Transcript
Page 1: Effect of soil texture and CaCO3 content on water infiltration in crusted soil as related to water salinity

Irrig Sci (1985) 6:281-294 Irrigation

: clence © Springer-Verlag 1985

Effect of Soil Texture and CaCO3 Content on Water Infiltration in Crusted Soil as Related to Water Salinity *

M. Ben-Hur, I. Shainberg, D. Bakker, and R. Keren

Division of Soil Physical Chemistry, ARO, Bet Dagan, Israel

Received July 29, 1984

Summary. The effect of soil texture and CaCO~ content on water infiltration rate in crusted soil was studied with the use of a rain simulator. Two types of soils with low exchangeable sodium percentage (ESP < 3.0%) were studied: (i) calcareous soils (5.1-16.3% CaCO3) with a high silt-to-clay ratio (0.82-1.47) from a region with < 400 mm winter rain; and (ii) non-calcareous soils with a low silt-to-clay ratio (0.13-0.35) from a region with > 400 mm winter rain. Soil samples with clay percentages between 3 and 60 were collected in each region. Distilled water (simulating rainfall) and saline water (simulating irrigation water) were sprinkled on the soil. The soils were exposed to "rain" until steady state infiltration and corresponding crust formation were obtained. For both types of soils and for both types of applied water, soils with ~ 20% clay were found to be the most sensitive to crust formation and have the lowest infiltration rate. With increasing percentage of clay, the soil structure was more stable and the formation of crust was diminished. In soils with lower clay content (< 20%), there was a limited amount of clay to disperse and, as a result, undeveloped crust was formed. Silt and CaCO3 had no effect on the final infiltration rate for either type of applied water, whereas with saline water, increasing the silt content increased the rate of crust formation.

The formation of surface crusts by rain has been investigated in many studies, due to their important effect on many soil phenomena, e.g., water infiltration and seedling emergence.

Studying the structure of the crust microscopically, McIntyre (1958) found the crust to consist of two parts: an upper skin seal, 0.1 mm thick, attributed to compaction by raindrop impact; and a deeper, "washed-in" region, 2 mm thick, of decreased porosity, attributed to fine-particle movement and accumulation. Con-

* Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 1130-E, 1984 series

Page 2: Effect of soil texture and CaCO3 content on water infiltration in crusted soil as related to water salinity

282 M. Ben-Hur et al.

versely, Gal et al. (1984) found that on soils with ESP < 1.0, the crusts consisted of the compacted skin seal layer only; whereas, on soils with ESP > 1.0 exposed to rain, the crust consisted of naked sand and silt grains over a dense "washed-in" layer (Chen et al. 1980; Gal et al. 1984).

Based on the effect of rain drops' impact and the chemical properties of the soil water system, it was postulated that crust formation is due to two mechanisms (McIntyre 1958; Agassi et al. 1981; Kazman et al. 1983).

1. A breakdown of the soil aggregates caused by the impact action of the raindrops over the soil surface. The destruction of the aggregates reduced the average size of the pores of the surface layer. Also, raindrops' impact caused compaction of the uppermost layer of the soil. These factors produced the thin skin seal (Epstein and Grant 1967; Farres 1978; Morin and Benyamini 1977).

2. A chemical dispersion of the soil aggregates and the soil clays which can then migrate into the soil with the infiltrating water and clog the pores immediately beneath the surface ("washed-in" layer) (McIntyre 1958; Agassi et al. 1981; Gal et al. 1984).

The infiltration rate (IR) is affected by both the soil sodicity (Kazman et al. 1983) and by electrolyte concentration of the perculating water (Agassi et al. 1981). Increasing the soil ESP in the range between 1.0 and 5.0 resulted in a sharp decrease in the final IR when exposed to distilled water (simulating rainwater) rain. The intensity of chemical dispersion and the movement of the clay to the "washed- in" layer decreased as the electrolyte concentration of the applied water increased. By increasing the electrolyte concentration in the applied water, crust formation was diminished and the final IR of the crusted soils was maintained at higher values. Thus, it is possible that in soils containing minerals that readily release soluble electrolytes, such as calcareous soils, the formation of crust will diminish when the soils are subjected to distilled water "rain".

