Saline-sodic clayey soil
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Ameliorating the saline-sodic soil process represents an important target in the agricultural security program of Egypt. In this concern, a field trial was conducted for improving a salt-affected clay soil provided with a tile drainage... more
Ameliorating the saline-sodic soil process represents an important target in the agricultural security program of Egypt. In this concern, a field trial was conducted for improving a salt-affected clay soil provided with a tile drainage system at Mehallet Mousa, Kafr El-Shiekh Governorate, Egypt. The main target of this work was at identifying the effective role of applied gypsum, as a soil chemical amendment, with different rates on physico-chemical and hydrological properties of such soil as well as maximizing its productivity from maize and wheat crops. The applied gypsum treatments were categorized into: i. control without applied gypsum, ii. 3.75 ton gypsum/fed ≈ 75 % of gypsum requirements (GR) for the uppermost 15 cm, iii. 5 ton gypsum/fed ≈ 100 % GR and iv. 6.25 ton gypsum/fed ≈ 125 % GR. The applied gypsum rates were uniformly spread on surface and thoroughly mixed with the soil top 15 cm, and then followed by a recycle of wetting and drying was repeated four times through a period of about two months.. A recycle of wetting and drying was repeated four times through a period of about two months. Soil samples at depths of 0-15, 15-30, 30-45 and 45-60 cm were periodically collected after 3, 6, 9 and 12 months from starting the experiment to determine soil physico-chemical, i.e., ECe, ESP, salt leaching index, bulk density, infiltration rate, aggregation index and quickly drainable pores. Moreover, the shape of water table between drains, water table depth were monitored as well as the drainage intensity factor "a" and the rate of water drawdown were calculated.
The obtained results revealed that the reduction percentages of soil salinity after 3, 6, 9 and 12 months from starting the experiment reached 30.3, 33.1, 35.4 and 45.0 % for the applied gypsum rates 75 % GR vs 34.6, 36.9, 45.6 and 53.3 % for 100 % GR and 35.0, 66.6, 69.9 and 75.7 % for 125 % GR, respectively. That was true, since additional gypsum in excess of the requirement helped speedily soil amelioration process. In general, the soil salinity reached the safe limits of soil salinity (ECe=< 4.0 dS/m) and sodicity (ESP= < 15 %) after 6 months of applying 100 and 125 % GR. Also, the values of ECe and ESP were tended to a gradual decrease with increasing the experimental time, but the reverse was true for the values of salt leaching index that showed gradual increases.
Concerning soil physical soil properties, the obtained results showed a pronounced increase in infiltration rate, where the increase percentages ranged 42.3-56.0, 43.7-60.9 and 55.4-91.5 % at 75, 100 and 125 % GR, respectively. A similar and parallel trend was also observed for the values of quickly drainable pores. Such favourable effect refers to the released Ca2+ from gypsum that leading to improve soil structure, creation of friable granules and conductive pores that enhancing water penetration, and then promote a sufficient cycle of wetting and drying. Also, a parallel increase was achieved for the aggregation index values as time elapsed and increasing gypsum rates, where the corresponding relative increase percentages ranged between 18.0-89.3, 55.0-120.0 and 108.0-140.3 % at 75, 100 and 125 % GR, respectively. Moreover, a noticeable decrease was observed for soil bulk density due to adding gypsum as an amendment comparing with the control treatment.
Regarding soil hydrological properties, it was clearly showed a marked drop in water table level differs from one day to another as well as the applied gypsum rates, probably due to the nature of the stratified layering of such Nile alluvial soil. The average rate of water table drawdown after one year of gypsum application mounted 35.2, 44.8 and 95.0 % for soils treated with 75 %, 100 % and 125 % GR as compared with the initial state, respectively. In general, lowering the water table has given the top soil a chance to dry, shrink and creating water passageways. It was also noticed that the drainage intensity factor (a) tended to increase with increasing the applied gypsum rate, where its greatest value was achieved at 125 % GR, may be due to the increase of released Ca2+ and its positive action to link clay particles, and in turn enhance soil internal drainage and water movement to drains. In addition, a parallel pronounced decrease in the total water resistance was associated with increasing the applied gypsum rate, i.e., 7.69, 23.07 and 30.77 % at 75, 100 and 125 % GR, respectively. This means that applied gypsum led to improve the soil structure which helped in creating a more permeable soil medium with less resistance to water flow towards tile drains.
The achieved amelioration in physico-chemical and hydrological properties of the studied soil positively reflected on the increases of grain yields of both summer maize and winter wheat, which were approached 27.8, 50.0 and 61.1 % for maize vs 25.7, 42.9 and 57.1 % over the control for wheat at 75, 100 and 125 % GR, respectively. Finally, the obtained results suggest that this work is considered as scientific and logic fundamental base for a successful agricultural development of such salt affected area as well as possible to increase unite area income.
The obtained results revealed that the reduction percentages of soil salinity after 3, 6, 9 and 12 months from starting the experiment reached 30.3, 33.1, 35.4 and 45.0 % for the applied gypsum rates 75 % GR vs 34.6, 36.9, 45.6 and 53.3 % for 100 % GR and 35.0, 66.6, 69.9 and 75.7 % for 125 % GR, respectively. That was true, since additional gypsum in excess of the requirement helped speedily soil amelioration process. In general, the soil salinity reached the safe limits of soil salinity (ECe=< 4.0 dS/m) and sodicity (ESP= < 15 %) after 6 months of applying 100 and 125 % GR. Also, the values of ECe and ESP were tended to a gradual decrease with increasing the experimental time, but the reverse was true for the values of salt leaching index that showed gradual increases.
