||South from Nakhom Phanom, western floodplain of river Mekong, near Ban Saenpan village. Vegetable cultivation – onion. Onion has been the main cultivar since about 1990. In some years and localities it may be replaced by tobacco, tomato, cabbage etc. Two crops within one year, after onion the next is usually pumpkin. Rather few weeds were recorded. Fertilizers and pesticides, as well as irrigation with river water, are used. Usually onion is sown without much soil cultivation after flooding and will be harvested after two months. Pumpkin will be the next. And then the next flood will come. Floods by Mekong are regular. The impact of the river has decreased since 2017 when the dike was built at the shore, but high water comes over the dike. The water brings along sediments. Dominant and other common plant species : Onion. Vegetable cultivation by a cooperative of farmers. Two transects were made, 160m with 8 points (20m steps), perpendicular to Mekong. (Sample no 8) is the closest to Mekong. Four geochemical samples were collected: Transect 1 (NPV1, northern) sample 1 (pooled points 1…4), sample 2 (pooled 5…8), Transect 2 (NPV2, southern) analogous.