The tendency of soils to form a crust depends also on the stability of their structure. Stability of the soil's aggregates increases with increase in clay content. Thus, the stability of the aggregates against the impact action of the rain drops should also increase with an increase in clay content. Kemper and Koch (1966) found a good correlation between clay content (in the range between 5 and 90%) and wet sieve aggregate stability. Increasing the clay content resulted in a hyper- bolic increase of the wet s ieve aggregate stability. This was attributed to clay particles acting as cementing material holding the particles together in the aggregates. Thus, as a result of this mechanism, formation of crust should be slowed down by increase in clay content. Conversely, Moldenhauer and Kemper (1969), studying the effect of clay content and soil aggregate stability on the infiltration rates of four types of soils that were exposed to rain, found that the final infiltration rates of the crusted soils decreased as the percentage of clay in the soil increased.

Organic matter and silt content in the soil also have an effect on the aggregate stability (Cary and Evans 1974; Wischmeier and Mannering 1969). They found that soils with low organic matter and high silt content usually have low aggregate stabilities. Similar results were obtained by Moldenhauer and Long (1964), who investigated the effect of the soil texture on the energy required to initiate runoff (an indication of crust rate formation); there was good agreement between the silt content and the rate of crust formation.

Page 3: Effect of soil texture and CaCO3 content on water infiltration in crusted soil as related to water salinity

Effect of Soil Texture and CaCO3 Content on Water Infiltration in Crusted Soil 283

The objective of the current study was to determine the effect of soil texture and CaCO3 content on crust formation and its properties by the use of a rain simulator.

Materials and Methods

Two types of soils with various clay contents were used in this study: 1. Calcareous soils from the northern Negev and the Pleshet Plain in Israel.

The average annual precipitation in these regions is 200-400 mm. These soils contain 5-16 % lime and have a high silt/clay ratio (0.82-1.47) (Table 1).

2. Non-calcareous soils that were sampled from the Coastal Plain and from the Golan Heights in Israel. The average annual precipitation in these regions is 600 and 1,000 mm, respectively. The silt/clay content in these soils is low (0.13-0.35). Some chemical and physical properties of these soils are presented in Table 1. The low silt content of the non-calcareous soils suggests that these soils might be more stable to crust formation.

In order to maintain the same ESP ( ~ 2.0), in all the soil samples, 1 m 2 plots of soil were leached in the field, with 120 liters of 0.2 M chloride solution with a Sodium Adsorption Ratio (SAR) of 2.0. Leaching was performed by three applica- tions of 401 portions of the 0.2 M solutions, with a one-week interval between applications. Finally, the plots were leached with 40 1 of 0.01 M solution of the same SAIl, air-dried (in the field), and soil samples from the 0.10 m layer were taken to the laboratory for further studies. This technique of leaching the soils in the field was used to reduce soil structure breakdown, which usually takes place when soil samples are leached in the laboratory with the desired solutions. The soil samples were screened to 0-4 m m aggregate size and the soil texture, CaCO3 content and final ESP were determined by standard methods (US Salinity Lab. Staff 1954). Soil samples were placed in 30x50 cm perforated trays, 2.0 cm deep, over a layer of coarse sand (four replicates). The trays were placed in a rainfall simulator (Morin et al. 1967), at a slope of 5%, and saturated with tap water (0.85 dSm -1) from underneath. Thereafter, the soils were subjected to rainfall of distilled water (DW) with electrical conductivity (EC) of =0.01 dSm -1 (simulating rainwater) and of saline water (SW) with SAR 2 and EC--- 5.0 dSm -~ (simulating saline irrigation water). Typical mechanical parameters of the applied rain were: rainfall intensity of 31.6 mmh -1, rainwater median diameter, 1.9 mm; median drop velocity, 6.02 ms-l; and total kinetic energy, 570 J m -2 h-L The volumes of runoff and of water infiltration were recorded. The soil loss was measured by drying the runoff water and weighing the eroded material.

