Germination Of Weeds Research Articles

Actividad fitotóxica de un extracto N-Hexano obtenido de la corteza de Drimys Winteri sobre cuatro especies de malezas

El objetivo de esta investigación fue determinar el efecto fitotóxico de un extracto obtenido con n-hexano de la corteza de Drimys winteri sobre la germinación y el crecimiento de Convolvulus arvensis, Setaria pumila, Daucus carota y Cichorium intybus. El efecto fitotóxico del extracto sobre la germinación de las malezas se determinó mediante bioensayos en placas de Petri y la aplicación del extracto en el medio de germinación en concentraciones de 100 a 1.000 mg L-1. En bioensayos en macetas, se determinó el efecto fitotóxico del extracto sobre la emergencia y crecimiento de las plántulas de malezas, en los cuales se aplicó el extracto mezclado con el sustrato de cultivo en concentraciones de 500 a 4.000 mg kg-1. También se determinó el efecto fitotóxico del extracto asperjado sobre plantas de malezas en concentraciones de 800 a 6.400 mg L-1. En los ensayos de germinación, el extracto retrasó la germinación y redujo el crecimiento de tallo y radícula de todas las malezas, el porcentaje de germinación disminuyó en todas las malezas, excepto en C. arvensis. La aplicación del extracto al sustrato de cultivo disminuyó y retrasó la emergencia de todas las malezas. Las plantas tratadas con extracto presentaron menor altura y hubo disminución de la biomasa acumulada. De igual modo, la aplicación del extracto al follaje de las malezas redujo la altura y la biomasa acumulada y llegó a causar la muerte de C. intybus, S. pumila y D. carota.

Inibição do desenvolvimento inicial de plantas de girassol, milho e triticale por palhada de capim-colchão

O objetivo deste estudo foi avaliar os possíveis efeitos alelopáticos da massa seca de plantas de capim-colchão (Digitaria horizontalis), incorporadas ao solo em diferentes densidades, sobre a germinação e o crescimento inicial de milho, girassol e triticale. O experimento foi realizado em casa de vegetação, e as parcelas foram constituídas de uma planta, conduzida em vasos com capacidade para 2,5 L, dispostos inteiramente ao acaso. Material seco de capim-colchão nas quantidades equivalentes a 0, 2,5, 5,0 e 10 t ha-1 foi incorporado à terra. A emergência foi avaliada diariamente até 10 dias após a semeadura, quando se calculou a porcentagem final de emergência e o índice de velocidade de emergência (IVE). A altura e a massa seca das plantas foram avaliadas 35 dias após a semeadura. A incorporação da palhada da planta daninha não interferiu na germinação e no IVE das espécies avaliadas. A massa seca e a altura de plantas de todas as espécies foram influenciadas pela palhada, decrescendo de acordo com o aumento da concentração da palhada incorporada ao solo, com exceção do triticale, que não teve alteração quanto à altura.

Exposure to red light, temperature and exogenous gibberellins influenced germination of some winter weeds

Red light, temperature and gibberellins are well known for their capacity to induce higher germination in dormant seeds of several plant species. In the current study, we investigated the effect of various temperature (10, 13, 16, 19, 22 and 25°C) and gibberellic acid (GA 3 ) and GA 4+7 concentrations (0.1, 1, 10, and 100 uM) on germination of Poa annua, Alopecurus aequalis and Stellaria aquatica seeds incubated under continuous dark or treated with red light pulse of 80 mol m -2 s -1 red light (660 nm) for 10 min after 12 h of dark period. We found that incubation temperature and gibberellins (GAs) significantly enhanced seed germination in red light treated seeds, as maximum germination was observed for A. aequalis (67.3% at 13°C), P. annua (61.3% at 13°C), and S. aquatica (42% at 19°C) in such treatments. Exogenous GA 4+7 significantly promoted germination of P. annua and A. aequalis seeds, while GA 3 induced higher germination in S. aquatica seeds. It was observed that GAs were more effective in the presence of red light as least germination stimulation was recorded for GAs under dark condition and no germination was found in weed seeds at control and 0.1 mM GA 3 and GA 4+7 treatments. It can be concluded that lower temperature (13°C) and GA 4+7 in conjunctions with red light pulse, induced maximum germination in dormant weed seeds. Key words : Germination, temperature, nitrogen-containing compounds, red light, gibberellins.

