JWSS - Journal of Water and Soil Science

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Combining herbicides for controlling broadleaf weeds and grasses in wheat farms has not been studied under Isfahan environmental conditions. Thus, this experiment was conducted in 1995-96 at the Agricultural Research Station, Isfahan University of Technology, in order to investigate the issue. In this study, 2,4-D+MCPA (U46 Combi Fluid 6), bromoxynil, metribuzin, diclofop-methyl and tralkoxydim and their combinations in 11 treatments plus weed-free and weedy checks were evaluated using a randomized complete block design with 4 replications. Goldbachia laevigata and Avena fatua were the dominant weeds. Cirsium arvense and Convolvulus arvensis were of less importance. Efficacy of bromoxynil on annual broadleaf weeds was higher than 2,4-D+MCPA, while 2,4-D+MCPA was more effective on perennial broadleaf weeds. Diclofop-methyl and combination of bromoxynil with tralkoxydim were the most effective on A. fatua, while differences between treatments containing diclofop-methyl or tralkoxydim on decreasing A. fatua numbers were non-significant. The most and the least visual damages to wheat plants were caused by metribuzin and bromoxynil, respectively. Wheat yield was not significantly affected by treatments. However, the highest yield was obtained by tralkoxydim + bromoxynil treatment, which produced the lowest total dry weight of weeds at terminal spikelet and heading stages of wheat. The results obtained here indicate that combination of bromoxynil with tralkoxydim might be the best treatment for the control of all annual weeds under conditions similar to this experiment. But if perennial broadleaf weeds and wild oat are dominant in the field, combination of 2,4-D+MCPAwith diclofop-methyl might be preferred.

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In order to find the critical period of weed control, the best time of weed control beginning (i.e. herbicide application time), and the length of weed control period (i.e. herbicide persistency) in corn, field experiments were conducted in Bajgah and Kooshkak in Fars Province in 1995 using a randomized complete block design with 14 treatments and four replications. Treatments consisted of different times of weed control beginnings (20, 30, 40, and 50 days after corn emergence), different duration of weed control periods (10, 20, and 30 days), a weedy check, and a weed-free check during the period of corn growth.

 In Kooshkak, a 10-day duration of weed control period had significantly lower corn yields than 20 and 30-day periods. In Bajgah, a 10-day weed control period had significantly lower corn yields than a 30-day period. Time of weed control beginning was not significant at both locations however, the interaction between beginning time and the duration period of weed control was significant. It appears in both locations that a minimum 20-day control period at the initial stages of corn and weed growth, and a minimum 30-day control period before corn pollination are necessary to prevent corn yield losses. In order to prevent corn leaf area decline at both locations, a 20-day weed control period until 40 days after crop emergence is necessary.

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Solarization of field soil through mulching with transparent polyethylene sheets alone and in integration with farm yard manure (40 T/ha) and/or metalayl (25 kg/ha) during summer 1994-95 for five weeks in Isfahan resulted in an increase in temperature of 10 °C (± 1) and moisture preservation of up to 82%. Solarization effectively reduced foot-rot of cucumber (Phytophthora drechsleri) in the above treatments up to 88%, 96% and 95%, respectively.

Solarization, farm yard manure and their integration reduced the infection of Meloidogyne javanica up to 50%, 57% and 83% while plant parasitic nematodes were also reduced to 72%, 75% and 86%, respectively. The populations of free living nematodes increased only in farm yard manure and in integration with solarization by 30% and 53%, respectively.

Solarization effectively reduced the populations of almost all weeds by around 100%, except for Cyperus rotundus and Sonchus asper which were reduced by 59% and 44%, respectively.

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In orther to determine the critical period for weed control in the Chitti bean (Phaseolus vulgaris) line KS-21467 a field study was conducted at the Bean Research Station of Khomein by a randomized completele block design in 2001 and 2002. The treatments included weed free and weed infested period until 20, 28, 36 and 44 days after planting (DAP) with two weed free and weedy checks. The results indicated that the critical period at 5% allowable yield loss was 20-53 DAP (between first-trifoliate and flowering stages) in 2001 and 35-51 DAP ( between blossom and flowering stages) in 2002. Weed dry weight decreased averaglly 81% in weed-free period until 44 DAP compared to the weedy check. Yeild decreased averaglly 63% in weedy check compared to the weed free check. Weed competition increased the height of bean, wherease 100-seed weights and the number of seeds per pod were not substantially affected. There was a negative and significant correlation of weed dry weight with the number of pods per plant, the number of seeds per plant and yeild.

