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Changes in Soil Properties Under the Influences of Cropping and Drip Irrigation During the Reclamation of Severe Salt-Affected Soils
Agricultural Sciences in China
October 2009
2009, 8(10): 1228-1237
Changes in Soil Properties Under the Influences of Cropping and Drip Irrigation During the Reclamation of Severe Salt-Affected Soils TAN Jun-li1, 2, 3 and KANG Yue-hu1 Key Laboratory of Water Cycle and Related and Land Surface Processes, Institute of Geographic Sciences and Natural Resource Research, Chinese Academy of Sciences, Beijing 100101, P.R.China 2 Graduate School, Chinese Academy of Sciences, Beijing 100039, P.R.China 3 College of Civil Engineer and Water Conservancy, Ningxia University, Yinchuan 750021, P.R.China 1
Abstract Reclamation of salt-affected land plays an important role in mitigating the pressure of agricultural land due to competition with industry and construction in China. Drip irrigation was found to be an effective method to reclaim salt-affected land. In order to improve the effect of reclamation and sustainability of salt-affected land production, a field experiment (with reclaimed 1-3 yr fields) was carried out to investigate changes in soil physical, chemical, and biological properties during the process of reclamation with cropping maize and drip irrigation. Results showed that soil bulk density in 0-20 cm soil layer decreased from 1.71 g cm-3 in unreclaimed land to 1.44 g cm-3 in reclaimed 3 yr fields, and saturated soil water content of 0-10 cm layer increased correspondingly from 20.3 to 30.2%. Both soil salinity and pH value in 0-40 cm soil layer dropped markedly after reclaiming 3 yr. Soil organic matter content reduced, while total nitrogen, total phosphorus, and total potassium all tended to increase after cropping and drip irrigation. The quantities of bacteria, actinomycete, and fungi in 0-40 cm soil layer all greatly increased with increase of reclaimed years, and they tended to distribute homogeneously in 0-40 cm soil profile. The urease activity and alkaline phosphatase activity in 0-40 cm soil layers were also enhanced, but the sucrase activity was not greatly changed. These results indicated that after crop cultivation and drip irrigation, soil physical environment and nutrients status were both improved. This was benefit for microorganism’s activity and plant’s growth. Key words: reclamation, drip irrigation, changes of soil properties, salt-affected soil
INTRODUCTION Land used for agriculture is confronted with many pressures with the development of society and the increase in population in China. Moreover, the demand for food and fiber is increasing. Saline soil is an important land resource for agriculture and the area where salt-affected soil is widely distributed is usually abundant in resources of light and heat, and thereReceived 19 May, 2009
fore has great potential to develop agriculture. Soil salinization is one of factors of soil degradation in the world (Qureshi et al. 2008), and it tends to become increasingly serious. It was estimated that there were 99.13 million ha salt-affected soil in China (Wang et al. 1993). The formation of salt-affected soil is not only related to soil parent material, climate, and topography, but also induced by anthropogenic activities particular in improper irrigation and drainage. Inappropriate irrigation leads the ground water table
Accepted 27 August, 2009
Correspondence KANG Yue-hu, Ph D, Professor, Tel: +86-10-64856516, Fax: +86-10-65856516, E-mail: [email protected]
© 2009, CAAS. All rights reserved. Published by Elsevier Ltd. doi: 10.1016/S1671-2927(08)60333-8
Changes in Soil Properties Under the Influences of Cropping and Drip Irrigation During the Reclamation of Severe
be uprised and makes the salts be accumulated on the upper soil layer through capillary rise. This process results in the secondary salinization (Kitamura et al. 2006). Usually, leaching salts in the root zone to the crop tolerance with excess irrigation and drainage are applied for reclamation of salt-affected soils (Qadir et al. 1998; Manjunatha et al. 2004; Feng et al. 2005; Qureshi et al. 2008). Drip irrigation was thought to be an effective method to reclaim salt-affected soil. Many research results showed that the leaching efficiency with drip irrigation was higher than other irrigation methods (Mokady and Brelser 1968; Bresler et al. 1982). The distribution of soil water and salts under drip irrigation is benefit for crop growth. The soil water content in the inner of wetted volume is higher than that in the outer where salts accumulate. The key issue of the salt-affected