Evaluation of Some Crops Tolerance to Granstar (Tribenuron methyl) Herbicide Soil Residual

Tribenuron methyl (granstrar) is one of the most important sulfonylurea herbicides using in Iranian wheat field. their residue persistence in soil is one of the main environmental and agronomical problems. In order to study the sensitivity of seven crops to tribenuron methyl soil residual، a bioassay experiment was conducted at Ferdowsi University of Mashhad at 2009. Experimental type was completely randomized design in a factorial arrangement with three replications. Treatments included crops (pea، bean، lentil، corn، rape seed، sugar beet and tomato) and tribenuron methyl residual simulated concentration in soil (0، 0. 00009، 0. 0002، 0. 0004، 0. 009، 0. 001 and 0. 002 mg kg-1 soil). For analysis of results plants emergence was determined after a week of planting and their survival percentage، shoot and root biomass production measured 30 days after their emergence. Plants response to tribenuron methyl residue was fitted with sigmoidal 3 and 4 parametric equations to the shoot biomass data as a function of the herbicide residue concentrations and was used to calculate the doses for 50% inhibition of shoot (ED50). Results showed، crop emergence، shoot and root growth were affected significantly (P≥ 0. 01) by tribenuron methyl soil residue. But tribenuron methyl residue didn’t effect (P≥ 0. 05) on crop survival. The highest (80. 96%) and the lowest (26. 83%) shoot dry matter lost were observed in rape seed and bean respectively. Root biomass production in all crops reduced as increasing tribenuron methyl soil residual concentration as like as shoot biomass. The highest (91. 27%) and lowest (31. 3%) root dry matter lost were observed in rape seed and bean respectively. Based on ED50 parameter for shoot، bean (0. 0078 mg kg-1 soil) and sugar beet (0. 00002 mg kg-1 soil) appeared to be the most tolerant and susceptible crops to tribenuron methyl soil residue respectively. Other crops as their susceptibility to tribenuron methyl followed the order: tomato < bean < pea < corn< lentil