Results and Discussion

The IR of the two types of soils as a function of the cumulative rainfall when subjected to DW rain are presented in Fig. l. It is evident that the IR of all the soils dropped sharply as the depth of cumulative rain increased until final or steady state IR values were obtained. The decrease in the IR is due to the formation of crust on

Page 4: Effect of soil texture and CaCO3 content on water infiltration in crusted soil as related to water salinity

284 M. Ben-Hut et al.

o

~s

o

0

o

o

o

~ 0 ~ 0 ~

. ~ . = . ~ 0

o o o ~

0 0 0 . ~ 0 - 5 . 5 - 5 o . a

~ 0

0 0 0 0 0 0

o

0 Z

0 0 0 0 0 0

) ) ) ) ) )

0 o s o =

"~o o ".~ 4= o

o ~ o ~

0

Page 5: Effect of soil texture and CaCO3 content on water infiltration in crusted soil as related to water salinity

Effect of Soil Texture and CaCO3 Content on Water Infiltration in Crusted Soil 285

3 2 k - - I I I I I I I I I I _

"S"kL':~ N \ 2 3 - . ~ . \ - _ - " \ \ ~ . . " ~ ' N NONCALCAREOUS SOILS __

28 _ :\ \ [,w RA,N _

2 4 -- : • "~ • -,~ ~ " . \ ~ SANDY SOIL - - I ~ _

: : \ • - . . . . SANDY SOIL _ 2 0 -- \ / \ \ \ . . . . LOAMY S A N D _

1 6 - - ":\ \ \ \ \ " ~ . . . . . SANDY L O A M - -

", ', \ ' ~ " \ ~ , - - - - SANDY CLAY LOAM - - - - \ : . \ . . ~ . ' ~ - - ' - - CLAY SOIL - -

S - \.. \ . ~ ~ ' ~ . 65.2

~ ' . . " ~ ...~. " ~ - - " ~ . . . . . . . 7.8_ W 4 - - ""~'- " ' ' "~ "~"~. . -~- . . . -T ' . -~ - - ~ 32.0

. . . . . . 12/3

n,- 0 I I I I I I I I I 1 1 9 2

3 2 ~ Z \ " ' ~ = CALCAREOUS SOILS -

0 ~ " ~ ~ " ~ D W R A I N -

- ; N .

2 4 SANDY SOIL -

\ \ ----LOAMY S' O ? -= 2 0 _ ... -\ \ . . . . SANDY LO M

16_-- ", \

- \ . "" ~ - : " ' ~ - ,oo- 4 ~ * ~ " ' " - - - . - ~ ' ~ . . . . . . . 3 9 . 9 - -

22.4 - -

0 J I I I i I I I I I o 5 I0 15 20 25 30 35 40 4.5 .50

CUMULATIVE RAINFALL (ram)

Fig. I. The infdtradon rates of two types of soils as a function of the cumulative rainfall when subjected to distilled water (DW) rain

the soil surface (Morin and Benyamini 1977). The final IR values and the rates of decrease of the IR's with the cumulative rain were different for the various soils. In the non-calcareous sandy soil (2.3% clay) there was no measurable drop in IR and therefore the rate of rain application was determining the measured IR. However, the final IR recorded - 30.6 mm h -1 - had a high value compared with other soils which suggest that only a weak crust was formed due to the low percentage of clay in this soil. There was not enough clay in the soil to clog the soil pores or to form a crust.

With increase in clay concentration in the range up to 19.2% clay, the rate o f the drop in IR increased and the final IR decreased. As the clay percentage increased above 19.2%, the rate at which the IR dropped was lower and the final IR was maintained at higher values compared with the other soils. It is evident that the clay fraction of the soil has two opposing effects: (a) The clay is the substrate for crust formation; thus, in soils with a low clay content, the rate o f crust formation

Page 6: Effect of soil texture and CaCO3 content on water infiltration in crusted soil as related to water salinity

286 M. Ben-Hur et al.

increased and the steady state hydraulic conductivity of the crust decreased as the clay content increased. (b) The clay acts as a cementing material, stabilizing the soil aggregates against the beating action of the raindrops; thus, increasing the clay content of the soil aggregate prevents their disintegration and crust formation.

Similar results were obtained with the calcareous soils exposed to DW rain (Fig. 1). The rate of the drop in IR with the depth of rain increased, and the final IR decreased, with an increase in clay percentage up to the loamy soil with 22.4% clay. As the clay percentage increased to 39.9%, the final IR was maintained at a greater depth of rain and its value increased.