soils reclamation using drip irrigation is that a reasonable irrigation regime needs to be made to ensure not only the normal crop growth but also surplus water for salts leaching. Recently, Kang et al. (2008) and Jiao et al. (2007, 2008) reported a study of reclamation of heavy-textured severely salt-affected soils by drip irrigation with the soil salinity and bulk density in 0-30 cm soil layer averaged 21 g kg-1 and 1.71 g cm-3, the ground water table was at about 0.6 m during the growing season, and only halophyte plant can grow. By controlling the soil matric potential at 20 cm depth right under the emitter at the range of -5 to -25 kPa, waxy corn and oil-sunflower can grow. They found both waxy maize and oil-sunflower got the highest yield when the soil matric potential was controlled over -5 kPa, and the yields decreased with the decrease of soil matric potential. They also observed that the differences of crop yield and growth among different soil matric potential treatments were decreased with increasing cultivation year. However, the changes in soil properties during the reclamation of such severely salt-affected soils have not been well clarified yet. Therefore, the objectives of the paper are: i) to investigate the changes in soil physical, chemical, and biological properties under the influences of cropping and drip irrigation; and ii) to offer information for better salt-affected soil management.
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MATERIALS AND METHODS Experimental site Field experiments were carried out at Qingtongxia Agriculture Integrated Development Experimental Station, Ningxia Hui Autonomous Region of China. The station (latitude: 37°36´N; longitude: 105°39´E; 1 156 m asl.) is located in the middle part of Qingtongxia irrigation district where the irrigation water is diverted from the Yellow River. It is a typical mid-temperate continental climate. The mean annual temperature is 8.5°C and the mean annual precipitation is 185 mm, most of which occurred in summer. The potential evaporation is about 2 085 mm. The ground water table was at about 0.6 m during the growing season. The terrain slope of experimental site is about 0.8% and there was a 1.0 m width, 0.5 m depth ditch to drain surface water westward 50 m distance from experimental site.
Experimental design The three fields were selected which were reclaimed in 2004 (3 yr), 2005 (2 yr), and 2006 (1 yr), and whose areas were 144, 360, and 250 m2, respectively. And an undisturbed land neighbor to experimental field as the initial condition. Each field was divided into three subsites as three replicates. All fields were planted with waxy corn and applied with drip irrigation and plasticfilm mulching. The matric potential right under the 20 cm depth emitters was controlled at -10 kPa, i.e, when the readings of tensiometer were lower than -10 kPa then drip irrigating was carried out. The amount of the 1st irrigation in three fields was about 35 mm for leaching salt in the upper soil layer. Then tensiometer was uesd to trigger irrigation and 5 mm water was applied at early growth stage every time and 10 mm at later growth stage. Soil texture and field capacity of the tested soils in the 0-90 cm proile are listed in the Table 1. Table 1 Texture and field capacity of tested soils in the 0-90 cm profile Soil layer (cm) Sand (g kg -1) Silt (g kg-1) 0-20 20-40 40-90
346 295 626
618 679 359
Clay (g kg-1)
Field capacity (%)
36 26 15
16.3 20.3 27.5
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The 0-40 cm soil is silt loam textured. Electrical conductivity and pH value of 0-40 cm soil in different reclaimed years before sowing are presented in Table 2.
Agronomic practices Before sowing, 225 kg ha -1 compound fertilizer (monoammonium phosphate: 18% N, 46% P2O5, 1.5% SO42-) and 150 kg ha-1 K2SO4 fertilizer were uniformly sprinkled to each field as base fertilizer. During the waxy corn growth stage, total 300 kg ha-1 urea and 75 kg ha -1 dipotassium hydrogen phosphate were topdressed to the fields accompanying with drip irrigation. All experimental fields were ploughed with a tractor and were raised beds. Each bed was 0.4 m wide and 0.15 m high, and the distance between two bed centers was 0.8 m. One row of waxy corn (Zea mays L. ceratina Kulesh., variety Zhongnuo 1) was sowed on every bed tops manually with a 0.2-m interval. The drip tapes, with the emitters spaced 0.2 m apart and the emitter discharge of 0.75 L h-1, were placed on the center of the bed. Then, a white polyethylene film with 0.038 mm thickness was covered over the beds. Each field had an individual drip irrigation and fertilization system.
