Differential changes in leaf area of plants were used to assess the fertility status of soils. For this method subterranean clover plants were raised in solutions with different levels of nutrients and transferred either into complete solutions or to solutions lacking one of the elements. Response of plants to addition of nutrients was measured by the increase in leaf area over a 7-day period after transfer. In field experiments quantitative relationships were investigated between differences in leaf area as measured by application of the above technique and responses of clover yields to fertilizers containing P or S. Highly significant correlation coefficients were found for both elements.The uptake of these nutrients during the experiment seemed to be related to their functions in the metabolism of the plant. During the first 3 days of recovery from P stress, the uptake and translocation of P into the aerial parts of the plant were rapid. Between the 3rd and the 7th day a redistribution of P into newly developed leaves took place and only a little P was taken up from the solution. On the contrary the uptake of S continued during the whole experimental period, which fact suggested, that S compounds in solution were more accessible to meet demands for new growth than S present in other plant parts.
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