Vergleich von Trockenheitsindizes zur Nutzung in der Landwirtschaft unter den klimatischen Bedingungen Mitteldeutschlands

Abstract

Döring, S., Döring, J., Borg, H., Böttcher, F.: Comparison of drought indices for use in agricultureunder the climatic conditions of central Germany. - Hercynia N.F. 44 (2011): 145 – 168.Droughts may lead to lower agricultural yields. To quantify such conditions so-called drought indicesare used in agricultural consulting. There is a large number of drought indices of which eight were chosenfor this work to be checked for their suitability to quantify agricultural drought in central Germany.Artern was used as a representative site. It is typical for the dry region of central Germany and, due toits (for Germany) very low annual rainfall, ideal for the investigation of drought indices. To assess thesuitability of the eight indices various criteria were considered.The “Harlfinger-Knees-Index” came out best overall. The other indices are comparable for the actualassessment of drought, but must be inverted to improve their sensitivity or require data which are moredifficult to obtain. This study revealed that all indices have major weaknesses and are not a good tool todescribe drought. None could reflect the effect of drought on the time course of the soil moisture statusor, ultimately, on yield. The reason for this failure is that none properly considers the amount of waterstored in a soil. This is important, however, since stored water can buffer a temporary rainfall deficit. Acertain period without rain therefore need not lead to drought stress in a plant, if there is enough water inthe soil. For that reason any drought index which does not or not correctly consider the amount of waterstored in the soil is inadequate.For central Germany a drier climate is predicted for the future, especially during the growing season.Hence, in the coming years drought will become an ever more important issue in agricultural consulting.Consequently, a tool is needed to assess agricultural drought properly. There are various computer modelsof different complexity, which can simulate the soil moisture status and its effect on plant growthand yield. Hence, in a further study it should be investigated, if and at what level of complexity suchmodels are better in the description of drought than drought indices.