Soil sampling and analysis After corn harvesting, soil samplers in 0-5, 5-10, 1020, and 20-40 cm layers were taken for analysis soil microflora, enzymes activities, and soil nutrients at each subsite on the ridge between two corns. A mixed sample of three soil cores was taken at each subsite. The corresponding soil samples were taken on the undisturbed land, then the soils were stored in a refrigerator at 4°C until the microorganisms count experiment was completed within one week. The surplus soils were airdried and sieved 1 mm completely, and then a portion of soil was separated with quartering method and sieved
0.15 mm. The former sample was used to measure soil enzyme activities, electrical conductivity (EC), and pH; the latter was used to determine soil organic matter, total nitrogen, total phosphorus, and total potassium. The EC and pH were determined using EC meter and pH meter, respectively, suspension was made with a ratio of 1:5 soil and water. Total nitrogen was determined by Kjeldahl’s method. Soil samplers were digested with H2SO4-HClO4 to measure total phosphorus with molybdenum-antimony anti-spectrophotometric method. Total potassium was measured with the method of alkali fusion and flame photometer. Soil organic matter was measured by dichromate oxidation with heating. Urease, sucrase, and alkaline phosphatase activities were measured by spectrophotometer method described by Guan (1986). The counts of soil microorganisms were measured by the method of dilution plate count and bacteria were cultured in beef-protein medium, actinomycetes in Gaoshi 1 medium and fungi in Czapek’s medium. Soil bulk density and saturated water content were determined gravimetrically using a 100-cm3 ring.
Statistics The treatments were run as one-way analysis of variance (ANOVA) with SAS ver. 8.0. The ANOVA was performed at α = 0.05 level of significance to determine if significant differences existed among treatment means.
RESULTS Physical properties Bulk density As shown in Fig.1, soil bulk density of 0-5, 5-10, and 10-20 cm soil layer with cropping and drip irrigation treatments decreased significantly on
Table 2 Electrical conductivity (EC) and pH value of 0-40 cm soil in different reclaimed years before sowing Reclaimed years Unreclaimed 1 yr 2 yr 3 yr
EC (ds m-1)
pH value
0-5 cm
5-10 cm
10-20 cm
20-40 cm
0-5 cm
5-10 cm
10-20 cm
8.84 4.51 5.56 3.23
6.16 4.17 4.99 2.37
5.59 3.91 4.33 3.03
3.59 3.76 4.38 2.79
8.53 8.27 8.21 8.23
8.59 8.27 8.34 8.32
8.48 8.25 8.30 8.68
20-40 cm 8.41 8.18 8.43 8.57
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Changes in Soil Properties Under the Influences of Cropping and Drip Irrigation During the Reclamation of Severe
the reclaimed fields as compared with the unreclaimed land. The decrease was averagely 0.29, 0.24, and 0.32 g cm -3 for 0-5, 5-10, and 10-20 cm soil layer, respectively. Moreover, soil bulk density of upper soil layers tended to continuously decrease with the reclaimed years although there was no significant difference. However, as for 20-40 cm soil layer, bulk density tended to increase with the reclaiming years. It didn’t change for 40-90 cm soil layer. The results indicated that the upper soil gradually became loose and the amount of porosity increased as influenced by cropping and drip irrigation. This was in favor for soil microorganisms and crop growth. Saturated water content Saturated soil water content of 0-5 and 5-10 cm soil layer increased markedly through cropping and drip irrigation (Table 3). Moreover, saturated soil water content of 5-10 cm soil layer tended to increase with the increase of cropping years, which was 18.6% at natural land, 25.6% at the 1st cropping year, 28.8% at the 2nd cropping year, and 29.4% at the 3rd cropping year. It showed that the porosity of 0-10 cm soil increased significantly after cropping and drip irrigation.
