EFFECTS OF SOIL SAMPLING METHODS ON THE N ITRATE (N(MIN))-VALUES OF SOILS

Effects of boring systems and of borer species on the N(min)-values of soil samples taken from 0 cm to 30 cm, 30 cm to 60 cm and 60 cm to 90 cm depth were investigated. At the experiment station Ihinger Hof (Ho henheim University) during autumn and winter 1990/1991 at several date s soil samples were collected from 2 different fields. At first the co rrectness of the N(min)-values of samples taken by hand with a several -piece borer system was examined. To this method of reference 4 boring systems (Hand/hammer, Dutzi, N-caterpillar, Drilling-machine) in comb ination with different one-piece borer species were compared. - Import ant results were: particularly at strong nitrate gradients high over-e stimations of the N(min)-values resulted from the boring systems ''Han d/hammer'' and ''Dutzi''. With the system ''Drilling-machine'' combine d with a drilling borer an underestimation occurred. In contrast to th ese results the N(min)-values of soil samples taken by the system ''N- caterpillar'' corresponded very well with the values of the method of reference. Except the drilling borer the used borer species had no imp ortant effect on the N(min)-values of soil samples.