IRANIAN JOURNAL OF WEED SCIENCE
Year:2014 | Volume:10 | Issue:2 |Papers Count:8

A survey was conducted to compare the potential of ANN and logistic regression in predicting weed presence of 33 dryland chickpea fields in Kurdistan province. Climatic and edaphic factors as independent variable and presence or absence of weeds with highest abundance as dependent variables were entered in the logistic regression and ANN models. The developed ANN was a Multi Layer Perceptron with nine neurons in the input layer, one and two hidden layer(s) of various numbers of neurons and two neurons in the output layers. Catchweed (Galium aparine L. ) and field bindweed (Convolvulus arvensis L. ) with the highest abundance indices were the dominant weeds in the chickpea fields. The logistic regression did not fit a model for catchweed, however, the ANN could develop the best suited models for predicting the catchweed and field bindweed presence in dryland chickpea fields. Sensitivity analysis revealed that altitude and rainfall are the most significant parameters in modeling weed presence in dryland chickpea fields. For the optimal model, the values of the model’ s outputs correlated well with actual outputs and its application for this purpose is recommended.

Field experiments were conducted to evaluate the effect of various adjuvants on reducing Hordeum spontaneum damage in wheat fields at Karaj, Kamyaran and Marvdasht during 2013 and 2014. Treatments comprised sulfosulfuron, sulfosulfuron + ammonium sulfate, sulfosulfuron + volck oil, sulfosulfuron + fenitrothion (a phosphorus insecticide), sulfosulfuron + metsulfuron all in recommended doses and check plots. Results revealed that there were similarities among locations of experiment. Furthermore, sulfosulfuron + ammonium sulfate had the highest efficiency to control H. spontaneum compared to other treatments. In general, although herbicide + adjuvant applications in second nod of the weed had the highest effect on fresh and dry weight, weight and seed diameter (10, 15, 18, and 9 percent respectively) of H. spontaneum, its application in tillering stage was superior because of better control of other weeds and likewise enhanced wheat characteristics. Also, sole application of sulfosulfuron had the lowest effect on H. spontaneum control. According to these results applying sulfosulfuron + ammonium sulfate in the tillering stage of H. spontaneum was recommended in infested areas.

This experiment was conducted during 2009-2010 in Kangavar, Iran, to study the effect of seedbed preparation time and weed management method on sugar beet yield quality and weed population. The experimental design was split plot in the form of a randomized complete block design with four replications. The main factor was seedbed preparation time (A) in three levels (a1-Seedbed preparation in the fall with barley, a2-Seedbed preparation in the fall without barley and a3-Seedbed preparation in spring). The sub factors were weed management methods (B) in three levels (a1-Integrated weed management, a2-Chemical weed control and a3-Weedy check). The results showed that weed biomass was significantly affected by seedbed preparation time. Before sugar beet drilling, weed dry weight of seedbed preparation in spring was 2 fold of seedbed preparation in the fall. The seedbed preparation treatment in the fall with barley as mulch caused 28% reduction in weed biomass and consequently 16% increase in root yield of sugar beet. Integrated weed management was more affective (85%) than that of chemical weed control (70%). The analysis of variance (ANOVA) indicated that seedbed preparation time significantly affected root yield. The highest root yield (64 t ha-1) was achieved in the fall seedbed without barley and the lowest root yield (54 t ha-1) was recorded in spring seedbed preparation time. The ANOVA showed that main effect of weed management method was significant (P<0. 01) for root, sugar and white sugar yield of sugar beet. The highest root yield (73 t ha-1) was achieved in the integrated weed management treatment and weed infested control had the lowest root yield (35 t ha-1). There was no significant difference between root yield of sugar beet in chemical weed control (71 t ha-1) and that of integrated weed management treatment. Therefore, preparing the seedbed fully in the fall and drilling sugar beet in the first possible time in spring, and applying the suitable weed management method, it is possible to increase yield and quality of sugar beet. In this system, soil water may be save due to reducing tillage and also there is a chance for early drilling sugar beet in the spring.

In order to compare two commercial forms of clopyralid (30% SL) under the trade names of Lontrel and Watch and their high dose effects on canola, an experiment was conducted in randomized complete blocks design with 12 treatments and 4 replications in Fars and Khuzestan provinces during 2008-9. Treatments included post-emergence application of Lontrel and Watch at 0. 6, 0. 8, 1, 1. 2 and 1. 4 L.-ha., pre-emergence application of quinmerac+metazachlor (Butisan Star, 42. 1% SC) at 2. 5 L.-ha. and weed free check. All plots were sprayed with 0. 75 L.-ha. of haloxyfop-R-methyl ester (Galant Super 10. 8% EC) post emergence against grass weeds. Results indicated that both types of clopyralid were safe on canola up to 0. 8 L.-ha. One L.-ha. of clopyralid caused slight damage to canola, but soon recovered and did not affect yield, while better control of weeds was observed. Control of dominant weeds (Cardauus pycnocephalus L. and Polygonum aviculare L. ) in Fars province, by one L.-ha. of both commercial forms of clopyralid resulted in highest canola yield increase (28%). Control of dominant weeds in Khuzestan, including Silybum marianum L., Ammi majus L., Melilotus officinalis (L. ) Pallas and Malva spp., by one L.-ha of both commercial forms of clopyralid increased canola yield by over 200 per cent.