Fig. 1 Soil bulk density in the 0-90 cm soil profile in different reclaimed years. The error bars are LSD (P 0.05).
Table 3 Saturated water content of 0-5 and 5-10 cm in different reclaimed years Reclaimed years Unreclaimed 1 yr 2 yr 3 yr
Saturated water content (%) 0-5 cm 21.9 c 28.6 b 31.4 a 31.0 ab
Same letters are not significantly different at P
5-10 cm 18.6 25.6 28.8 29.4 0.05. The same as below.
b a a a
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Chemical properties Soil salinity On the unreclaimed salt-affected land, a mass of salts accumulated in soil surface, and it reduced linearly with soil depth. After cropping and drip irrigation, soil salts at all sampled layers significantly decreased, especially in 0-5 cm soil layer, in which the salts reduced from 10.45 ds m-1 on natural land to 1.65, 3.49, and 0.94 ds m -1 on the 1st, 2nd, and 3rd cropping year’s fields, respectively (Fig.2). Electrical conductivity of field of the 2nd yr was higher than that of the 1st yr, which might be attributed to the fact that the harvesting date of the 2nd yr was earlier than that of the 1st yr. Moreover, the salts tended to distribute homogeneously in 0-40 cm soil profile through crop cultivation and drip irrigation. It showed that these measures could inhibit the salts buildup in the root zone and the effect became more significant with the increase of reclaimed years. Soil pH in water The soil pH value in 0-40 cm soil layers on the natural land was higher than 8.8. It significantly decreased through cropping and drip irrigation (Fig.3). On the field of reclaimed for 3 yr, the soil pH value in 0-40 cm soil layers decreased below 8.5. This showed that alkalinity of soil reaction decreased markedly after cropping and drip irrigation and the soil environment was suitable for crop production. Soil organic matter Compared with natural land, the content of soil organic matter in 0-40 cm layers tended to decrease after cropping and drip irrigation (Fig.4). Particular in 0-5 cm, it was averagely reduced by 2.02 g kg-1. Nevertheless, soil organic matter brought back to rise at the 3rd reclaimed year. That may be related to two reasons. On one hand, soil organic matter was quickly decomposed and mineralized duo to the disturbance of tillage in the 1st 2 yr; on the other hand, the crop root and debris were decomposed and the new organic matters were formed in the soil with the increase of cropping years. Total nitrogen The content of total nitrogen in 0-40 cm soil layers gradually increased with the increase of reclaimed years (Fig.5). It was only about 0.33 g kg-1 on natural land, 0.35 g kg-1on 1 yr , 0.46 g kg-1 on 2 yr, and 0.6 g kg-1 on 3 yr reclaimed land. The main reason may be that the initial nitrogen content was very low on the unreclaimed land, and therefore it was greatly sensitive to nitrogen fertilization and increased quickly.
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Fig. 2 Electrical conductivity of 0-40 cm soil in different reclaimed years before sowing and harvest.
Fig. 3 Soil pH value of 0-40 cm soil in different reclaimed years before sowing and harvest.
Fig. 4 Soil organic matter content of 0-40 cm soil in different reclaimed years.
