Research Paper EAEF 4(1) : 25-32, 2011

Improvement of Salt-affected Soils by Deep Ploughing

―Part 2: Plot Field Tests in a Sodic Soil (Solonetz) Region*―

Xuanrui XONG*1, Huijun ZHANG*2, Ken ARAYA*3, Chinao TERAMOTO*4, Kazuhiko OHMIYA*5, Baoguo ZHU*6, Shucun YANG*7

Abstract A method was investigated for improvement of salt-affected soils in regions where a sufficient amount of rainfall to percolate into subsoil occurs in summer. A coarse layer is provided in the subsoil by deep tillage, making soil clods to cut off the capillary rise from groundwater. This paper deals with plot test fields constructed by hand in a local spot of a sodic soil (solonetz) region. The results showed that deep tillage up to the subsoil (C horizon) was beneficial for improvement of the solonetz soil. Application of the gypsum also reclaimed the solonetz soil, and should be mixed into the A horizon. The pH values decreased from about 10 to 9. The EC values decreased from about 8 dSm-1 to 2 dSm-1. [Keywords] sodic soil (solonetz), salt-affected soil, soil improvement, deep ploughing

I Introduction surface. It was shown that the salts accumulating in the A horizon were leached out by rainfall, which then decreased Salt-affected soils are formed in dry areas of the world. In the pH values to acceptable levels. this paper, the sodic soil (solonetz) in the salt-affected soils In order to cut off the capillarity, deep ploughing had been distributed in the People's Republic of China was examined. achieved (Antipov, 1954; Botov, 1959; Cairns, 1962; 1976a). The sodic soil in China is called meadow alkali soil (Fig. 1), which is common in the Heilongjiang, Jilin and Liaoning provinces (about 35 Gm2). As this soil contains sodium carbonate (Na2CO3), it belongs to the sodic soil group (solonetz) according to pedological classification (Dudal, 1969; Scheffer & Schatschabel, 1976; Abrol et al., 1988; Cardon & Mortvedt, 2001). If this soil is left undisturbed for a long time, white crystals of efflorescence (alkali spots) accumulate on the soil surface, and no plant can survive (Fig. 2). In the previous paper (Guo et al., 2006), a method of soil improvement was discussed for the salt-affected soils with sufficient rainfall to percolate into subsoil in summer Fig. 1 Typical sodic soil (solonetz) in Dajing City, season; basically, a coarse layer was provided below the B Heilongjiang Province, P. R. of China. Ana horizon, soil horizon (subsoil). It was demonstrated with soil column where sodium carbonate accumulates; A horizon, humic soil experiments that the capillary water from groundwater could with organic matter; B horizon, soil where A horizon be cut off, thus preventing the rise of dissolved salts to the soil leaches; C horizon, parent material.

* Partly presented at the JSAM Conference-Hokkaido in September 2009 *1 Environmental Science, University of Hokkaido, Sapporo 060-8610, Japan *2 Faculty of Engineering, University of Hokkaido, Sapporo 060-8628, Japan *3 JSAM Member, Corresponding author, Environmental Science Laboratory, Senshu University, Bibai, Hokkaido 079-0197, Japan, e-mail: [email protected] *4 Environmental Science Laboratory, Senshu University, Bibai, Hokkaido 079-0197, Japan *5 JSAM Member, Faculty of Agriculture, University of Hokkaido, Sapporo 060-0009, Japan *6 Jamusi Branch, Academy of Agricultural Sciences, Jiamusi, Heilongjiang Province, People’s Republic of China *7 Foreign Expert Bureau of Heilongjiang Province, Minjiang Road, Nangang District, Harbin, Heilongjiang Province, People's Republic of China

26 Engineering in Agriculture, Environment and Food Vol. 4, No. 1 (2011)

Table 1 shows the chemical properties of the solonetz soil in this study. Every horizon is extremely alkaline with pH of about 10, and the pH value of the soil surface (Ana) where

