فهرست مطالب ali monsefi

Conservation tillage practices and the presence of crop residues on the soil surface have a positive effect on crop yields by reducing the germination and establishment of weeds during crop growth. The presence of weeds is one of the most important factors that reduce agricultural products in the world and it leads to a large reduction in the yield of agricultural products. Weeds, as one of the effective limiting factors for canola cultivation, cause a decrease in the yield of canola due to the competition in absorbing the environmental resources of growth such as nutrients, radiation, and water. On the other hand, mixing weed seeds with canola reduces the quality of its oil. Therefore, this experiment was conducted with the aim of investigating the integrated management of weeds and alternating plowing on the yield and some agricultural characteristics of canola in the conditions of Ahvaz.

In order to investigate the effect of sequential tillage and weed management, research was conducted in the year 2021-2022 in the research farm of the Faculty of Agriculture of Shahid Chamran University of Ahvaz, Ahvaz. The lay out of this research was an experimental design of split plots in the form of randomized complete block design with 3 replications. The main factor of tillage in three levels: 1) zero tillage-zero tillage, 2) reduce tillage-conventional tillage and 3) Conventional tillage-zero tillage and the sub-plot of weed control in six levels: 1) control, 2) hand weeding, 3) cycloxidem herbicide 2 liters per hectare in installments of 15 and 30 days after sowing, 4) cycloxidem herbicide 2 liters per hectare at 30 days after sowing, 5) crop residues as surface mulch (maize @ 5 tons per hectare) and 6) crap residues + cycloxidem herbicide was 1.5 liters per hectare at 30 days after sowing. Statistical analysis of data was done using SAS software and comparison of averages with LSD method.

The results of the experiment showed that the highest seed number per silique, the highest seed yield, the highest biological yield, and the percentage of oil in the treatment were related to the mutual effects of conventional tillage and manual weeding. The highest silique number per plant and 1000 seeds weight were in the conditions of conventional tillage and the application of 2 liters of herbicide per hectare in installments. The highest rate of harvest index was obtained with 26.80 percent in the condition without tillage and the application of 2 liters of cycloxidum herbicide per hectare in installments.

The use of conventional tillage and the use of cycloxidum herbicide 2 liters per hectare in division along with manual weeding can be effective in controlling weeds and increasing crop yield. In other hand the use of integrated management of weeds and the use of an effective combination of different methods of weed control with sequential tillage, which is effective in terms of society and the environment, and can reduce the damage caused by weeds and burning of residue.

Heat stress is a growing threat to food security and agricultural production. Terminal heat stress is a major abiotic stress especially in tropical and sub-tropical regions dramatically affecting crop growth and yield. The use of early-heading bread wheat cultivars is an appropriate method for many grain-producing regions experiencing terminal heat stress. In this experiment, the effect of terminal heat stress was assessed on morpho-phenological and yield traits of bread wheat cultivars and near-isogenic lines. The objective of this study was to use cultivars and near isogenic lines with early flowering to investigate the effect of earliness on grain yield and some phenological and agronomic traits of bread wheat in order to obtain superior cultivars and isogenic lines in terms of tolerance to heat stress caused by late sowing date.

The experiment was carried out in split-plots based on randomized complete block design with three replications in Shahid Chamran University of Ahvaz, Iran, in 2022-2023. The main plots included two sowing dates, November 23 and January 23 (normal and late sowing dates, respectively), and the sub-plots consisted seven bread wheat cultivars and near-isogenic lines (Roshan, Kalheydari, Mahdavi, Roshan’s near-isogenic line, Kalheydari’s near-isogenic line, Mahdavi’s near-isogenic line, and Mehrgan as control). Sowing date with desired temperature was considered as control, and late sowing date was considered as heat stress to ensure heat stress coincided with flowering and grain-filling phases. The data regarding grain yield, spike weight, grain number per spike, grain weight per spike, 1000-grain weigh, biological yield, harvest index, plant height, days to heading, and days to maturity was recorded.