The IR's of the calcareous and non-calcareous soils, exposed to SW rain, are presented in Fig. 2. It is evident that when saline water was used instead of distilled water the final IR is maintained at higher values. As indicated in the Introduction, with SW the chemical dispersion of the soil clays is not as great. Thus, it is primarily the mechanical impact of the rain drops which forms the crust. Consequently, the rate of crust formation is slower, the structure of the crust consists of only a thin skin layer on the surface of the soil, and the hydraulic properties of this layer are such that the final IR is higher than the IR of the crust formed on soils "rained on" with DW.

The same trend observed in DW, namely that soils with 20% clay are the most susceptible to crust formation, is also obtained with SW.

The final IR of the soils may serve as a good index to characterize the structure and the strength of the soil's crust. Thus, in order to study the effect of soil texture and CaCO~ content on crust properties, the final IR's of the various soils, as shown in Figs. 1 and 2 as a function of the clay percentage are presented in Fig. 3 and in Table 2 with their standard deviation (SD). The final IR's of the same soil with ESP > 4.6% (Kazman et al. 1983) are also presented in Fig. 3. It should be remembered that in the present study the ESP of the soils was _-< 2.5 (Table 1).

The following characteristics are noted: 1. At any given clay content in each soil type, the final IR's obtained with DW

rain were lower than the final IR's obtained with SW rain. The final IR's of the soils exposed to SW were 4.0-6.0 m m / h higher than the final IR's obtained with DW. Similar results were obtained and discussed by Agassi et al. (1981).

2. The final IR's of the calcareous and non-calcareous soils at any given clay content were similar for both the DW and SW. The high concentrations of CaCO3 in the calcareous soils (5-16%) did not have any effect on the final IR. Similar results were obtained by Kazman et al. (1983) with sandy loam and silty loam soils.

However , in studies on the effect of CaCO3 on the hydraulic conductivity (HC) of sodic soils, it was found that the presence of CaCO3 maintained the structure of the soils and prevented the HC decline of sodic soils (Felhendler et al. 1974; Shainberg et al. 1981; Shainberg and Gal 1982). It was proposed (Shainberg et al. 1981) that when calcareous soils were leached with DW, the CaCO3 released electrolytes at a rate sufficient to maintain the concentration of the soil solution above the floccula- tion value of the soil clay; thus, clay dispersion and pore clogging were prevented. It is evident that, at the soil surface, the rate of CaCO3 dissolution was too low and the soil solution concentration was determined solely by the concentration of the applied water; thus, aggregate dispersion took place at the soil surface, even in calcareous soils.

Page 7: Effect of soil texture and CaCO3 content on water infiltration in crusted soil as related to water salinity

Effect o f Soil Texture and CaCO~ Conten t on Water Infil tration in Crusted Soil 287

A

E E

f i g

Z _O

h l a . _z

52

28

24

20

1 6

12

8

4

O 32

28

24

2O

16

12

8

m I I I I I I I I I I _

\ .~. ~.3

"\ \ \ ( \ ~ . NONCALCAREOUS SOILS -

- v \ , . ' , \ - ' ~ , s w R A . .

\ \ '\:\\ \ " . . . " ) ',,?-.

- . . . ~ \ \

- - SANDY SOIL \ \ . " - . \ ~ - - . . . . ~ - - _ _ .... SA,oy SO,. ~ ~ . : : .

. . .. ~ ~ . . . . 32708 - -

L O A M Y S A N D ~ ~ . . . . . . . . . . [ 2 . o - -

- - - . . . . S A N D Y L O A M " ' " ~ . . . . . . : _ . 1 9 2 . - -

- - - S A N D Y C L A Y L O A M

- - - ' ~ C L A Y S O I L

I I / I I I l 1 I ,

CALCAREOUS SOILS .~- SW R A I N

-

- \ \ ~ ' \ \ - ~ ~ \

\ \ _ . ~ \ - : ~ ~ ~,~.,.-

~.' .,,, " \ ~ - . .

