The study was conducted to measure the most compatible range of Metribuzin(Sencor, 4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5-(4H)-one) doses to control of annual grasses and broad-leaf weeds on transplanted tomato fields. Interpretation of obtained data was compared with the results from Napropamid(Devrinol, 2-(1-naphthoxy) N,N-diethyl propionamide) and two times hand weeding plots. Crop plants were 60 days old seedlings of tomato cultivar $quot;Daehyungboksu #2$quot;, and April 20, 1979, the plants were transplanted at clay loamy soil in the college farm/Chonnam University, Kwangjoo, in space of 60×40㎝. Experimented design was triplicately used by randomized block design. The results obtained are as follows.
1. Most dominant weed species were Digitaria sp., Echinochloa sp., Portulaca sp., Annual Cyperus sp., Chenopodium sp., and Amaranthus sp., etc. in order of emerged degree, respectively.
2. Decreasing of weed competition and crop tolerence as affected by gradual increment of Metribuzin doses, tomato yield response could be fitted as a quadratic regression equation as Y=66-41.61x+14x²(Multiple correlation coefficient=0.943).
3. The other hand, main weed species in dry weight responses showed to be possibly fitted as semi-log formed quadratic regression equation in statistically high significance level. (Refer to Table 2.)
4. Through the graphic modelling method, the range of Metribuzin doses for the 90% stability of tomato yield maxima should be detected as 0.75∼2.15㎏ ai/㏊, and the tomato productivity under those range showed more improved than under Napropamid or two times hand weeding checks.
5. In case of major weed species, most compatible Metribuzin doses which computed as least residual weed weights as 20% of maxima (intercept) detected at 0.5∼0.9㎏ ai/㏊, however Chenopodium sp. at 1.27㎏ ai/㏊.
6. As a conclusion, the ranges of most compatible doses of Metribuzin for crop yield stability may be suggested as 1.27∼2.15㎏ ai/㏊, however, the proper dosage could be estimated as 0.7∼1.3㎏ ai/㏊.
7. Advanced trials to detect the most compatible dosage under different soil type and for tank-mixture with other herbicides should be followed.
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