The results of this experiment showed that there was a significant difference between bread wheat cultivars and isogenic lines in terms of most studied traits. Heat stress induced by late sowing caused a significant decrease in grain yield of cultivars and near-isogenic lines through a significant reduction in spike weight, grain number per spike, grain weight per spike, and 1000-grain weight. Reduction values ​​of the traits in cultivars were more than their near-isogenic lines. Heat stress led to a significant decrease in the grain yield of Roshan cultivar, Roshan’s near-isogenic line, Kalheydari cultivar, Kalheydari’s near-isogenic line, Mahdavi cultivar, Mahdavi’s near-isogenic line, and Mehrgan cultivar by 36, 35, 31, 31, 35, 32, and 30%, respectively, compared to normal sowing date as control. Decrease values in cultivars were almost similar to their near-isogenic lines, but Mahdavi’s cultivar and near-isogenic line as well as Mehrgan cultivar showed the highest grain yield in both sowing dates compared to other cultivars and isogenic lines. The isogenic lines were approximately 7 to 14 days earlier in maturity than their cultivars. In near-isogenic lines of Roshan, Kalheydari and Mahdavi, reducing the number of days from sowing to heading (5, 6, 11 days, respectively), and the number of days from sowing to full maturity (8, 7, 14 days, respectively) as two main components of earliness, caused to minimize exposure to terminal heat stress during the flowering and grain filling phases, and higher grain yield and stability.

Overall, the results of this experiment showed that the studied near-isogenic lines were superior to cultivars in term of grain yield, and agronomic and morphological traits. Mahdavi’s near-isogenic line using the earliness strategy and shortening the number of days to flowering and maturity had the highest grain yield and stability, it is recommended along with Mehrgan cultivar for both normal and late sowing date conditions in Khuzestan region.

A field experiment was conducted in experimental farm of Sugarcane Research Institute of Khuzestan province at 2019-2020 growing season, in order to examination of fertilizer type and weed management on sugar cane quantitative and qualitative yield.  Experimental design was factorial on randomized complete block design (RCBD) with three replications. The treatments include first factor (fertilizer type) with three levels (Control (Without fertilizer), Foliar application of N, P, K and compost of sugar cane bagass and the second factor was weed management with four levels (Control, weed free, spraying with Allion herbicide, Spraying with Sencor herbicide). In this study, quantitative traits such as stem height, number of stems, stem diameter stem dry weight, sugarcane yield, qualitative traits such as purity percentage, soluble sucrose and sucrose yield were measured.The results showed that complete weed control treatment and compost application (sugarcane bagasse) significantly increased sugarcane yield (84.09 tons per hectare) and sucrose yield (10.09%). Therefore, it can be suggesting that using a complete control treatment and use compost in Ahvaz can be effective and economical. dry weight of stems as well as total dry weight of sugarcane increased with decreasing weed interference time. fertilizer type also had a significant effect on the studied traits. Weed free management and application of Allion herbicide reduced dry and wet weight and density of jungle rice weed in sugarcane. Sucrose yield was increased by application of compost and foliar application of elements. Also, the highest percentage of purity and soluble sucrose was obtained by using compost. According to the results, it can be suggesting that the use of organic fertilizers (bagasse compost) in sugarcane cultivation is one of the solutions that can be used to nourish and improve plant growth and in addition to protecting the environment

Wheat (Triticum aestivum L.) is one of the most strategic crops, which is very important in terms of level and nutritional value, and is known as one of the most important and most consumed crops in the world. According to the report of the World Food and Agriculture Organization (FAO), in 2017, the world production of wheat was about 772 million tons, of which Iran's share was reported to be about 14 million tons. Increasing the yield of wheat per unit area depends on certain factors, one of which is the correct management of weeds to reduce their damage. Therefore, the aims of this study was to use different time of application of pre and post emergence herbicide to reduce use of herbicide for improving productivity of wheat.

A field experiment was conducted in a randomized complete block design with three replications in the research farm of Shahid Chamran University of Ahvaz in the year 2019-2020. Treatments in this experiment include; Uncontrolled, hand weeding, pendimethalin + atlantis, pendimethalin + metribuzin, trifluralin + atlantis, trifluralin + metribosin, pendimethalin + 2,4-D, trifluralin + 2,4-D, green mungbean + 2,4-D and 2,4-D intercropping. Wheat cv. ‘Mehregan’ was sown at 20 cm row spacing on 28 November in 2019. A seed rate of 120 kg ha-1 along with recommended fertilizer dose of 120:60:40 kg N-P2O5-K2O ha-1 was followed uniformly. Wheat matured in the 2nd week of April.