Choosing varieties with high weed competitiveness is important in integrated weed management (IWM). This experiment was carried out in order to study weed tolerance and competition indices of 18 wheat genotypes under natural weed interference or without interference at the research field of agricultural faculty, University of Mohaghegh Ardabili, during 2010-2011 growing season. Significant differences were found in the indexes of wheat genotypes. Stress tolerance index of genotypes was between 110. 3 to 915. 0 kg ha-1. More tolerance indices such as Mean Productivity, Harmonic index and Weed Interference Tolerance Index were higher for N-80-19 and Alvand genotypes and lower for Dabira and Toos than others. Among the tolerance indices, weed interference tolerance index (WITI) and ability of weed competition (AWC) were more efficient to classify wheat genotypes to weed tolerance. Alvand and C-85-9 genotypes had the highest competitive index (CI). This finding can be used for non-chemical weed management programs.

To investigate the level of datura seed dormancy in the soil after the seed rain, a factorial experiment based on randomized complete blocks design was conducted in three replications, during 2011– 2012 in Karaj. Factors comprised three moisture regimes (moisture levels inclouded 1-dry (H1), 2-alternate wetting and drying (H2), 3-moisture (H3) ) and four temperatures of seed storage (temperatures in four months of the seed rain to restart growth integrated December and January (T1), February and March (T2), April (T3) and at the end of May and June (T4)) in a factorial combination were applied on Datura seed mass. After applying each treatment, germination tests at temperatures of 8, 14, 20, 28 and 35° C were performed. Then according to the estimated parameters, the relationship between temperature and moisture with Hydro-Thermal models which was investigated. Results indicated that response of germination percentage adequately described with segmented functions, continually. When the seeds were completely at dry conditions, a gradual increased in temperature increases the rate of germination. However, this increase was negligible compared with the increase observed in response to the two other levels of moisture levels (H2-H3). No germination was found at temperatures 4 & 7° C, irrespective of moisture levels. While with increasing temperature up to 15 and 23° C, the rate of germination increased considerably, especially for alternate wetting and drying conditions.

In order to detect the probability of ACCase inhibitor herbicides target-site based resistance of 13 wild oat (Avena ludoviciana Deuri. ) biotypes, molecular experiments were performed using CAPS and dCAPS methods. Biotypes were collected from khuzestan province and which showed cross-resitance to ACCase inhibitors. The above-mentioned molecular methods were used to identify the locations of four important mutations (Isoleucine-2041-Asparagine, Cystein-2088-Arginin, Isoleucine-1781-Leucine and Aspartic acid-2078-Glycine) responsible for target site based herbicide resistance in the carboxyltransferase domain of ACCase enzyme. Both approaches involve DNA extraction, PCR using specific primers and restriction digests of PCR products with restriction enzymes. Results of experiments showed that Isoleucine-1781-Leucine and Aspartic acid-2078-Glycine mutations were observed in 53. 8% and 7. 6% of resistant wild oat biotypes, respectively. Among the investigated biotypes, only one biotype had two mutations (Isoleucine-1781-Leucine and Aspartic acid-2078-Glycine). Thus, different mutations in the carboxyl transferase domain of ACCase enzyme were the reason of various cross resistance patterns among wild oat biotypes.

In order to survey emergence pattern of seedling and ramet of Johnson grass (Sorghum halepense), an experiment was conducted in the research field of department of agriculture of Tehran University. Evaluations were performed in corn and potato' fields, and two fallow fields (with and without wheat residual that we say hereafter bare field). Johnsongrass seedlings and rhizome sprouting shoots were counted at one-week intervals throughout the season. Results indicated that in residual treatment, cumulative emergence of seedling of S. halepense reached to maximum amount in upper thermal time (1278 TT) in comparison with other treatments. Also in the field with residual, rate of emergence of seedlings per unit of thermal time was more (974 seedlings). In corn field required TT to reach 50% rhizome emergence was more than other treatments (1118 TT). The most cumulative emergence of seedling and rhizome shoot observed in bare soil treatment, was 1034 and 1541 seedlings, respectively. Emergence of seedlings quickly stoped under corn and potato canopy while emergence of rhizome shoots continued to the end of the season. The present study demonstrated that the emergence of Johnson grass seedlings is faster rhizomes in early season and thus early plowing at the beginning of season can be an effective practice to control its emergence.