Investigating the Effect of Chemical Management on Weeds Population, Agronomical Traits and Yield of Garlic (Allium sativum L.) in Mazandaran Province

Garlic (Allium sativum L.) is an important winter crop in northern of Iran with a total of 9580 ha which produces approximately 90, 197 tons per year. It is the second most widely cultivated species of the genus, Allium after onion (Allium cepa). Also, Garlic along with onions and leeks are three major cultivated species in Alliaceae family. This plant because of high economic and medicinal values is cultivated in 2610 hectares of agricultural lands of Mazandaran Province, Iran. Slow growth rate, low height, and a thin canopy that does not cover the soil enough to sup-press weeds make garlic a poor competitor against the latter until the beginning of spring. According results, reported 71% yield losses in garlic crop if weeds are allowed to grow during the crop season. Weed interference is affected by the time of weed emergence relative to the crop’s phenological development. The weeds, which emerge early or simultaneously with the crop, are highly competitive and should be managed by farmers. Most weed management strategies in cereals target seedlings, as they are the most sensitive stage of the weed. However, emergence of weed seedlings varies every year in timing, extent and intensity. Therefore in this study, the effect of chemical management on reducing the density and biomass of weeds, yield and agronomic characteristics of garlic were studied in Mazandaran Province, Iran.
After the selection of location test, in order to determine the physical and chemical properties before the preparation of soil for planting, sampling from the soil was carried out from the depth of 0 to 30 cm at some point. The farm was plowed using a moldboard plow, then the used fertilizers in this study were added to the soil twice before planting and then the fertilizers were incorporated with the soil using a Disc. The amount of used fertilizers in this study according to soil test were including: 200 kg Urea per hectare that 100 kg as the base and 50 kg in two foliage stage and 50 kg in 4 foliage stage of garlic, 200 kg superphosphate triple per hectare, and 100 kg potassium sulfate. The research was performed in a land with area of 300 m2 containing 30 plots with dimensions of 3×3 m2. The planting process was done after disinfection of garlic seed varieties of Mazand for 24 hours in a solution of 2% carboxin thiram with the distance of 30×15 cm and the density of 23 plants per m2on 23/10/2012. After about two weeks from planting of garlic, germination was fully performed. The studied factors in 10 dosages of herbicide are including: 1.5, 2 and 2.5 liters per hectare of Trifluralin (Terflan) via formulations (EC 48%), 1.5, 2 and 2.5 liters per hectare of Oxyfluorfen, 1.5 liters per hectare of Oxyfluorfen in two stages (the half in first stage and the rest 18 days later) via formulations (EC 24%), hand weeding control and lack of weeding control (the number of replications of these two treatments were two folds of others (2 replications in each block and 6 replications in total)). Two weeks before planting Trifluralin herbicides were incorporated with the soil and Oxyfluorfen herbicides as post-emergently were applied in the 3 to 4 foliage stages of weeds using a backpack sprayer pump from the side of the nozzle sag (T-Jet). After 145 days from planting, 10 plants per plot were selected and plant heights measured. After maturity of garlics, 10 plants of garlic were eradicated and the number of cloves per bulb was counted and weight of 100 cloves of garlic was weighed. After full maturity of garlic, a square meter of each plot was harvested on 7.5.2013 and the harvested plants was placed for 48 hours in the farm and then bulb yield and biological yield were weighed and harvest index was also calculated. Statistical analysis software SAS (version 9.1) was used for analysis and the obtained averages were compared by means of the Duncan least significant difference test.
Results showed that the use of different doses of various herbicides had a significant difference on the plant height, weight of 100 cloves, economical and biological yield and harvest index of garlic. In contrast, under treatments of the usage of 1.5 liter of Oxyfluorfen in two stages and hand weeding treatment, plant height of garlic was increased due to lack of competition with weed species and no significant difference was observed between the above treatments with the usage of 1.5, 2 and 2.5 liters of Oxyfluorfen. The adverse effect and phytotoxicity of garlic under the use of different doses of 2 and 2.5 liters of Oxyfluorfen caused disturbances in the production of cloves per bulb of garlic and the plant spent their photosynthetic products in the reclamation of its shoots. In contrast, the highest number of cloves per bulb were counted under the treatments of using 1.5 liter of Oxyfluorfen, hand weeding and 1.5 liter of Oxyfluorfen in two stages. The results showed that the highest economical yield of garlic was obtained in the treatment of using 1.5 liter of Oxyfluorfen, hand weeding treatment and splitting of 1.5 liter of Oxyfluorfen in two stages, and there were no significant differences between the above treatments. The plant used the best from the resulted ecological niche in normal conditions, and it could transfer more photosynthetic materials to the reproductive organs and it could increase the bulb yield with more producing of cloves per bulb with higher weight.
The results obtained from experimental trials on plant height, cloves number in the bulb, cloves weight and ultimately economic yield of garlic (bulb) showed that the treatment of using 1.5 liters of Oxyfluorfen in 3 to 4 foliage stages of weed species was the best treatment.