MOBILIZATION AND UTILIZATION OF SPARINGLY SOLUBLE P BY RAPE AND RADISH UNDER P-DEFICIENCY

The capacity of rape and radish, plants of two different ecotypes, to mobilize and utilize sparingly soluble phosphates, AlPO4 and Ca3(PO4)2 was demonstrated by quartz sand culture. The results showed that when supplied with only one insolule phosphate, both rape and radish could mobilize AlPO4 and Ca3(PO4)2 by a large degree. When fertilized with AlPO4,the shoot P amount of radish reached 90 percent of the one supplied with the same amount of soluble phosphates, for rape supplied with Ca3(PO4)2. the percentage was 49%. The analysis of plants dry weight indicated that soil sparingly soluble phosphates, Ca3(PO4)2 and A1PO4 were able to improve the growth of rape and radish. Howerer, there was divergence in the degree by which rape and radish utlized the two insoluble phosphates. Comparatively, radish grown in acid soils had much higher ability to absorb P from A1PO4 than from Ca3(PO4)2, whereas rape native to calcareous soils utilized Ca3(PO4)2 more efficiently than AlPO4.