Effects of Environmental Factors on Germination and Emergence of Siam Weed (Chromolaena odorata)

Abstract Laboratory and greenhouse studies were conducted to determine the effect of several environmental factors on seed germination and seedling emergence of Siam weed (Chromolaena odorata). Seeds germinated over a range of 10 to 35 with optimum germination at 25. Low temperature markedly restricted germination, with no germination occurring at 5. Siam weed was moderately photoblastic, with 38% germination occurring in the dark. Germination decreased with increasing water potential, and germination was totally inhibited at osmotic stress higher than -0.8 MPa. Germination was greater than 65% at less than 50 mM NaCl and greater than 20% at 200 mM NaCl, with no germination at 300 mM NaCl. Maximum emergence occurred when seeds were planted on the soil surface. No seedlings emerged when planted 3.5 cm deep. These results suggest that the future range of Siam weed in China will be restricted largely to the Southern China.

Effect of Heat Treatment and Short-Duration Composting on Germination of Weeds in Green Waste

The use of minimally processed green (or yard) waste as a mulch for tree crops and vines has the potential to spread weeds. In a laboratory study, the germination of cootamundra wattle (Acacia baileyana) and tomato seeds in green waste was determined at four temperatures (35C, 45C, 55C, and 65C) and three moisture contents (40%, 50%, and 60% w w-1 w.b.). Moisture content had no significant effect on tomato seed germination at 35C or 45C. At 55C, seed germination was generally greater at 40% or 50% than at 60% moisture content, but the differences were not significant after the first hour of exposure. Cootamundra wattle seeds survived more than 5 h exposure to 55C and 65C with no decrease in germination and were not affected by increasing moisture content. In field composting conditions conducted in windrows, 8% of cootamundra wattle seeds germinated after 136 h exposure to temperatures above 55C. Bermudagrass did not survive much longer than eight days on the outside edge of a windrow (3.3% of stem fragments germinated after eight days), but the bulbils of watsonia (Watsonia meriana) were able to germinate after more than 5 days buried 1 m deep in a windrow (3.3% germination) where temperatures reached over 60C. This study indicates that in order to control heat-resistant weeds like cootamundra wattle, green waste feedstock should be adequately prepared for composting and managed with careful process control, especially when the duration of composting is short.

Herbicidal activity ofWithania somnifera againstPhalaris minor

Herbicidal activity of Withania somnifera (L.) Dunal. was studied against Phalaris minor Retz., one of the most problematic weeds of wheat in Pakistan. In laboratory bioassays the aqueous, methanol and n-hexane extracts of 5, 10 and 15% w/v (fresh weight basis) of the roots and shoots of W. somnifera were applied. Extracts in the different solvents exhibited markedly variable herbicidal activities against germination and seedling growth of the target weed species. The methanol extracts showed the highest toxicity. Different concentrations of methanol shoot and root extracts declined the germination of P. minor by 21–71%, its shoot length by 40–72%, its root length by 50–99% and the plant biomass by 32–83%. The aqueous extracts proved to be comparatively less toxic than the methanol extracts, where generally the highest concentration of 15% exhibited pronounced toxicity against the target weed species. There was up to 48, 51, 99 and 55% suppression of the weed's germination, shoot length, root length and plant biomass, respectively, due to the 15% aqueous root and shoot extracts. Generally, the n-hexane extracts of both roots and shoots exhibited insignificant or stimulatory effects against weed shoot length and plant biomass. In a foliar spray bioassay, aqueous and methanol shoot extracts of 10% w/v (dry weight basis) concentration were sprayed on one- and two-week old pot grown P. minor seedlings. Two subsequent sprays were carried out at five day intervals each. The aqueous extract significantly reduced the shoot and root dry biomass of one-week old P. minor plants. In a residue incorporation bioassay, crushed shoots of W. somnifera were incorporated in the soil at 1, 2, … 5% w/w. Phalaris minor seeds were sown one week after residue incorporation and plants were harvested 45 days after sowing. The lower concentrations of 2 and 3% significantly reduced, while higher concentrations of 4 and 5% of residue incorporation completely arrested, the germination of P. minor. The present study concludes that both roots and shoots of W. somnifera contain herbicidal constituents against P. minor.