Concerning soil physical soil properties, the obtained results showed a pronounced increase in infiltration rate, where the increase percentages ranged 42.3-56.0, 43.7-60.9 and 55.4-91.5 % at 75, 100 and 125 % GR, respectively. A similar and parallel trend was also observed for the values of quickly drainable pores. Such favourable effect refers to the released Ca2+ from gypsum that leading to improve soil structure, creation of friable granules and conductive pores that enhancing water penetration, and then promote a sufficient cycle of wetting and drying. Also, a parallel increase was achieved for the aggregation index values as time elapsed and increasing gypsum rates, where the corresponding relative increase percentages ranged between 18.0-89.3, 55.0-120.0 and 108.0-140.3 % at 75, 100 and 125 % GR, respectively. Moreover, a noticeable decrease was observed for soil bulk density due to adding gypsum as an amendment comparing with the control treatment.
Regarding soil hydrological properties, it was clearly showed a marked drop in water table level differs from one day to another as well as the applied gypsum rates, probably due to the nature of the stratified layering of such Nile alluvial soil. The average rate of water table drawdown after one year of gypsum application mounted 35.2, 44.8 and 95.0 % for soils treated with 75 %, 100 % and 125 % GR as compared with the initial state, respectively. In general, lowering the water table has given the top soil a chance to dry, shrink and creating water passageways. It was also noticed that the drainage intensity factor (a) tended to increase with increasing the applied gypsum rate, where its greatest value was achieved at 125 % GR, may be due to the increase of released Ca2+ and its positive action to link clay particles, and in turn enhance soil internal drainage and water movement to drains. In addition, a parallel pronounced decrease in the total water resistance was associated with increasing the applied gypsum rate, i.e., 7.69, 23.07 and 30.77 % at 75, 100 and 125 % GR, respectively. This means that applied gypsum led to improve the soil structure which helped in creating a more permeable soil medium with less resistance to water flow towards tile drains.
The achieved amelioration in physico-chemical and hydrological properties of the studied soil positively reflected on the increases of grain yields of both summer maize and winter wheat, which were approached 27.8, 50.0 and 61.1 % for maize vs 25.7, 42.9 and 57.1 % over the control for wheat at 75, 100 and 125 % GR, respectively. Finally, the obtained results suggest that this work is considered as scientific and logic fundamental base for a successful agricultural development of such salt affected area as well as possible to increase unite area income.
The removal of sodium salts from saline soils by salt tolerant crops, as alternative for costly chemical amendments, has emerged as an efficient low cost technology. Lysimeter experiments were carried out on a highly saline sodic soil... more
The removal of sodium salts from saline soils by salt tolerant crops, as alternative for costly chemical amendments, has emerged as an efficient low cost technology. Lysimeter experiments were carried out on a highly saline sodic soil (ECe = 65.3 dS m −1 , ESP = 27.4, CEC = 47.9 cmole (+) kg −1 , and pH = 7.7) and irrigated with canal water (EC = 2.2 dSm −1 , SAR = 4.8) to investigate reclamation efficiency under four different treatments: control (no crop and no gypsum application) (C), gypsum application equivalent to 100% gypsum requirement (G 100), planting sea orach (Atriplex halimus) as phytoremediation crop (Cr), planting sea orach with gypsum application equivalent to 50% gypsum requirement (CrG 50). Soil salinity (ECe) and exchangeable sodium percentage (ESP) were significantly reduced compared to the control. Average ESP and ECe (dS m −1) in the top layer were 9.1, 5.8 (control), 4.8, 3.7 (Cr), 3.3, 3.9 (CrG 50), and 3.8, 3.1 (G 100), respectively. Atriplex halimus can be recommended as phytoremediation crop to reclaim highly saline sodic clay loam soils.
Hexavalent chromium is mobile and hazardous in the environment. Electrokinetic remediation of chromium (IV)-contaminated soils is intended either to remove or to reduce Cr (VI) to Cr (III). This study examines the effectiveness of... more
Hexavalent chromium is mobile and hazardous in the environment. Electrokinetic remediation of chromium (IV)-contaminated soils is intended either to remove or to reduce Cr (VI) to Cr (III). This study examines the effectiveness of utilizing EDTA and acetic acid solutions as alternative electrolytes in the electrokinetic (EK) process, with coupled nano-scale zero-valent iron (nZVI) as a barrier for the remediation of Cr (VI)-contaminated clay. An nZVI barrier was installed adjacent to the anode, and different electrolyte solutions (0.1 M EDTA and 1 M acetic acid) were used to investigate the effect of both on the electrokinetic remediation efficiency. Soil was contaminated to 300 ppm of Cr (IV), and a constant DC voltage gradient of 1 V/cm was applied to the soil sample for 72 h. It was found that an nZVI permeable reactive barrier (PRB) could improve the Cr (VI) remediation efficiency and reduce electrical energy consumption. Results also showed that acetic acid as electrolyte promoted the reduction of Cr (VI) to Cr (III), while EDTA application as electrolyte led to more chromium removal and reduction than an EK-nZVI barrier.