ABSTRACT
In this study the efficacy of solarization (S), dazomet (D) and metam-sodium (MS) treatments on some weed species and their potential as alternative to methyl bromide (MB) was investigated in strawberry growing areas in Aydin province of Turkey. Efficacies of treatments were variable for weed species. Total five weed species, namely common purslane, annual bluegrass, common chamomille, horseweed and shepherds purse were considered in this study. Highest efficacy on weeds was provided by MB application, but S is a safe alternative to MB under suitable climatic conditions, because its application is economic and safer to environment and user. In case of horseweed none of the treatments reduced the coverage of this species significantly.
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DOI: 10.3923/ajps.2003.1215.1219
URL: https://scialert.net/abstract/?doi=ajps.2003.1215.1219
INTRODUCTION
Strawberry production is carried out on 9,700 ha with total production of 117,000 tons. About 40% of total strawberry production of Turkey was realized in Aydin Province in 2001 (Anonymous, 2001). Weeds are one of the most important yield limiting factors in growing areas. Survey studies carried out in Aydin province of Turkey showed weed species such as common purslane (Portulaca oleracea L.), pigweed species (Amaranthus spp.), purple nutsedge (Cyperus rotundus L.), heliotrope species (Heliotropium spp.), bermudagrass (Cynodon dactylon L. Pers.), large crabgrass (Digitaria sanguinalis L. Scop.), wild radish (Raphanus raphanistrum L.), lambs quarters (Chenopodium album L.), foxtail (Setaria spp.), barnyardgrass (Echinochloa cruss-galli L.), black nightshade (Solanum nigrum L.), johnsongrass (Sorghum halepense L. Pers.), sowthistle (Sonchus sp.) and puncture vine (Tribulus terrestris L) were the most common species from planting stage to mulching on raised beds (late summer to autumn). And horseweed (Conyza canadensis L.), common purslane, purple nutsedge, redroot pigweed (Amaranthus retroflexus L.), common chamomille (Matricaria chamomilla L.), annual bluegrass (Poa annua L.), shepherds purse (Capsella bursa-pastoris L.) Medik., prostrate knotweed (Polygonum aviculare L.), common chickweed (Stelleria media L. Vill.) and lamb squarters were found as the most common weed species in strawberry growing areas before and during harvest time (Boz et al., 2002).
In addition to the yield decrease in strawberry fields due to weed competition, weeds also cause secondary negative effects to crop by serving as host plants to some diseases and insects, especially to mites or cause difficulties during harvest. Although weeds cause such great problems in strawberry production, there are a few control methods practiced by farmers. Weed control in strawberry is usually carried out by hand weeding, hoeing or mulching with black polyethylene sheets. These practices provide generally sufficient control of weeds, but a more effective and safer method is needed in order to protect the strawberry seedlings from damage caused by mechanical cultivation.
Soil fumigation with methyl bromide controls wide spectrum of weeds and it is used commonly in strawberry fields. However this fumigant will be banned in Turkey by 2008 due to its ozone depleting characteristics and therefore alternative methods for controlling weeds are need to be investigated. Other fumigants such as dazomet and metam-sodium are harmless to ozone layer and used to control weeds in strawberry growing areas. As another alternative to methyl bromide, there is an increasing interest to control pests by physical control methods. Especially in the regions with high summer temperature such as in Israel, solarization is applied in order to control weeds, soil-borne diseases and nematodes (Katan and De Vay, 1991).
In this study the efficacy of solarization (S), dazomet (D) and metam-sodium (MS) and methyl bromide (MB) applications on weed species of common purslane, annual bluegrass, common chamomille, horseweed and shepherds purse was investigated in strawberry growing areas in Aydin province of Turkey.
MATERIALS AND METHODS
Trial was conducted as randomized block design. Plots were sixty square meter in size with 6 m in width and 10 m in length.
Table 1: | Maximum temperatures of solarized (S.A.) and non-solarized (N-Sol) areas (oC) |
Treatments were solarization (S), methyl bromide (MB), metam-sodium (MS) and dazomet (D) each had 3 replicates. An untreated plot served as control at each block.
For S, moistened soil was covered manually with a polyethylene sheet (thickness: 110 Fm) from June 10 to July 14th. Soil temperature was weekly recorded from 0, 10 and 20 cm depths of the soil (Table 1). For the MS application, drip irrigation pipes were laid on the soil and the soil was covered with polyethylene sheet and then MS was applied one time (100 ml per square meter) in liquid form in July 2nd and the soil was covered until July 14th. The D was applied in granular form as 50 g per square meter in moistened soil and it was mixed to the soil by rotary tillers to 10-15 cm soil depth. Soil was also covered after D application from July 2nd to 14th. For MB application soil was tilled in 40 cm depth and covered with polyethylene sheet before the application. The MB was applied 50 g per square meter and the cover stayed for three days after the application. After removal of transparent sheets, raised beds were prepared for all plots and strawberry seedlings cv. Camarosa were planted on raised beds in July 17th, 1999. Farmers practices were applied to grow plants such as growing plants on raised beds, seedlings were planted 25 cm in width and 30 cm in length rows and drip irrigation was used to water plants. The weeds were sampled in six different, 0.15 square meter-area (0.5x0.3 m) on each plot by visual determination. The weeds were removed by hoeing after each observation. Observations were taken nine times during 1999-2000 and twice in 2001-2002 growing seasons between raised beds. In addition, the weeds were sampled nine times from the hole around the strawberry seedlings during 1999-2000 growing season.
Statistical Analyses: Data from trials were subjected to the variance analysis and standard errors for each analyze were given in tables.
