Spray deposit and drift on the Ultra-Low Volume spraying by helicopter were obtained by the activation analysis techniques. The solution of Manganese Sulfate in the KASUMIN was applied under the various conditions of flight height (6-14m) and speed. To the distance of 180m from the flight path on both sides, the deposits was investigated by using the filter paper set on the sampling plate. And to the distance of 20m from the flight path on both sides, the deposits on the filter paper stuck to the upper, middle and lower parts of the rice plant and on the rice plant itself were investigated. The results are as follows.
1) The quantity of the background for the filter paper set to the sampling plate on the sprayed day showed about 0.3ml/10a, and by this value 1/167 of spray deposit was assumed as limit of identification.
2) The irregularity of the deposits on the sampling plate was very large, and significant difference of deposits among the flight condition was not recognized. The mean value of deposits on the fixed swath width was 17-31% of the applied spray volume.
3) Under the condition of 1-2.4m/sec wind, the drift to the lee side was recognized, and the deposit was approved as n-th order of the distance from the flight path. The deposit on the location of 54-83m from the flight path was 1% of applied volume.
4) Because the filter paper was stuck to the rice plant on the day before the sprayed day, the quantity of background was very much and different among the samples. But we can appreciate the significant difference among the test sections, and a relation of exponential function is showed between the spray height and the deposits. To get a high spraying efficiency, it is necessary to utilize the descending current by helicopter as effective as possible. At the 6m and 4m spray heights the deposits was 5.8% and 26.6% of the applied volume. There is little deposit on the middle and lower parts of the paddy plants.
5) Because the background of the rice plant is great, we do not appreciate the deposit on the rice plant.
