AbstractâBy spraying applying Brilliant Blue as tracer, the improvements of a 1 year and a 5 year rice cultivation practice were quantitatively described in fields ...
Influence of Rice-cultivation on Preferential Flow of Sodic Alkaline Soil in Northeast of China Luo Jinming; Wang Yongjie
Deng Wei
Department of physical and geography, Qqhru, Qiqiha’er, P R C China
Institute of Mountain hazards and Environment, CAS Chengdu, P R C China
Ye Yajie
Zhang Xiaoping; Wen Guang
Department of chemical and engineer, Qqhru, Qiqiha’er, P R C China
Northeast Institution of Geography and Agr-ecology, CAS Changchun, P R C China
Abstract—By spraying applying Brilliant Blue as tracer, the improvements of a 1 year and a 5 year rice cultivation practice were quantitatively described in fields in comparison with a control in a sodic alkaline soil in Da’an county, Jilin Province of China. Brilliant Blue FCF solution with a concentration of 0.088 mol L-1 was applied to the treated soils. Dye image was photographed layer by layer in the field after 24 h of spraying.. Results show that rice cultivation can improve alkaline soil structure and crack blocky structure to provide preferential flow. preferential pathway exists above 30 cm in the plot of 5-yearcultivation rice soil and 20 cm in the plot of 1-year-culitivation rice soil in contrast with control which virtually no obvious preferential in exists. Keywords-rice cultivation; preferential flow; alkaline soil; dye tracer
INTRODUCTION Water loss and nutrient leach in rice fields have been a great concern for researchers and growers. The presence of preferential flowpath in soils facilities the solution transports and the preferential flow is the main way that water moves downward (Helling et al., 1991; Allaine-lenry et al., 2000a, 2000b; Wahl et al., 2004). The formation of preferential pathway in soils is affected by various factors, such as soil structure, tillage, worm cavity and root channeling rupture (Beven et al., 1982; Helling et al., 1991). There are several types of preferential flow, such as bypass flow, finger flow, channeling flow and macropores flow (Beven et al., 1982; Helling et al., 1991; Öhrström et al., 2002, 2004). In sodic alkaline soils, however, mainly because the blocky structure in the surface layer limits earthworm cavity and plant root penetration, and heavy texture prevent water infiltration (Wang et al., 1993), downward water movement along profile is weak or virtually non-exist (Yu,1982; Wang et al.,1993; Song et al., 2003). With rice cultivation, preferential flow may develop in alkaline soils and become main pathway to facilitate water down movement. Growing rice will provide wet and dry alternation to the soil as seasonal changes require flood and drain to the rice field alternatively, and alkaline soils swell and shrink accordingly. This process may crack the blocky structure and thus, allow preferential pathway to develop. Salt leaching down to sub-layer may also occur, when field is
flooded. This process will make the blocky structure of the soil weaken and beneficial for the formation of preferential flow. Rice cultivation is effective to create preferential flow in alkaline soils (Wang et al., 1993), and the presence of preferential pathway in rice field may lead to significant loss of water and nutrients (Allaine-lenry et al., 2000a, 2000b; Öhrström et al., 2002, 2004; Pot et al., 2005). The biggest area of sodic saline soil in China lies on semiarid Songnen Plain in Northeast of China (Liu et al., 2001). Da’an county is one of the areas in Songnen Plain where its agricultural production is most seriously affected by the presence of saline soils (Zhang et al., 2001). Adapting rice cultivation increases crop production and farmer’s income. Research and agricultural practice have been active in this region since 1999 (Liu et al., 2001; Zhang et al., 2001; Song et al., 2003). Over years, with the development of preferential flow in the sodic soils in Da’an, the losses of water and nutrients may speed up and reach a significant level. Determination of preferential flow formation of the sodic alkaline soil over time under local rice growing conditions will improve our understanding of the soil development under this agricultural practice. The background obtained would be useful in production operations such as optimizing agricultural water supply, nutrient leach control, determining fertilizer supplements and controlling secondary salinization. Therefore, the aim of this study was to discuss preferential flow development of the sodic alkaline soil in Da’an under rice cultivation. MATERIAL AND METHODS Study site The experimental site is located in Da’an County, Jilin Province in Northeast China (45°37′42″N; 124°04′21″E) . The soil belongs to sodic alkaline soil (Genetic Soil Classification System of China, Li et al. 1983). The irrigation system was built in 1999 to deliver water from Nenjiang river to the rice fields. Nowadays, the total area of paddy soil in the study area has exceeded 1000 ha. Two rice fields with an area of 20×30 m2 each were selected to conduct this experiment; one has been growing rice for 1 year and another for 5 years. Control was kept in natural condition without cultivation for many
Under the auspices of the great innovation project of Chinese Academy of Sciences (No. KZCX1-SW-19-02) and Chinese National Natural Scientific funds (No. 40871259)
years. The three fields are adjacent to each other, so that the original soil properties were supposed to be similar (Fig. 1).