Na2CO3 was accumulated was more than 10. A pH value more than 8.5 is characteristic for the sodic soil

group (solonetz) which is mainly due to Na2CO3, and that less than 8.5 is for the saline soil group (solonchak) which is

mainly due to CaCO3 (Abrol et al., 1988; Cardon & Motvedt, 2001). The soil in this study, therefore, belongs to the solonetz group according to this parameter. The EC of the solonetz group is less than 4 dSm-1, and that of the solonchak group is more than 4 dSm-1 (Abrol et al., 1988; Cardon & Fig. 2 White efflorescence (alkali spots) on the soil surface of Motvedt, 2001). The EC values of the Ana and A horizons solonetz field in Daqing City, Heilongjiang Province, P. R. of of the soil in this study were greater than 4 dSm-1. The ESP China. value less than 15% is for the solonchak group, and that more However, above deep ploughing was performed by a than 15% is for the solonetz group (Abrol et al., 1988; Cardon back-hoe (Cairns, 1962) or a single mouldboard plough & Motvedt, 2001) and the ESP values of this soil were much (Bowser & Cairns, 1967), and so every soil horizons were greater 15%. Taking into account all values of pH, EC, ESP perfectly mixed. The A horizon in Fig. 1 contains pretty and Na2CO3, we determined that the soil in this study belongs amount of organic matter and are fertile, and should not be to the solonetz group on the whole. mixed into the lower infertile horizons (Guo et al., 2002). The CEC value of the soil surface (Ana horizon) of this soil Antipov & Pak (1965) and Cairns (1976b) also reported that was a little smaller than those in other horizons because the the A horizon should be retained on the surface during deep soil particles of the Ana soil are coarse (Guo et al., 2004). ploughing. The CEC values of the other horizons (A, B and C horizons) We envisaged a four-stage subsoil plough which tilled the were a little higher because of the presence of heavy clays subsoil up to 600 mm deep, retaining the A horizon and was (Fujiwara et al., 2003). modified from the plough for improvement of planosol (Guo The humus content in the topsoil (A horizon) of this soil et al., 2002). was about 2%, and that in the subsoil (B and C horizons) was In the current paper, we constructed plot test fields in a about 5%. In the planosol which is distributed in the local spot in a solonetz region. The goal of this study is to Heilongjiang Province, the humus content in the topsoil was improve salt-affected soils by deep ploughing. In 2004, the about 5%, and that in the subsoil was about 1% (Araya, 2001). four kinds of plot test fields were prepared, and in 2005, two In the meadow soil which is also distributed in Heilongjiang more kinds of plot test fields were constructed. After one Province, humus content in the topsoil was about 20%, and year (2005), two years (2006) and three years (2007), about 3% in the subsoil (Zhang, et al., 2000). The humus vegetation on the soil surface and soil properties were investigated. Table 1 Chemical properties of solonetz in Daqing City, II Materials and Methods Heilongjiang Province, P. R. of China

1. Chemical properties of solonetz soil Figure 1 shows a typical solonetz from a natural pasture field in Daqing City, Heilongjiang Province, P. R. of China, where no irrigation system is applied. On the top, the Ana horizon (pH 10.34) is a thin (50 mm) layer of accumulated

Na2CO3 and whitish soil (suffix na means sodium). The A horizon (pH 9.93) is a 200 mm layer of humic, black and brown soil which contains organic matter. The B horizon (pH 9.81) is a 200 mm layer of brown soil into which the fine clayey soil particles leach from the A horizon due to rainfall. Below all of this is the brown parent material of the C horizon ( pH 9.84). XONG, ZHANG, ARAYA, TERAMOTO, OHMIYA, ZHU, YANG : Improvement of Salt-affected Soils by Deep Ploughing - Part 2: Plot Field Tests in a Sodic Soil (Solonetz) Region - 27

