Optimizing the Efficacy of Some Post Emergence Herbicides of Sugar Beet using Adjuvants and Split Application of Herbicide

Introduction: Increasing the environmental concerns emerged from the extensive use of herbicides have caused to work and introduce new approaches for their application by weed scientists. Nonetheless, weeds limit crop production especially when herbicides are removed from the weed management strategies. Optimizing herbicide doses, by increasing farmer’s knowledge about various options of herbicide application, is one of the most important strategies for reducing herbicide application. Tank-mixed herbicides, adjuvants, and split application of herbicide are more interesting, users friendly, and effective to implement this approach. Post-emergence herbicides require adjuvants to be tank-mixed or built into the formulation to enhance their performance. Utilizing these methods is very essential for crops which are very weak competiveness against weed, because of herbicides application is a common method in them. Sugar beet is an important crop grown in the most cultivation areas of Iran under cultivation about 82.5 thousand hectares over average yield 42 ton ha-1. This study was done to increase the performance of some post-emergence herbicides for controlling weeds in sugar beet using adjuvants, tank-mixed herbicide, as well as herbicide split-applied herbicide treatments. Materials and methods: A factorial experiment based on randomized complete block design with three replications was conducted at the research field of Ferdowsi University of Mashhad (985 m altitude, longitude 59˚ 28´ and latitude 36˚ 15´) in 2013. The factors included the method of herbicide application (full and split application), herbicides (chloridazon (5 Kg ha-1) plus desmedipham (6 L ha-1), desmedipham plus phenmedipham plus ethofumesate (3 L ha-1) and chloridazon (5 Kg ha-1) plus desmedipham plus phenmedipham plus ethofumesate (3 L ha-1)), and adjuvants (Non-adjuvant, Adigor (%1.5 v/v), Citogate (%0.2 v/v) and Ammonium sulfate (%0.5 v/v)). Furthermore, two control treatments were considered as weed free and weed infested for each replication. Herbicides were applied with a backpack sprayer equipped with 8002 flat fan nozzles that calibrated to deliver a spray volume of 400 L ha-1 at 275 kPa. Commercial sugar beet seeds, ‘005’ Monogerm provided from Improvement Research Institute of sugar beet, Karaj were planted on April 25 by hand to the depth 2 to 3 cm of the soil. Each plot consisted of four rows of sugar beet spaced 50 cm apart and 5 m long and density of sugar beet was 12 plants