Co–application effect of herbicides and micronutrients on weeds and nutrient uptake in flooded irrigated rice: Does it have a synergistic or an antagonistic effect?

Abstract

In submersed rice fields, weeds are considered the main source of nutrients removal. Hence, reduction in yield and grain quality is realized. Thus, a two–year field experiment was performed to find out the best cooperative effect between herbicides and micronutrients for controlling rice weeds with yield in mind. Two herbicides (halosulfuron–methyl and bentazone) and three micronutrients (Fe, Mn and Zn) were arranged in a strip plot design with three replicates. Results exhibited that in plots treated by halosulfuron–methyl, the control treatment (without fertilizing) showed the maximum reductions in weed N, P and K uptake, however, it statistically equaled Fe and Mn treatments in weed N uptake and Mn, Fe and Zn treatments in weed K uptake. With controlling weeds by halosulfuron–methyl herbicide, Zn treatment was as similar as Fe and Mn treatments for increasing plant height, straw yield and grain yield of rice. The interactions of halosulfuron–methyl x Zn treatment (for N and P in rice grain) and halosulfuron–methyl x Zn or Fe treatments (for P in rice grain) had synergistic effects. Moreover, the highest increases in Fe, Mn and Zn contents in rice grains were recorded with halosulfuron–methyl plus Fe, Mn and Zn treatments, respectively. In conclusion, rice producers should be aware of the synergism and co–operative effects between herbicides and micronutrients. The synergistic effect could be exploited for reducing the hazardous impacts of weeds, and hence, it raises yield potentiality and quality.