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Changes in Soil Properties Under the Influences of Cropping and Drip Irrigation During the Reclamation of Severe
Ratio of C to N Table 2 shows that ratio of C to N of different soil layers had a decreasing tendency with the number of years since the 1st reclaimed year. The average ratios in 0-40 cm soil of the undisturbed saltaffected land, the 1st, 2nd, and 3rd yr were 6.05, 4.82, 3.35, and 3.26, respectively. It indicated that the increasing rate of nitrogen exceeded that of carbon after reclamation. In order to preserve the sustainability and stability of salt-affected soil ecosystem, more organic matter should be added to this ecosystem. Total phosphorus As seen from Fig.6, compared with the natural salt-affected land, the total phosphorus content did not change in 5-40 cm soil layer except increase in 0-5 cm soil layer on the field of reclaimed 1
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yr. Obviously it increased in the whole 0-40 cm soil layers at the end of the 2nd and the 3rd reclaimed year. The former increased 0.24, 0.18, 0.05, and 0.15 g kg-1 respectively, and the latter increased 0.24, 0.15, 0.16, and 0.15 g kg-1, respectively. Total potassium From Fig.7, it could be seen that the change of total potassium content was not as significant as the changes of total nitrogen and total phosphorus. At the end of the 1st and 2nd reclaimed year, only in 0-5 cm soil layer, the total potassium c o n t e n t i n c r e a s e d b y 1 . 6 9 a n d 1 . 5 3 g k g -1, respectively. At the end of the 3rd reclaimed year, the total potassium content in 0-5, 5-10, 10-20, and 20-40 cm soil layers all increased and by 3.03, 1.96, 1.03, and 1.53 g kg-1, respectively.
Fig. 5 Soil total nitrogen content of 0-40 cm soil in different reclaimed years.
Fig. 6 Soil total phosphorus content of 0-40 cm soil in different reclaimed years.
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TAN Jun-li et al.
Fig. 7 Soil total potassium content of 0-40 cm soil in different reclaimed years.
Table 3 Ratio of C to N in 0-40 cm soil at different reclaimed years Soil depth (cm)
Reclaimed years Unreclaimed 1 yr 2 yr 3 yr
0-5
5-10
10-20
20-40
9.60 a 5.72 b 4.01 b 3.58 b
7.58 a 5.30 ab 4.14 b 3.44 b
6.06 a 5.61 a 3.52 a 3.23 a
4.78 4.09 2.90 3.15
a a a a
Biological properties Soil microflora On the undisturbed salt-affected land, the colony forming unit (CFU) of bacteria was very few, and it was only 1.05 × 107 count g-1 dry soil in 05 cm soil layer and about 0.02 × 107 count g-1 dry soil in 5-40 cm soil layers. After cultivation for 1 yr, the CFU of bacteria in 0-5, 5-10, 10-20, and 20-40 cm soil layers increased by 9.9, 171, 342, and 8.8 times, respectively (Table 4). After cultivation for 2 and 3 yr , the CFU of bacteria in corresponding layers increased by 1.3, 426, 47, and 54 times, and 3, 465, 603, and 592 times, respectively. This indicated that the soil environment was improved and it was more favor for bacteria to grow after reclamation. In addition, the distribution of bacteria in 0-40 cm soil profile tended to be homogeneous.
Taking one with another, the CFU of actinomycete in 0-40 cm soil increased with the increase of reclaiming years. At the 3rd reclaimed year, the CFU of actinomycete in 0-5, 5-10, 10-20, and 20-40 cm soil layers greatly increased and the increment were 27.9 × 10 3, 18.1 × 103, 31.6 × 103, and 27.5 × 103 count g-1 dry soil, respectively. Moreover, the differences in CFU of actinomycete among soil layers decreased. The CFU of fungi in 0-40 cm soil layers on the unreclaimed salt-affected land was rather few. After reclamation, it significantly increased. Compared with the unreclaimed salt-affected land, the CFU of fungi in 0-5 cm soil layer increased by 28, 67, and 103 times on the 1, 2, and 3 yr reclaimed land respectively. Moreover, The CFU of fungi in 5-40 cm soil layer also greatly increased, and gradually tended to that in the surface layer. Enzyme activities The urease activity in every soil layer of 0-40 cm all gradually increased with the reclaiming years. It was about higher 30.1, 15.7, 14.1, and 6.3 g NH4+-N g-1 dry soil h-1 in 0-5, 5-10, 10-20, and 20-40 cm soil layers at the 3rd reclaiming year than that on the original salt-affected land (Table 4). Alkaline phosphatase activity in 0-40 cm soil layer
Table 4 The quantity of bacteria, actinomycete and fungi in 0-40 cm soil in different reclaimed years Soil depth (cm) 5-5 5-10 10-20 20-40
Bacteria (× 107 count g-1 dry soil) Unreclaimed 1.05 0.02 0.02 0.02
a a a a