Fig.1 Infield design of soil core sampling and dye tracer.
Soil Analysis The soil texture was determined using pipet method (Gee et al., 1982). The soluble cation concentration (Na+, K+, Ca2+, Mg2+), cation exchange capacity (CEC) and exchangeable sodium were measured using the method presented by Kamra (2002). The exchangeable sodium divided by CEC is defined as the exchangeable sodium percentage (ESP). The pH were determined using the electrode method (Rhoades, 1982). In the control treatment, four layers were identified along with the profile of the sodic alkaline soil based on the classification criteria (Zhang et al., 2001). They are: alkalized layer (Aa, 0-10 cm), alkaline layer (AB, 10-28 cm), basic layer (B, 28-100 cm) (Fig.2).
profile can provide useful information for quantify preferential pathway (Öhrström et al., 2004). In each of the three experimental sites, two 50×50 cm2 areas were selected (Fig.1). A volume of soil with a surface area of 40×40 cm2 was dug down to a depth of 40 cm for photographing purpose. The digitized photographs were analyzed according to procedure of Hangen et al (2002) and Öhrström, et al.(2002, 2004).. Breakt hrough experiment The concept of transport volume (θst) presented by White et al. (1984) and Jury et al. (1986) is accepted to quantify preferential flow (Ren et al., 1999, 2001; Li et al., 2000), which means the volume of soil moisture to participate the solute transport. The bromide ion breakthrough experiment was conducted according to Lee et al. (2001) to attain transport volume (θst). The effluent concentration (Cout(t)) can be expressed as function of time (t) as following (Ren et al. 2000): t
Cout(t)/Cin(t)=
∫ g (t )d t
(1)
0
Where g(t) is the transfer function of bromide ion in the breakthrough process. The transport volume (θst) can be expressed as following equation (Ren et al., 2001): θst=q0×T0.5/L (2) Where q0 is the mean infiltration intensity of in the surface of the cores, T0.5 represents the time Cout(t)/Cin(t) reach 50%. RESULTS AND DISCUSSION
Fig. 2. Soil profile structure of three treatments.
