Reduced Weed Biomass Research Articles

The effect of sowing date, stale seedbed, row width and mechanical weed control on weeds and yields of organic winter wheat

SummaryThree field experiments were carried out in organically grown winter wheat in Denmark. The treatments were sowing time (normal or late sowing) and false seedbed, row width (12 and 24 cm) and weed control method [untreated; mechanical weed control (weed harrowing at 12 cm supplemented with inter‐row hoeing at 24 cm); and herbicide weed control]. Weed biomass in midsummer was greatest on plots sown at the normal sowing time (compared with delayed sowing) and was reduced by mechanical or chemical weed control (compared with untreated plots). Row width alone had no influence on weed biomass, but in the experiment with high weed pressure, the more intensive mechanical weed control used at a row width of 24 cm reduced weed biomass. Normal sowing time tended to give higher yields, but this was only statistically significant in one of the three experiments. Wide rows gave a yield decrease in the experiment with low weed pressure. The effect of weed control on yield was dependent on the weed pressure. At low weed pressure, mechanical weed control caused a yield decrease compared with untreated or herbicide treated. At intermediate weed levels there were no differences, whereas at high weed pressure, mechanical weed control and herbicide treatment caused a yield increase compared with untreated. False seedbeds were shown to contribute to a decrease in the soil seed reserve.

Economic Comparison of Initial Vine Density, Nitrogen Rate, and Weed Management Strategy in Commercial Cranberry

A 2-year field trial examined the interaction of nitrogen rate, vine density, and weed management options for establishing new cranberry (Vaccinium macrocarpon) plantings. Utilizing the vigorous hybrid, `Stevens', the cost-efficiency of the treatment combinations was evaluated by combining cranberry and weed biomass data with various economic estimates. The most cost-effective production scheme for establishing new cranberry beds is to plant vines at a low density, use moderate rates of nitrogen, and apply an annual application of a preemergence herbicide. This combination produced substantial vine coverage at very low cost, reduced weed biomass by 85% compared to untreated plots, and gave the best weed control per dollar spent. Growers may opt for other reasonably successful combinations that involve higher labor costs if they can produce their own cuttings (reducing initial costs) or if they are farming with the intent to reduce overall synthetic inputs.

Effect of Glyphosate Application Timing and Row Spacing on Weed Growth in Corn (Zea mays) and Soybean (Glycine max)1

Corn and soybean were planted in narrow- and wide-row spacings to study the effects of glyphosate application timing and row spacing on light interception and subsequent weed growth. Corn planted in narrow rows (38 cm) had greater light interception than corn planted in wide rows (76 cm) from 35 to 55 d after crop emergence. Soybean planted in narrow rows (both 19 and 38 cm) had greater light interception throughout the growing season than soybean in 76-cm rows. At maximum canopy closure, narrow-row soybean (both 19 and 38 cm) intercepted more light than narrow-row corn. Biomass of weeds emerging after glyphosate application was greater when soybean was planted in 76-cm than in 19- or 38-cm rows. However, weed biomass was generally similar in both row spacings of corn. Sequential glyphosate applications reduced weed biomass in corn each year compared with a single glyphosate application at the 5-cm weed height. Sequential glyphosate applications that followed initial glyphosate application to 10- or 15-cm-tall weeds did not reduce weed biomass compared with a single application.Nomenclature: Glyphosate; corn, Zea mays L. ‘DK 493RR’; soybean, Glycine max (L.) Merr. ‘Pioneer 92B71’.Additional index words: Light intensity, narrow-row corn, narrow-row soybean, shading, weed control, weed interference.Abbreviations: DAE, days after crop emergence; POST, postemergence.

Herbicidal effects under field conditions of Ailanthus altissima bark extract, which contains ailanthone

