Application of 14 C-Labeled Herbicides in Lysimeter Studies

Most herbicides are applied preemergence onto bare soil or during the early stage of plant development. Therefore, the major part of the active ingredient either reaches the soil surface immediately or later with decaying plant material. The further fate of the herbicide depends largely on the physicochemical behavior of the respective compound, the amount and method of application, and a number of soil, plant, and climatic factors influencing the persistence and bio availability of organic compounds in a given soil (5, 7). Especially in the upper 2-cm soil layer, drastic changes in temperature and moisture content during a growing season have a great influence on the degradation and adsorption of herbicides in soil (10, 31).