The control methods of hand weeding and pendimethalin+atlantis had a positive effect on increasing the weight of 1000 seeds and the treatment of trifluralin+2,4-D had a negative effect on the weight of 1000 seeds. Examining the changes in wheat grain yield among weed control levels showed that hand weeding and pendimethalin+Atlantis treatment levels had an average grain yield of 3.86 and 3.93 tons per hectare, respectively, which was more than the control, but in the rest of the experimental treatments, lower grain yield was observed. According to the obtained results, the use of pendimethalin pre-planting herbicide along with atlantis herbicide and metribuzin increased yield compared to the control treatment and the use of trifluralin herbicide.

In general, the results of this research showed that hand weeding treatments, pendimethalin+atlantis, pendimethalin+metribuzin, improved the growth and performance characteristics of wheat by reducing the amount of weed interference and increasing the amount of absorption of nitrogen, phosphorus and potassium elements in aerial organs.

The field experiment was to investigate the effects of crop residue management and chemical control of weeds on the depletion of nutrients by weeds and uptake of nutrients by wheat as influence of incorporation, burning and removal of residues and chemical control of weeds. This study was performed as split plots design with three replications. Treatments include management of crop residues viz: incorporated, burning and removing sesame residues; Weed control treatment viz 2,4-D+MCPA @ 1.5 lit ha-1(POE), Atlantis @ 1.5 lit ha-1(POE) and metribuzin @ 200 g ha-1(POE). The wheat cultivar was Mehregan. At the 30 DAS, the dry weight of weeds in terms of burning and removal of residue was 12.4 and 12.1 g m-2, respectively, which is much higher than the average dry weight of weeds in terms of incorporated residue. The highest amount of nitrogen depleted by weeds was related to unweeded and Atlantis under burning. The highest amount of nitrogen uptake in the grain with an average of 87.46 kg ha-1 was related to metribuzin in terms of incorporated residues, which had a statistically significant over other levels of treatments. In general, the results showed that in terms of dry weight of weeds and the amount of nutrients depleted by different components of wheat and weeds, there is a statistically significant difference between the types of residues, that return residues in dry matter weight loss and increase the competitiveness of the wheat plant with weeds is due to the provision of better growth conditions for wheat.

This study was conducted as a split plot in a randomized complete block design with three replications. The main This study was conducted as a split plot in a randomized complete block design with three replications. The main plot including 3 residue managements (e.g. removal, burn and incorporate). Sub-plots including 4 fertilizer managements that were: 1. chemical fertilizers of nitrogen, phosphorus and potassium; 2- Combination of vermin-compost fertilizer + potassium sulfate (before planting), super nitro-plus fertilizer + fertile fertilizer 2 (as seed treated) at planting time, humixcin organic fertilizer (foliar application) and one third of nitrogen fertilizer split; 3- (Combined 2): compost fertilizer + potassium sulfate (before planting), super nitro-plus fertilizer + fertile fertilizer 2 (as seed treated) at planting time and one third of nitrogen fertilizer split; 4- (Combined 3): Farm yard manure + potassium sulfate (before planting), Super nitro-plus fertilizer as seed treated, organic humixcin fertilizer (foliar application) and one third of nitrogen fertilizer split. Yield and yield components was selected and calculated from a surface equivalent to 2 m2. To determine the weight of the first internode (peduncle) from the pollination stage to maturity, the first internode was sampled with an interval of 10 days and placed in the oven to determine the dry weight. The most important indicators for calculating dry matter transfer efficiency were calculated.

