Improvement of Salt-affected Soils, Part 1: Interception of Capillarity

Biosystems Engineering, 2006

In this paper, a new method is discussed for the soil improvement of salt-affected soils in regions where a sufficient amount of rainfall occurs in summer. The sub-soil is made coarse by soil sintering, and the capillarity from groundwater is cut off. Thus, the rise to the soil surface of salts which are dissolved in the groundwater can be prevented, and even if the groundwater level is high, the evaporation of water from the soil surface can be reduced. Moreover, the salts that accumulate in the topsoil can be washed out by rainfall (leaching) during the summer season. Consequently, this method has the same effect as when the groundwater level is lowered. This paper deals with the determination of the degree of aggregation of the soil particles and the height of water raised by capillarity due to different soil sintering temperatures.

Vadose Zone Journal

Drip irrigation is a useful method for the application of low-quality water because it does not wet the foliage and limits the spread of contaminants. Nevertheless, when using water containing high levels of dissolved salts, drip irrigation may be insufficient for leaching and can lead to soil salinization. A new conceptual model was tested experimentally and numerically to examine if manipulation of the distribution of soils with different textures could promote the removal of salts from the root zone and increase leaching efficiency. The manipulated root zone consisted of a volume of coarse soil, located under a drip irrigation emitter, surrounded by finer texture soil. We hypothesized that the differences in hydraulic properties between the two soils and the capillary barrier developed at their interface would generate a one-directional flow path of the salty water from the location of irrigation to the fine soil. This would enforce salt accumulation beyond the root zone. The concept was tested in a series of lysimeter and Hele-Shaw chamber experiments, together with a two-dimensional flow model created in HYDRUS-2D. Results showed preferential salt accumulation beyond the coarse segment of the manipulated soil, providing a volume of leached soil sufficient to support a healthy root system. Under conditions of homogenous soil texture, a notable buildup of salinity was observed in the central root zone, whereas under the manipulated texture conditions, such salt buildup was not observed.

Agriculture (Pol'nohospodárstvo), 2019

The research work was started on the preliminary knowledge that the risk of secondary salinization is high in the hobby gardens around Karcag as the water of the aquifers used for irrigation is saline, nevertheless irrigation in the drought periods is essential for vegetable production. A complex experiment was set up in 12 simple drainage lysimeters at the lysimeter station of the Research Institute of Karcag in 2012 in order to simulate the conditions of irrigation characteristic in the region with the goal of finding a solution to mitigate the harmful effects by means of optimization of irrigation. In 2017–2018 three approaches were applied for the scientific establishment of the problem studying the effect of different irrigation frequencies, different irrigation water qualities, and soil conditioning on the moisture content and the salt profile of the soil. The soil conditioner (Neosol) applied was found to have a positive effect on the water and salt regime of the soil, partly...

Environment Control in Biology, 2013

Characteristics of rainfall-induced salt leaching was investigated in a field after wheat (Triticum aestivum L.) cultivation under irrigation by synthetic saline water, which was prepared by mixing sodium chloride (NaCl) with fresh water pumped from a borehole well. The treatments of the experiment-I1: root zone soil with salinity 0.12 dS m 1 , and I2, I3, I4 and I5: root zone soils with salinity 0.39, 0.51, 0.69 and 0.86 dS m 1 , respectively-had three replications. The soil salinities were developed due to irrigation by fresh water (of 0.385-dS m 1 background salinity) for I1 and by saline water of 4, 7, 10 and 13 dS m 1 salinity for I2, I3, I4 and I5, respectively. Soil samples were collected from each plot from 0 20, 20 40 and 40 60 cm soil layers at 15 (in a few cases at 30) days interval during rainy season (April September 2011) after harvesting of the crop. By measuring electrical conductivity (EC) on saturation extracts of the samples salt dynamics at the three soil layers under the five irrigation treatments were characterized. Variation of soil pH due to the leaching process was also evaluated by measuring pH of the soil extracts. At the end of rainy season, the salt that accumulated in the soil due to irrigation by saline water leached almost completely out of the top 0 20-cm soil layer in all treatments. The salt from the upper layer leached down and initially elevated salinity of the lower layers. Salinity in the bottom layer of I2 I5 treatments did not reduce to pre-irrigation non-saline level, implying that rainfall, although a substantial amount (1673 mm) could not wash out the imposed salinity from the root zone soil. At the early period of leaching, both the frequency and quantity of rainfall were relatively small, but the rate of reduction of EC in the soil profile was quite substantial and rapid, especially in the soil with high salinities (e.g., I4 and I5). At the later period, on the other hand, the rate of EC reduction slowed down although the frequency and quantity of rainfall were higher than at the early period of leaching. The salt removal rate was thus inversely related to its concentration in the soil. It is concluded that, irrigation by saline water of EC 4, 7, 10 and 13 dS m 1 caused accumulation of salt in the soil in excess of that washed out by the monsoon rainfall.

Soil salinity and alkalinity have been reported to reduce crop production in approximately seven million hectares in India. The area under this category is increasing due to faulty water management coupled over with irrigation, seepage loss, impeded drainage, rapid rise of water table causing water-logging and secondary salination etc. The soil problems differ from location to location. The important ones are: (i) Soil salinity, (ii) soil sodicity, (iii) soil acidity, (iv) highly permeable light textured soil, (v) less permeable heavy textured soil, (vi) soils with surface crusting , (vii) presence of heavy clay pan in the subsoil, (viii) soil with impeded drainage etc. These soils are characterised by the presence of water soluble salts like chlorides, sulphates, carbonates, and bicarbonates of calcium and magnesium in the root zone and surface of soil. When suitable agronomic management practices are adopted, the saline soils can also give reasonably good yields. Some of the methods that can be adopted are classified as: (i) Irrigation management practices, (ii) leaching out of salts, and (iii) drainage systems. Some of the irrigation management practices that can be tried are; furrow irrigation, and broad bed furrows, double row beds, frequent sprinkler irrigation or giving number of light irrigations. The basic principle in all these is to irrigate frequently and adequately following the principle of leaching requirement of soil so that the salts are washed away from the root zone or the seeds. When poor quality waters are used throughout, the crops will be affected by changes in the physical and chemical properties of the soil. Consequently the crop productivity will also be affected. Accumulation of salts in the surface soils leads to development of salinity of soils. Water table also significantly modifies the effect of soil salination. For example, if the water table is maintained below the critical depth, the total salt content above the ground water table would diminish since the salts will move with ground water due to downward movement of solution. On the other hand if it is above critical depth, there would be a permanent increase in the salt content of the soil profile due to upward movement of salt solution. Management practices adopted for saline water are also discussed in the present study; in order to reduce the adverse effects crops.