Weed control ís the most ímportant íssue ín organíc farmíng systems that límít crop growth and theír yíeld. Fíeld experíments were conducted ín organíc soybean (Glycine max Merrí/l) to evaluate the weed suppressíon effects of salt and seawater treatment. Weed populatíon and fresh weíght were monítored after 6 weeks of saft and seawater treatments. The most ímportant weeds were Dígítaría sanguínalís, Portulaca oleracea, Tradescantía reflexa and Chenopodíum album var. centrorubrum, but also 6 other specíes were observed ín soybean arable fíeld. Soybean crops under seawater or theír solíds applicatíon were well grown. The results treated wíth salts and seawater índícate decreases by 13.4-30.8% ín weed densíty and by 18.0-43.2% ín theír fresh weíght and soíl hardness íncreases of up to 2.1-fold. Salt and seawater províded good addítíonal weed control, but they were caused a seríous problem ín deteríoratíon of soíl physícal propertíes.

The effects of seawater on growth of fettuce(Lactuca sativa L.), leaf perilla(perilIa frutescens var. japonica Hara), red pepper(Capsicum annuum L.) and cucumber(Cucumis sativus L.) seedlings were investigated in the glass greenhouse. These effects were studied on seedlings, and diluted seawater (1%, 5%, 10%, 20%, 50%, 100% v/v) was sprayed enough on feaves. The tested four vegetable crops have well grown up to 10% diluted seawater, but the tested vegetable crops were damaged from increasing salt levels. Of these, lettuce was provided salt-tolerant vegetable crop and red pepper was considered salt-sensitive vegetable crop. The salt tolerance of vegetable crops is different between crops and complicated because of additional detrimental effects caused by accumulated ions or specific ion toxicities in their leaves. These results show that agricultural use of seawater may be benefit crop cultivation in organic farming system as well as in conventional farming system.

In organic farming agriculture, integration of cover crop into cropping system is recommended to improve the soil quality, prevent soil erosion, and control weeds. The aim of this study was to control weeds in soybean fields by integration of cover crops such as hairy vetch and rye. Due 10 cover crop mulching, weeds occurrence and growth were radically decreased. One month later after transplanting, weed growth inhibition rate of hairy vetch and rye treatment were 98% and 89% respectively, while crimson clover treatment were 50%. These effects last long over two month. The soybean yield of hairy vetch treatment was best. Therefore using hairy vetch as cover crop was highly recommended in organic soybean field.

Vinegar has been considered as a potential organic herbicide, but more knowledge is needed about acetic acid concentration, application volume and use of adjutants on weed control. In this study, we determíned optímum acetic acid concentration and spraying time on several weed species. Vinegar is more effective in broadleaf weeds than grasses. Vinegar is also effective in controlling younger weeds such as 3rd weeks to 4th weeks after emergency. For example, 3rd weeks after emergency weeds were easily controlled at 2-3% of vinegar solution. But 4th weeks after emergency weeds were controlled at 4-5% of vinegar. Therefore vínegar concentration was recommended about 5%, and application time was when the weeds were young - within 31eaf stage.

Among the developed bío-degradable polymer fílms as compared wíth transparent fílm(Whíte), black polymer fílm was sígnífícantly more effectíve for controllíng weeds ín red pepper. Also, we found that whíte and black polymer mulchíng had 81.8% and 97.9% of managing weed controllíng effects in rice, respectively. Compared to nonmulched rice paddy with water supply, the non-mulched rice paddy wíthout any water supply has stopped its growth at 41 days after transplantíng, whíle polymer -mulched rice paddy without water supply had about 60% of normally growing rice plants. This shows the polymer treatment has a remarkable effect on water and power saving, solution of herbicidal resistance, avoidance of herbícidal influence to eco-system etc. When the naturally decomposíng polymer was used, a temperature was elevated as high as 4.7 ℃ on maximum and 2.6 ℃ on average. Also the naturally decomposing polymer accelerated rooting by 7 days and lowered a stress level from transplanting. The weed control effect mulched by polymer was remarkable as 98. 7%. The p이ymer now, after 294 days treated on the rice paddy, has been completely decomposed.