Vízügyi Közlemények, 1936 (18. évfolyam)

Kivonatok, mellékletek - Kivonat a 4. számhoz

21 of course, places of different character may often occur, and these are to be taken into special consideration. The examination may be made in a test pit with dimensions of 1.5x 1.0 m and 1.5 m depth. In the test pit the following characteristics are to be ascertained : the general order of strata, the kinds of precipitates (salt crystals, concretion of gypsum, calcium, iron, etc.), then the calcium content (foaming with hydrochloric acid), and the pH value by means of Kühn'

s colorimetric method. Samples have to be taken from all different layers of the whole profile. Accumulation horizons, if any, have to be treated separately and with great care. When examining on the spot, special importance has to be attached to the conditions of the vegetation and the form of the roots. Alkali soils can, for instance, be recognised by poor vegetation and shallow roots, even when no other symptoms can be ascertained. In the laboratory air-dry samples are examined. As a general rule, the dry soil is sifted through a 2 mm sieve in order to separate gravel and stone. For the purposes of agricultural engineers the ascertainment of the following properties is sufficient : pH value in water or in normal solution of KCl, hydrolytic acidity, calcium carbonate, water content of the air-dry soil, capillary rise, minimum water capacity (possibly volume of voids), and in alkali soils the total quantity of soluble salts and soda. From these data the most important properties and the type of the soil can be ascertained with some sertainty. The examinations are performed by generally-known methods (references in the Hungarian text) ; it is observed that the percentage of the water content of a truly air-dry soil multiplied by 2.2+0.4 gives a good approximate value of Mitscherlich's hygroscopicity. If the kinds and quantities of dissolved salts are known, the dead water and, by including other data, the water balance of the soil can be computed. The results of examinations may be interpreted from different points of view. For agricultural engineering the behaviour of the soil towards water is decisive ; besides, the acidity or alkalinity and the salt content are of special importance. The classification of Kreybitj, based on the coherence and the water conditions relating to the five-hour capillary values has proved satisfactory. As to waterconditions, the soils may be divided into homogeneous and unhomogeneous soils. Homogeneous soils evince the same or similar behaviour towards water in all strata of the profile. In unhomogeneous soils the properties of the most unfavourable stratum are decisive for the conditions of water. Salty and alkaline soils are to be treated quite separately ; their water conditions are bad. The bad water conditions of the alkali soils are brought about partly by the great content of soluble salts and partly by the saturation of the absorption complex with sodium. A special poisoning effect is exerted only by a considerable quantity of soda. The most important plant-food materials are, besides the calcium of the humus, phosphoric acid, potassium and nitrogen. These are available for plants only in solution. There are several methods of determining the easily soluble foodsubstances ; these methods are empirical and give results correct to 60—70 per cent. Tables XII. (Table of profile) and XIII. (Table of analyses) contain some properties of Hungarian soils. For largo units of land the charting of soils may be carried out by showing their different types. Soil charts drawn on a small scale (e. g. 1 : 25,000) are not