Study On The Soil Fluorine And Its Transfer To Some Crops In Fujian Province

Investigated in this paper were the fluorine contents of 12 crops and the corresponding surface soils which were collected from the suburbs of 8 counties of Fujian province. The extraction method for available F in acid soil, the F availability and its influencing factors, and the transfer characteristics of F from soils to the edible parts of the crops were studied. The main results were as follows:1. The contents of the total F in the surface soils ranged between 177.65 and 1010.74 mg.kg^-1 with an average being 475.67mg.kg^-1. There were significant correlations with the total soil F and the contents of soil organic matter, free iron and clay (<0.002mm), showing that the increase in soil organic matter, free iron and clay favoures the accumulation of F in the soils.2. Among the three extractants, HC1, CaCl₂ and H₂O, deionized water was found to be best for extracting available F in acid soils. The suitable conditions for the H₂O extraction were set as fllows: ratio of solution to soil = 10:1, shaking time = 60 minutes, shaking velocity = 180 rpm, extraction temperature = 25 °C. The water-extractable F in the soils varied from 0.92 to 25.56mg.kg^-1 with an average of3. The availability degree of soil F (ratio of water-extractable F to total F) was in the range between 0. 33% and 12. 72% with a mean of 1.81%. The water-extractable F decreased with the increase of total F and the contents of organic matter and clay, while increased with increasing soil pH, indicating that the increase in soil pH promotes soil F availability whereas the increase in total soil F, organic matter and clay inhibits it.4. The F concentration of the edible parts of the crops were between 0.08-6.87 mg.kg^-1 (fresh weight basis for vegetables,dry weight basis for rice) with a mean of 0.87 mg.kg^-1. Both the apparent transfer factors based on total F (TF_total) and available F (TF_avail) were calculated. The TF_total values ranged between 0.0003 and 0.0130 while the TF_avail were between 0.012 and 0.914. The TF_total values tended to decrease with the increase of soil available F.5. The representative apparent TF_avail values for each crop were estimated based on the regression equations between the TF_avail values and soil available F and at the point of 8 mg·.kg^-1 of available F. The apparent TF_avail values of the crops were in the following order: rice (0.914)>garlic(0.105)>leaf...