호밀 리빙멀치, 토양환원, 예취처리가 유기농 콩밭 잡초 발생에 미치는 영향

ABSTRACT In organic agriculture, cover crops are used for weed control. Cover crops inhibited weed germination or growth by allelopathy or shading effects. In this study, we used rye as cover crop to control weed in organic soybean field. The main treatment was rye using method such as living mulch, incorporating and mowing. Sub-treatment was rye planting density and soybean planting density. One month after soybean sowing, weed emergency and growth had been highly suppressed by rye in all treatments. Living mulch treatment was the best effective way to control the weed about 92%, and mowing treatment was the second about 75% compare to control. The weed control efficiency between rye planting densities was similar during one month. Soybean planting density treatment was same result as rye planting density. As a result of this experiment, we recommend rye as living mulch in one row planting. Key words: cover crop; living mulch; organic agriculture; rye; soybean; weed control. 서 언 피복작물은 토양의 유실과 유거수를 방지하고 수분보전, 투수성 개선, 토양 물리성 개량, 잡초억제 및녹비활용 등 다양한 목적과 효과를 위하여 오랫동안 이용되어 왔다(Andy 2007; Reddy 2003). 여러 종류의 피복작물 중 호밀은 내한성이 높고 건물 생산량이 많아 피복작물로 특히 많이 활용되어 왔

Modelling the effect of light intensity and duration of exposure on seed germination of Phalaris minor and Poa annua

Ohadi S, Rahimian Mashhadi H, Tavakkol‐Afshari R & Beheshtian Mesgaran M (2010). Modelling the effect of light intensity and duration of exposure on seed germination of Phalaris minor and Poa annua. Weed Research50, 209–217.SummaryPhotocontrol of weeds requires a better understanding of the effect of light on seed germination. Therefore, the effect of light intensity and exposure duration was tested on seed germination of two winter annual weeds, Phalaris minor and Poa annua. Photo‐sensitised seeds of both species were subjected to four light intensities, including 130, 250, 500 and 1000 μmol m−2 s−1, each at six exposure durations of 0.1, 1, 10, 100, 1000 and 10 000 s. Light stimulated the germination of both weeds. A modelling approach was used to describe the relationship between light intensity and exposure duration with the germination of weed seeds. A combination of logistic and Gaussian models provided good fits to P. minor percentage germination data, whereas in the case of P. annua, the incorporation of logistic and quadratic models better described the relationships. According to the model, increasing light intensity from 0 (full darkness) to 1000 μmol m−2 s−1 increased the germination of P. minor and P. annua from 28% to 57% and from 0% to 35% respectively. The seed germination of both weed species increased with exposure duration, but declined at duration periods longer than 100 s in P. minor or 1000 s in P. annua. The model predicted a trade‐off between light intensity and light duration for both weeds. That is, a high light intensity irradiated for a short time exposure may result in the same percentage germination as one with a low light intensity, but at longer exposure duration.

Competitive Ability and Phytotoxic Potential of Four Winter Canola Hybrids as Affected by Nitrogen Supply

Low inputs in nitrogen may affect canola (Brassica napus L.) competitiveness and allelopathic potential as well as grain and oil yields. A 2‐yr study was conducted to assess nitrogen supply effect on the ability of four canola hybrids to compete with corn poppy (Papaver rhoeas L.) as well as its effect on canola seed and oil yields. Phytotoxic potential of canola hybrids on germination and growth of winter wild oat (Avena sterilis spp. ludoviciana L.), corn poppy, and wild mustard (Sinapis arvensis L.) was also determined using a perlite‐based bioassay. At canola blossom, corn poppy plant number in nitrogen‐treated plots was 23% less than that in the nitrogen‐untreated ones. Canola seed and oil yield was reduced 18.6 and 23.7%, respectively, by the competition of 100 corn poppy plants m−2, with ‘Elan’ and ‘Titan’ the most productive hybrids. Nitrogen supply did not increase in all cases the competitive ability or the seed and oil yields. In the laboratory, germination of the winter weeds was completely inhibited by the greatest extract concentration (5 g 100 mL−1) of all hybrids. Nitrogen supply did not affect, in most cases, the phytotoxicity of canola hybrids, while phytotoxicity did not significantly differ among hybrids. Conclusively, the hybrids Elan and Titan, cultivated without any herbicide or nitrogen fertilizer, could be viable as a short‐term alternative crop system for canola seed and oil production, especially in organic or low‐input fields infested by corn poppy.

