Upland Weeds Research Articles

Inter-specific competition between finger millet and Guinea grass for growth and nutrient uptake under nutrient-limited conditions

ABSTRACT Crop–weed interactions in nutrient-deficient environments can induce strong intra- and inter-specific competition for such nutrients. The study investigated nutrient uptake by finger millet (FM; Eleusine coracana (L.) Gaertn.) in the presence of the upland weed, Guinea grass (GG; Panicum maximum Jacq), under nutrient-limited conditions. A pot experiment was conducted with different neighbor-densities of the two species, including monocultures and mixed cultures. The effects of inter-specific/intra-specific competition on nutrient uptake and growth of the two plant species were measured. Varied plant combinations impacted on plant dry weight, uptake, and use efficiency of nitrogen, phosphorus, and potassium by FM. Root and shoot dry weights of FM were markedly reduced in the presence of GG compared to that when neighbors were from the same species. The largest reduction of tissue nutrient concentration of FM was recorded in FM:GG plant combination of 1:2. The results indicated that the growth and nutrient uptake of FM was suppressed when it co-existed with GG due to strong inter-specific competition under nutrient-limited conditions. GG maintained similar biomass irrespective of the fertilizer treatment and plant combinations, demonstrating its ability to outcompete neighboring species when resources are limited in the growing environment. The present study also provides scientific evidence that GG is well adapted to nutrient-poor environments, which is attained through enhancing the use efficiency of limited nutrients in biomass formation. This might have helped GG to gain the competitive advantage over other plants in the same habitat and dominate in most agro-ecological systems as an invasive weed species.

Community composition and seasonal dynamics of upland weeds for establishing weed control systems in Okinawa, Japan

Community composition and seasonal dynamics of upland weeds for establishing weed control systems in Okinawa, Japan

Rice–weed competition in response to nitrogen form under high and low transpirational demand

AbstractImplementation of water‐saving irrigation practices in lowland rice results in increased availability of nitrate (NO3−) in the soil and favours germination of upland weeds. Since plant species show a specific preference for either ammonium (NH4+) or NO3− as nitrogen (N) source, changes in both soil NO3− concentration and weed flora may affect the competition between rice and weeds. Further, the transpirational demand of the atmosphere might affect growth and competitiveness of lowland (wetland) and upland (dryland) weeds differently due to their adaptation to different ecological environments. Therefore, the study aimed to evaluate the effects of N source on growth, N uptake and competition between rice and common upland and lowland weeds under high and low vapour pressure deficit (VPD). Two rice (Oryza sativa) varieties (NU838 and KD18) differing in growth characteristics and two weed species (Echinochloa crus‐galli and Solanum nigrum) differing in their natural habitat were selected and grown hydroponically as monoculture or mixed culture at low or high VPD. N was supplied as 75%/25% or 25%/75% NH4+/NO3−. N uptake rates were measured in the first week, whereas dry matter (DM), N concentration in the plant, total N uptake and the activities of nitrate reductase and glutamine synthetase in the fresh leaves were determined two weeks after the onset of treatments. Independent of N source, both rice varieties and E. crus‐galli took up a larger share of NH4+, whereas S. nigrum took up a larger share of NO3−. N uptake of rice and E. crus‐galli was hardly affected by N source, whereas high NO3− led to significantly higher N uptake rates and total N uptake of S. nigrum. NU838 showed a higher competitiveness against weeds than KD18. In competition, high NO3− decreased the competitiveness of E. crus‐galli against NU838 but increased the competitiveness of S. nigrum against NU838. High VPD did not affect DM but increased N uptake of S. nigrum, leading to increased competitiveness of the weed at high transpirational demand. Competitiveness for N uptake appears to be an important trait as the relative N concentration in mixed plant communities was correlated with the activity of N‐assimilating enzymes and leaf growth, with a stronger response in rice than in weeds. Our results support the hypothesis that increased availability of NO3− in aerobic rice soils may be advantageous for the competitiveness of upland weeds, especially at high VPD, whereas it may be disadvantageous for common lowland weeds.