Extracts of Ailanthus altissima stem bark were evaluated for herbicidal effects under field conditions in two outdoor trials. Previous investigations had shown A. altissima bark, extracted with methanol, yielded a strongly phytotoxic extract that contained ailanthone as one of the major herbicidal compounds. The first field trial investigated the level of activity and selectivity of the extract. A. altissima bark extract was sprayed post-emergence onto 17 species of weeds and crops at rates of 366, 177, 93, 47, 23, and 0 kg ha−1. These application rates provided herbicidal activity equivalent to 4.5, 2.2, 1.1, 0.6, 0.3, and 0.0 kg of pure ailanthone per hectare, based on the results of a laboratory bioassay of extract and pure ailanthone. Strong herbicidal effects were observed within several days. Even the lowest rate caused mortality and injury in excess of 50% for nine of the 17 species, and a significant reduction in shoot biomass for 13 species. The second field trial tested the ability of bark extract to control weeds under field conditions with horticultural crops (bush bean, cauliflower, sweet corn, tomato). A. altissima bark extract was sprayed post-emergence at rates of 99, 50, 26, 13, and 0 kg ha−1, providing herbicidal activity equivalent to 1.1, 0.6, 0.3, 0.14, and 0.0 kg of pure ailanthone per hectare. Extract treatment provided partial weed control (greatest reduction in weed biomass was 40%), but also caused serious crop injury. Bush bean was the only crop that showed a significant increase in shoot biomass and fruit yield, compared to the non-weeded control. None of the crops, regardless of application rate, showed a level of shoot biomass or fruit yield comparable to the hand-weeded control. The herbicidal effects of A. altissima bark extract declined within the first few weeks after application, supporting previous evidence that ailanthone is rapidly degraded under field conditions.

Comparison of different weed management systems and their effects on yield of coconut plantations in Sri Lanka

The influence of five different weed management systems on nut yield of coconut were evaluated to determine an economical and effective method of controlling weeds in coconut plantations in the low country, dry zone in Sri Lanka. Treatments imposed included slashing and mulching around the palms with slash (T1), slashing and removing the slash (T2), application of glyphosate (N‐(phosphonomethyl)‐glycine) alone at 1.44 kg ai ha−1 (T3), application of glyphosate alone at 2.88 kg ai ha−1 (T4) and cover cropping with Pueraria phaseoloides (T5). All treatments were applied twice a year, except for the cover cropping treatment, T5. Based on a reduction in weed biomass, treatments T3, T4 and T5 were found to be significantly effective over other treatments. Coconut yield was increased significantly (P < 0.05) in glyphosate‐applied plots at both tested rates. Control of weeds with the lower concentration of glyphosate (1.44 kg ai ha−1) resulted in a 25% increase in nut yield over the uncontrolled weed plots. At this rate, it was found to be the most effective and economical method of controlling weeds in coconut plantations. Cover cropping with Pueraria phaseoloides was effective in controlling weeds in the long‐term, but was not economical compared with the glyphosate application.

Weed Control as a Rationale for Restoration: The Example of Tallgrass Prairie

Blumenthal, D. M., N. R. Jordan and E. L. Svenson 2003. Weed Control as a Rationale for Restoration: The Example of Tallgrass Prairie. Conservation Ecology 7(1):6. https://doi.org/10.5751/ES-00480-070106

Allelopathy of buckwheat: Assessment of allelopathic potential of extract of aerial parts of buckwheat and identification of fagomine and other related alkaloids as allelochemicals

The allelopathic potential of buckwheat (Fagopyrum esculentum) was investigated. Field study showed that living buckwheat reduced weed biomass compared with plots without buckwheat. Laboratory study revealed that root exudates suppressed root and shoot growth of weeds and reduced weed dry weight. Sequential partitioning of the aqueous ethanolic extract of the aerial parts of buckwheat showed that the chloroform extract caused an 80% reduction in radicle elongation of lettuce seedlings at a concentration of less than 100 p.p.m. Fagomine, 4‐piperidone and 2‐piperidinemethanol were isolated and identified by 1H and 13C nuclear magnetic resonance from the chloroform extract. These compounds caused a 50% inhibition of radicle elongation in lettuce seedlings at concentrations of less than 100 p.p.m. These results suggest that compounds 1, 2, and 3 might act as allelochemicals and affect the growth or germination of different plant species.

Impact of Gliricidia sepium and Cassia spectabilis hedgerows on weeds and insect pests of upland rice