Allelopathic effect of itchgrass (Rottboellia cochinchinensis) on seed germination and plant growth

Herbicides produce a wide range of toxic side‐effects that pose a potential hazard to the environment. The development of natural allelochemicals is one method of addressing these issues. Here, we describe the allelopathic activity of itchgrass (Rottboellia cochinchinensis), which can inhibit the seed germination and growth of weeds. Farmers in Lampang, northern Thailand, have been cultivating itchgrass and using it as a mulching material to control other weeds in vegetable fields. It has long been observed that itchgrass interferes with the growth of other plants. This study showed that the density of weed species in the itchgrass‐infested areas was lower than that in the itchgrass‐uninfested areas. The shoot and root growth of Bidens pilosa, Mimosa pudica, Ageratum conyzoides, Echinochloa crus‐galli, Oryza sativa var. RD 6, and Lactuca sativa var. OP were significantly reduced in soil previously planted with itchgrass. Water‐soluble extracts from all parts of itchgrass had inhibitory effects on the growth of some test plants. Allelochemicals from itchgrass can inhibit seed germination and plant growth better at a 1 cm distance than at a 3 cm and 5 cm distance from itchgrass. Our results suggest that itchgrass has a strong competitive ability and possible allelopathic activity to other plant species. The allelopathic activity of itchgrass in the soil can influence the germination of adjacent species, causing reduced growth of seedlings.

Evaluation of allelopathic effect of fifty Sorghum bicolor L. Genotypes on Germination and Growth of some weed in vitro and in vivo

The effect of root exudates of fifty Sorghum genotypes on seed germination and seedling growth of millet were studied in vitro. The fifty genotypes were divided into four groups according to their effect on percentage reduction in root and shoot and whole plant average lengths of millet seedling growth. The first group caused slight stimulation, the second slight inhibition, the third gave limited inhibition and the fourth caused high inhibition. In seedling growth. Five genotypes of sorghum were selected, one from group two and four from group four. These five genotypes were cultured in the field in Autumn 2007 and at the end of the season plants were removed, dried and grind. Three concentrations of each of these genotypes powder were prepared, in addition to the control treatment, (0.0, 3.0, 6.0 and 9.0) g/kg soil to study their effects on the growth of Amaranthus retroflexus which cultured in pots and kept in experimental field. Data on number of leaves, lengths of shoot and root and whole plant were taken as well as wet and dry weight were measured. Percentage of Amaranthus retroflexus seeds germination were evaluated in an experiment cultured in Petri dishes containing concentrations (0.0, 5.0 and 10.0%) of aqueous extracts of each of the five genotypes powder. Results showed high significant inhibition for the four genotypes from group four in comparison with the one genotype from group two. Significant differences among these genotypes in their inhibition on such parameters as shoot, root, whole plant growth, number of leaves, and wet and dry weight. The genotype 2005-K-Type 1050 gave the highest reduction in plant length 53.2% incomparing with the genotype 2005-K-Type 1033 which gave 0.7%. The percentage of seed germination of Amaranthus retroflexus was significantly reduced as the concentration of the aqueous extract increased and there were significant differences among genotypes on this parameter. The concentration of the powder of each genotype added to the soil produced significant reduction in all parameters studied and the effect increased as the concentration increased in soil. This research discusses the potential of the allelopathic effect of some Sorghum genotypes on weed germination and growth reduction and the possibility of employing them in weed control program with the intention to use less herbicide.