Table 2 Soil treatment and yields in each plot test field

Fig. 3 Plot test fields. No. 1, A○, B○; No. 2, A○, B○ (m); No. 3, A○(m), B×; No. 4, A○, B× prepared in 2004; No. 5a, A○ (g), B○; No. 5b, A○ (g), B×; No. 6, A○, B○ (upside down) prepared in 2005. See Table 2. deep) were dug out by a shovel, and then the B horizon (including a part of C horizon) was tilled (about 35 cm deep) content of the solonetz soil in this study, especially in Ana and by the shovel to produce soil clods with the size of 100-140 A horizons, was low because the vegetation on the soil mm which size was suitable for interception of the capillarity surface is poor (Fig. 2) and the amount of organic matter rise (Araya et al., 2010). The soil clods on the soil surface produced in one year is small. of the tilled B horizon were pulverized a little, in order to The amount of exchangeable sodium (Na2O) in all horizons prevent collapse and loss of volume of the A horizon (Araya of this soil was more than 5000 mg kg-1, and the deeper two et al., 2010). Then, the Ana and A horizons were returned horizons had double that amount. The available phosphate back onto the coarse B horizon without soil mixing of the A (P2O5) was low in all horizons of the solonetz soil in this and B horizons (A○, B○) study, and all horizons had a deficiency of phosphate. In No. 2 field, when the B horizon was tilled, organic (cow) Consequently, P2O5 should be supplied with a chemical manure was mixed into the B horizon (2 kg m-2) [A○, B○ (m)]. fertilizer or other source. The solonetz soil in this study had The size of soil clods produced in the B horizon was 100-140 appropriate exchangeable calcium (CaO), exchangeable mm. magnesium (MgO) and exchangeable potassium (K2O). In the No. 3 field, manure was mixed into the A horizon. The soil in this study had sufficient available nitrogen (N) The B horizon was not tilled [A○(m), B×]. The manure has and was a little fertile. The available nitrogen in the topsoil two effects: neutralization with its organic acids and the of the planosol was 25 mg kg-1, and that in its subsoil was 8 replacement of the exchangeable sodium Na for Ca or Mg mg kg-1 (Araya, 2001). The topsoil of the meadow soil had （Abrol et al., 1988; Guputa et al., 1983; Kochaba et al., an available nitrogen of 103 mg kg)-1, and the subsoil 2004; Swarup, 1980; Swift & Posner, 1972; Yamada, 2002; contained 13 mg kg-1 (Zhang et al., 2000). Compared to Yamada et al., 2003） these soils, the solonetz soil in this study is relatively fertile. In the No. 4 field, the A horizon was tilled, and the B 2. Plot test fields horizon was not tilled (A○, B×). The A horizon was easily Figure 3 shows four kinds of plot test fields (No. 1-No. 4) pulverized with the organic matter and the produced average constructed in 2004, and two more plot test fields (No. 5 and size of the soil clods was 30 mm. No. 6) constructed in 2005 in Daqing City, Heilongjiang In 2005, two more plot test fields were prepared. The No. Province. The size of each field was 5 m by 5 m. Field No. 5 is a gypsum field, and it was divided into halves (Fig. 3). 5 was divided into adjoining plots 5a and 5b (described In the No. 5a field, the A horizon was dug out, and then the below); each measured 2.5 m by 5 m. The seven kinds of B horizon was tilled, producing soil clods. The A horizon test fields were established close to each other as a was returned back on the coarse B horizon without soil randomized complete block design in three replicates. mixing. At this time, 12.5 kg of gypsum (CaSO ·2H O）（in Table 2 shows the soil treatment in each test field. The 4 2 the percentage of 1 kg m-2) was mixed into the A horizon by No. 0 field is a bare land (control, CK) seen in Fig. 2 where shovels [A○(g), B○]. horizons were never tilled (A×, B×). This served as an In the No. 5b field, the same amount of gypsum was firstly overall control field. spread on the soil surface, and then the A horizon was tilled. In the No. 1 field, the Ana and A horizons (about 25 cm

28 Engineering in Agriculture, Environment and Food Vol. 4, No. 1 (2011)

The B horizon was not tilled [A○(g), B×]. 1997; Sakai et al., 2004). It has been reported that the application of the gypsum is No. 6 field is an inverted field where the A horizon and B useful as an ameliorate material to replace the exchangeable horizon were reversed [A○, B○ (upside down)]. sodium in the soil, which is toxic for plants, for calcium Alfalfa was seeded on all test fields in 2004 and 2005. (Amezketa et al., 2005; Aydemir & Najjar, 2005; Endo et al., 3. Investigated items 2002; Khosla et al., 1979; Lebron et al., 2002; Overstreet et In order to know the degree of soil improvement quickly, al., 1980; Sahin et al., 2003; Li et al., 1998; Ohkura et al., following six parameters were investigated in every year:

2001). The calcium sulphate (CaSO4) is a byproduct grass height, yield, soil penetration resistance, pH value, EC produced from coal power stations where sulphur dioxide value and soil water content.

