Sampling and substrate application methods for pesticide mineralization experiments in undisturbed soil samples

Different strategies for pesticide mineralization experiments have been pro posed in the literature. The structural state of the soil as well as the me thod for applying pesticide to the soil can be anticipated to affect the mi neralization of the pesticide. Also the soil water content during mineraliz ation is important for the degradation of pesticide. The present study focu sed on different sampling and application methods. A new method was develop ed which used cores of undisturbed soil, sampled in tubes of 6.1 cm i.d, an d 8.55 cm long, avoiding compression of the soil when sampling. C-14-mecopr op was drip applied to soil cores under suction. The new method was compare d to our previous method taking samples in 15 cm long tubes with i.d. 5 cm, and applying pesticide by injection to the soil at the water content found when sampled. The new methodology produced the same mineralization pattern of applied pes ticide that was observed for the traditional method. A non-linear model gav e a good description of the kinetics of the mineralization. It was conclude d, that the degradation kinetics of 14C-mecoprop was not dependent on the s ampling and application methods. However, an analysis of variance indicated that the suction application method produced reduced variance between repl icates compared to our traditional technique.