Evaluation of Pre and Post Emergence Herbicides Efficacy on Upland rice (Oryza sativa L.) Weeds in Fogera Hub, Ethiopia

Rice (Oryzae sativa L.) is by far the most important stable food crop for over half of the world population for both developing and developed nations, where its consumption has increased considerably due to food diversification and its calorie demand. However, its productivity and quality are highly limited by the occurrence of diseases, insect pests and high weed infestations. Weeds can reduce rice yield by over 30% and this makes farmers to incur 70% of their cost to manage it because of the availability of ample moisture with in the rice field and long period of infestation. The objective of this study was aimed to evaluate the efficacy of broadleaf and grass weed targeted herbicides of upland rice and recommend the most effective ones. An experiment was conducted at Fogera National Rice Research and Training Center experimental station for two consecutive years (2017-2019) using NERICA 4 Variety. It was carried out in aerobic soil condition. Eight treatments, two pre-emergences (S-metolachlor 290 g/l + atrazine 370 g/l and S-metolachlor 960 g/l) herbicides, four post-emergence herbicides (Bispyribac-sodium 10% SC, Pyroxsulam45 g/l, Lodosulfuron-methyl-sodium 7.5g/l+ Mesosulfuron methyl 7.5 g/l and 2,4-D dichlorophenoxy acetic acid 720 g/l acid), two times manual weeding and control check (weedy check) were used for evaluation. The treatments were arranged in randomized complete block design with three replications. Weed population and agronomic parameters data were recorded. The result revealed that post-emergence herbicides were highly effective over pre-emergence herbicides to manage upland rice weeds. Two times of manual hand weeding followed by Bispyribac-sodium 10% EC and Pyroxsulam45 g/l herbicides treatments gave high grain yield (3243.4 and 3063.6 kg ha-1), respectively. Therefore, it can be concluded that Bispyribac-sodium 10% EC could be recommended for upland weeds management followed by Pyroxsulam45 g/l herbicide with integration of other management practices.

우리나라 농경지에 발생하는 잡초 현황

2013년부터 3년동안 농촌진흥청 국립농업과학원과 도 농업기술원, 농과대학, 연구기관 등 11개 기관이 전국 규모로 논, 밭, 과원 그리고 목초지에 발생하는 잡초를 조사하였다. 우리나라 농경지에 발생하는 잡초는 81과 619종이다. 이들 잡초는 논에는 28과 90종, 밭에는 50과 375종, 과수원에는 63과 492종, 목초지에는 52과 275종이다. 이들 잡초를 과별로 분류하면, 국화과 96종(15.5%), 화본과 81종(13.1%), 마디풀과 39종(6.3%), 두과 34종(5.5%), 사초과 32종(5.2%), 십자화과 27종(4.3%), 꿀풀과 24종(3.9%), 장미과 21종(3.4%), 현삼과 19종(3.1%), 메꽃과 15종(2.4%)으로 상위 10과가 388종으로 전체의 62.7%를 점유하고 있다. 또 계절별에 구분하면, 동계잡초는 65과 477종, 하계잡초는 72과 526종이다. 주요 우점잡초는 바랭이, 쇠비름, 깨풀, 흰명아주, 돌피 순이었다. 생활형으로 구분하면, 다년생잡초가 308종으로 전체의 49.8%를 차지하였고, 그 다음으로 일년생잡초가 209종(33.8%), 그리고 동계 일년생잡초가 102종(16.4%)이었다. 외래잡초는 28과 166종으로 흰명주, 망초, 개비름, 미국가막사리, 토끼풀 등이 우점하였다. 2000~2004년 농경지 잡초조사에서는 68과 433종으로 10여년만에 13과 186종이 증가하였다. 이는 잡초방제법 변화에 따른 제초제 저항성잡초 증가와 같은 발생잡초 변동과 조사방법 차이 등의 의한 것으로 사료된다. The nationwide weed survey was conducted in arable land, paddy field, upland, orchard and pasture, over whole country of Korea during 3 years from 2013 to 2015. Also, these survey were conducted in order to determine a change of weed community and to identify a major dominant weed species, and problem weeds. Weeds of arable land were composed of 619 species belonging to 81 families. Weeds occurred in paddy field were 90 species belonging to 28 families, upland weeds were 375 species of 50 families, orchard weeds were 492 species of 63 families and pasture weeds 275 species of 52 families. Among total 81 families, the Asteraceae (15.5%) was the biggest family, followed by Poaceae (13.1%), Fabaceae (5.5%), Cyperaceae (5.2%), Polygonaceae (6.3%), respectively. And these weed species were composed of annual weeds of 209 species (33.8%), winter annual of 102 species (16.4%) and perennial weeds of 308 species (49.8%). Exotic weeds naturalized in Korea were investigated as 166 species. Weed flora in Korean cultivation area have been increased as much as 13 families and 186 species for 10 years compared to 2000~2004 weed survey result of 68 families and 433 species. The increment could be resulted from the change of weed population such as increase of the herbicide-resistant and the difference of investigation method.

