GEOGRAPHICAL DISTRIBUTION OF TRACE ELEMENTSDEFICIENT SOILS IN CHINA
Liu Zheng, Zhu Qi-qing, Tang Li-hua, Xu Jung-xiang and Yen Chu-liang (Institute of Soil Science, Academia Sinica, Nanjing)
The geographical distribution of soils deficient in trace elements including boron, molybdenum, manganese, zinc and copper in China has been studied. Five nationwide maps of the content of these elements are compiled based on the soil map of China on the scale of 1:10,000,000. These maps show that in the country there are not only the soils which result in trace elements deficiency of plants, but also the soils which result in the imbalance of trace elements of plants, all these soils will affect the crop yield. There are large areas of boron-deficient soils in the eastern and southern China. The content of boron in soils varies with the soils types and parent materials. Laterite, lateritic soil and red earth derived from granite and other igneous rocks, gneiss and sandstone are lower in total and available boron. Symptoms of borondeficiency of crops may be observed on these soils. In the cases of severe boron-deficiency, even complete failure of rape yield was found. Many molybdenum-deficient soils are distributed in China including two main Modeficient soil regions. One of these is the region of loessial soils and lightcolored meadow soils derived from alluvium of the Yellow River, in which the contents of total and available molybdenum are low. The other one is the region of laterite, lateritic soils, red earth and yellow earth, in which the content of total molybdenum is high and content of available molybdenum is low. Good response of leguminoues crops to molybdenum fertilizers has been found on these soils. Manganese-deficient soils mainly distribute in the area of calcareous soils of northern China, especially derived from alluvium of the Yellow River. The manganese deficient soil map is compiled according to the content of the active manganese. It is found that the distribution of manganese-deficient soils ceincides with the distribution of calcareous soils. Zinc-deficient soils are also mainly distributed in the area of calcareous soils. However, the symptom of zinc-deficiency can be observed on orange and tung trees in acid soil area of south China, and on rice in calcareous paddy soil area. The supply of copper in majority of soils in China is adeguate with the exception of the organic soils of which the area is very small. Purplish soils derived from purplish sandstone and shale as well as lateritic soils derived from granite are low in available copper according to the results from chemical analysis, but without calibration of field experiments. Deficiency of trace elements are closely correlated with plant varieties. Trace element deficiency affect both the yield and quality of crops. Reasonable application of trace element fertilizers are beneficial to plants on the trace element-deficient soils. The distribution of the localities of crop response to trace element fertilizers coincides basically with the distribution of trace elements-deficient soils on the maps.
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