Investigating The Effect of Foramsulfuron and Rimsulfuron Residues in Soil on Growth, Nodulation and Nitrogen Fixation of Chickpea (Cicer arietinum L.)

Sulfonylurea (Su) is one of the important groups of herbicides which control weeds through inhibition of the acetolactase synthase enzyme, a key enzyme in the synthesis of amino acids. Their main character by which can be distinguished from other groups are their low cost, effectiveness against wide spectrum of weeds in cereal crops (mostly broad leaved plants), operator safety, and activity at low concentrations. However, many of the crops and vegetables which are grown in rotation with cereals are very sensitive to Su residues. Among crops, legumes are very sensitive at low levels (as low as 0.5 ppm). Therefore much less than 5% of recommended application rates for controlling weeds, will be applied cause not to damage other crops. Root growth is particularly sensitive to Su residues. Since the studies have not been conducted in the country in connection with possible effects of soil residue of foramsulfuron and rimsulfuron herbicides on growth,nodulation and biological fixation in chickpea (Cicer arietinum L.), The objective of this research was to study the effect of soil residue of mentioned herbicides in soil on chickpea, growth, nodulation and nitrogen fixation in control conditions. A greenhouse experiment was conducted at the Research Greenhouse of Ferdowsi University of Mashhad in 2012. Experimental design was completely randomized design in a factorial arrangement with three replications. Treatments included chickpea genotypes (Hashem, Ilc482, Kaka and Kermanshah), herbicides (foramsulfuron and rimsulfuron) and herbicide residues in soil (0, 1, 2.5, 5, 10, 15, 20, and 30% of the recommended dose of application). At the beginning of reproductive stage (48 days after planting), plants shoot, root and nodule biomass, nodule number and plants total nitrogen amount were measured. For statistical analysis, data were changed to percentage of control. Data were subjected to ANOVA using SAS 9.1 software and treatment means were compared using Fisher’s protected LSD at the 0.05 level of significance.Non-linear regression analysis was employed using 3 (equation 1) and 4 (equation 2) logarithmic logistic dose-response model described by (Equation 1) where Y is the response (dry weight), c is the lower limit, d is the upper limit, b is the curve slope, e denotes the dose required to give a response halfway between the upper and lower limits (ED50 (Effective dose required for 50% inhibitation)); and x is the herbicide dose. The analysis of dose-response curves were determined by R, utilizing the drc package. Results Results showed that residues of foramsulfuron and rimsulfuron herbicides in soil affected all traits of chickpea genotypes significantly. All chickpea genotypes trails decreased significantly with increasing of residue concentrations of foramsulfuron in soil. However, shoot biomass of Ilc482 and Kaka genotypes and nodulation of all genotypes except of Kaka were simulated at the lowest level of residues of foramsulfuron in soil. Kermanshahi genotype produced the lowest shoot and root biomass in rimsulfuron soil residue levels. Rimsulfuron decreased nodule number and biomass of Ilc482 and Kaka genotypes. Among the studied genotypes; total nitrogen of Kaka and Kermanshah genotypes negatively affect more than the other genotypes due to foramsulfuron residues in soil. Rimsulfuron soil residues levels also decreased nitrogen in all chickpea genotypes. According to ED50 (Effective dose required for 50% inhibitation) for shoot biomass, Kaka was the lowest and Hashem was the highest tolerant genotype. Kermanshah and Ilc482 were the lowest and the highest tolerant genotypes for root biomass production respectively. Kaka was the lowest and Ilc482 was the highest tolerant genotypes in nodulation, were identified to residues of foramsulfuron in soil. In general, the results of this study showed that herbicide residues of foramsulfuron could be caused to high susceptibility in chickpea. Therefore, limitation of crop rotation is one of the most important problems for using foramsulfuron in crops before the peas. Since the residues of rimsulfuron were investigated in this study, had very low negative effect or even had estimulative effect on growth characteristics of chickpea genotypes, it would be introduced as selective herbicide in chickpea field.