Comparison of Weed Seedbanks in Different Rice Planting Systems

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.

Plant species composition and diversity in wetlands under forest, agriculture and urban land uses

We investigated the full range of vegetation diversity in six wetlands under different land uses of Ethiopia. In total, 122 vascular plant species that belong to 86 genera and 37 families were identified. The family Poaceae and Asteraceae contributed the highest number of species. The beta and Shannon diversity ranged from 3.7 to 10.7 and 1.5–3.4 and differed significantly across wetlands. When considering the land uses, the agricultural and urban wetlands could even be more diverse than the forested wetlands and therefore, were not significantly different. The ranges of plant species diversity among the impaired wetlands were observed to be related to disturbance and competitive exclusion processes, and environmental heterogeneity. As observed, disturbances due to drainage, overgrazing, cultivation and pollution reduced the plant diversity through removing sensitive species, and increase species diversity through creating diverse habitats suitable for invader species. The dominant (or characteristic) species of each wetland showed that the urban and agricultural wetlands were highly degraded when compared to forested wetlands. The principal component analysis revealed highest similarity between Boye and Merewa wetlands can be explained from their extensive environmental heterogeneity. Moreover, these impaired wetlands were invaded by upland weeds by outcompeting socioeconomically and ecologically important native species. Thus, data of species and their environmental stresses in wetlands of Ethiopia could be used to prioritize and develop management strategies for east African wetlands.

Vegetation Changes Viewed from Pollen Analysis in Rarotonga, Southern Cook Islands, Eastern Polynesia

This study presents accelerator mass spectrometry (AMS) radiocarbon dates and pollen assemblages of 400-cm core sediments collected from the Karekare Swamp in Rarotonga, Southern Cook Islands, to investigate vegetation changes on the island, in particular those induced by human impacts. Eight 14C dates of charcoal and higher plant fragment samples indicate that the sediments accumulated since ∼6.0 cal kBP, with an apparent interruption of deposition (hiatus) from 130 to 132 cm in depth, corresponding to ∼2.8 to 0.7 cal kBP. The appearance of Chenopodiaceae pollen from upland weeds, and Cucurbitaceae and Vigna pollen grains from cultivated plants suggest that human influence existed in core sediments above 130 cm in depth. The increased abundance of Pandanus pollen and monolate-type fern spores also implies the existence of human activity.

Vegetation Changes Viewed from Pollen Analysis in Rarotonga, Southern Cook Islands, Eastern Polynesia

This study presents accelerator mass spectrometry (AMS) radiocarbon dates and pollen assemblages of 400-cm core sediments collected from the Karekare Swamp in Rarotonga, Southern Cook Islands, to investigate vegetation changes on the island, in particular those induced by human impacts. Eight14C dates of charcoal and higher plant fragment samples indicate that the sediments accumulated since ∼6.0 cal kBP, with an apparent interruption of deposition (hiatus) from 130 to 132 cm in depth, corresponding to ∼2.8 to 0.7 cal kBP. The appearance of Chenopodiaceae pollen from upland weeds, and Cucurbitaceae andVignapollen grains from cultivated plants suggest that human influence existed in core sediments above 130 cm in depth. The increased abundance ofPandanuspollen and monolate-type fern spores also implies the existence of human activity.

Salt Marsh-Upland Ecotones in Central California: Vulnerability to Invasions and Anthropogenic Stressors

Ecotones, zones of abrupt biological transition typically reflecting strong physical gradients, may be particularly sensitive to changes in environmental conditions. Our characterization of the ecotone between salt marshes and uplands in the Elkhorn Slough watershed in central California revealed that extent of appropriate habitat for native high marsh species endemic to this zone is extremely limited. The ecotone is highly invaded, with non-native upland weeds accounting for a significant proportion of cover. We investigated responses to two anthropogenic landscape management strategies, restriction of tidal exchange through water control structures and cattle grazing. Moderate tidal restriction resulting in muted tidal exchange dramatically decreased ecotone width, native marsh plant richness, and cover by native ecotone specialists. Even stronger tidal restriction resulting in very low tidal exchange led to a seaward shift of the ecotone into the area formerly occupied by mid-marsh vegetation; upland plants now occupy the former ecotone zone so net loss of wetland habitat has occurred. Cattle grazing led to a very substantial increase in bare ground, a significant decrease in native marsh plant richness and a significant increase in non-native plant cover. Thus, both of these management regimes can have significant negative impacts on rare salt marsh ecotone extent and biodiversity.