Dye tracer technology Among several methods proposed to character preferential flow in soils, such as direct counting in fields (Timmerman et al., 1996; Feyen et al., 1998), computed tomography (Timmerman et al., 1996), dye tracer (Allainelenry et al., 2000a, 2000b) and resin impregnation techniques (Schwartz et al., 2000), the dye tracer technology is generally considered to be efficient (Öhrström, et al., 2002, 2004). The digitized array is used to express the feature of preferential flow (Kamra et al., 1999; Hangen et al., 2004, 2005; Öhrström et al., 2002, 2004), and dye covered area along with soil
Morphological changes in the soil profile under rice cultivation The aquifer of Songnen Plain contains an elevated concentration of sodium ion (Na+) (Chen et al., 1962; Li et al. 1963, 1964), which induces the formation of alkalized layer (Aa) in soils. By growing rice, Na+ concentration in cultivated layer would be decreased due to leaching (Chen et al.,1962). The physical properties of three sites were given in Table 1 and chemical properties of control treatment and 5 years rice cultivation treatment were given in Table 2. After 5 years of continuous rice cultivation, great changes appeared in both physical and chemical properties in cultivated layer, when compared with the control treatment, the bulk density and content of clay above 10 cm has appeared to be decreased. The salinity above 30 cm decreased a lot. Similarly, ESP decreased from 71.95% to 11.08% above 5 cm and 75.03% to 14.86% in 5-10 cm. Surface soil pH declined from above 9.33 to 7.85 in 5 years rice cultivation treatment. Below 30 cm, the level of pH and ESP of control and 5 years rice paddy appeared to be identical. The lowered ESP and pH means the leach of Na+. As indicated in Table 2, the concentration of soluble Na+ decreased from 893.18±416.84 mg L-1 to 216.95±53.99 mg L1 in the 0-5 cm and from 1143.93±263.53 mg L-1to
266.42±19.65 mg L-1 in the 5-10 cm over 5 years rice cultivation. TABLE 1. SOIL PHYSICAL PROPERTIES OF THREE TREATMENT (EACH POINT REPRESENTS A MEAN OF THREE MEASUREMENTS; VALUES FOLLOWED BY DIFFERENT LETTERS (A, B AND/OR C) ARE DIFFERENT (P < 0.05)
Bulk density (g cm-3)
Sand
Particle size distribution (%)
Silt
Clay
Cultivation treatment
Depth (cm)
Control
1-year
5-year
0-10
1.56 (a)
1.56 (a)
1.43 (b)
10-20
1.63
1.58
1.58
20-30
1.55
1.57
1.56
0-10
69.33
70.13
72.55
10-20
70.73
70.50
71.00
20-30
75.59(a)
71.38(c)
74.71(b)
0-10
12.50
12.19
15.41
10-20
13.13
12.53
14.08
20-30
14.38
13.46
14.74
0-10
18.17
17.68
12.64
10-20
16.14
16.97
15.92
20-30
10.03
15.16
10.55
Leach of Na+ would result in Morphological changes in soil profile (Chen et al., 1962; Yu et al., 1982; Wang et al., 1993). Morphological changes in soil profile with different treatment can also been observed in Fig. 2. With the treatment of 1-year cultivation, the Aa horizon was leached and shrinking obviously, the Alkalized layer (Aa) was almost disappear. Greater changes observes in the treatment of 5-year rice cultivation, the Cultivated layer (A) has appeared at the depth of 0-10 cm. And the AB layer was replaced by plowpan layer )
. Distribution of dye Cultivation and management practices influence the development of preferential pathway in soil (Wahl et al., 2004). The rice soil was ploughed annually in the spring, then flooded. Before harvest in the fall, the field is drained. Both of the plough and wet-dry cycle operation affect production of preferential pathways and the influence may be accumulative over years. As indicated above, determining the dye covered area along with soil profile would provide useful information for quantifying the preferential water flow pathway (Öhrström et al., 2004). Different dye distribution patterns along with the soil profile as influenced by the three treatments were discovered (Fig.3). Under the control treatment, only about 510% of the areas in the 0-5 cm surface soil were stained by dye. With increased soil depth, the stained area was fast shrunken. At the depth of 15 cm from the surface, the stained area was close to zero, indicating there was virtually no preferential water movement at this depth and thereafter. After 1-year rice cultivation, however, the dye stained area increased to about 15% at the depth of 10 cm. The stained area was developed downward and researched to the depth of 25 cm. After 5-year of rice cultivation, on the soil surface (2 cm depth), between 30 and 35% of area in the soil profile was stained. The dye invaded into a much greater depth in comparison with that under 1-year rice cultivation treatment. Even at the depth of 30 cm, between 5 to 10% of the area was stained, indicating great development of the preferential pathway in the soil profile by the continuous rice cultivation. Because the development of stain covered area along soil profile is highly descriptive by the mathematical equations for the different years in rice cultivation (P ≤ 0.0001∼0.002),
TABLE 2. INFLUENCE OF 5-YEAR RICE CULTIVATION ON SOIL CHEMICAL PROPERTIES (EACH INDIVIDUAL VALUE PRESENTS A MEAN OF 3 SAMPLES)
Treatment Control 5-y cult. Control 5-y cult. Control 5-y cult. Control 5-y cult. Control 5-y cult. Control 5-y cult.
