Eine Split-root-Technik zur Untersuchung der Nährstoffverfügbarkeit in Abhängigkeit vom Wassergehalt im Boden

A Split-Root Technique for the Investigation of the Relationship between Nutrient Availability and Soil Water content . Nutrient availability in soils depends among other factors on soil water content. In order to investigate the quantitative relationship between availability and soil water content a special technique was developed. This split-root technique has to fulfil several conditions. 1. This technique must be able to allow to differentiate between the direct influence of water supply on plant growth and the influence of soil water content on nutrient availability and the effect of the latter on plant growth. 2. It must grant a sufficient supply of water oxygen and all nutrients to the plant with the exception of that nutrient the availability of which is to be examined. 3. A predetermined water content or water tension should be maintained as constant as possible during the experiment. These requirements are best met with by means a split-root technique. The experiments were carried out in such a way that the plants were grown in a container consisting of three compartments of which the centre one contained quartz sand whereas the two outer compartments were filled with soil (fig.1). Each plant had half of its root system growing in the sand and half of it in the soil. The quartz sand was supplied with a nutrient solution containing all nutrients except the one the availability of which is to be examined. The water content of the soil was regulated by means of ceramic filter candles which were linked to a water reservoir. This water reservoir was kept under negative pressure according to the required water tension in the soil. The water tension in the soil was monitored by 2–4 tensiometers in each of the soil compartmens (tab.1). Water tension up to pF 2.7 could be established and maintained in the soil. There was little variation of water tension during an experiment (3 weeks) and the moisture distribution in the soil was uniform. In order to obtain good reproducibilities the experiments were carried out in growth chamber.