Residual effect of a few herbicides on chlorophyll content and primary productivity of succeeding crops and associated weeds
The residual effect of a few herbicides viz: Atrataf (atrazine), 2,4-D and Aresin (monolinuron) sprayed in the previous season on the pigment concentration and primary productivity of the crops (viz: <i>Zea mays</i> and <i>Cajanus cajan</i>) grown in rotation, as well as their associated weeds has been studied. The results indicate that the residues of all the three herbicides were non toxic to <i>Zea mays</i> and toxic to <i>Cajanus cajan</i> as an increase in chlorophyll content and primary productivity occurred in the former, whereas the contrary is true for the latter. Weeds from residual plots have shown a considerable decrease in the chlorophyll content and primary productivity. The most susceptible weed to all the three herbicides was <i>Acalypha malabarica</i>, while <i>Echinochloa colonum</i> is susceptible to the residues of Atrazine but is tolerant to the residues of the other two herbicides. Recommendations based on the observations are presented in the paper.