SCH6DTER, H. und TIETJEN, C., 1971. Statistische Betrachtungen zur Frage der Abh/ingigkeit der Nitrifikation yon Bodentemperatur und Bodenfeuchtigkeit. (Statistical studies on the relation between nitrification and soil temperature and soil moisture.) Agric. Meteorol., 9: 77-91.
By means of linear, linear-transformed and non-linear statements, the relationship is discussed between soil temperature and soil moisture on the one side and nitrification in the upper layers of a bare soil on the other. The results of the methods are compared. It is established that a non-linear model gives more information than any other. By means of the linear statements only the influence of soil temperature is discovered, whereas the non-linear model gives the combined action of soil temperature and soil moisture on the formation of NOa-N.
The non-linear model is based on a known model of the weather-yield statistics. By means of a square function, a hyperplane is fitted on the observed data and is resolved into components, resulting in a response hyperboloid, of which the surfaces of equal response are conic sections. By means of known formulae from analytic geometry, the Eigen-values and Eigen-vectors of the square form are calculated from the coefficients of the components to determine the type of the conic sections and they are used for criteria of the effectiveness of the parameters. The Eigen-vectors show that soil temperature and soil moisture are independent in their influence on the nitrification, while the Eigen-values indicate that the efficiency of the parameters is almost identical.
The amount of NOa-N increased with rising soil temperature. In the relation to soil moisture there is an optimum near the field capacity. Falling soil temperature in autumn and winter results in a decrease of NOa-N, but only towards a fixed minimum. Calculations by use of the non-linear model result in a minimum of nearly 2 p.p.m., which is in conformity with common observations. A considerable increase of NOa-N in spring, indicative of the beginning of micro-organic activity, results only after the soil temperature exceeds 5 °C, even if the soil moisture is near the optimum. All results are valid only according the material used and are therefore to be regarded more qualitatively than quantitatively. ZUSAMMENFASSUNG Mit Hilfe linearer, linear transformierter und nichtlinearer Ans~itze wird die Frage der Abh~ingigkeit des Nitratstickstoffgehaltes der oberen Bodenschicht eines vegetationsfreien Bodens yon Bodentemperatur und Bodenfeuchtigkeit behandelt. Die Ergebnisse der Auswertmethoden werden einander gegeniiberge-