r. deihimfard

In order to evaluate different nonlinear regression models for estimating cardinal temperatures of Lepyrodiclis holosteoides as an invasive weed, an experiment was carried out at Biodiversity Laboratory of Environmental Sciences Research Institute at Shahid Beheshti University. 8 germination temperatures (0, 5, 10, 15, 20, 25, 30 and 35 °C) and humidity potential (0, -0.2, -0.4, -0.6 and -0.8 MPa) with four replications. Were arranged in a completely randomized design with for replications. Then, germination rate and percentage of seeds were measured. To predict the response of germination rate to temperature in Lepyrodiclis holosteoides, some regression models including dent-like, segmented, beta (four and five parameters) were applied. Some statistical estimators like Root Mean Squared of Error (RMSE), Akaike Information Criterion (AIC) and coefficient of determination (R2) were used to evaluate goodness of fit for different regression models. Results showed that the highest germination percentage (72%) was obtained at 20 °C. Results also indicated that beta four and five-parameter models were amongst the superior functions in describing the response of germination rate to temperature in Lepyrodiclis holosteoides largely due to their higher R2 (0.99 for both beta models), lower AIC (-73.16 and -73.27) and RMSE (0.0092 and 0.0091). Generally, base, optimum and ceiling cardinal temperatures for Lepyrodiclis holosteoides were estimated 4.29, 19.76 and 37.55 °C for beta four-parameter models and 4.22, 19.72 and 37.83 °C for beta five-parameter model. The findings of the current study (i.e. cardinal temperatures) could be used in prediction of Lepyrodiclis holosteoides germination and emergenceunder various temperatures.

Six field experiments were conducted in 2006 in Iran to investigate the efficacy of different herbicide options for weed control in maize. Treatments consisted of entire weed-infested control, pre-and post-emergence applications of amicarbazone at 350, 525, and 700 g ai ha-1, post-emergence applications of nicosulfuron at 60 g ai ha-1, foramsulfuron at 450 g ai ha-1, rimsulfuron at 10, 11.25, and 12.5 g ai ha-1 plus non-ionic surfactant at 0.2% (v/v), nicosulfuron plus rimsulfuron at 26.25, 30 and 33.75 g ai ha-1 plus non-ionic surfactant at 0.5% (v/v), 2,4-D plus MCPA at 1080 g ai ha-1, pre-plant applications of atrazine plus alachlor at 800+ 2400 g ai ha- 1, respectively, and EPTC at 4920 g ai ha-1. Post-emergence herbicides were applied at three-to-six leaf stage of maize. The results indicated Correspondence to: Eskandar Zand, E-mail: eszand@yahoo.com 60 E.Zand et al that nicosulfuron, and rimsulfuron at the two highest doses were the most efficient herbicides for weed control. Foramsulfuron and EPTC also acted well in this respect. Application of these herbicides also led to high grain yield of maize. Amicarbazone when applied as pre- and post-emergence did not show a consistent response at different locations.