Stilbenes from Deguelia rufescens var. urucu (Ducke) A. M. G. Azevedo leaves: effects on seed germination and plant growth

The Amazon biodiversity may provide plants whose chemical substances are capable of controlling weeds. In this study we report the isolation and identification of five stilbenes from the leaves of "timbó vermelho" (Deguelia rufescens var. urucu): 4-methoxylonchocarpene (1); 3,5-dimethoxy-4´-hydroxy-3´-prenyl-trans-stilbene (2), lonchocarpene (3), 3,5-dimethoxy-4´-O-prenyl-trans-stilbene (4) and pterostilbene (5). Compounds 2 and 4 are new natural products although 2 has been previously cited as synthesis product. Potential allelopathic activity for 1, 2 and 4 was evaluated over seed germination and plant growth of Mimosa pudica weed. The observed effects on seed germination did not vary significantly (p > 0.05) when the analysis of phytotoxicity was performed with the substances alone, the maximum inhibition did not exceed 20%. The most intense inhibitions on radicle and hypocotyl development were found for compound 4 (p < 0.05). When tested in pairs, showed antagonism for seed germination and synergism for radicle and hypocotyl development.

The impact of Gunnera tinctoria (Molina) Mirbel invasions on soil seed bank communities

Aims In recent years, there has been an increasing interest in the impact of invasive alien plant species on the soil seed bank. Soil seed banks play an important role in determining the composition and dynamics of the vegetation through time. Therefore, an ability to form a persistent seed bank and/or a capacity to alter the structure of the seed bank of invaded communities could be important factors in determining the success of many alien plant species. In this study, we report on a detailed assessment of the characteristics of the seed bank community associated with the herbaceous plant invader, Gunnera tinctoria, a newly emerging and potentially globally significant invasive plant species. This species, native to South America, is invasive in a range of wet habitats in Europe, Australasia and the USA. Methods A comprehensive assessment of the seed bank of invaded and comparable uninvaded areas was made at two points in time (May and October), at three sites in western Ireland. The seedling emergence approach was used to assess the structure (diversity, dominance and abundance) of the soil seed bank. Differences between invaded and uninvaded seed bank communities were investigated at the spatial scales of site, plot and depth. Important Findings Gunnera tinctoria formed a large persistent seed bank at the study sites. Approximately 30 000 seedlings per square metre emerged from soils collected from invaded areas, of which 30% were found in deep soil layers. Seedlings of this invader represented 53–86% of the total number of seedlings associated with invaded areas. Both the transient and the more persistent component of the seed bank of invaded communities were significantly less diverse and abundant than those of uninvaded areas, and were characterized by higher dominance, even when seedlings of the invader were not included in the analysis. The seed bank of invaded areas was largely composed of seeds of agricultural weeds in addition to those of the invader. These results suggest that G. tinctoria has the capacity to profoundly alter the seed bank of invaded communities. These results have direct relevance for the development of control and management strategies, for this and other comparable invasive species, which should account for both quantitative and qualitative alterations in the seed bank community. Our study also suggests that control measures that result in disturbance of areas colonized by G. tinctoria could promote the germination of undesirable weeds.

THE INFLUENCE OF BIOFUMIGATION ON MYCORRHIZAL FUNGI AND GROWTH OF STRAWBERRIES

Green manure from Brassica plants reduced the micro-organisms in the soil due to biocidal effect. Biofumigation with glucosinolates from Brassica juncea, Sinapis alba and Eruca sativa only partially influenced the mycorrhizal fungi of the strawberry cv. 'Marmolada'. In the field trial the differences in mycorrhizal parameters were not statistically significant between treatments (Brassica juncea, Sinapis alba, Eruca sativa, dazomet, control). The highest frequency of roots with mycorrhizal fungi (F) was observed in the chemical treatment with dazomet (50.3%). In the control, F was 49.2% and it was the lowest in the B. juncea treatment (43.4%). In pot trials, the average F was found in B. juncea, 57.9%, followed by S. alba, 54.9%, E. sativa, 66.8%, dazomet, 2.9% and control, 60.8%. The average intensity of fungi infection (M) was found in B. juncea, 7.4%, then in S. alba, 9.8%, E. sativa, 7.5%, dazomet, 0.0%, and control, 7.1%. The growth of weeds differed a great deal between the trials. In the field trial the number of weeds was higher in the treatments with biocidal plants than with dazomet or in the control. In pot trials S. alba had the biggest influence on the germination of weeds. Differences in yield observed in the field trial were not statistically significant. In pot trials the number of fruits per plant was the highest in E. sativa (8.1), S. alba (7.0), B. juncea (6.9), control (3.7) and dazomet (1.8). Increase of the yield at the treatment with biocidal plants was the result of incorporation of organic matter into the soil and undisturbed activity of mycorrhizal fungi.