Differences between levels of crop residue management, fertilizer management and their interaction in terms of yield components, grain yield, biological yield, harvest index, nitrogen and grain protein, remobilization rate, remobilization efficiency, remobilization share, current photosynthesis rate, Current photosynthesis efficiency, share of current photosynthesis, grain formation rate and biological yield were statistically at 1% probability level. The highest grain yield was observed in treatment of removal of residues and chemical fertilizers (4.45 t ha-1) and the removal of residues and fertilizers (1) (4.29 t ha-1) and the lowest was recorded in treatment of incorporated residues and fertilizers (2) (2.33 t ha-1). The highest grain yield formation rate was observed in the treatment of residue and chemical fertilizer removal (24.72 kg ha 1 day-1) and removal of residues and compound fertilizer (1) (23.86 kg ha 1 day-1).The lowest grain yield formation rate was obtained in the treatment of residue and integrated fertilizer (2) (12.85 kg ha 1 day-1). The highest rate, efficiency and contribution of photosynthesis were obtained in the removal of debris and the use of synthetic fertilizer (1) and the lowest was obtained in the incineration of waste and the use of synthetic fertilizer (3).

The results showed that treatments based on intensive agriculture (removal of crop residues and completely chemical management) have produced the highest grain yield. While treatments based on sustainable agriculture (Incorporated of crop residues with organic and biological fertilizers) with the highest percentage of grain protein, in fact have produced the highest product quality. On the other hand, although in Khuzestan province there is water shortage and drought stress in most cropping seasons, but according to the results obtained by incorporated crop residues, chemical fertilizers and integrated fertilizers, can increased plant growth, quality of crop production and reserve moisture in the soil and ultimately the stability of the system.

Despite the many benefits of tillage to crop establishment and production in the past, new herbicide and minimum-tillage management systems have drastically changed today's methods of crop production. Although tillage systems are used to increase soil porosity, they are a short-term solution that has negative consequences on surface soil structural stability, surface crop residue, and surface soil organic carbon, which are critical features that control water infiltration and subsequent water transmission and storage in soil. Physical and chemical properties of soil such as organic matter of soil is a key attribute of quality that affects water infiltration and soil aggregation. The use of conservation tillage along with the application of appropriate management methods such as conservation of residues, the use of proper rotation and weed control caused to stabilize the particles of soil, prevent the destruction of soil structure and increase soil organic matter. Therefore, changing the method of tillage systems from conventional to conservation, especially in crop rotation cycles, is inevitable. Our objectives were to summarize these findings and present additional information with particular emphasis on changes physical and chemical characteristics in different soil depths due to adoption of conservation tillage in corn-wheat crop rotation.

The present study was performed to investigate tillage systems (4 levels including ZT-ZT: Zero Tillage-Zero Tillage; ZT-CT: : Zero tillage-Conventional Tillage; CT-CT: Conventional Tillage-Conventional Tillage and CT-ZT: Conventional Tillage-Zero Tillage) and 4 levels of weed management (including W1: Control; W2: Post-emergence Nicosulfuron herbicide + hand weeded in cultivation of corn and post-emergence Metribuzin herbicide + hand weeded in cultivation of wheat; W3: Pre-emergence Atrazine + post-emergence Nicosulfuron herbicides in cultivation of corn and post-emergence Clodinafop + post-emergence Bromoxynil+MCPA herbicides in cultivation of wheat; W4: Wheat residues as a mulch + post-emergence Nicosulfuron herbicide in cultivation of corn and corn residues as a mulch + Metribuzin herbicide) on some physical and chemical properties of soil depths (D1: 0 -15 and D2: 15-30 cm) in corn-wheat rotation during the 2021-22 croping year in the farms of Shavur Agricultural Service Center of Shush city was implemented as a split-factorial in the form of a randomized complete block design with three replications and 96 samples.

