[Residual of exogenous iodine in forest soils and its effect on some wild-vegetable plants]

To cultivate iodine-enriched forest vegetables in the mountainous regions of northeast China, a series of iodine application experiments were conducted. Iodine fertilizer (potassium iodide, KI) was added to the forest soils supporting a variety of wild-vegetable plants, with a dosage gradient of 1.00, 3.33, 10.00, 16.67 and 50.00 mg.kg-1. The results showed that iodine application was an effective approach to obtain iodine-rich vegetable materials, and the iodine contents in treated plants could be 2-40 times higher than control. But, the residual of added iodine in soil was generally not high, only occupying 40%-5% of the application dosage. The accumulation of iodine in plants did not consistently increase with the dosage, which tended to slow down when the application amount increased to 10.00 mg.kg-1. In a comprehensive consideration of soil iodine residual, plant iodine accumulation and application cost, the proper iodine dosage should be approximately 10 mg.kg-1. Soil conditions had significant influence on the efficiency of iodine application, and the cultivated lands should be chosen at fine-textured, fertile, and upper-sloped sites, while sandy soils and down-sloped sites were unfavorable to the preservation of added iodine and to plant absorption.