Study On The Transfer Characteristics Of Boron In Soil-Plant System And Boron-tolerance Of Crops

The B contents in the edible parts of more than 20 kinds of crop varieties and the corresponding surface soils collected from 13 different areas over Fujian Province were investigated. The influencing factors for the B contents of the soils and the crops, the B accumulation ability of the crops from the soils and the impact factors were studied. The highly-sensible and the highly-tolerant varieties were selected by water-culture. The main results were as follows:1. The total B contents of the soils ranged between 0.49 and 696.73 mg·kg-1 with an average being 30.28 mg·kg-1. The available B contents of the soils were from 0.005 to 1.721 mg·kg-1 with a mean of 0.258 mg·kg-1. The available B of 36% of the soils were≥0.5 mg·kg-1, meaning 74%of the soils were lack of B. The activation rate (the ratio of available B to total B) of the soil B ranged between 0.01% and 16.99% with an average of 1.21%, of which 87.5% of the soils were less than 2%.2. The total B of the soils had no significant correlation with the contents of organic matter and free iron, CEC, pH and the contents of clay and silt. The available B of the soils had significant and positive exponential correlations with CEC and free iron content, significant and positive linear correlations with the contents of clay and silt. The activation rate of B of the soils decreased with the total soil B.3. The B contents (FW) of the crop edible parts were in the range between 0.49 and 3.85 mg·kg-1. In general, green leaf vegetables and beans contained more B than the others while the aquatic vegetables and food crops contained less. The B contents of cabbage, garlic and cowpea were significantly and positively correlated with the total soil B. The B contents of the edible parts of all the crops had significant and positive correlation with the available B. However, as for the individual crop, only the B contents of cauliflower, Chinese cabbage, garlic, cowpea, lettuce and water spinach had significant and positive correlation with the available B of the soils.4. The median of the transfer factors (total B based) were between 0.0230 and 0.1529. The transfer factors of 18 crops significantly correlated with the total soil B. The transfer factors (available B based) were between 2.84 and 46.89. The medians of the transfer factors of more than half of the crops had significant and negative correlations with the available soil B. Among the crops, cowpea had strongest whereas tomatoe and radish had weakest ability to accumulate B from the soils.5. There existed three types of B toxicity symptoms of the crops. The characteristics of the first type were that the poisoning symptoms first appeared on the old (lower) leaves and gradually spread to the younger (top) leaves with the old leaves finally being damaged the most seriously. The characteristics of the second type were that the poisoning symptoms first appeared on the top leaves and gradually spread to the old leaves with the old leaves finally being damaged the more seriously. The third type was characterized by that the poisoning symptoms first appeared on the top leaves and gradually spread to the old leaves with the central leaves finally being poisoned more seriously.6. Among the crops, red bean, cowpea and cucumber were more sensitive to B toxicity than the others with red bean being the most sensitive one. Cabbage was found to be the most tolerant to B toxicity.