To investigate the effect of weed interference and weed-free periods on Balangu (Lallemantia royleana Benth. in Wall) and to evaluate the critical period of weed control (CPWC) in this oilseed crop, an experiment was conducted as a randomized complete block design with three replications in Naghadeh region in 2018. Experimental consisted of two groups of treatments; weed infestation treatments (infestation for 144.2, 345.9, 574, 848.2, 1147.6 and 1451.3 growing degree day (GDD) after transplanting and then plots were remained weed-free the rest of the growing season) and weed-free treatments (weeding for 144.2, 345.9, 574, 848.2, 1147.6 and 1451.3 GDD after transplanting and then plots were remained infested until harvesting time). In each block, one weed free and weed infested control was for all the growing season. Results indicated that the density and dry biomass of weeds were increased as weed removal was delayed. In contrast, density and dry biomass of weeds were decreased as weeds establishment was delayed. Height, tetrachenes fruits, ripened achenes, 1000-seed weight and biological, seed and relative yields of Balangu were decreased and increased as the duration of weed-infested and weed-free period increased, respectively. Also, logistic and Gompertz curves fitted to data showed that the beginning and end of the CPWC based on a 10% yield loss of relative yield, was estimated to be from 11 to 108 days after transplanting (97 days weed-free period) in order to prevent a noticeable yield loss.

Cover crops are an effective tool in the non- chemical weed management in sustainable agriculture. In order to evaluate the effect of type and time planting of cover crops on weed control in tomato, a factorial experiment was established using a randomized complete block design with three replications at 2013 on personal farm located about 65 kilometers from Shiraz province. The factors were included the type of cover crop at four levels (rye, red clover, rapeseed and control (no mulch)) and time of planting in three levels (one month before tomato transplanting, at the same time and one month after transplanting).The results showed that the type and time of planting of cover crops had a significant effect on the weed density and weed dry weight and tomato yield. Planting cover crops decreased weed density up to 35% and the weed dry weight of 67% compared with control. Also, cover crops reduced density of Convolvulus arvensis, Portulaca oleraceae and Echinochloa crus-galli as 8, 4 and 6 times compared with control. Tomato yield increased 60.42% with cover crop. The results showed that cover crops are appropriate tool for weed management in sustainable agricultural systems and can be used in integrated weed management.

In order to study and compare chemical and non-chemical methods of weed management in saffron (Crocus sativus) fields, two field experiments were carried out in a randomized completely block design with three replications at Research Field Station of Gonabad during 2009 to 2011. Treatments included cover crops of barely, Mushroom bed mulch, herbicides of haloxyfop R methyl ester (EC10%), iodosulfuron methyl sodium+mesosulfuron. methyl+mefenpyr. diethy (WG6%) l, hand weeding (DF75%) and control. For determining the ability of treatments for weed control, dry matter of weed, leaf dry weight of saffron, stigma and saffron flower yields were determined. Results showed that dominant weed species were mouse barely (Hordeum murinum), wild barley (Hordeum spontaneum) Hoary cress (Cardaria draba), and yarrow (Achillea millefolium). Herbicides of iodosulfuron methyl sodium+mesosulfuron methyl+mefen pyr. Diethy (WG6%) destroyed grasses and broadleaf, but it destroyed saffron plant too. Haloxyfop. R methyl ester damaged grasses but decreased stigma yield and leaf of saffron. Applied mulch was not be able to control the weeds, however, it increased saffron stigma yield. Cover crops of barley significantly decreased weed dry matter weights. Barley caused least weeds dry matter weight similar to hand weeding. In conclusion, the treatments of cover crops showed the best performances in weed control and saffron yield comparing to other studied weed management methods.

In order to investigate the effects of different weed control methods and moisture regimes on safflower (Carthamus tinctorius), a field split plot experiment based on randomized complete block design with 4 replications was conducted in Takestan Iran, during growing seasons of 2007-8. Three irrigations regimes (normal irrigation, restricted irrigation at stem elongation and restricted irrigation at flowering stage) were assigned to the main plots and nine chemical weed control method (complete hand weeding, treflan with 2 L/ha as pre plant herbicide, sonalan with 3 L/ha ad pre plant herbicide, estomp with 3 L/ha as pre plant herbicide, gallant super with 0.75 L/ha as post emergence herbicide, treflan with 2 L/ha as pre plant herbicide+ gallant super with 0.75 L/ha as post emergence herbicide, sonalan with 3 L/ha as pre plant herbicide + gallant super with 0.75 L/ha as post emergence herbicide estomp with 3 L/ha as pre plant herbicide + gallant super with 0.75 L/ha as post emergence herbicide and without hand weeding) to sub- plots. At the end of growing period traits like number of head per plant, number of seed per head, 1000 grain weight, percent of seed oil, yield of seed oil and grain yield were measured. Results indicated that treflan + gallant super treatment in restricted irrigation at stem elongation stage had the lowest dry weight of weeds. In this study maximum grain yield (2927 Kg/ha) was achieved from hand weeding + usual irrigation treatments. In general treflan + gallant super treatment was the most effective treatment on safflower yield and weed control.