Actinomycete (× 103 count g-1 dry soil)
Fungi (× 10 count g-1 dry soil)
1 yr
2 yr
3 yr
Unreclaimed
1 yr
2 yr
3 yr
Unreclaimed
1 yr
2 yr
3 yr
11.4 a 4.37 a 7.20 a 0.20 a
2.39 a 10.8 a 1.0 a 1.12 a
3.86 a 11.8 a 12.7 a 12.1 a
1.41 b 0.36 a 0.74 b 1.21 ab
7.63 b 3.94 a 0.26 b 0b
9.72 b 22.5 a 12.4 b 16.5 ab
29.3 a 18.5 a 32.3 a 28.7 a
0.75 c 0a 0a 0a
21.9 bc 46.1 a 5.25 a 1.57 a
51.0 ab 50.5 a 13.4 a 42.3 a
78.1 18.7 14.2 20.5
a a a a
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Changes in Soil Properties Under the Influences of Cropping and Drip Irrigation During the Reclamation of Severe
also gradually increased. After 3 yr cultivation, Alkinine phosphatase activity in 0-5, 5-10, 10-20, and 20-40 cm soil layer increased by 10.5, 4.4, 2.3, and 2.7 times, respectively. Sucrase activity didn’t change greatly. However, the differences among different soil layers gradually became small. On the original salt-affected land, the ratio of sucrase activity in 0-5 cm soil layer to that in 20-40 cm soil layer was 2.5. On the 1st year reclaimed land, it hardly changed. On the 2nd and 3rd year, the ratios both decreased, which were 0.7 and 0.8 respectively.
DISCUSSION AND CONCLUSION There are several obstacles for crop production in saltaffected soil such as poor fertility, low activity of soil organisms, high salinity, and osmotic potential. The changes of environment induced by irrigation and other agronomic practices received more and more attentions (Ilyas et al. 1997; Barbiéro et al. 2001; Herrero and Pérez-Coveta 2005; Pilatti et al. 2006; Alvarez-Rogel et al. 2007). In this study, soil bulk density of 0-20 cm soil layer reduced quickly at the 1st 3 yr of reclamation and the soil becomes loose and could hold more water and air. Then aeration condition in the root zone would be improved. The result could be verified by the increase of soil saturated water content. It improved from 21.9% in 0.1 m soil of undisturbed saline land to 30.2% of the 3rd yr field. The soil bulk density of 0-20 cm soil changed from 1.71 g cm-3 on the undisturbed saline land to 1.44 g cm-3 on the 3rd year field. Akhter et al. (2004) also observed that soil bulk density decreased from an average value of 1.62 to 1.53 g cm-3 in the upper 0.2 m soil through planting Kallar grass 5 y and soil porosity increased from 38.9 to 42.8%. Soil bulk density of 20-40 cm layer tended to increase by 0.1-0.2 g cm-3 after 2 and 3 reclaimed years. The
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reason was that the upper soil was tilled and became loose, while the soils in the deeper soil layers were impacted during the mechanical tillage. On the other hand, frequent drip irrigation could leach some fine soil particles to the deeper soil layers and made soils of these layers more compact. Soil aeration was a problem to discuss when soil matric potential was controlled above -10 kPa. For only soil matric potential of 0.2 m depth right under the emitter was above -10 kPa and those of outer of the wet volume were below -10 kPa. Addtionally, Jiao et al. (2007, 2008) reported that waxy corn and oil-sunflower were got the highest yield when soil matric potential of 0.2 m depth right under the emitter was -5 kPa at the same experimental site. It indicated that the effect of soil areation on corn growth was not significant when soil matric potential was -5 kPa in this study. At the same time, average salinity of 0-40 cm soil was dropped from 8.8 ds m-1 in undisturbed land to 2.24 ds m-1 in the 3rd yr field. In addition, the soil pH values in the root zone were reduced after reclamation from 8.88 to 8.36 correspondingly. The results were similar with those of Shi et al. (2006), who reported that soil EC and soil pH values steadily decreased after reclamation in coastal saline lands. Soil C and N are two essential elements in the soil ecosystem. Soil organic matter in the 0-40 cm soil reduced at the 1st 2 yr, and then increased at the 3rd yr. Total nitrogen content increased with the increase of reclaimed years. It indicated that total nitrogen content depended on the nitrogen fertilizer greatly. Changes of soil organic matter and total nitrogen caused changes of ratio of C to N. The ratio of C to N declined with the increase of reclaimed years from 6.05 in undisturbed salt-affected land to 3.26 in the 3rd yr field. To preserve the sustainability and stability of salt-affected soil ecosystem, adding organic matter such as farmyard manure, green manure, and crop residual should be required (Zhang et al. 1997; Tejada et al. 2006; Li et al.