I - ~ SANOY so , , " ~ - ~ : ' : \ " - " . . . . . . ,o.o_

I - - ' - LOAMY SAND " ~ ' ~ , ~ - , - - - . . . . ~:o'- I . - . . . . S A N D Y L O A M . . . . . . . . . . . . 2 2 . 4 _

4 [ ' ~ . . . . . L O A M Y SOIL

I , - - - - C L A Y L O A M

O / I I I I I I I I I I 0 5 I0 15 20 25 30 35 40 45 50

CUMULATIVE RAINFALL (mm )

Fig. 2. The infiltration rates o f two types o f soils as a function o f the cumulat ive rainfall when subjected to saline water (SW) rain

Fig. 3. The final infil tration rates of the various soils, as a funct ion o f the clay percentage

A

E 34- E

(/) 30 LIJ

n,"

Z 0 12

n." h ~ h

z - - 4

_z o h 0

: : NONCALCAREOUS SOILS

A . - - = CALCAREOUS SOILS

~:;-.-.-o SOIL WITH MODERATE ESP _

" ~ ' ~ ' ~ ~ Z . . . . . . . . . . .

I0 20 30 40 50 60 70

CLAY PERCENTAGE

Page 8: Effect of soil texture and CaCO3 content on water infiltration in crusted soil as related to water salinity

288 M. Ben-Hur et al.

Table 2. The final IR of calcareous and non-calcareous soils as a function of the clay content

Soil texture Clay Type of water content % Distilled water Saline water

mean SD a mean SD °

mm/h mm/h

Calcareous soils Sandy soil 3.8 7.6 0.56 12.4 1.5 Loamy sand 10.0 4.4 0.3 11.0 0.98 Sandy loam 15.0 3.0 0.4 7.8 0.8 Loamy soil 22.4 2.0 0.15 7.0 0.62 Clay loam 39.9 3.6 0.2 8.0 0.7

Non-calcareous soils Sandy soil 2.3 30.6 3.8 30.6 3.2 Sandy soil 7.8 4.4 0.32 9.8 0.82 Loamy soil 15.0 2.6 0.2 7.6 0.6 Sandy loam 19.2 2.0 0.18 6.0 0.54 Sandy clay loam 32.0 3.2 0.25 9.0 0.9 Clay soil 65.2 7.0 0.54 13.0 1.1

" SD = standard deviation

3. The silt/clay ratio in the calcareous soil was 0.82-1.47, compared with 0.13-0.35 for the non-calcareous soils (Table 1). Since the final IR in both soil groups was similar at a given clay content (Fig. 3), it is evident that the soil's silt content did not have an effect on the final IR or on the properties o f the crust. These results do not agree with those of other studies (Cary and Evans 1974), which suggest that the soils with high silt content have low aggregate stability and are susceptible to crust formation. Moreover, the high surface runoff in arid regions and the susceptibility of these soils to crust formation was explained by the high content o f silt in the soil texture (Hillel 1967).

4. Loamy soils with 20% clay were found to be the most susceptible to crust formation and to have the lowest final IR with both water qualities (Fig. 3 and Table 2). In the soils with lower clay content (< 20%) there was not enough clay to disperse and clog the pores at the soil surface. Thus, as the clay percentage increases in this range, the IR decreases. The effect of clay content on crust formation at this range was similar with distilled and saline water.

Crusts formed also in structureless sandy soils (the soils with 3.8 and 7.8% clay) when they were subjected to either D W or SW. In those soils, the initial IR was

100 m m / h (Morin et al. 1981) and the final IR, with DW rain, dropped to 7.6 and 4.4 m m / h for the soils with 3.8 and 7.8% clay, respectively, and with SW rain to

12.4 and 9.8 m m / h , respectively. This indicates that compaction o f the soil surface by the impact of the rain drops plays a dominant role in crust formation. In structureless soils, destruction o f aggregates and the resultant decrease in the average size of particles and the pores in the crust is not possible. The compaction

Page 9: Effect of soil texture and CaCO3 content on water infiltration in crusted soil as related to water salinity

Effect of Soil Texture and CaCQ Content on Water Infiltration in Crusted Soil 289

mechanism is complemented by clay dispersion and clay accumulation in the "washed-in" layer when the sandy soils are subjected to DW rain.

