We investigated the weed management system with herbicides in sod culture of orchard. Thus we examined the characteristic of six herbicides which were available in orchard and the best application system that showed their herbicide characteristics. And it is important to establish the weed management system that did not apply the same mode of action herbicides in a year, but apply the herbicides acting the diffrent mode because of the appearance of herbicides resist ance weed in sod culture of orchard. Furthermore we tried to establish the weed management system including the soil appllied herbicides tha extended the term of weed suppression and had the different mode of action. We investigated the term of weed growth suppression by herbicides and the seasonal variation in weed emergence.
1. The term of weed suppression of bialaphos, glufosinate and glyphosate in summer were longer than in spring. However the term of weed suppression of paraquat/diquat in spring was longer than in summer.
2. The weed suppression term of the mixture of DCMU with foliar herbicides was more than 50 days in any season.
3. The weeds appeared all the year in sod culture of orchard, whereas weeds from soil seed bank emerged at limited term, and paused in January to May and Auguest to September.
4. It was the most reasonable for the weed management system that the application of the mixture of DCMU with foliar herbicides in spring when many weeds emerged from soil seed bank and the application of the phosphorylated amino acid derivative herbicides in summer when weeds emergence paused.

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The time components of the operations were investigated on the rice paddy field operations by radio-controlled helicopter. The net time of operations, seeding and application, were less than a quarter of the total required time in the field. The most interesting is how to decrease the time of hop-off and landing. In this paper seeding density itself is taken under a new look and the describing method of seeds distribution is discussed. Voronoi diagram was introduced to define and condider the spacing of individual rice paddy hill. Extremely wide range of the distribution of seeding density are not supposed by the common method based on the concept of mean values and the aggregate of plants.
The results obtained are as follows;
1) Nearly a half of total working time was required for moving between landing point and application cite.
2) The measured distribution of particles swathed (coated seed, herbicide and fertilizer) showed the positions of peeks were same-sided.
3) The swath width of herbicide particle was narrower than those of coated seed and fertilizer.
4) The area of individual hill distributed in wide range can be quantified by introducing Voronoi polygon method, and discussed in relation to the yield and its components of individual hill.
5) The results of quadrangle sampling simulation by employing the previous consideration (presented as 4) shows the large area and small number of sampling quadrangle was not recommendable in accuracy, and the small area and many number of random sampled quadrangles was suggested.

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