In order to study efficacy of prosulfuron+dicamba for control of wheat broadleaf weeds, an experiment was conducted in randomized complete block design with four replications at Zarghan, Dezful, Karaj and Mashhad regions during 2018-2019 cropping season. The treatments were included of bromoxynil+MCPA (1.5 l ha-1 of Bromicide-MA® 40%), bromoxynil + 2,4-D (1.25 l ha-1 Buctril Universal 56%), bazagran+dicloprop ( 2 l ha-1 Basagaran-DP® 6.56%), triasulfuron+dicamba (165 g ha-1 Lintur® 70%), and the new herbicide prosulfuron+dicamba (300, 400 and 500 g ha-1 alone or mixed with adjuvants). The results showed that prosulfuron+dicamba in all doses, alone or mixed with adjuvants, caused a decrease in the dry weight of the dominant weeds in Karaj (75 to 100%), Zarghan (85 to 93%), Dezful (70 to 100%) and Mashhad (42 to 97 percent), but compared to other herbicides, there was no significant difference in saving wheat yield in most areas. Lintur® was the most inefficient (50%-75%) and Buctril Universal® was the most efficient (more than 85%) herbicide in our experiment. The most important weeds include Descuriania sophia, Fumaria vailantii, Galium tricornutum, Centaurea depressa, Carduus sp., Rapistrum rugosum, Veronica persica, Malva neglecta and Sinapis arvensis. As a recommendation, prosulfuron+dicamba can be used in the dose of 300 g ha-1, alone or mixed with adjuvants (0.5% v/v of Cytogate). No visual damages were observed from prosulfuron+dicamba application on wheat.

Now a day winter cover crops planting has been attended to reduce herbicide application. An experiment was carried out at the Research Farm of Agriculture Faculty, Bu- Ali Sina, University, in 2009. The experiment was a randomized complete block design with three replications. The trial included of five treatments consists of no cover crop, rye, winter oilseed rape, barley and triticale. The results showed that winter cereals were produced more biomass than winter oilseed rape. living mulch of rye, barley, oilseed rape and triticale reduced winter weeds biomass 89, 86, 82 and 70 percent respectively, in compare to control. Cover crop treatments showed significant different weeds control of potato at 3 time (15, 45 and 75 DAPG) compare to control treatment. Residues mixed to soil of oilseed rape and rye had the most inhibition affects on summer weeds. These treatments, average weeds biomass decreased 61 and 57 percent respectively, in compare to control. Oilseed rape and rye in compare to control reduced weeds density in potato 36 and 35 percent, respectively. Significant negation correlations of weeds plant population, weeds dry matter with average tuber weight and potato yield. The treatments, oilseed rape and rye in compare to control increased tuber yield of potato 54 and 50 percent, respectively. These treatments, the average tuber weight increased 74 and 38 percent in compare with control, respectively.

In an experiment in randomized complete blocks design with four replications and 17 treatments, combinations of trifluralin (Treflan 48% EC) with metazachlor + quinmerac (Butisan Star, 41. 6% SC) were tried to achieve a better control of canola weeds, especially Brassica family in Khuzestan, Golestan, Mazandaran and Fars provinces. Treatments included Treflan at 2 L/ha. ppi + clopyralid (Lontrel, 30% SL) at 0. 8 L/ha. post emergence of broadleaf weeds, Treflan at 1. 5, 2 and 2. 5 L/ha. ppi, Butisan Star at 1. 5, 2 and 2. 5 L/ha., preemergence, combinations of Treflan+Butisan Star at doseges used above, weed-free check. Haloxyfop-R-methyl ester (Galant Super 10. 8% EC) at 0. 75 L/ha was sprayed over the whole experiment to control grassy weeds. Results indicated that In Fars and Golestan, combinations of the two herbicides caused serious injury to canola and the weed control efficacy of herbicide combinations was not much better than Butisan Star alone. In Mazandaran results were similar, but canola did not show injury as a result of herbicide combinations. In Khuzestan, herbicide combinations not only did not damage canola but also had a better control of weeds and increased canola yield. Due to different types of soil in various regions, results varied, and therefore, it was recommended that before applying combination of above herbicides in any new place, they should be tested.

In order to quantifying emergence pattern of rapeseed weeds, this experiment was conducted in 40 plots (40 quadrates at Agricultural Sciences and Natural Resources University of Khuzestan, and 30 fields of Bavi (30 quadrates), Ahvaz, Iran, in 2016-2017 growing seasons was monitored, counted and recorded weekly. Three different emergence pattern of nine weed species were identified, Prickly lettuce (Lactuca serriola L. ) and Wild mustard (Sinapis arvensis L) were identified as early-emerging species. Also salt sandspurry (Spergularia marina L. ) and furrowed melilot (Melilotus sulcatus), were categorized as late-emerging species. However, five species including; mallow (Malva spp), rigid ryegrass (Lolium rigidum), sea beet (Beta vulgaris subsp. maritima), milk thistle (Silybum marianum L) and nettle-leaved goosefoot (Chenopodium murale L) were identified as medium-emerging species. Estimation of GDD50 (time required to reach 50% emergence) showed that the minimum (323. 62 ℃ d)) and maximum (608. 93 ℃ d) growing degree day required by Lactuca serriola and Spergularia marina (L. ), respectively. Whereas, 10% emergence of Spergularia marina and Melilotus sulcatus required 362. 42 ℃ d and 426. 37 ℃ d, respectively. The results of weeds emergence pattern in rapeseed crop showed that the soil herbicides with longer half-life should be applied, and the application of post emergence herbicides and agronomic practices such as plant density and competitive ability of rapeseed cultivars are necessary components in integrated weed management.

In order to study the competitiveness of potato varieties against weeds, a field experiment was conducted in 2002 at agricultural research center of Hamedan. The experimental design was split plot in complete randomized blocks with four replications. In main plot, there were seven potato varieties (with variance in reaching), and subplots were divided into two treatments, one, with weeding, another without weeding. In this experiment, weed had natural growth. The results showed that medium-late varieties such as Cosmos and Diamante with the highest Competitive Index (CI) were competitor, Agria and Moren medium-late and lateseason varieties with the same CI were semicompetitor and Novita with the lowest CI was the weakest variety. The analysis of Ability of Withstand Competition (AWC) showed the medium-late and lateseason varieties such as Agria, Cosmos, Diamante and Moren (lateseason) were more tolerant varieties and on the other hand medium-early varieties such as Novita, Draga and Marfona had the lowest AWC so were recognized as sensitive varieties against weeds.