The results showed that interaction of the studied treatments significant effects of the all studied traits except for soil pH. The minimum of soil bulk density was observed in conventional tillage-zero tillage × Wheat residues as a mulch + post-emergence Nicosulfuron herbicide in cultivation of corn and corn residues as a mulch + Metribuzin herbicide as weed management treatment × 0-10 cm soil depths treatment with an average of 1.390 g/cm3, also, the highest hydraulic conductivity of the soil was obtained in conventional tillage-conventional tillage × pre-emergence Atrazine + post-emergence Nicosulfuron herbicides in cultivation of corn and post-emergence Clodinafop + post-emergence Bromoxynil+MCPA herbicides in cultivation of wheat × 0-15 cm soil depths treatment (with an average of 0.994 cm/h). The highest amount of organic matter (with an average 0.771 percent) and phosphorus and potassium elements was achieved in zero tillage-zero tillage × wheat residues as a mulch + post-emergence Nicosulfuron herbicide in cultivation of corn and corn residues as a mulch + Metribuzin herbicide × 0-15 cm soil depths treatment (with averages of 13.96 and 234.7 mg/kg, respectively). Interaction effects results (tillage system × sampling depth) indicated that highest amount of total nitrogen was achieved in the zero tillage-zero tillage (ZT-ZT) on soil surface layer (0-15 cm sampling depth) with an average 122.0 kg / ha with an increase of 40.1% compared to the other treatment such as zero tillage-conventional tillage (ZT-CT), conventional tillage-conventional tillage (CT-CT) and conventional tillage-zero tillage (CT-ZT) and soil substrate (15-30 cm sampling depth, with an average of 0.87 kg/ha). In addition, the preservation of residues in the form of mulch and the use of post-emergence Nicosulfuron and Metribuzin herbicides led to maintaining the balance of soil pH in the corn-wheat rotation.

Steady-state soil chemical and physical properties was greater under zero tillage than under conventional tillage as a result of soil structural improvements associated with surface residue accumulation and lack of soil disturbance. In addition, our data indicate that conservation tillage along with the application of crops residues in corn-wheat crop rotation is a viable management strategy to improve soil quality in the warm, semiarid region of Khuzestan Province. This strategy could lead to high production, minimal negative environmental impacts, and a socially acceptable farming system. Therefore, the use of previous crop residues in tillage systems will have a positive effect on improving the physical and chemical properties of the soil.

In order to investigate the effects of chemical and integrated weed management on yield and yield components of grain maize and weed population, the study has been conducted as a randomized complete block design with three replications in 2018-19 in Shavar Research Center in Shavar region of Shousha city. Treatments include unweeded (control), hand weeding, 1.5 liters of atrazine, 1 liter of atrazine + straw mulch, 175 g of ultima, 150 g of ultima + straw mulch, 1.5 liter 2,4-D + MCPA, 1 liter 2,4-D + MCPA + straw mulch, 1.5 liters cruise, and 1 liter of cruise + straw mulch. Results show that the highest grain yield has been obtained in hand weeding treatment as well as 1 liter of cruise + straw mulch by 14.4 and 13.2 t ha-1, respectively. The highest biological yield is recorded in hand weeding treatment (31.5 t ha-1). In case of harvest index, 1.5 liters of cruise show the highest value (55.7%), followed by 1.5 liters of 2,4-D + MCPA and 1.5 liters of atrazine by 53.6% and 47.7%, respectively. In terms of weed population dynamics, hand weeding, and 1 liter of cruise + straw mulch cause the greatest decrease in weed population and dry weight which reduce crop competition and increase productivity. In general, based on the results, the adoption of integrated approaches (chemical + cultural + mechanical) can make a significant contribution to increasing corn yield and reducing environmental pollution.

The competition of weeds with crop plants in agricultural ecosystems is one of the most important biological stresses, which causes a high decrease in yield, so their control can have a great effect on increasing crop production. A high population of weeds, especially in the early stages of wheat growth, which have a strong competition for nutrition resources, can reduce the tillering of wheat. The research conducted in the field of plant residue management and chemical control of weeds shows that each of the residue management methods affects the soil and the quantitative and qualitative yield of the next crops. Therefore, considering the direct effect of plant residue management and chemical control of weeds on grain yield of crop plants, especially in double cropping system, this research was conducted to investigate the effect of sesame residue management and chemical control of weeds on weeds population, and wheat yield and yield components.

To investigate the effect of sesame residues and weed control on wheat yield and weed population, a research was conducted in split-plot based on randomized complete block design with three replications in the research farm of Faculty of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Iran, in the crop year 2019-2019. Residue management at three levels (returning or mixing plant residues with soil, burning residue and removing all residues from the soil) were considered as the main plots and weed control at four levels (chemical control with Metribozin, Atlantis and 2,4-D+MCPA herbicides as post-emergence, and without weeds control as check) as sub-plots, and the studied wheat variety was Mehregan. The traits studied in this research included the number and type of weed species and wheat grain yield and yield components.

