Controlled release method for herbicides in rhizosphere to prevent aggression of Spartina alterniflora in intertidal zone

To guard effectively against the ecological aggression of the smooth cord-grass Spartina alterniflora growing in intertidal zone, a new method was considered to apply herbicides in rhizosphere soil with controlled release techniques. Three types of controlled release materials, vermiculite particles, polyethylene (PE) and chitin membrane, were tested on their herbicide-releasing characteristics, meanwhile, three herbicides, including glyphosate, parauat and basta, were evaluated on the effects of killing the smooth cord-grass. The results show that the controlled herbicide-releasing ability of vermiculite particles is weaker than the other two materials, and its initial releasing quantity is bigger, so it can be used for the muddy beach. On the contrary, that of PE was stronger, and therefore it is suitable for a sandy beach. Furthermore, that of chitin membrane is between the vermiculite particles and PE membrane. The three herbicides, glyphosate, paraquat and basta, can kill the grass effectively after 2-6 days of cultivation in 0.25-1.00 0.09-0.23 and 0.28-2.30 g/L solutions, respectively. One dimensional model for solute infiltration in saturated soil was used to modulate the herbicide migration, and the modulation result suggested that the distant between any two herbicide-releasing points should be set at less than 50-60 cm in field weeding practice. The experiment proved it is feasible in practice to guard against the ecological aggression of smooth cord-grass by controlled release of herbicides in rhizosphere