Double hedgerows of two leguminous multipurpose trees Gliricidia sepium (Jacq.) Walp. and Cassia spectabilis DC. were established in highly eroded, low organic matter, acid uplands in northern Mindanao, Philippines. Alleyways were grown with upland rice Oryza sativa L. and fertilised with G. sepium green manure or C. spectabilis mulch (or in combination) and assessed for weed and insect pest suppression. Mulch reduced weed biomass which was mostly composed of grasses on infertile soil. Green manure favoured broadleaf weeds and increased weed biomass reducing the effect of mulching. Greater weed suppression may be achieved. Improvement in soil fertility increased the crops’ competitiveness against weeds by concentrating it to crop furrows. Greater crop nutrition from hedgerow biomass resulted in increases of rice seedling maggot Atherigona oryzae Malloch and stem borer (mainly Sesamia inferens (Walker)) damage and white grub (mainly Holotrichia mindanaoana Brenske and Leucopholis irrorata (Chevrolat)) larval densities over the control. Terrace formation reduced white grub densities the first year. The trend reversed in the second year as shade from the hedgerows and mulch probably favoured survival of white grub larvae by reducing soil temperature and increasing soil moisture. Despite higher insect pest densities, the moderate tillering UPLRi5 tolerated weeds and insect pest damage to produce higher yields in the biomass treatments than the control. But hedgerows may increase the incidence of rice blast Pyricularia oryzae Cav. by decreasing air movement. As purchased fertilisers provide limited crop response on depleted soils, alley cropping provides an economical means to overcome that constraint in small-scale tropical agriculture.

Herbage, oil yield and oil quality of patchouli [ Pogostemon cablin (Blanco) Benth.] influenced by irrigation, organic mulch and nitrogen application in semi-arid tropical climate

A field experiment was conducted during 1999 and 2000 at Bangalore in the semi-arid tropical climate of South India, to study the influence of irrigation, organic mulch and nitrogen application on its growth, herbage, oil yield and quality of patchouli [ Pogostemon cablin (Blanco) Benth.] grown on Alfisol. Irrigation at 1.0 IW:CPE ratio (irrigation water:cumulative pan evaporation), 5 t ha −1 distilled waste material of palmarosa, or 200 kg N ha −1 produced maximum herbage and oil yields. Organic mulch reduced weed biomass significantly. The oil content varied from 0.61 to 0.73%. The highest oil content was recorded with irrigation at 0.8 IW:CPE ratio, no mulch and 100 kg N ha −1. The quality of the essential oil with 50.66–54.31% patchouli alcohol, 9.86–10.26% α-bulnesene and 4.27% α-patchoulene was found to be good and readily accepted in the market.

Effect of Steam Application on Cropland Weeds1

Plot-scale field studies were conducted to evaluate the efficacy of steam for the control of cropland weeds in comparison with common herbicides. Weed densities, biomass, or emergence after treatment were measured. Steam (3,200 kg/ha, energy dosage equivalent to 890 kJ/m2, speed of 0.8 m/s) and glyphosate (560 g ai/ha) gave similar control (> 90%) of seedling common lambsquarters and seedling redroot pigweed. Applied at heading, steam was comparable to glyphosate in reducing green foxtail biomass at heading 2 wk after application. Steam applied at a rate of 3,200 kg/ha significantly reduced weed biomass (mixed stand, treated at seedling stage) 9 wk after application compared with the control, whereas steam applied at a rate of 1,600 kg/ha (1.6 m/s) did not. Biomass of downy brome treated with steam was reduced more at anthesis than at the seedling growth stage. Emergence of common lambsquarters, redroot pigweed, and black nightshade was not affected by steam application. Amount of steam applied, weed species, and growth stage are key factors in determining control effectiveness.Nomenclature: Glyphosate; black nightshade, Solanum nigrum L. #3 SOLNI; downy brome, Bromus tectorum L. # BROTE; common lambsquarters, Chenopodium album L. # CHEAL; green foxtail, Setaria viridis L. # SETVI; redroot pigweed, Amaranthus retroflexus L. # AMARE.Additional index words: Kochia scoparia L. Schrad., KOCSC, paraquat, pelargonic acid, SALIB, Salsola iberica Sennen & Pau.

Effect of seeding method and fertilizer application on weed biomass and yield of wheat (Triticum aestivum)

A field experiment was conducted on sandy loam soil analysing low in N and medium in P and K during rabi season of and at Varanasi to 1993-94 1994-95 evaluate the effect of different methods of sowing and fertilizer application in wheat (Triticum aestivum L. emend. Fiori & Paol.). Line sowing and placement of fertilizer in rows 5 cm below the seed showed significant reduction in weed biomass and increased the yield of wheat over broadcast sowing and fertilizer application. Seed emergence was markedly reduced when fertilizer and seed were mixed and then sown in rows. The root weight of plants grown with broadcast sowing was lower than of row sown crop. The row sowing of seed and placement of fertilizer in rows or broadcast of fertilizer but sowing of seed in rows removed higher amount of N, P and K than broadcast of seed and fertilizers.