RESULTS AND DISCUSSION
Efficacy of treatments on the coverage of weeds between rows: The temperature values recorded during solarization on solarized and non solarised plots were shown in Table 1. It was observed that solarization increased the soil temperature up to 13°C.
During observations it was determined that common purslane, annual bluegrass, common chamomille, horseweed, shepherds purse were the most common species on experimental plots.
In terms of the efficacy of different weed control measurements on all weeds; no effect of treatments were observed at four observations, carried out between 6.9.1999 and 1.11.1999. At the observation date on 29.11.1999 MB, S and MS treatments reduced the weed coverage significantly, whereas D showed no effect on weeds. On 21.1.2000 it was observed that all treatments reduced the weed density as compared to non treated plots significantly. Similarly all applications affected the weed coverage on 8.4.2000 significantly, but the highest effect was observed with MS. Results from 20.5.2000 was similar to 21.1.2000. Observation from 15.5.2001 showed that only MB controlled weeds effectively, all other treatments showed no effect on weeds (Fig. 1, Table 2).
From these common purslane was affected only by MB application on 20.05.2000 significantly (Fig. 1, Table 2). On all other observation times the coverage of this weed was not significantly different from untreated plots. However, Defilippi et al. (1998) stated that S provided effective control of weed species such as common purslane, Convolvulus arvensis, Veronica persica and barnyardgrass. In contrast Tekin et al. (1997) pointed out that common purslane could not be controlled effectively by S and MB, but S+MB controlled this weed effectively. In terms of MS, MacDonald et al. (2001) showed that MS application reduced the germination of common purslane by over 95%. Hartz et al. (2001) investigated the efficacy of 1,3-dichloropropene, MS and chloropicrin on Malva parviflora, prostrate knotweed and common purslane and found that common purslane was the most sensitive weed species to all compounds.
Coverage of annual bluegrass was reduced significantly by MS application on 21.01.2000. Although all other treatments reduced the coverage of this weed, this reduction was not statistically significant (Fig. 1, Table 2). In terms of S, this application reduced this weed 89-100% in the upper 5 cm of soil and MS (930 L.ha-1) the most effective treatment for reducing the viable annual bluegrass (Peachey et al., 2001).
The coverage of common chamomille was reduced by all applications on 1.11.1999, but this reduction is not reliable, because of very low density of this weed on untreated plots at this date.
Table 2: | Weed coverage at different observation times after different treatments |
*Comparison of means was carried out only within each observation date. Means with similar letters are not significant. C: Control, MB: Methyl-bromide, S: Solarization, MS: Metam-Sodium, D: Dazomet |
Fig. 1: | Coverage of the weed species in inter-rows after some treatments. |
Dominant weed species are; | Common purslane (Portulaca oleracea) |
Annual bluegrass (Poa annua) | |
Common chamomille (Matricaria chamomille) | |
Horseweed (Conyza canadensis) | |
Shepherds purse (Capsella bursa-pastoris) |
In general MB and MS applications reduced the coverage of this weed significantly, except for 2 observation times (Fig. 1, Table 2).
In case of horseweed none of the treatments reduced the coverage of this species significantly (Fig. 1, Table 2).
The coverage of shepherds purse was reduced by all applications on 1.11.1999. On 20.5.2000 MS and D treatments reduced the coverage of this weed significantly (Fig. 1, Table 2). In study by Tekin et al. (1997) it was found that S, S+MB (30 g m-2) and MB (60 g m-2) applications were found to be effective against this weed. Also Fennimore et al. (2000) reported that the biomass of this weed was decreased by 59-79% with MS application.
Efficacy of treatments on the coverage of weeds on the rows around seedlings: Observations on 21.1.2000, 4.5.2000 and 20.5.2000 showed that all treatments reduced the coverage of weeds significantly.
Fig. 2: | Coverage of the weeds from the hole around the strawberry seedlings after some treatments |
Dominant weed species are; | Common purslane (Portulaca oleracea) |
Annual bluegrass (Poa annua) | |
Common chamomille (Matricaria chamomille) | |
Horseweed (Conyza canadensis) | |
Shepherds purse (Capsella bursa-pastoris) |
Despite a decrease in the weed coverage by all treatments on 29.11.1999 and 8.4.2000, the coverage of weeds on S plots was not significantly different from those on untreated plots (Fig. 2, Table 2).
As results of this study are summarized, efficacies of treatments are variable according to weed species and/or observation dates. In general none of the treatments reduced the coverage of horseweed. Also no treatment showed higher efficacy on weeds than methyl bromide, but solarization applicable under suitable climatic conditions, because its application is economic and safer to environment and user.
ACKNOWLEDGMENTS
Thanks go to Dr. Seher Benlioglu, Dr. Ayhan Yildiz, Dr. Galip Kaskavalci, farmer Nihat Özyigit to provide his lands for these studies. And to Dr. M. Nedim Dogan, Dr. Zahide Özdemir and Dr. Kazim Kara for statistical consultant.
REFERENCES
- Tekin, I., I. Kadiolu and I. Uremio, 1997. Studies on soil solarization against root-knot nematode and weeds in vegetable greenhouses in the Mediterranean Region of Turkey. Proceedings of the 2nd International Conference on Soil Solarization and Integrated Management of Soilborne Pests Aleppo, March 16-21, Syrian Arab Republic, pp: 604-615.
- Fennimore, S.A., M.J. Haar and H. Ajwa, 2000. Weed control options in California strawberry without methyl bromide. Proceedings of the Annual International Research Conference on Methyl Bromide Alternatives Emissions Reductions, Nov. 6-9, Orlando, Florida, pp: 6-9.
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