Effects of bentonite on water infiltration in a loamy sand soil
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Effects of bentonite on waterinfiltration in a loamy sand soilRezvan Talebnezhad a & Ali Reza Sepaskhah aa Irrigation Department , Shiraz University , Shiraz , IranAccepted author version posted online: 10 Jul 2012.Publishedonline: 06 Aug 2012.
To cite this article: Rezvan Talebnezhad & Ali Reza Sepaskhah (2013) Effects of bentonite on waterinfiltration in a loamy sand soil, Archives of Agronomy and Soil Science, 59:10, 1409-1418, DOI:10.1080/03650340.2012.708926
To link to this article: http://dx.doi.org/10.1080/03650340.2012.708926
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Effects of bentonite on water infiltration in a loamy sand soil
Rezvan Talebnezhad and Ali Reza Sepaskhah*
Irrigation Department, Shiraz University, Shiraz, Iran
(Received 26 March 2012; final version received 28 June 2012)
Water loss as deep percolation is considerable in furrow irrigation in light soilsdue to the high infiltration rate. Application of soil conditioners such as bentonitereduces the infiltration rate and improves irrigation application efficiency (Ea) inthese soils. The effects of bentonite application rates (BAR) of 0, 2, 4 and 6 g L71
on infiltration of a loamy sand soil were determined in a soil column in thelaboratory. The exponent of the Kostiakov infiltration equation was notinfluenced by BAR. Maximum reduction in infiltration equation coefficient andfinal infiltration rate (if) occurred with 2 g bentonite L
71 and this reduction waslower on increasing BAR from 2 to 4 and 4 to 6 g L71 compared with control.The effect of 2 g L71 BAR on infiltration and its effect on the design of furrowirrigation in a field with a loamy sand soil indicated that in the first irrigation afterfield ploughing and seed planting, longer furrow length, lower deep percolationand higher Ea are obtained.
Keywords: infiltration rate; soil conditioners; furrow irrigation; irrigationapplication efficiency
When water resources are scarce, water loss should be prevented. In this regard,irrigation application efficiency (Ea), especially in light-textured soils, and surfaceirrigation should be improved. In furrow irrigation in light soils, deep percolation ishigh due to the high infiltration rate (IR) and saturated hydraulic conductivity (Ks).Therefore, a short furrow length, which results in this condition, is not desirable infurrow irrigation design and nor is the use of farm machinery with a low Ea.
The design and efficiency of surface irrigation are dependent on the infiltrationequation (Walker and Skogerboe 1987). In surface irrigation, the inflow rate shouldbe greater than the infiltration rate for water advancing along the border or furrow.The water advance rate in surface irrigation in light-textured soils, especially in thefirst irrigation after field ploughing and seed planting, is slow due to the highinfiltration rate. Therefore, the application of soil conditioners that reduce theinfiltration rate of light-textured soils may result in a higher water advance rate.With the application of soil conditioners, the coefficient of infiltration equation ischanged such that there is an increase in furrow length and Ea.
Soil hydraulic properties are dependent on the particle size distribution, soilstructure, bulk density, organic matter and clay types (Mingorance et al. 2007).
*Corresponding author. Email: firstname.lastname@example.org
2013 Taylor & Francis
Archives of Agronomy and Soil Science, 2013http://dx.doi.org/10.1080/03650340.2012.Vol. 59, No. , 1409 1418, 70892610
Therefore, soil conditioners can be used to improve these properties and decrease theinfiltration rate (Ibrahim-Saeedi and Sepaskhah 2011; Gholizadeh-Sarabi andSepaskhah 2012).
The effect of a gel material (Jalma) on some physical properties of light-texturedsoils was studied by Al-Darby (1996). Al-Darby proposed that application of 0.4%Jalma can decrease Ks and deep percolation by a considerable amount. Lentz (2003)mixed polyacryamide (PAM) into the soil surface layer at a rate of 45 kg ha71 andmeasured the infiltration rate. Lentz showed a greater reduction in infiltration rate ina silt loam compared with loamy sand soil. Application of PAM also reducedseepage from the irrigation canal (Lentz and Freeborn 2007). Young et al. (2009)studied the effect of PAM on Ks of sandy soils and indicated that mixing PAM withthe soil surface layer resulted in a reduction in Ks.
Bentonite contains smectite clay with 2:1 layers with a high specific surface areathat is expandable and absorbs a great amount of water. Chalermyanont andArrykul (2005) reported that a mixture of sand and bentonite of 5% reduced Ks byfour times compared with sand. An increase in the amount of bentonite in thebentonitesand mixture did not decrease Ks further. Furthermore, Komine (2004)studied the effect of different mixtures of sand and bentonite (10, 20 and 30% ofbentonite) on Ks and expansion force. By increasing the percent of bentonite theexpansion force increased and resulted in smaller effective pores and Ks. Ibrahim-Saeedi and Sepaskhah (2011) studied the effect of irrigation water with differentbentonite concentrations on Ks of a loamy sand soil. Their results indicated thatbentonite concentration of 0.2% reduced Ks of the soil surface layer by 56% and theKs of the subsurface layer by 30%. Therefore, it was indicated that bentoniteapplication was more effective at Ks reduction in surface soil. Ebina et al. (2004) andYeo et al. (2005) reported that Ks of a mixture of sand and Na-bentonite was reducedto 1.0 6 1079 cm s71 and this reduction was lower for Ca-bentonite (Sivapullaiahet al. 2000; Sallfors and Oberg-Hogsta 2002; Abichou et al. 2002; Lee andShackelford 2005). Ameta and Wayal (2008) found that the lowest Ks value occurredin a 10% mixture of bentonite and sand.
According to the study of Ibrahim-Saeedi and Sepaskhah (2011), a bentonitemixture with water can reduce Ks of the soil surface. Application of this findingmight be used in water-loss reduction in irrigation channel construction in light soiltextures. However, the effect of a mixture of bentonite and water on the infiltrationrate and the coefficients of infiltration equation has not been investigated. Thefinding of such an investigation could be applied in surface irrigation design toimprove furrow length and water application efficiency in light-textured soils. Theobjectives of this study were to investigate: (1) the effects of different concentrationsof bentonite in water (0, 2, 4, and 6 g L71) on coefficients of the Kostiakovinfiltration equation in a loamy sand soil in a soil column in the laboratory; and (2)the effects of a modified infiltration equation on the design of furrow irrigation.
Material and methods
In this study, a loamy sand soil was used. The physical properties of the soil areshown in Table 1. Sodium bentonite was used and the chemical properties ofbentonite are presented in Table 2. The effect of bentonite on infiltration wasmeasured in soil columns. The column was made of a polyvinyl chloride (PVC) tubeof 85 mm i.d. and 470 mm height. A gravel filter with a thickness of 75 mm was
R. Talebnezhad and A.R. Sepaskhah1410
placed in the bottom of the soil column. The bottom ends of these cylinders wereclosed by a layer of foam and equipped with a drain tube connected to the gravellayer (Figure 1). These columns were filled with soil to a height of 300 mm. Toprepare the soil columns, air-dried soil samples were pass