| Abstract: | Estimation of the nutrient distribution around plant roots by separate analysis of rhizo and bulk soil A procedure is described to separate rhizo soil from bulk soil. For this purpose the living plant roots along with the strongly adhering soil are taken out of the surrounding soil. After a short period of drying, roots are separated from rhizo soil by gently sifting. Chemical analysis of the samples has shown that the nutrient content of rhizo soil usually differs markedly from bulk soil. Phosphate and potassium content of the rhizo soil of wheat and maize is lower than in bulk soil. Percentagewise, these differences are higher by using water as an extractant when compared to the slightly acid lactate or formate solutions. The water soluble calcium content of several wheat fields was in most cases higher in the rhizo than in the bulk soil. In sandy soil the depletion zone of phosphate does not exceed the length of the root hairs markedly whereas in the case of potassium it does. This is concluded from data showing that the potassium content, but not the phosphate content, was decreased in the bulk soil if compared to the uncropped soil. In heavier loess soils the nutrient concentrations of rhizo and bulk soil were not always found to be markedly different. It is assumed that the depletion zones are smaller than in sandy soils. In addition, because of aggregation, rhizo soil cannot be separated from bulk soil as neatly as in sandy soils. Therefore, in heavier soils the method does not yield satisfactory results. |