Depth (cm) 0-5
5-10
10-20
20-30
30-40
40-50
Soluble cation concentration (mg L-1)
ESP (%)
Salinity
pH
(%)
Na+
Ca2+
Mg2+
893 ± 417
0.54 ± 0.07
9.33 ± 0.23
72.0 ± 8.14
0.54 ± 0.07
9.33 ± 0.23
217 ± 54.0
0.13 ± 0.01
7.85 ± 0.17
11.1 ± 1.88
0.13 ± 0.01
7.85 ± 0.17
1144 ± 264
0.4 4± 0.04
9.69 ± 0.26
75.0 ± 7.63
0.44 ± 0.04
9.69 ± 0.26
266 ± 20
0.08 ± 0.01
8.11 ± 0.26
14.9 ± 3.66
0.08 ± 0.01
8.11 ± 0.26
1004 ± 230
0.15 ± 0.03
9.55 ± 0.29
76.5 ± 11.9
0.15 ± 0.03
9.55 ± 0.29
265 ± 42
0.06 ± 0.00
8.32 ± 0.22
19.4 ± 6.02
0.06 ± 0.00
8.32 ± 0.22
523 ±301
0.09 ± 0.03
9.38 ± 0.21
55.2 ± 21.3
0.09 ± 0.03
9.38 ± 0.21
367 ±142
0.04 ± 0.01
8.99 ± 0.24
31.9 ±11.3
0.04 ± 0.01
8.99 ± 0.24
349 ±195
0.05 ± 0.03
9.02 ± 0.22
35.7 ± 18.8
0.05 ± 0.03
9.02 ± 0.22
334 ± 126
16.50 ± 7.56
1.91 ± 0.40
35.9 ± 13.1
0.05 ± 0.02
9.15 ± 0.23
281 ± 158
17.57 ± 12.05
1.37 ± 0.46
31.2 ± 11.0
0.04 ± 0.02
8.99 ± 0.20
265 ± 96
10.67 ± 2.49
1.71 ± 0.45
32.4 ± 9.8
0.03 ± 0.02
9.50 ± 0.18
prediction of the development of preferential pathway as
cultivation over years. The preferential pathway was staiend by
Fig.3 Change in the area covered by dye along soil profile in the control (no rice cultivation), 1-year rice cultivation and 5-year rice cultivation treatments (Each point represents a mean of two measurements).
influenced by rice cultivation in this soil is possible. Overall, as indicated by the dyed pattern, the existence of preferential pathway only occupied a small fraction of the total soil profile. The preferential flow revealed, however, can lead to faster water moving in certain parts of the soil as opposed to uniform flow (Allaine-lenry et al., 2000a, 2000b; Öhrström et al., 2002, 2004). The significance of preferential flow in water and nutrient loss can not be neglected.. Variation of transport volume As indicated by Ren (2001), the transport volume (θst) can be used to quantify the preferential flow. Transport volume ratio is defined as a ratio of transport moisture volume divided by the total moisture in soil (θst/θ). The bromide ion was applied as tracer to calculate the transport volume of cultivated layer in three treatments. The results show that 88.9% of soil water can participate the transportation of bromide ion in the undisturbed cores sampled from 5-year rice cultivation treatment, and 60.8% in the cores of 1-year rice cultivation treatment by comparison with 19.1% in control treatment. The larger transport volume ratio suggests more preferential pathway developed over times of rice growing, because the transport volume are pretty correlated with preferential flow (White et al., 1984; Jury et al., 1986; Ren et al., 1999, 2001). CONCLUSIONS After the text edit has been completed, the paper is ready for the template. Duplicate the template file by using the Save As command, and use the naming convention prescribed by your conference for the name of your paper. In this newly created file, highlight all of the contents and import your prepared text file. You are now ready to style your paper; use the scroll down window on the left of the MS Word Formatting toolbar. The influence of rice-cultivation on preferential flow of alkalized soil including 1 year rice culitivation and 5 years rice cultivation treatment was discussed by applying dye tracer method. The results show that soil morphology and properties have appeared to be great changes by growing rice treatment. The preferential pathway is developed under the environment of wet-dry alternately and plough practice by rice-
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