Strigolactones, signals for parasitic plants and arbuscular mycorrhizal fungi

Although strigolactones play a critical role as rhizospheric signaling molecules for the establishment of arbuscular mycorrhizal (AM) symbiosis and for seed germination of parasitic weeds, scarce data are available about interactions between AM fungi and strigolactones. In the present work, we present background data on strigolactones from studies on their seed germination activity on the parasitic weeds Orobanche and Striga, the importance of nitrogen and phosphorus for this seed germination activity, and what this could mean for AM fungi. We also present results on the susceptibility of plants to AM fungi and the possible involvement of strigolactones in this AM susceptibility and discuss the role of strigolactones for the formation and the regulation of the AM symbiosis as well as the possible implication of these compounds as plant signals in other soil-borne plant-microbe interactions.

EFFECT OF PERIOD OF CULTIVATION ON THE ABUNDANCE AND DISTRIBUTION OF WEED SEEDS IN THE SOIL PROFILE

An experiment was laid down in the greenhouse to determine the distribution of weed seeds at different soil depths and period of cultivation on the distribution of weed seed bank in the soil profile in Muzarabani. Soil samples from different depth levels (0-10, 10.1-20, 20.1-30 cm) were collected soon after harvesting from three different sites namely Gutsa, Mufudzi and Muringazuva of Muzarabani district. The soil samples were put in trays in the greenhouse and watered after every two days to field capacity. Weed seedlings were identified, counted, recorded and discarded for a period of 3 months. Soil samples were disturbed every week to allow more germination of dormant weeds. Depth (P=0.000) and site (P=0.005) had highly significant effects on the total number of weeds that emerged from the soil samples. The 0-10 cm of the soil had the highest weed seedlings that emerged. There was an equal weed seed distribution in the 10-20 cm and the 20-30 cm of the soil. Gutsa had the largest seed bank and there was no significant difference in seed bank size between Mufudzi and Muringazuva. Some weed species were site specific, Senna obtusifolia was only found in Muringazuva and absent in other sites. Eleusine indica was found in Mufudzi and was absent in other sites.

Effects of Preplant and Postplant Rotary Hoe Use on Weed Control, Soybean Pod Position, and Soybean Yield

Demand for organic food products has consistently increased for more than 20 yr. The largest obstacle to organic soybean production in the southeastern United States is weed management. Current organic soybean production relies on mechanical weed control, including multiple postplant rotary hoe uses. Although postplant rotary hoe use is effective at the weed germination stage, its efficacy is severely compromised by delays due to weather. Preplant rotary hoeing is also a practice that has been utilized for weed control but the effectiveness of this practice to reduce the need for multiple postplant rotary hoeing for organic soybean production in the southeastern United States has not been investigated. Preplant rotary hoe treatments included a weekly rotary hoeing 4 wk before planting, 2 wk before planting, and none. Postplant rotary hoe treatments consisted of zero, one, two, three, and four postplant rotary hoe uses. Weed control was increased with preplant rotary hoeing at Plymouth in 2006 and 2007 but this effect disappeared with the first postplant rotary hoeing. Multiple postplant rotary hoe uses decreased soybean plant populations, decreased soybean canopy height, lowered soybean pod position, and decreased soybean yield. Plant mapping revealed that the percentage of total nodes and pods below 30 cm was increased by increased frequency of postplant rotary hoe use.

