AUTOMATIC-CONTROL OF A FINGER WEEDER WITH RESPECT TO THE HARROWING INTENSITY AT VARYING SOIL STRUCTURES

When finger weeders are used for weed control the treatment effect wil l vary, depending on the state of the soil. In 1995, a pilot project w as carried out to examine the possibility of using sensor/control tech nology to reduce variations in the weed control caused by variations i n soil conditions. The object was to verify that weed covering depends on working depth and that reduction of this variation could be achiev ed by controlling the tine angle on the basis of working depth measure ments. A finger weeder was equipped with a sensor for measuring the wo rking depth, and the signal from this sensor was transmitted to a cont rol system. The purpose of the control system was to maintain a fixed working depth by controlling the angle of the harrow tines. Experiment s were carried out in experimental plots sown with ''weed plants''. Th e experiments showed a clear relationship between the working depth an d the weed covering achieved, Furthermore, the experiments showed that the sensor/control system is able to keep the working depth almost co nstant and so minimize variations in weed covering by soil. (C) 1998 S ilsoe Research Institute.