(SO4) in the exhaust gas is absorbed by lime (CaCO3). (1) Grass height

CaSO4 is less costly than gypsum （Matsumoto, 1995 & The grass height of ten millets (described below) selected

Fig. 4 Vegetation on the soil surface in 2006 in each plot test field. No. 0, A×, B×; No. 1, A○, B○; No. 2, A○, B○ (m); No. 3, A○(m), B×; No. 4, A○, B×; No. 5a, A○ (g), B○; No. 5b, A○ (g), B×; No. 6, A○, B○ (upside down). XONG, ZHANG, ARAYA, TERAMOTO, OHMIYA, ZHU, YANG : Improvement of Salt-affected Soils by Deep Ploughing - Part 2: Plot Field Tests in a Sodic Soil (Solonetz) Region - 29 at random in each plot test field was measured. The total of Soil and Fertilizer, 2003). The soil samples were taken at thirty data obtained in each treated sites were evaluated for four depths: 0 mm (Ana horizon), 100 mm (Ap horizon), 300 the values in the No. 0 field (CK), using a t-test (P≤0.05) of mm (Bca horizon) and 500 mm (C horizon). Three samples the statistical function of Microsoft Excel. were taken at each depth and the mean value was determined. (2) Yield (5) Electric conductivity (EC) The dry mass of whole grasses (salt-tolerant grass and The EC values were determined by a commercial EC meter millet) in 1 m2 was determined. Three points were selected using the same aqueous solution of the pH. at random in each plot test field. The total nine data (6) Soil water content obtained in each treated sites were evaluated using for the The soil water content was measured by an infrared lay moisture meter (Society of Soil Physics, 1987) with a 5 g soil sample. III Results and Discussion 1. Vegetation on soil surface Figure 4 shows the vegetation on the soil surface in eight plot test fields. The vegetation in 2006 is shown as a

Fig. 5 Soil penetration resistance of each plot test field (2007, cone penetrometer, 30 deg. cone angle and 16 mm base diameter). No. 0, A×, B×; No. 1, A○, B○; No. 2, A○, B○ (m); No. 3, A○(m), B×; No. 4, A○, B×; No. 5a, A○ (g), B○; No. 5b, A○ (g), B×; No. 6, A○, B○ (upside down).

values in the No. 0 field (CK), using a t-test (P≤0.05) of the statistical function of Microsoft Excel. (3) Soil penetration resistance The soil hardness (soil penetration resistance) was measured by a cone penetrometer (30°cone angle, 16 mm Fig. 6 pH values. No. 1, A○, B○; No. 2, A○, B○ (m); No. 3, base diameter). Three to five tests were made each time. A○(m), B×; No. 4, A○, B×; No. 5a, A○ (g), B○; No. 5b, A○ (g), (4) pH (H2O) B×; No. 6, A○, B○ (upside down); See Table 2; □, Ana horizon, 0 The pH (H2O) values were determined by a commercial pH mm deep; ○, A horizon, 100 mm deep; △, B horizon, 300 mm meter. The soil sample (10 g) was put into a beaker, and deep; ◇, C horizon, 500 mm deep. distilled water (50 g) was added (1:5) and mixed well (Society

30 Engineering in Agriculture, Environment and Food Vol. 4, No. 1 (2011) representative. There was no alfalfa seeded in 2004 and 2005 but the wild grasses [salt-tolerant grass (Aneurolepidium Chinese Kitag) and millet] survived. The alfalfa seeded did not germinate due to draught. Table 2 shows the mean grass height and mean dry yield. The No. 0 field is the bare land where the alkali spots were found and the vegetation was very poor. At a single glance, the vegetation in the No. 1, No. 3 and No. 5a fields was excellent. There were bald spots of grass on the soil surface in the No. 2, No. 4 and No. 5b fields. No grass was found on the No. 6 field. From the results of Fig. 4 and Table 2, following things could be known. ① Compared to the No. 1 and No. 4 fields, and compared to the No. 5a and No. 5b fields, the tillage should be deep up to the C horizon and the capillary rise should be intercepted at the subsoil. ② Compared to the No. 2 and No. 3 fields, the