Mechanism of herbicidal action of the component I from Pythium aphanidermatum

The herbicidal mechanism of the components extracted from Pythium aphanidermatum was examined in this study. Component I was isolated using the HPD500 macroporous adsorption resin and HPLC. Its impact on seed germination and plant growth of weeds was determined and the contents of MDA, superoxide anion radical, and the activities of hills and roots were examined. The root length of weed plants was inhibited under illumination while the stem height was inhibited evidently under darkness. The relative electric conductivity of Digitaria sanguinalis and Amaranthus retroflexus under illumination was 94.55 μS·cm−1 and 58.75 μS·cm−1, respectively, whereas that under darkness was 85.25 μS·cm−1 and 36.25 μS·cm−1, respectively. The MDA contents of Digitaria sanguinalis and Chlorella pyrenoidosa were 0.08385 μmol·L−1 and 0.1742 μmol·L−1 under illumination, respectively, while those were 0.0129 μmol·L−1 and 0.01935 μmol·L−1 under darkness, respectively. Simultaneously, superoxide anion radical content was higher under illumination than under darkness. These results showed the photosynthesis was affected by component I extracted from Pythium aphanidermatum.

Effects of ferrous iron (Fe) on the germination and root elongation of paddy rice and weeds

Laboratory experiments were conducted to analyze the iron (Fe) tolerance of paddy weeds and rice varieties (Oryza sativa) for germination and root elongation. Under a waterlogged soil condition, the Fe(II) content in a soil solution increased with an increase in the ratio of rice straw to the soil. In the presence of 0.9% (w/w) straw to soil, which corresponds approximately to 8 t of straw applied to an area of 1 ha × 10 cm depth in the field, ∼80 mg L−1 of Fe(II) was produced in the soil solution. Based on this result, the seeds of rice and the weeds were incubated in a solution with &lt;100 mg L−1 of Fe(II). The presence of 100 mg L−1 of Fe(II) suppressed the germination of Echinochloa crus‐galli var. crus‐galli, Cyperus serotinus, Cyperus difformis, and Monochoria korsakowii. However, it had no effect on the germination of Echinochloa oryzicola, Schoenoplectus juncoides (= Scirpus juncoides var. ohwianus), and Monochoria vaginalis. This level of Fe tolerance was the same as that of rice. These findings suggest that E. oryzicola, S. juncoides, and M. vaginalis can grow under more severe conditions than E. crus‐galli, C. serotinus, C. difformis, and M. korsakowii. In relation to seminal root elongation, the order of tolerance of Fe toxicity was O. sativa cv. Dunghan Shali &gt; O. sativa cv. Hoshinoyume &gt; E. oryzicola &gt; M. vaginalis &gt; S. juncoides. Thus, the results show that the tolerance of rice is greater than that of E. oryzicola, which had a comparatively strong tolerance among the weeds examined, and also that there are differences in tolerance among the rice varieties. These findings suggest that the difference in Fe tolerance is involved in weed control systems when organic materials are applied. If this difference is an important factor in the weed control system, Fe‐tolerant rice varieties, like cv. D. Shali, could facilitate weed control systems due to their higher Fe tolerance ability.

An Assessment of the Suitability of Backyard Produced Compost as a Potting Soil

Current scientific knowledge of compost is largely derived from research into commercially produced green compost. This has shown that such compost tends to have high pH, high conductivity, and potential for organic and/or mineral pollutants and therefore can be problematic for use in growing media at high inclusion rates. Little work has been undertaken at an amateur composting scale and it is unclear whether these problems are prevalent in amateur-produced compost. This paper describes trials assessing the suitability as growing media of different composts produced using a range of amateur gardener methods. The resultant compost was then used to produce potting soil mixes with different compost inclusion ratios (with loam acting as the diluent) and assessed by growing tomatoes and lettuce. When comparing the effects of the compost mixes, the open vessels exhibited significantly higher weed germination counts than the wooden and plastic vessels. Turning the compost also significantly increased the weed count. In terms of seeds (lettuce and tomato), significantly lower germination counts were determined in the undiluted mixes when compared to the diluted mixes earlier in the assessment period. By the end of the assessment period these differences were reduced. By the final harvest, tomato heights and biomass were significantly greater in the undiluted mixes when compared to the diluted mixes and were comparable to the control mixes. Backyard produced compost would appear to have some value as a potting soil but the method of production needs to be taken into account when considering its use.