Increase of the final IR's with increasing clay content in the range above 20% clay for both types of soil and both kinds of applied water is apparently due to the cementing action of clay stabilizing the soil aggregates against the impact energy of the raindrops.

5. The final IR's of soils with moderate ESP ( ~ 4.6%) were found to be lower than the final IR's of soils with low ESP (=< 2.5%) at any given clay content. In the soils with moderate ESP, the stabilizing effect of the clay on the soil aggregates was not as pronounced (Fig. 3). It seems that increasing the ESP of the soils weakens the binding forces within the aggregates and increases the tendency of clay to disperse. Consequently, the soils are more susceptible to crust formation and the resultant drop in the IR.

The effect of clay content in crust formation is also shown in Fig. 4 a and 4 b. The soils in the photographs were subjected to 50 mm DW rainfall and subse- quently dried. The non-calcareous sandy soil (2.3% clay) formed a weak crust and small craters or pits were formed on the soil surface by the impact of raindrops. Conversely, the surface of the soils with a clay content up to ~ 20% has a smooth crust and the aggregates are completely destroyed. The white spots on the surface consist of naked sand grains from which the clay skins were removed by clay dispersion. On the soils with high clay content (> 20%), the soil surfaces are covered with aggregates that did not break down in spite of crust formation. The size and amount of the aggregates increased with the increase in clay content. Also, the cracks in the soil surface grew in depth and width with the increase in clay content. These cracks may increase the permeability of the crust in successive storms in soils with high clay content, as demonstrated by Kemper and Noonan (1970). Similar findings are observed on the calcareous soils (Fig. 4 b).

The soils texture also affects the rate of crust formation (Figs. 1 and 2). The rate of crust formation was calculated in this study as a percent of runoff from rainfall at storm depth, where the final IR was obtained.

The percent of runoff in the two types of soils as a function of clay content and water qualities is shown in Fig. 5. It is evident that the percent of runoff (the rate of crust formation) increases with a rise in clay content in the low clay content range (< 20%). As the clay content increased above 20%, the rate of crust formation decreased. The maximal percent of runoff was obtained in the loamy soils. In the low clay content range (< 20%), the decrease in the rate of crust formation with decrease in clay content was apparently due to insufficient clay in the soil matrix for crust formation. Conversely, in the high clay content range (> 20%), the rate of crust formation diminished with increase in clay content, because the clay stabilized the soil aggregates. It should also be noted that when rained with DW, the rate of crust formation was similar in the calcareous and non-calcareous soils. On the other hand, the rates of crust formation were found to depend on the CaCO3 and silt content of the soils when rained with SW. The rates of crust formation in the calcareous soils were faster than in the non-calcareous soils. These differences in the rate of crust formation when the soils were subjected to SW rain were probably caused by the higher silt content of calcareous soils (Table 1), which weakens the aggregate stability (Cary and Evans 1974). When the soils are rained with DW,

Page 10: Effect of soil texture and CaCO3 content on water infiltration in crusted soil as related to water salinity

290 M. Ben-Hur et al.

a NONCALCAREOUS SOILS

SANDY SOIL SANDY LOAM

( 2.3 % CLAY ) ( 19.2 % CLAY )

SANDY SOIL

( 7.8 % CLAY )

SANDY CLAY L O A M

( 32 % CLAY )

LOAMY SAND C L A Y SOIL

( 12 % CLAY ) ( 65.2 % CLAY )

crust formation is due to chemical and physical dispersion. The high intensity of these mechanisms masked the differences in aggregate stabilities between cal- careous and non-calcareous soils. Conversely, when the soils were rained with SW, crust formation was due mainly to the physical mechanism with low dispersion energy. When the physical mechanism predominated, the effect of silt in weakening the soil structure became evident and the rate of crust formation in the silty soils was higher than in the non-calcareous soils.