Weed control in rice (Oryza sativa) nursery

An experiment was conducted during rainy (kharif) season 1991-93 to study weed control in rice (Oryza sativa L.) nursery in medium black soil, with 6 treatments consisting 3 herbicides (butachlor 1.5 kg, thiobencarb 1.5 kg and anilophos 0.3 kg a.i.lha) and other treatments being hand-weeding at 20 days after sowing, Gliricidia leaves 1 kglmZ as mulch and unweeded control. The fresh weight of rice seedlings due to application of herbicides and hand-weeding once were found significantly superiorto the unweeded control. The significant reduction in weed biomass was due to application of herbicides and hand-weeding once in comparison with the treat- ments of unweeded control and Gliricidia leaves. The saving due to use of weedicides and Gliricidia leaves for 0.10 ha nursery area over manual weeding was Rs 225 and 153 respectively.

Yield and economics as influenced by nitrogen scheduling, weed management and rice establishment methods in transplanted rice (Oryza sativa)

A field experiment was conducted during the rainy (kharif) seasons of 2010 and 2011 at Varanasi, Uttar Pradesh, to evaluate the effect of nitrogen scheduling, riceestablishment methods and weed management on BPT 5204 rice (Oryza sativa L.) cultivar. The major group of weed species observed in the experimental field were grasses followed by broad-leaf weeds and sedges. Significant reduction in weed biomass was recorded in puddled transplanting as compared to unpuddled transplanting and in butachlor 1.50 kg/ha followed by cono- weeding at 20 days after transplanting (DAT) amongst the weed-management treatments. However, in the nitro- gen scheduling treatments, significantly lesser weed biomass was recorded in initial reduced dose and delayed ni- trogen application (one-fourth at 10 days, half at tillering stage and one-fourth at panicle-initiation stage) than con- ventional scheduling of nitrogen application (half at basal, one-fourth at tillering stage and one-fourth at panicle- initiation stage). Puddled transplanting resulted in significantly more grains/panicle, panicle length, panicles/hill, grain yield (t/ha), nitrogen uptake and nitrogen-use efficiency, net returns and benefit: cost ratio than unpuddled transplanting and in butachlor 1.5 kg/ha followed by cono-weeding at 20 DAT as compared to the other weed- management treatments. An initial reduced dose and delayed nitrogen application (one-fourth at 10 DAT, half at tillering stage and one-fourth at panicle-initiation stage) recorded significantly higher values of yield attributes, yields, net return and benefit: cost ratio than conventional scheduling of nitrogen application.

Influence of weed management practices on weed dynamics and yield of urdbean (Vigna mungo) under rainfed conditions of Jammu

Experiments were conducted during kharif 2007 and 2009 in Inceptisols, to study the effect of different pre (PE) and post-emergence (POE) herbicides along with two hand weedings (HW) at 20 and 40 days after sowing (DAS) and weedy check on urdbean {Vigna mungo (L.) Hepper}. Highest seed yield was observed with two HWs at 20 and 40 DAS and the values were found statistically at par with POE application of imazethapyr 25 g/ha at 20 DAS. The highest weed control efficiency and lowest weed biomass was recorded with two HWs at 20 and 40 DAS fol- lowed by application of imazethapyr 25 g/ha (post-emergence) at 20 DAS. Application of Fenoxaprop-p-ethyl, quizalofop-p-ethyl, chlorimuron-p-ethyl as post-emergence and their combinations also reduced weed biomass and improved seed yield and yield attributing parameters as compared to weedy check. Treatment weedy check registered the highest values of weed count and weeds biomass and lowest seed yield and yield attributing char- acters in both the years of study. Rainfall was directly related to weed count and weed dry matter accumulation with the coefficient of 0.65 and 0.61, respectively. Weed dry matter accumulation was directly related with sun- shine hours with an accuracy of 67%, whereas, weed count was lesser related with sunshine hours of the day with an accuracy of 34%. Grain and biological yield of urdbean crop decreased at the rate of 3.3 and 7.5 kg/ha under weedy check with an accuracy of 88 and 73%, respectively.