Two field experiments were carried out in order to evaluate the effect of planting date, method and date of weed control on weed density and biomass in the experimental research field, Faculty of Agriculture, Ferdowsi University of Mash had, during 2006 and 2007. Treatments included planting date (30 December, 20 January an 30 February), weeding date (first true leaf, start of branching and beginning of flowering stages) and weed control methods (hand weeding, fire treatment and control). The results showed that there were significant differences in the number of weeds between different sowing dates, weeding dates and control methods. The highest mean density and biomass of weeds were obtained on the planting date, 30 February, and when weed was controlled at the first leaf appearance stage with fire treatment. The most appropriate time for weed control was at the beginning of cumin flowering. Fire treatment reduced weed growth in the first half of growing season. However, hand weeding significantly reduced weed density and biomass in the second half of cumin growing season. The first planting date caused the lowest mean weed biomass and the highest cumin yield compared to later planting dates. Hand weeding treatment contained lower mean weed density and biomass compared to fire treatment, however, cumin yield was lower in hand weeding plots than fire treatment.

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.

Both planting pattern (with changes in canopy structure) and soil water availability (which affects growth and development) exert a strong effect on crop-weed competitiveness. Therefore, the effect of different planting patterns on the wheat yield and weed biomasses under different irrigation conditions were evaluated. The experimental design was a split plot with three replications, with irrigation treatments as the main plot, and planting pattern as the sub plot. Main plots included three irrigation regimes: normal irrigation, deficit irrigation (irrigation after planting and in start of flowering) and rainfed. Subplots were four planting patterns (three rows of wheat on the ridge, three rows of wheat inside the furrow, one row on the ridge and one row inside the furrow). The results showed that wheat grain yield significantly affected by both irrigation treatments and planting pattern. In irrigated condition, using the pattern of three rows on the ridges resulted in higher wheat grain yield (3437.8 kg.ha-1), while in the deficit irrigation and rainfed condition, the pattern of “one row inside furrow” had greater grain yield, whereas the average grain yields were 2574.3 and 1868.2 kg.ha-1, respectively. Results also showed that, weed biomasses were the lowest in one row inside furrow pattern in all irrigation treatments. However, lowest weed biomasses on the ridges obtained in the “one row inside furrow pattern” at irrigation and rainfed condition and in the “three rows on the ridges pattern” at deficit irrigation. Average over all irrigation treatments, the “one row inside the furrow pattern” decreased weed biomass by 67.4, 14.9 and 60% compared with three rows inside the furrow, three rows one the ridge and one row on the ridge patterns, respectively.

Background and objectives: Understanding the interaction between crop-weed competition and herbicide doses may, in many cases, result in a recommendation to reduce the consumption of the herbicide, which is both environmentally and economically important. Nitrogen fertilizer also influences the competitive balance through changes in weed density and biomass, and also contributes to environmental pollution. Hence, the evaluation of the interaction of herbicide doses and nitrogen fertilizer application is necessary for proper management of weeds and achieving acceptable economic yield along with minimizing environmental negative impacts. Materials and methods: A field experiment was conducted as split plots in a randomized complete block design with four replications at Ramin Agriculture and Natural Resources University of Khuzestan. Nitrogen fertilizer included five levels of 0, 50, 100, 200 and 350 Kg ha-1 of urea was considered as the main plot and the herbicide dose of “ iodosulfuron-methyl sodium + mesosulfuron methyl + mefenpyr-diethyl” in six levels of 0, 0. 2, 0. 4, 0. 6, 0. 8 and 1 times the recommended dose (1. 5 L ha-1) was considered as the sub plot. Half of the nitrogen fertilizer was distributed before sowing and the other half was distributed in mid-tillering stage of wheat. Four weeks after spraying (late of wheat tillering stage), destructive sampling was done using a quadrate with a surface area of 0. 25 m2 from four points of each experimental plot. Total biomass of weeds and wheat were weighed in each plot after three days of placement in an oven at 80 ° C. Results: The response of weed and wheat biomass to herbicide doses was described, respectively, with dose-response and sigmoid models, and developed in response to an increase in nitrogen fertilizer consumption. Based on the combined model, the dosage required for reducing the weed biomass to less than 50 g m-2 with consuming of 140, 210 and 300 Kg ha-1 of urea fertilizer was predicted to be 100, 85 and 60% of the recommended dose, respectively. Also, to achieve about 700 g m-2 of wheat biomass, using 230 kg ha-1 of nitrogen fertilizer plus 100% of the recommended herbicide dose, or applying 270 kg ha-1 of nitrogen fertilizer and 60% of herbicide recommended dose or applying 350 kg ha-1 of nitrogen fertilizer and 40% of the recommended dose of herbicide. Also, application of 230 kg ha-1 of nitrogen fertilizer plus 100% of the recommended herbicide dose or application of 270 kg ha-1 of nitrogen fertilizer and 60% of the recommended herbicide dose or application of 350 kg ha-1 of nitrogen fertilizer with 40% of the recommended herbicide dose led to the achievement of about 700 g m-2 of wheat biomass. Conclusion: Increasing the competitive ability of weeds in response to increasing nitrogen use led to a higher loss of wheat biomass at higher levels of fertilizer application. Application of herbicide at higher levels of fertilizer application, which the competitive ability of weeds in these conditions was much higher than that of low fertilizer levels, led to a greater increase in wheat biomass. Increasing environmental concerns has led to the development of low input systems (low fertilizer and herbicide use). However, our results showed that weeds grown in low nitrogen levels were much more tolerant to herbicide than plants grown at higher levels of fertilizer application.