Page 11: Effect of soil texture and CaCO3 content on water infiltration in crusted soil as related to water salinity

Effect of Soil Texture and CaCO3 Content on Water Infiltration in Crusted Soil 291

b CALCAREOUS SOILS

SANDY SOIL LOAMY SOIL

( 3.8 % CLAY ) ( 22.4 % CLAY )

LOAMY SAND CLAY LOAM

( 10% CLAY ) ( 39.9 % CLAY )

SANDY LOAM

( 15 % CLAY )

Fig. 4a and b. Various crusted soil surfaces after drying (a non- calcareous soils; b calcareous soils)

The dispersed soil particles at the soil surface can be transported by the runoff water (washed erosion) or by the splash (splash erosion). Under field conditions, splash material is subjected to displacement and transport downslope. With labora- tory simulators, splash material is frequently not returned, and hence does not become a component of the runoff water. Measuring the concentration of eroded material runoff water as a function of the cumulative rainfall, Epstein and Grant (1967) found that in the beginning of a rainstorm the concentration of eroded

Page 12: Effect of soil texture and CaCO3 content on water infiltration in crusted soil as related to water salinity

292 M. B e n - H u r et al.

70

60 b... b_ 0 Z 5O :::> n.,"

4 o F..- z

b J L ) 30 n," ILl 13_

2O

I0

i I i [ ~ I ] I i I J I ~ I

/ SW RAIN ~

_ / P - ' - - - - 3 \ 4 -/'¢/ -

= = NONCALCAREOUS SOILS

_ ~ - ~ , CALCAREOUS SOILS

..... I I I I i I I I I I i I I I 0 I0 20 30 40 50 60 70

C L A Y P E R C E N T A G E

Fig. 5. P e r c e n t a g e o f r u n o f f ( ra te o f c rus t f o r m a t i o n ) o f v a r i o u s soils, as a f u n c t i o n o f t he c lay p e r c e n t a g e

i I I i I I I i 1 ' I i I i

_~ ,6 ~ Dw RA,N

~" K ' \ v

Z o O I I t I i i i I i I F I i

!

t 6 - . A . SW RAIN

12 ~" : ~

¢-n

- = = NONCALCAREOUS SOILS -

w 4 A---A CALCAREOUS SOILS

0 i I [ I I I I I i I I I I 0 I0 20 30 4 0 50 6 0 70

C L A Y P E R C E N T A G E

Fig . 6. E r o d e d m a t e r i a l c o n c e n t r a t i o n o f v a r i o u s soils as a f u n c t i o n o f the c lay p e r c e n t a g e

Page 13: Effect of soil texture and CaCO3 content on water infiltration in crusted soil as related to water salinity

Effect of Soil Texture and CaCO3 Content on Water Infiltration in Crusted Soil 293

material is high; subsequently, the concentration drops sharply, until a steady state concentration is obtained.

The steady state concentration of eroded material in runoff as a function of the clay content is presented in Fig. 6. When DW was used, this concentration was found to be dependent on clay content (at the range of 7.8-65.2%) showing a maximum value at soils containing 20% clay (loam soil), and then decreased at higher clay content. The high runoff in the loamy soils also produced a high concentration of eroded particles in the runoff water. When the soils were exposed to SW rain, the concentration of eroded material in the runoff was less dependent on the clay content in the soil, ranging between 8 and 15 g/1 (whereas in the DW rain, the concentration of eroded material ranged between 3 and 16 g/l). The big difference in eroded material concentration between the DW and SW rain is between the sandy and clay soils: the concentration of clay in the runoff of SW is higher (8-15 g/l) than that of the DW (4 g/l). At low and high clay content, the IR is relatively high, even in DW rain (Fig. 1). Thus, it is possible that part of the clay which dispersed from the surface migrated into the soil with the percolating water and only a small part was eroded with the runoff water. However, when the soils are exposed to SW, chemical dispersion and clay migration into the soil do not occur. Therefore, the stable soil aggregates which cannot migrate down into the soil profile can move with the runoff water. In the loamy soil, exposed to DW rain, the IR is lower than that of the SW treatments (Fig. 3). Thus, the downward movement of the suspended particles is limited and the concentration of eroded material is similar to that in SW.

Conclusions

The clay content of a soil has a significant effect on the rate of crust formation and its properties. For calcareous and non-calcareous soils with low ESP (< 2.5%) that were subjected to DW and SW "rain" soils with ~20% clay were found to be the most sensitive to crust formation. With increasing percentage of clay, the soil structure is more stable and the formation of clay is diminished; in soils with lower clay content, there is a limited amount of clay to disperse and to form a crust.