The results of this research on the number of weeds showed that the highest number of narrow- and broad-leaved weeds was related to the removing plant residues and without weed control treatment. Regarding the wheat yield components, the observations of this experiment showed that the highest number of grains per spike with an average of 49.1 was related to the returning plant residues with the use of Metribuzin (48.7) and Atlantis (49.2) herbicides. The highest wheat grain yield with an average of 4.15 and 4.89 tons/ha was obtained from the treatments of returning plant residues and controlling weeds with Metribuzin herbicide, respectively, and the lowest grain yield (1.85 ton/ha) was recorded for no weed control. The results of this experiment showed that the weeds were effectively controlled by the post emergence application of Atlantis and Metribuzin, respectively.

The results of this experiment showed the effectiveness of weed biomass and wheat grain yield in the incorporated sesame residues and weed control treatments. Decrease in the weed population due to the use of chemical herbicides and plant residue management can be attributed to the difference in the biomass of the wheat and weeds in the experimental treatments. Incorporating the plant residues with the soil increased wheat yield components, especially the number of grains per spike, and increased the grain yield and wheat harvest index.

The aim of this study was to investigate the effects of tillage and integrated weed management on growth, yield, yield components, resource use efficiency and inputs such as energy and herbicides in wheat.   

Material and methods:

This research was conducted in split plots and randomized complete block design with three replications in the research farm of the Faculty of Agriculture of Shahid Chamran University of Ahvaz in the 2018-19. The treatments included three tillage practices, viz. conventional tillage (disc plow + disc), low tillage (disc + the retractor) and zero-tillage (direct linear planting), as main plot and six weed management options, viz.  (no control, manual weeding 30 days interval after sowing, bromoxynil + MCPA herbicide @ 1.5 liters per hectare, plant residue (mulch) + Atlantis @ 1.5 liters per hectare, Atlantis @ 1.5 liters and metribiosine @ 150 grams per hectare. Hectares) as post-emergence was considered as a sub-plot that was applied on wheat of Mehregan cultivar (especially in the semi-arid climate of the south).

Among the studied traits, grain yield was only affected by the main effect of weed control. The lowest grain yield was observed under uncontrolled conditions with an average of 1.93 t.ha-1 and the highest grain yield in weed management treatment was observed in bromoxynil + MCPA with an average of 4.14 t.ha-1. There was no statistically significant difference between the weed control methods. In terms of energy and economic benefits, the lowest total cost in conventional tillage systems, minimum, and no-tillage was related to uncontrolled treatment.

In general, due to the higher ratio of profit to cost of the no-tillage system as compared to the conventional tillage system, it seems that this method is suitable tillage system to assess proper weed control in wheat cultivation, especially in order to prevent moisture lost and degradation of structure in soils of Khuzestan province.

Weeds often pose severe constraints in the potential yield of wheat, if not controlled at a critical period of the first 30 days after sowing. Several methods are developed to control weeds, viz. cultural, mechanical, and chemical have their own merits and demerits. Tillage is an age-old practice to control weeds. Tillage influences weed infestation, and thus interactions between tillage and weed control practices are commonly observed in crop production. Good tillage delays the emergence of weeds and provides a more favorable environment for early crop establishment. So, the competition for nutrients will be less.

This study was conducted to investigate the weed population and evaluate the nutrients uptake by wheat and weed in a split-plot design with three replications in the research farm of the Shahid Chamran University of Ahvaz in the year 2018-19. Tillage at three levels, including conventional tillage, minimum tillage, and zero tillage, as the main plot and weed control at six levels (uncontrolled, hand weeding, bromoxynil + MCPA herbicide, crop residue + Atlantis, Atlantis, and metribusin) as Post-emergence were considered in sub-plots applied on wheat of Mehregan cultivar.

In terms of the weed population, the highest weed population was observed in the zero tillage compared to conventional tillage and minimum tillage. In this regard, under uncontrolled treatment, the highest weed populations with an average of 16.3, 14.2, and 12.5 plants per square meter were observed at 30, 60, and 90 days after sowing, respectively. In the case of an interaction effect, it was found that in all three tillage systems, the highest amount of nutrients, including nitrogen, phosphorus, and potassium, absorbed by weeds was in the uncontrolled treatment. The reason was due to higher dry matter production and higher competition with wheat as it was incremental.

