labile C substrate availability and soil microbial biomass and activity. Nevertheless, grass cultivation could decrease SOC stabilization as indicated by the increased SOC lability in the grass-planting systems.
The present study reports the influence of sludge application on understory abundance and species richness in an eight year-old maritime pine forest. Four types of sludge (liquid, dewatered, limed and composted sludge) were applied at a rate equivalent to 3 tons dry weight per ha-1 per year-1. Understorey vegetation was monitored before treatment and for three successive years following initial sludge application. Species richness, the biodiversity index and plant community cover naturally occurring in maritime pine forests were measured. Results showed a significant increase in species richness two year after initial sludge application. In fact, eighteen additional species (Aira caryophyllea, Cerastium glomeratum, Conyza canadensis, Danthonia decumbens, Geranium robertianum, Gnaphalium sylvaticum, Hypericum humifusum, Hypericum perforatum ssp perforatum, Jasione montana, Lonicera periclymenum ssp periclymenum, Ornithopus compressus, Phytolacca americana, Rhamnus frangula, Teesdalia nudicaulis, Veronica arvensis, Vicia sativa angustifolia and Vulpia myuros) were appeared after sludge application compared to unamended plot. Most of these species were observed in solid limed or composted sludge treatments. Then, it declined at the following year highlighting the temporary effect on species diversity. Nevertheless, the cover by these eighteen new species was low and did not exceed 1% except for Hypericum perforatum and Jasione montana for limed sludge treatment and Vulpia myuros for the liquid sludge treatment. Additionally, sludge reduces significantly bare soil percentage, which was ranged between 5 and 18% compared to the control (38%). According to sludge type, treatment led also to a significant change in species dominance of the understorey plant communities naturally occurring in maritime pine forests. Indeed, the cover of Molinia caerulea decreased in spite of an increase in Agrostis capillaris and/or Holcus lanatus following application of solid limed, liquid or composted sludge.
Potato (Solanum tuberosum L.), an important food crop of Northwest China, is commonly grown using transparent plastic film mulch for water conservation since both irrigation water and precipitation are scarce. In order to improve production efficiency, field experiments were conducted at Shiyanghe Experimental Station, China Agricultural University, Wuwei, Gansu Province, China using plastic mulch and drip irrigation to study the influence of two typical plastic mulches (transparent and black) and three wetted soil percentages on potato root distribution, evapotranspiration, tuber yield and quality, and water use efficiency (WUE) in 2014 and 2015. Using a wetted soil percentage of 55%, three soil surface treatments were tested: transparent plastic mulch, black plastic mulch, and a non-mulched check. With the transparent plastic mulch, three wetted soil percentages 35%, 55%, and 75% were evaluated. The soil retained moisture better in the mulched treatments than in the non-mulched treatment. As the plant canopy increased, the differences diminished. Potato grown without plastic mulch developed more roots than potato grown with mulch. The soil water fluctuations in the top of the bed with black plastic mulch were greater than with transparent plastic mulch. Potato grown with either plastic mulch had greater yield and WUE than potato grown without plastic mulch. Potato grown with transparent plastic mulch had 10% and 7% greater WUE in 2014 and 2015, respectively than potato grown with black plastic mulch but the differences were not statistically significant. For different wetted soil percentages, the irrigation frequency was higher with the 35% wetted soil treatment than with 55% or 75%. The irrigation at 35% principally only affected the soil water in the upper soil in contrast to the 55% or 75% treatments. The 35% wetted soil treatment had more root development in 2015. Potato evapotranspiration increased as the wetted soil percentage increased. The 75% wetted soil treatment had significantly more evapotranspiration than the 35% wetted soil treatment in 2015. The 35% wetted soil treatment had the highest WUE, 17% and 25% higher than the 75% wetted soil treatment in 2014 and 2015, respectively. The 35% wetted soil percentage irrigation regime combined with transparent plastic mulch merits wider testing for potato production in arid Northwest China.