Impacts and interactions of multiple human perturbations in a California salt marsh

Multiple disturbances to ecosystems can influence community structure by modifying resistance to and recovery from invasion by non-native species. Predicting how invasibility responds to multiple anthropogenic impacts is particularly challenging due to the variety of potential stressors and complex responses. Using manipulative field experiments, we examined the relative impact of perturbations that primarily change abiotic or biotic factors to promote invasion in coastal salt marsh plant communities. Specifically we test the hypotheses that nitrogen enrichment and human trampling facilitate invasion of upland weeds into salt marsh, and that the ability of salt marsh communities to resist and/or recover from invasion is modified by hydrological conditions. Nitrogen enrichment affected invasion of non-native upland plants at only one of six sites, and increased aboveground native marsh biomass at only two sites. Percent cover of native marsh plants declined with trampling at all sites, but recovered earlier at tidally flushed sites than at tidally restricted sites. Synergistic interactions between trampling and restricting tidal flow resulted in significantly higher cover of non-native upland plants in trampled plots at tidally restricted sites. Percent cover of non-native plants recovered to pre-trampling levels in fully tidal sites, but remained higher in tidally restricted sites after 22 months. Thus, perturbations that reduce biotic resistance interact with perturbations that alter abiotic conditions to promote invasion. This suggests that to effectively conserve or restore native biodiversity in altered systems, one must consider impacts of multiple human disturbances, and the interactions between them.

沖縄県の畑作物，果樹，雑草等における植物寄生性線虫相

沖縄県の畑作物，果樹，雑草等における植物寄生性線虫相

Control of Hard to Manage Weeds along Highway Rights-of-Way

SS-AGR-275, a 4-page fact sheet by Jason Ferrell and Ken Langeland, provides two tables of recommendations for control of upland weeds and aquatic vegetation. Published by the UF Department of Agronomy, September 2007.

배추나비고치벌 (Cotesia glomerata)에 대한 저독성 약제 및 잔류독성

고랭지배추 재배지에 발생하는 나방류 해충의 방제에 생물적방제와 화학적방제의 조화로운 이용을 위하여, 배추 재배 시 사용되는 약제 중 배추좀나방의 천적인 배추나비고치별 (Cotesia glomerata) 에 대해 저독성을 보이는 약제를 선발하고 잔류독성을 평가하였다. 배추나비고치벌에 대한 저독성 약제선발 방법으로 먹이처리법 (Diet treatment method), 잎침지처리법 (Leaf dipping method) 및 충제침지처리법(Body dipping method) 을 확립하였다. 배추에 등록되어 있는 주요 살충제 31 종을 추천농도로 희석한 후 배추나비고치별 성충을 충체침지처리한 결과 22종이 저독성 약제로 선발되었으며, 배추에 등록된 살균제 및 제초제 15 종은 배추나비고치별 성충에 모두 독성이 낮았다. 배추에 13 종의 살충제를 처리하여 일수별로 배추나비고치벌 성충에 대한 잔류독성을 평가한 결과, 약제처리 l일후에 방사해도 안전한 약제는 thiacloprid, acephate, chlorfenapyr, clothianidin의 4 종이었으며, 3 일후에 방사가 가능한 약제는 imidacloprid, deltamethrin, thiamethoxam, dimethylvinphos, emamectin benzoate이었다. For the development of integrated pest management system by harmonizing biological and chemical control, some experiments wee carried out to select low toxic pesticides against natural enemies. and their residual toxicity were evaluated. Leaf dipping method, body dipping method, and diet treatment method were set up for the toxicity evaluation against Cotesia glomerata adults. We had tested 46 different pesticides (31 insecticides, 11 fungicides, 4 herbicides) at recommending concentration commonly used to control diamond back moth, disease and up-land weeds in chinese cabbage field. Twenty three insecticides, eleven fungicides, and four herbicides were shown to be low toxic to C. glomerata adults in the treatment of body dipping. After insecticide spraying at recommending dose on the chinese cabbage, we examined residual effect of insecticides by introducing natural enemies on different days. Safety interval for the introduction of C. glomerata adults was established according to the residual toxicity of pesticides. Safe insecticides for the introduction of C. glomerata adults at one day after treatment (DAT) were thiacloprid, acephate, chlorfenapyr, clothianidin and at 3 DAT were imidacloprid, deltamethrin, thiamethoxam, dimethylvinphos, emamectin benzoate.