Alleviation of weed stress in wheat (Triticum aestivum) through herbicides and their combinations

A field experiment was conducted during the winter (rabi) seasons of 201213 and 201314 at Udaipur (Rajasthan), to study the effect of 12 different herbicide combinations to control complex weed flora in wheat (Triti- cum aestivum L.) crop. Pooled data of 2 years experimentation indicated that the application of various herbicide combinations significantly reduced density and biomass of complex weed flora. The yield attributes, viz. plant height, effective tillers, days to heading; days to maturity and 1,000-seed weight were significantly influenced by application of various herbicide combinations. The application of herbicides increased the yield, harvest index and monetary income of wheat crop compared to weedy check, although maximum grain yield was recorded under weed free plots. Amongst the herbicides, application of sulfosulfuron + metsulfuron @ 30 + 2 g a.i./ha rsulted in higher number of effective tillers (485.8/m2), the maximum grain yield (5.29 t/ha), harvest index (37.9%), net re- turns ( 79,480/ha) and benefit: cost ratio (3.06), which was superior to rest of the treatments, as the same treat- ment caused significant reduction in weed density (6.65/m2) and weed biomass (6.24 g/m2). Two-year study indi- cates that application of a ready-mixed herbicide (sulfosulfuron + metsulfuron) @ 32 g a.i/ha was best for weed- control, higher yield and net returns from wheat in southern plain zone of Rajasthan.

An Integrated Weed Management Strategy for Glufosinate-Resistant Corn (Zea mays)1

Abstract: Early canopy closure and manipulation of crop row spacing or density can reduce the amount and frequency of herbicide use in corn. Field studies were conducted at Woodstock, ON from 1996 to 1999 to evaluate the effect of corn row spacing, plant density, and frequency of glufosinate application on weed biomass and corn yield in glufosinate-resistant corn. Treatments included row width, corn density, and herbicide. The effect of row width and corn density on weed biomass was variable among years. In a wet year (1996), narrow (38 cm) rows provided greater weed suppression than wide (76 cm) rows regardless of crop density. In a dry year (1998), narrow-row high-density (100,000 plants/ha) corn had the lowest weed biomass. In other years, either narrow row or high density was equally successful in suppressing weeds. Effectiveness of herbicides in reducing weed biomass was not influenced by row width or corn density. Corn yield was influenced by row width or corn density. Although weed biomass was lowe...

Changes in weed community composition as influenced by cover crop and management system in continuous corn

Abstract Weed suppression by cover crops grown during the winter fallow period in continuous corn may lead to a reduction in herbicide use. Rye, crimson clover, and subterranean clover cover crops were compared with corn stubble under a conventional management system (CS) that included plowing and use of preemergence residual herbicides and a low-input management system (LIS) that included no-tillage and use of a presowing nonresidual herbicide for three consecutive years (1994–1996). Cover crop and above-ground weed biomass prior to desiccation were not influenced by management system. Cover crop biomass ranged from 1,420 to 5,657 kg ha−1 for rye, from 563 to 4,217 kg ha−1 for crimson clover, and from 563 to 4,248 kg ha−1 for subterranean clover. At crop planting, rye reduced weed biomass from 54 to 99%, crimson clover from 22 to 46% (with a negative value in 1995), and subterranean clover from 21 to 67%. Weed growth suppression was usually higher in years when cover crop biomass was higher. There were n...

Effect of cultivar, row spacing, and weed management on weed biomass, potato yield, and net crop value

Research was conducted to quantify the effects of potato cultivar, row spacing, and weed control treatments on weed biomass, crop yield, and net crop value. Cultivars evaluated included Russet Burbank, Russet Norkotah, Goldrush, Dark Red Norland, Snowden, and Atlantic. Inter-row spacings of 76 and 91 cm with an intra-row spacing of 30 cm were evaluated in 1996 and 1997. Weed control treatments included a herbicide tank-mix of metribuzin and metolachlor, cultivation, and a hilling-only control. Common lambsquarters and total weed biomass were greater in the 76-cm row spacing than in the 91-cm row spacing across all cultivars in 1996 and 1997. In 1997, chemical control resulted in less weed biomass than both the hilling-only and cultivation treatments. Total marketable yield was greater in the 91-cm row spacing than in the 76-cm row spacing across cultivars in 1996, but was similar across row spacings in 1997. Net crop value was greater across cultivars in the 91-cm row spacing than in the 76-cm row spacing in 1996. Reduced weed biomass in 1996 and 1997, coupled with greater total marketable yield and net return in 1996, indicated that the 91-cm row spacing was the optimal row spacing for Russet Burbank, Goldrush, Russet Norkotah, Snowden, and Atlantic cultivars in 1996 and 1997. Similar yields and net crop value among weed control treatments in 1996 and 1997 indicated that cultivation and possibly even hilling-only areas within fields can be viable alternatives to herbicide use.