Silt and CaCO3 had no effect on crust formation and its properties as determined by the final infiltration rate. On the other hand, the rates of crust formation in the calcareous soils were higher than in the non-calcareous soils when rained with SW. When the soils were rained with SW, crust formation was due mainly to the physical mechanism with low dispersion energy. Thus, the effect of silt in weakening the soil structure becomes evident and the rate of crust formation in the silty soils is higher than in the loamy soil.

Although the C a C Q in the soil has an effect on the HC, it appears to have a very limited and negligible effect on formation of crust properties. Dissolution of CaCO~ may be too slow to affect soil dispersion at the soil surface which may account for the soil surface being more sensitive to DW rain than is the soil profile.

Page 14: Effect of soil texture and CaCO3 content on water infiltration in crusted soil as related to water salinity

294 M. Ben-Hur et al.

References

Agassi M, Shainberg I, Morin J (1981) Effect of electrolyte concentration and soil sodicity on the infiltration rate and crust formation. Soil Sci Soc Am J 45:848

Cary J, Evans DD (eds), (1974) Soil crusts. Tech Bull No 214. University of Arizona, Tucson Chen Y, Tarchitzky J, Morin J, Banin A (1980) Scanning electron microscope observations on

soil structure and their formation. Soil Sci 130:49 Epstein E, Grant WJ (1967) Soil losses and crust formation as related to some physical

properties. Soil Sci Soc Am Proc 31:547 Farres P (1978) The role of time and aggregate size in the crusting process. Earth Surface

Processes 3: 243 Felhendler R, Shainberg I, Frenkel H (1974) Dispersion and hydraulic conductivity of soils in

mixed solution. Trans 10th Int Congr Soil Sci (Moscow) 1:103 Gal M, Arcan L, Shainberg I, Keren R (1984) The effect of exchangeable Na and phospho-

gypsum on the structure of soil crust - SEM observations. Soil Sci Soc Am J 48:872 Hillel D (1967) Runoff inducement in arid lands. Final technical report submitted to the U.S.

Department of Agriculture. A 10-SWC-36, The Hebrew University of Jerusalem, Faculty of Agriculture, and The Volcani Institute of Agricultural Research, Rehovot, Israel, pp 142

Kazman Z, Shainberg I, Gal M (1983) Effect of low level of exchangeable Na (and phosphogypsum) on the infiltration rate of various soils. Soil Sci 135:184

Kemper WD, Koch EJ (1966) Aggregate stability of soils from Western United States and Canada. USDA Tech Bull 1355

Kemper WD, Noonan L (1970) Runoff as affected by salt treatments and soil texture. Soil Sci Soc Am Proc 34:126

McIntyre DS (1958) Permeability measurements of soil crust formed by rain drop impact. Soil Sci 85:185

Moldenhauer WC, Kemper WD (1969) Interdependence of water drop energy and clod size on infiltration and clod stability. Soil Sci Soc Am Proc 33:297

Moldenhauer WC, Long DC (1964) Influence of rainfall energy on soil loss and infiltration rates. I. Effect over range of texture. Soil Sci Soc Am Proc 28:812

Morin J, Goldberg S, Seginer I (1967) A rainfall simulator with a rotating disc. Trans Am Soc Agric Engrs 10:74

Morin J, Benyamini Y (1977) Rainfall infiltration into bare soils. Water Resources Res 14:813

Morin J, Benyamini Y, Michaeli A (1981) The effect of raindrop impact on the dynamics of soil surface crusting and water movement in the profile. J Hydrol 52:321

Shainberg I, Gal M (1982) The effect of lime on the response of soils to sodic conditions. J Soil Sci 33:489

Shainberg I, Rhoades JD, Suarez DL, Prather RJ (1981) Effect of mineral weathering on clay dispersion and hydraulic conductivity of sodic soils. Soil Sci Soc Am J 45:287

Wischmeier WI-I, Mannering JV (1969) Relation of soil properties to its erodibility. Soil Sci Soc Am Proc 33:131


Top Related