Accelerated Reclamation of Alkaline Argillaceous Soils of Azerbaijan by Mukhtar Abduyev

Author:Mukhtar Abduyev
Language: eng
Format: epub
Publisher: Garnet Publishing (UK) Ltd
Published: 2014-07-31T04:00:00+00:00

Figure 8. Character of salt leaching when leaching with application of sulphuric acid:

a - 10 tonnes/hectare sulphuric acid;

b - 20 tonnes/hectare sulphuric acid; c - 30 tonnes/hectare sulphuric acid.

KEY: Abscissa: Salts (%). Ordinate: Depth (cm). (For further description, see Figure 2.)

Regarding total alkalinity, the picture observed in the present case is the opposite. In the second leaching, the HCO3 ion value increased in all the horizons of the studied thickness of the soil. Although the increase in the HCO3 ion content was not great and did not reach the level of toxicity (Table 28), the fact of the increase was of concern, because the application of sulphuric acid to the soil at the time of leaching [naturally] contributes to the formation of sodium carbonate. On the other hand, the data for individual salts were not so unfavourable. As seen from Table 29, the increase in the total alkalinity content contributed to a rise in only the amount of calcium bicarbonate in the profile of the studied thickness of the soil. The content of calcium sulphate in the surface horizon doubled, whilst calcium sulphate was subject to appreciable leaching-out in the deeper horizons. The same may be said of magnesium sulphate (Table 29).

It should be mentioned that, despite a considerable increase in the amount of sulphate salts in the surface horizon, overall the content of sulphates in the 2-metre thickness of the soil sharply decreased (by 37 tonnes/hectare for CaSO4; by 5 tonnes/hectare for MgSO4, and by 59 tonnes/hectare for Na2SO4). This indicates that in the second leaching not only were sulphate salts (mainly gypsum) leached out, but salts formed as a result of application of sulphuric acid to the soil were also leached out.

The sodium chloride data are noteworthy. In the upper horizons, the content of this salt was decreased by more than 9 times (from 2.389% to 0.249%). Sodium chloride was intensively leached-out across the thickness of the soil ground (Table 29). It suffices to say that the amount of sodium chloride was decreased by 212 tonnes/hectare in the first one-metre layer of the soil ground and by 208 tonnes/hectare in the second one-metre layer. Hence, the main mass of the salts which were leached out constituted sodium chloride. 516 tonnes/hectare of easily soluble salts was leached out from the two-metre thickness of the soil ground. A comparatively large total quantity of salts (281 tonnes/ha) was removed from the second one-metre layer.

The abovementioned figures are evidence of the high effectiveness of application of sulphuric acid in the dose 10 tonnes/hectare when leaching saline soils having low salt removal efficiency. However, the low occurrence of sodium carbonate at substantial depths of the soil ground (175-200 cm) makes us reluctant to jump to conclusions. The presence of sodium carbonate might be accepted as an accidental event if it were not the result of the subsequent leaching.

The following (third) standard application of leaching water failed to make firm the case for the effectiveness of sulphuric acid in soil desalinization; instead, it contributed to a considerable increase in the salt content in the surface half-metre layer of the soil.

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