The Use of Allelopathic Legume Cover and Mulch Species for Weed Control in Cropping Systems

Traditional weed control practices in Mexico use legumes as cover crops or manures. Legumes used in these practices play a dual role in agroecosystems by protecting the soil from erosion and by enriching it with organic matter and N through Rhizobium symbiosis. Farmers in the tropical regions of Mexico use Mucuna spp., Canavalia spp. and other legumes to control weeds in their fields. We conducted in vitro bioassays and greenhouse experiments to evaluate the toxic effect of four legumes velvetbean [Mucuna deeringiana (Bort) Merr.], jackbean [Canavalia ensiformis (L.) DC.], jumbiebean [Leucaena leucocephala (Lam.) de Wit], and wild tamarind [Lysiloma latisiliquum (L.) Benth.] on weed growth, and on the survival of insects and nematodes. The aqueous leachates (1%) of the four legumes were tested on three test plants by seed germination and radicle growth bioassays in petri dishes. The aqueous leachates of all four legumes exhibited strong phytotoxic effect on the radicle growth of the test plants. The effects of velvetbean and jackbean leachates were also evaluated on the survival of phytopathogenic nematodes. Both leachates had nematotoxic effects. Greenhouse experiments were conducted to evaluate the effect of the four legumes dried leaves incorporated as mulches to potting soil, on the number and biomass of weeds, and on the biomass of tomato (Lycopersicon esculentum L.) plants. The decomposition of velvetbean and jackbean leaves in potting soil significantly reduced (>50%) the development of phytopathogenic nematodes in the roots of tomato. A 5‐yr field experiment conducted at the University of Yucatan (UADY) evaluated the effect of velvetbean and jackbean used as living cover crops, and jumbiebean and wild tamarind used as dead mulches incorporated on soil surface, on weed growth, and corn (Zea mays L.) yield. The experimental field was treated with the traditional slash and burn system in February 1994. In July 1994 the experiment was performed using the local agricultural practices in a complete randomized block design with three repetitions. The treatments were: corn+velvetbean, corn+jackbean, corn+jumbiebean, corn+wild tamarind, corn+Paraquat (1,1′‐dimethyl‐4,4′‐bipyridinium ion) herbicide, corn weeded by hand, and plots without corn weeded by hand. The number, biomass, diversity, and relative importance of weeds, as well as corn yield, were evaluated. In addition, taxonomic composition of weeds was determined. All legumes reduced weed growth with velvetbean (as living cover crop) producing the largest weed biomass reduction (68%). These legumes also improved the yield of corn during the first 2 yr of the experiment. For better management of natural resources, the use of legumes as biological tools in agriculture to control weeds and improve soil conditions should be encouraged through coordinated efforts between farmers, academic, and governmental institutions.

Soil solarization for weed control in carrot

Soil solarization is a technique used for weed and plant disease control in regions with high levels of solar radiation. The effect of solarization (0, 3, 6, and 9 weeks) upon weed populations, carrot (Daucus carota L. cv. Brasília) yield and nematode infestation in carrot roots was studied in São Luís (2º35' S; 44º10' W), MA, Brazil, using transparent polyethylene films (100 and 150 mm of thickness). The maximum temperature at 5 cm of depth was about 10ºC warmer in solarized soil than in control plots. In the study 20 weed types were recorded. Solarization reduced weed biomass and density in about 50% of weed species, including Cyperus spp., Chamaecrista nictans var. paraguariensis (Chod & Hassl.) Irwin & Barneby, Marsypianthes chamaedrys (Vahl) O. Kuntze, Mitracarpus sp., Mollugo verticillata L., Sebastiania corniculata M. Arg., and Spigelia anthelmia L. Approximately 40% of species in the weed flora were not affected by soil mulching. Furthermore, seed germination of Commelina benghalensis L. was increased by soil solarization. Marketable yield of carrots was greater in solarized soil than in the unsolarized one. It was concluded that solarization for nine weeks increases carrot yield and is effective for controlling more than half of the weed species recorded. Mulching was not effective for controlling root-knot nematodes in carrot.