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This study was conducted in a sugar beet field at Collage of Agriculture Experimental Station, Ferdowsi University of Mashhad, Iran. In order to describe the pattern of spatial variations and density of Chenopodium album, Solanum nigrum, Amaranthus sp., Portulaca oleracea, Echinochla crus-galli, and Convulvulus arvense as the main prevalent annual and perennial weeds of sugar beet fields, geostatistic methods were used. Samples were taken by systematic method from the corners of (7m × 7m) grids, using (0.5m × 0.5m) quadrates in three stages (before application of herbicides, after herbicide treatment, and before harvesting sugar beets). The integrity of spatial variation of variables was determined by using variogram functions and distribution maps of species. The variograms indicated that variations of all variables did not happen by chance. The maximum and minimum ranges of variation were observed in Solanum nigrum (by 142.7m) and Portulaca oleracea (by 1.5m), respectively. Both maximum and minimum ranges of variations were related to pre herbicide application. The highest and the lowest spatial correlations were related to Amaranthus sp. (in the third sampling treatment) and Solanum nigrum (in the first stage of sampling), respectively. The spatial distribution maps confirmed the patchiness distribution of the weeds. The patch of weed was constructed from a dense point at the center, gradually tapering toward the edges. The patches were skewed across the rows and irrigation channels. The structure of patches altered during the growing season. Any information on the distribution of weeds in the fields can be useful to improve decision makings in relation to applying the herbicides, selecting the herbicide type or applying the amount of herbicide. Also it can be useful to better design of weed control programs.

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The effects of Chickpea (Cicer arietinum L.) varieties, and sowing dates on weed interference were investigated in a 2-year (2002-3, and 2003-4 growing season) field experiment in Agricultural Research Station of Kohdasht in Lorestan Province. The experimental design was a randomized complete block in factorial arrangement with 3 replications. The experiment had 3 factors: weed interference at 2 levels (weed free, and weed infested throughout the total growing season), planting date at 3 levels (autumn, winter, and spring) and Chickpea varieties at 3 levels (ILC482, Hasham, and Greet). Weed density in autumn sowing plots was more than 3 and 7 times greater in autumn chickpea than in winter and spring sowing plots, respectively. Weed biomass in autumn sowing was 2.5 times as much as winter or spring sowing. Wild safflower and volunteer barley were the most frequent among the weed species. Volunteer barley was mainly present in autumn and winter planting dates. Wild safflower was among the weed species that in addition to competition, caused much difficulty to chickpea harvesting. Based on the hyperbolic curve fitted to the data, Chickpea maximum biomass reduction due to weed competition was estimated to be 91.8 %.

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This study was performed in two barley fields, in Experimental Station, Agricultural College of Ferdowsi University of Mashhad in 2003. Sampling was done by systematic method in which samples were taken from the corners of 7m*7m grids using 0.5m 0.5m size quadrates in three stages (pre herbicide, post herbicide and pre harvesting stages). The results indicted that the density of annual weed seedlings in sugar beet- barley rotation was more than fallow- barley rotation, and the density of perennial weed seedlings in fallow-barley rotation was more than sugar beet- barley rotation. Map of species distribution and density confirmed patchiness distribution of the weeds. The shape and size of patches differed based on the field and weed species, but spatial distribution did not change considerably before and after the application of herbicide. Percentage of free weeds area was 11.5% and 1.5% in fallow-barley rotation and 0.6% and 0% in sugar beet- barley rotation in the first and second sampling stages, respectively. These results indicate beside emphasis on weed infestation. The result also indicates inefficacy of sugarbeet-barley rotation compared to follow-barley rotation. Apparently, the evaluation of management and paying special attention to weed dispersal within the field assist in the implementation of appropriate management strategy, which includes high efficacy, and profit for farmers as well as least damage to crops.

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Flora identification of each region plays an important role in the maintenance of natural resources of each country and it is a prerequisite to supplementary phylogenetics and genetic diversity studies. During February 1994 to August 1995, in a two-week interval, vineyards in two districts of Isfahan province, namely Zarinshahr and Tiran & Karvan were visited and weed samples were collected in flowering stages. All collected specimens were identified using specimens present in Herbarium of colleges of agriculture and natural resources of Isfahan University of Technology and other available references. The analysis revealed that in Tiran and Karvan, 84 species belonged to 71 genera and 26 families and in Zarinshahr 62 species belonged to 51 genera and 23 families. Species dominance in both districts belonged to Asteraceae and Gramineae families. Analysis of plant life forms using Raunkiaar method showed that Therophytes with 79.5% and Geophytes with 8.3% were the most frequent life forms in both Zarinshahr and Tiran & Karvan regions.

