Suolalisäyksen vaikutuksesta maan reaktioon

Authors

• Martti Salonen Yliopiston maanviljelyskemian laitos, Helsinki

DOI: https://doi.org/10.23986/afsci.71185

Abstract

The object of the investigation described was to determine how added salts reduce the pH of the soil and how soon the latter rises when the soil is irrigated and percolated by water. The experiment was performed in paraffined cardboard containers with holes in their bottoms to let the water out. The 5 different soil types used appear in Table 1. A same volume, 325 ml, of all the different soils was used, and the weight in grammes as Well the volume weight and the loss of ignition are shown in Table 1. 26.4 mg ekv. of each kind of salt were used per pot = 81.3 mg ekv./l of soil. The salts used also appear in Table 1. From time to time the pots were watered with distilled water and in the intervals were left to dry more or less, as happens in nature. The soil area of the pots being 50 cm2, 100 ml water used in irrigation corresponds to 20 mm rain. The amount of water used at different times as well as the outflow of water are given in Table 2, which also shows the pH observed at different periods. In order to give a clear view of the proceedings graphic representations of the chief results are given in Figs. 1—5, in which the outflow of water is marked on the abscissa and the pH values on the ordinate. The results show that the addition of salts (with the exception of CaC03) has initially clearly reduced the pH of the test soils, but on irrigation the percolating water has washed away the released H-ion and the pH of the soil rises. This rise appears most swiftly and clearly when KCl is used. It can be stated that it will eventually have raised the pH definitely above that of the untreated soil. An addition of CaCl2 also causes the pH to rise but more slowly and leaves it at about the same level as the pH of the untreated soil. In general an outflow of 100 mm water seems already sufficient to wash away from the soil the H-ion released by the addition of salts. As the amount of water which in Finland yearly percolates the soil, may be estimated to average 200 mm of rain, it may be concluded that neutral salts cannot cause a permanent increase in the acidity of soil but may on the contrary cause a slight decrease. I able 3 shows the amount of exchangeable K and Ca found in the soil on the end of the experiment. The added K has effected a considerable washing away of Ca, and similarly the added Ca has to some extent caused the K to be washed away. The greater part of the added K and Ca (omitting the CaCO2) has been washed away from the soil. Table 4 shows the hygroscopic moisture of the soil on the end of the experiment. It has been only slightly influenced by the added salts.