Table 5 Activities of urease, alkaline phosphatase, and sucrase in 0-40 cm soil in different reclaimed years Soil depth (cm) 0-5 5-10 10-20 20-40
Urease activity (g NH4+-N g -1 dry soil h -1) Unreclaimed 3.86 2.10 3.21 2.80
b b b b
Alkaline phosphatase activity (g Ph(OH) g-1 dry soil h -1)
1 yr
2 yr
3 yr
Unreclaimed
5.81 b 4.26 b 2.33 b 3.22 b
7.40 b 7.31 b 5.27 b 3.04 b
33.97 a 17.80 a 17.28 a 9.10 a
25.59 b 18.95 c 24.18 c 18.40 b
1 yr 192.78 ab 76.71 ab 45.60 bc 19.07 b
Sucrase activity (g Glu g-1 dry soil h-1)
2 yr
3 yr
Unreclaimed
1 yr
89.22 b 47.89 bc 54.66 ab 22.92 b
293.76 a 101.65 a 79.27 a 67.63 a
36.13 a 58.91 a 21.02 a 14.44 a
25.36 a 42.86 a 26.27 a 9.42 a
2 yr 21.92 23.83 15.38 31.72
3 yr a a a a
29.45 29.50 37.93 34.66
a a a a
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2006). Soil microorganisms in salt-affected soil are restrained by high salinity inducing osmotic stress (Yuan et al. 2007). In general, quantities of different kinds of microorganisms in salt-affected soil are very fewer than those in non-saline soils, which increased markedly through cropping and drip irrigation. In salt-affected soil, there were less fungi than bacteria and actinomycete in the 0-40 cm soil. With the increase of reclaimed year, except for the enhancement of the amount of bacteria, actinomycete and fungi, their distribution on the profile of 0-40 cm soil became even. Lin et al. (2006) observed that the bacteria, actinomycete, and fungi increased by 2.3, 4.3, and 71 times through planting Suaeda salsa L. in coastal saline soil. The main reasons were attributed two aspects: The decrease in soil salinity and the improvement in soil fertility created a relatively good environment for microbial growth and reproduction after cropping and drip irrigation; the root exudation and other organic material such as root debris in the soil offered “food” for microorganisms. Enzyme activity is an important indicator for evaluation of soil biological activity. Soil enzymes are catalyzer for many reactions and play an important role in the conversion of energy and cycles of nutrients. The improvements of the activities of urease and alkaline phosphatase not only occurred in the 0-20 cm soil but also in the 20-40 cm soil after cropping and drip irrigation. At the mean time, the activities of urease and alkaline phosphatase of 0-20 cm soil increased with the increase of reclaimed years. However, the activity of sucrase in 0-10 cm soil reduced with the increase of the number of cultivated years. That of 10-40 cm soil increased to some extent after reclaimed 2 and 3 yr. The conclusions in this study were based on only 3 yr of data sets. To assess the sustainability of the measurements of water and salt regulation in arid region, further researches should be carried out.