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  The response of bread wheat genotypes to weed interference was evaluated under dryland conditions. An experiment was conducted with 26 genotypes of bread wheat and two known cultivars, Sardari and Azar2, as checks in a strip plot (Split block) arrangement based on Randomized Complete Block Design (RCBD) with four replications in 2002-03 at Dryland Agricultural Research Institute, Srarood, Kermanshah. Weed-free and weedyconditions were assigned to horizontal factor with genotypes as vertical factor. Plant height, number of seeds per spike, number of spikes per square meter, grain yield, weed density and dry matter, and indices of Weed Interference Tolelance Index (WITI) and Competition Index (CI) were recorded. Mean comparison showed that genotypes 13, 1, 26 and 8 had higher grain yield than those of checks under both weed-free and weedy conditions. These genotypes also had higher WITI in comparison with the checks. According to CI values, genotypes No. 1, 9, 13, 26 and 27 including checks had a high potential of weed competition. Results of stepwise regression analysis based on WITI as the dependent variable indicated that the number of spike, plant height and number of seed per spike had positive and significant effects on WITI. On the wole, considering WITI and grain yield as two main attributes, genotypes 13, 26, 1 and 8 were selected as appropriate since they showed a high weed competitive ability and also produced higher grain yields under both weedy and weed-free conditions.

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In the conventional methods of herbicide and fertilizer application, a substantial amount of toxic chemicals is sprayed or broadcast into the furrows, which is later washed away by irrigation water and may contaminate ground water, human and animal environment. If herbicide and fertilizer application could be limited to the most needed parts of the field rather than overall broadcasting, the mentioned problems could be alleviated and the application efficiency could also be increased by reducing the consumption rate. In an attempt to achieve this goal, a combination cultivator capable of simultaneously performing cultivation practices such as weed control (mechanical + chemical), fertilizer application and pest control was developed and evaluated. This machine was able to perform band spraying (fungicide, insecticide and herbicide) and mechanical cultivation (within-the-row weed killing, furrow reforming and hilling) simultaneously and properly. The combination cultivator was able to reduce herbicide consumption up to 66%.

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A pot experiment was designed to investigate the effects of full, above and below ground interactions of wheat with wild oat on leaf characteristics and root to shoot ratio. This experiment was conducted as a factorial based on randomized complete design with four replications. The treatments included four interference levels (above ground, below ground, above and below ground and check wheat and wild oat) and four wild oat densities (2, 4, 6 and 8 plants/pot).The effects of full and root interference on wheat and wild oat traits was greater than shoot interference. For both species, full and below ground interaction significantly decreased the number of leaves, flag leaf area and chlorophyll content of flag leaf compared to above ground interaction and control. All traits of wild oat were reduced by above ground interaction compared to control. Number of leaves of wheat and wild oat showed greatest susceptibility to interaction treatments. There was no significant different between full and root interference. When wild oat density increased, the number of leaves, flag leaf area and chlorophyll content of flag leaf of wheat decreased. With strongest competition followed by enhanced wild oat density, root to shoot ratio in wheat and wild oat increased, which indicates more susceptibility of shoot than root to interference mean competition. This ratio for wild oat was more than wheat, thus, it is concluded that wild oat has higher rooting ability compared to wheat.

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The recent years' problems of herbicide use have led a growing number of researchers to seek alternative methods that are less reliant on herbicides. This research was conducted to determine the effect of long-term crop rotation, mineral fertilizer and herbicide on the weed infestation and grain yield of winter rye during 2004 and 2005 at the long-term experimental site of the University of Timiriazev, Moscow. Treatments were control (no weed control), herbicide, combined fertilizer (NPK) and NPK plus herbicide in field winter rye cultivated in continuous and crop rotation with other crops since 1912. Crop rotation significantly decreased weed density and dry mass. Long-term NPK application significantly decreased weed density, but had not any effect on weed dry mass. Crop rotation, NPK application and herbicide increased ground crop cover and decreased ground weed cover. In continuous crop, weed ground cover was 10 % in control plot and 3.33 % in plots where NPK was applied. Data showed that long-term crop rotation and NPK application can reduce weed infestation and increase grain yield of winter rye.

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