In general, considering the higher weed population in the zero tillage as compared to the conventional tillage, it seems that weed control in the zero tillage and minimum tillage, at least in Khuzestan province, is preferable to prevent moisture content and soil structure. Nutrient depletion by weed is less in conservation tillage so that nutrient availability will be as much as plant requirements.

Introduction :

Herbicides are chemicals that are used to inhibit the growth or to eliminate weeds in agricultural fields to increase the yield of crops in crop production. By the end of the 19th century, with the increasing labor supply problems, the need for chemical methods to control weeds became apparent. It was first reported in France in the 1980s, that sulfuric acid was used in the fight against weeds in sugar beet fields. Nowadays, most of the herbicides used are organic herbicides, which share organic carbon in their chemical structure.The use of herbicides since about a century ago has been suggested as an effective way of eliminating crop competitors, though herbicides that remain in the soil for longer periods of time prolong weed control and thus increase weed management efficiency. On the other hand, their increased stability in soil may be of a magnitude that can damage crops in the following crop rotations. Soil properties can have a significant impact on the stability of herbicides in soil.

Materials and Methods :

For this purpose, soil samples were taken from 0-30 cm depth from field of experiment No. 2 in College of Agriculture Shahid Chamran University of Ahvaz. After sampling and passing through 2 mm sieve, the physical and chemical properties were measured using standard methods. The pot experiment was conducted in a factorial completely randomized design with 32 treatments including soil salinity (at 2.5 and 6 dS / m), Ultimo herbicide rate (at 4 concentration levels of 0, 25, 50 and 100% Recommended dose) and planting time (60 and 120 days after herbicide application) with 3 replication. Wheat was selected as the experimental crop and variety was "Mehregan" which has been cultivated in most of Khozestan province. Herbicide was applied and soil was rested for 60 and 120 days then wheat was sown. For germination percentage, wheat seeds were sown directly in soil after germination test. After germination the percentages were recorded and kept in an equal number of plants in the pot. It should be noted that in order to eliminate the effect of nutrient deficiency on plant growth at appropriate intervals, nutrient solution was applied and irrigated according to the need of the plant.After 9 weeks (before flowering stage) the plant was harvested and the growth components including root length, root dry weight, shoot length, shoot weight and nutrient concentration including nitrogen (in plant dry matter), phosphorus, potassium, calcium, magnesium, iron, zinc, copper and manganese were measured in the extract obtained from dry digestion of plant tissue (aerial parts of plant). Statistical analysis was performed using SAS software and mean comparisons were performed by Duncan's multiple range test. Charts were drawn using Excel software.

Results and Discussion:

 According to the results, increasing the level of herbicide decreased the growth parameters of the plant, which is intensive under salinity stress. The results showed that considering 60 days sowing after herbicide application, shoot dry weight in 100% RD herbicide application in salinity of 2.5 dS/m was 1.6 g which was not showed significant difference with 50% herbicide application under salinity of 6 dS/m. Therefore, in higher salinity levels lower herbicide dose can damage the plant as much as higher levels of herbicides in lower salinity, and lower levels of herbicides in more soil salinity produce more negative effects. By increasing planting time from 60 to 120 days the residual effects of herbicides on soil decreased and plant showed better yield. By increasing salinity level from 2.5 to 6 dS / m, all growth components of wheat decreased, except for shoot length and shoot dry weight, this significant decrease was not reported for other components.

Conclusion :

Therefore, it can be concluded that selection of sowing time after herbicide application in crop rotations is very important and by selecting the correct time can greatly reduce the deleterious effects of consuming more herbicides.Planting wheat at 60 days after application of herbicide compared to 120 days after application of herbicide, decreased the growth components of the plant. Therefore, selection of wheat sowing time in crop rotation 60 days after application of herbicide (especially at 100% recommended dose) is not recommended in maize – wheat cropping system. Also considering soil chemical properties such as salinity as an influencing factor on herbicide behavior in soil can be effective in controlling residual effects of herbicides in soil and plant.