Department of Agronomy, Tocklai Experimental Station, Tea Research Association, Jorhat-785 008, Assam
Solubilization is a process in which certain surfactants confer lipophilic characters on a hydrophilic herbicide and hydrophilic characters on a lipophilic herbicide, resulting in enhanced herbicidal activity. Studies were conducted to determine the effect of solubilization on the activity of postemergence herbicides glyphosate [(N-phosphonomethyl) glycine] dalapon (2,2-dichloropropionic acid), MSMA (monosodium methanearsonate) and asulam (methyl sulfanilylcarbamate) on Imperata cylindrica, the most persistent perennial grass in tea. The commercial formulation of the herbicide under investigation was solubilized by using glycerol mono-oleate. Teepol-B 300 and kerosene. Experiments with glyphosate showed that, at equal[rates, solubilized glyphosate was more effective than normal glyphosate, and the initial effect was much faster indicating an apparent increase in herbicide absorption due to solubilization. Solubilization also enhanced the herbicide activity of MSMA which, in normal formulation, had little effect on I. cylindrica, but not of dalapon and asulam. This suggested that solubilization may be herbicide-specific.
In a separate study with Pteridium aquilinum, solubilized glyphosate, at equal rates, was more effective than normal glyphosate, at equal rates, was more effective than normal glyphosate in controlling this fern. Solubilization offered the possibility of reducing the optimum rate of glyphosate by 50% and cost of control of/. cylindrica and Pt.equilinum by Rs. 200/ha.