Evaluation of the Upland Weed Control Potentiality of Green Tea Waste – Rice Bran Compost and Its Effect on Spinach Growth

This study evaluated the upland weed control potentiality, germination inhibition ability and growth suppression efficiency of the five combinations of green tea waste - rice bran compost (GRC). GRC was prepared by mixing green tea waste and rice bran at five ratios, and allowed to decompose for 5 mo. Application of GRC suppressed weed growth up to 93.4% in number and 95.4% in dry weight in 2004, and 80.7% in number and 73.4% in dry weight of weeds in 2005, as compared with the untreated control (only soil) under the greenhouse condition. Among the five combinations of GRC, rice bran alone (RC) showed the significantly highest and green tea waste alone (GC) showed the lowest weed suppressing activity in both years. The weed control potentiality of GRC was increased by the increase of rice bran percentages in the mixture. The exudates of GRC inhibited the hypocotyl and radicle elongation of lettuce seedlings when examined by the sandwich method. The water extracts of GRC also inhibited the germination and radicle elongation of the test species in the seed germination tests. The growth inhibitory activity of RC was greater than that of GC, and radicle elongation was more sensitive than seed germination and hypocotyl elongation in all bioassays. The inhibitory activity of GRC water extract varied with the test species and was higher for the dicotyledonous species than monocotyledonous species. The inhibitory effect on seed germination and seedling growth increased as the extract concentration increased. The concentration dependent responses of test species to the water extract of GRC indicated that it might contain phytotoxic substances that were responsible for growth inhibition. Moreover, GRC promoted spinach growth significantly compared with the untreated control. These results suggest that the use of 30% green tea waste + 70% rice bran mixture compost (GRC-3) might be useful to control the upland weeds and enhance spinach growth among the five combinations of GRC, and it may reduce the use of hazardous synthetic agrochemicals. Optimization of the combination of composting materials is necessary for the multipurpose use compost.

Synthesis and herbicidal activity of 2-acylimino-3-phenyl-1,3-thiazolines—A new family of bleaching herbicides—

A novel series of substituted 2-acylimino-1,3-thiazolines was synthesized and their herbicidal activity against upland weeds and selectivity against crops was assessed. The structure–activity relationships were probed by substitution of the thiazoline nucleus and/or an imino group. Highest activity was seen with compounds which contain two substituents: a methyl group at the 5-position of the thiazoline nucleus and a trifluoroacetyl or a difluoroacetyl group on an imino moiety. Among the compounds examined, 2-(N-difluoroacetylimino)-5-methyl-3-(3-trifluoromethylphenyl)-1,3-thiazoline applied at rates between 62.5 and 125 g a.i./ha, showed excellent broad-spectrum pre-emergence herbicidal activity against grass and broadleaf weeds without injury to cotton.

湛水土壌の温度および埋土期間が数種畑雑草種子の発芽力に及ぼす影響

湛水土壌の温度および埋土期間が数種畑雑草種子の発芽力に及ぼす影響

畑地雑草種子のTTC法による生存確認

畑地雑草種子のTTC法による生存確認

一年生夏畑雑草の発生速度を有効積算気温及び土壌水分で説明するモデル

一年生夏畑雑草の発生速度を有効積算気温及び土壌水分で説明するモデル

Synthesis and Herbicidal Activity of 1<i>H</i>-2, 3-Benzoxazine Derivatives

A series of 1H-2,3-benzoxazine derivatives were synthesized and their herbicidal activity against upland weeds and selectivity against crops were assessed. Studies of the structure-activity relationship revealed that the strongest herbicidal activity was achieved when position-4 in the benzoxazine ring was substituted with a 3-chloro-4-fluorophenyl or a 3-bromo-4-fluorophenyl group. The treated weeds showed a strong bleaching symptom. Among the compounds examined, 4-(3-chloro-4-fluorophenyl)-1H-2,3-benzoxazine (23) and 4-(3-bromo-4-fluorophenyl)-6-fluoro-1H-2,3-benzoxazine (34), applied at 1.0 kg a.i./ha, showed strong pre-emergence herbicidal activity against upland weeds such as Echinochloa crus-galli and Digitaria ciliaris without affecting soybean.