Fig. 8 Soil water content. No. 1, A○, B○; No. 2, A○, B○ (m); No. 3, A○(m), B×; No. 4, A○, B×; No. 5a, A○ (g), B○; No. 5b, A○ (g), B×; No. 6, A○, B○ (upside down); See Table 2; □, Ana horizon, 0 mm deep; ○, A horizon, 100 mm deep; △, B horizon, 300 mm deep; ◇, C horizon, 500 mm deep. application of manure is effective for the improvement of the solonetz soil. It should not be mixed into the B horizon but rather mixed into the A horizon. ③ Compared to the No. 5a and No. 5b fields, the application of the gypsum has a good effect for the improvement of the solonetz soil. The gypsum should be mixed into the A horizon. ④ With No. 6 field, making upside down the A and B horizons has no meaning. That is making upside down the soil layer by the single mouldboard plough (Bower & Cairns, 1967) is not appropriate for the improvement of the salt-affected soils. 2. Soil penetration resistance Figure 5 shows the soil penetration resistance (2007). Fig. 7 EC values. No. 1, A○, B○; No. 2, A○, B○ (m); No. 3, That in the No. 0 field (bare land) was more than 5 MPa A○(m), B×; No. 4, A○, B×; No. 5a, A○ (g), B○; No. 5b, A○ (g), below the soil surface. In No. 3, 4 and 5b fields where the B B×; No. 6, A○, B○ (upside down); See Table 2; □, Ana horizon, horizon was not tilled, the soil penetration resistance was 0 mm deep; ○, A horizon, 100 mm deep; △, B horizon, 300 mm more than 5 MPa below 300-400 mm deep. In the No. 1, 2 , deep; ◇, C horizon, 500 mm deep. 5a and 6 fields, the soil penetration resistance was 1-2.5 MPa up to 600 mm deep. Therefore, the soil penetration XONG, ZHANG, ARAYA, TERAMOTO, OHMIYA, ZHU, YANG : Improvement of Salt-affected Soils by Deep Ploughing - Part 2: Plot Field Tests in a Sodic Soil (Solonetz) Region - 31 resistance did not return back to the previous level within 2) From the results of vegetation on the soil surface and three years after operation. yields, following things could be known. 3. pH value ① Tillage should be deep up to the C horizon and the Figure 6 shows the pH values measured in each plot test capillary rise should be intercepted at the subsoil. field. The pH values in any fields decreased from about 10 ② Application of manure was effective for improvement to about 9 until August 2006. Especially, at 0, 100 and 300 of the solonetz soil. It should not be mixed into the B mm deep in the No. 3 [A○(m), B×] field, reduction of about horizon but rather mixed into the A horizon. 1.5 in pH was obtained because of the manure application. ③ Application of the gypsum had also a good effect for However, in August 2007, the pH values increased except the improvement of the solonetz. The gypsum should be the A horizon in the No. 3 field. The precipitation in 2007 mixed into the A horizon. was about 200 mm which was one third of usual year. 3) The soil penetration resistance did not return back to the 4. EC value previous level within three years. Figure 7 shows the EC values measured in the each plot 4) The pH values in any fields decreased from about 10 to test field. The EC value of the alkali spots on the soil about 9. surface in the No. 0 field (0 mm deep of the Ana horizon) was 5) The EC values decreased from about 8 dSm-1 to about 12.38 dSm-1. 2 dSm-1 with the elapsed time. In the plot test fields The EC values decreased from about 8 dSm-1 to about 2 where the EC value (especially at the topsoil) was more dSm-1 in any plot test field, if any tillage was given. The pH than 3 dSm-1, their vegetation was poor. value increased in 2007 (Fig. 6) but the EC value did not 6) The soil water content in the plot test fields with good increase and so, the interception of the capillarity with the soil vegetation was great. clods will be still working. References In the No. 5a field, the mean EC value was about 1.5 dSm-1 Abrol, I. P., J. S. P. Yadav and F. I. Massoud. 1988. Salt-affected in August 2006 and on other hand, in the No. 5b field, it was soils and their management. Soil Resources, Management and about 3.0 dSm-1. Therefore, the application of gypsum and Conservation Service, Land and Water Development Division, Food the deep tillage gave a good effect for the improvement of the and Agriculture Organization, United Nations, p 5, 9, 14 solonetz. Amezketa, E., R. Aragues and R. Gazol. 2005. Efficiency of Compared to Fig. 4, in the plot test fields where the EC sulfuric acid, mined gypsum and two gypsum by-products in soil value (especially in the topsoil) was more than 3 dSm-1, their crusting prevention and sodic soil reclamation. American Society vegetation was poor. of Agronomy, 97, 983-989 5. Soil water content Antipov, K. I. N. 1954. The improvement of solonetz soil under Figure 8 shows the soil water content measured in the each irrigated and non-irrigated conditions in connection with the plot test field. Compared to the vegetation on the soil utilization of virgin and waste lands. Akad. Nauk. SSSR, Leningrad, surface in Fig. 4, the soil water content in the plot test fields Izvestiia, Seria Biologicheskaia, No. 4, 3-18 with good vegetation was great because the growing grasses Antipov, K. I. N, K. P. Pak. 1965. 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