Utilizing Eupatorium odoratum L. to Improve Crop Yields in Cambodia 1

EXTENSIVE soil fertility trials have been conducted cooperatively by the United States and Cambodia since 1956 at the Kok Patry Experiment Station which is located near Siemreap on the 13,000-hectare (32,500-acre) Baray Occidental Irrigation Project, also a joint development of the two governments. The average grain yields on this lowfertility, coarse-textured, acid soil is normally i/2 to 1 metric ton (1,100 to 2,200 pounds) of paddy rice per hectare. The soil of this area is representative of more than one-half of the 1*4 million hectares of land annually planted to lowland rice in Cambodia. Investigations at the Kok Patry Experiment Station with Eupatorium odoratum L. as green manure were first undertaken on lowland rice in 1958. These experiments were conducted because results to date with chemical fertilizer and farm manures were not sufficiently outstanding to increase grain yields nor were the results always consistent. Also, there were essentially no leguminous materials immediately available for inclusion as green manure in the trials planned for that station. Eupatorium is locally known as tontrean khet. It was originally introduced from the Antilles or West Indies by boat into Thailand and from there it spread rapidly to all of Indochina. Today it is seen growing throughout the country as a common perennial weed along roadways, fence rows, ditch banks, and waste places. It is reported by Petelot that in India this plant is toxic to fish, while in Martinique the plant is used to make a stimulating drink. In the latter instance, the stimulant is reported to come from the foliar glands. Agronomically, it has been reported by Barat that Eupatorium can be successfully used as a mulch to control a prevalent nematode-fungus complex which has been primarily responsible for reducing the Cambodian black pepper industry in the Kampot region