Acknowledgements This work was financially supported by the Chinese Academy of Sciences Action Plan for the Development of Western China (KZCX2-XB2-13), the Chinese Academy of Sciences Knowledge Innovation Project (KSCX2-YW-N-080), and the Project for 100 Outstanding Young Scientists supported by Chinese Academy of
TAN Jun-li et al.
Sciences.
References Akhter J, Murray R, Mahmood K, Malik K A, Ahmed S. 2004. Improvement of degraded physical properties of a salinesodic soil by reclamation with Kallar grass (Leptochloa fusca). Plant and Soil, 258, 207-216. Alvarez-Rogel J, Jiménez-Cárceles F J, Roca M J, Ortiz R. 2007. Changes in soils and vegetation in a Mediterranean coastal salt marsh impacted by human activities. Estuarine, Coastal and Shelf Science, 73, 510-526. Barbiéro L, Valles V, Régeard A, Cheverry C. 2001. Residual alkalinity as tracer to estimate the changes induced by forage cultivation in a non-saline irrigated sodic soil. Agricultural Water Management, 50, 229-241. Bresler E, McNeal, B L, Carter, D L. 1982. Saline and Sodic Soils: Principles-Dynamics-Modeling. Springer-Verlag, Berlin Heidelberg. Feng Z, Wang X, Feng Z. 2005. Soil N and salinity leaching after the autumn irrigation and its impact on groundwater in Hetao Irrigation District, China. Agricultural Water Management, 71, 131-143. Guan S. 1986. Enzyme in Soils and Their Study Methods. China Agriculture Press, Beijing. pp. 260-313. (in Chinese) Herrero J, Pérez-Coveta O. 2005. Soil salinity changes over 24 years in a Mediterranean irrigated district. Geoderma, 125, 287-308. Ilyas M, Qureshi R H, Qadir M A. 1997. Chemical changes in a saline-sodic soil after gypsum application and cropping. Soil Technology, 10, 247-260. Jiao Y, Kang Y, Wan S, Liu W, Dong F. 2007. Effect of soil matric potential on waxy corn growth and irrigation water use efficiency under mulch drip irrigation in saline soils of arid areas. Agricultural Research in the Arid Areas, 25, 144151. (in Chinese) Jiao Y, Kang Y, Wan S, Sun Z, Liu W, Dong F. 2008. Effect of soil matric potential on the distribution of soil salt under drip irrigation on saline and alkaline land in arid regions. Transactions of the CSAE, 24, 53-58. (in Chinese) Kang Y, Wan S, Jiao Y, Tan J, Sun Z. 2008. Saline soil salinity and water management with tensiometer under drip irrigation. In: Symposia on the Fifth Annual Meeting of Agricultural Land and Water Engineering of Chinese Society of Agricultural Engineering. pp. 124-131. Kitamura Y, Yano, T, Honna T, Yamamoto S, Inosako K. 2006. Causes of farmland salinization and remedial measures in the Aral Sea Basin-Research on water management to prevent secondary salinization in rice-based cropping system in arid land. Agriculture Water Management, 85, 1-14.
© 2009, CAAS. All rights reserved. Published by Elsevier Ltd.
Changes in Soil Properties Under the Influences of Cropping and Drip Irrigation During the Reclamation of Severe
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Li X, Li F, Bhupinderpal S, Cui Z, Zed R. 2006. Decomposition of maize straw in saline soil Biol. Fertilizer Soils, 42, 366-
Qureshi A S, McCornick P G, Qadir M, Aslam Z. 2008. Managing salinity and waterlogging in the Indus Basin of Pakistan.
370. Lin X Z, Chen K S HE P Q, Shen J H, Huang X H. 2006. The
Agricultural Water Management, 95, 1-10. Shi Z, Cheng J L, Huang M X, Zhou L Q. 2006. Assessing
effects of Suaeda salsa L. planting on the soil microflora in coastal saline soil. Acta Ecologica Sinica, 26, 801-807. (in
reclamation levels of coastal saline lands with integrated stepwise discriminant analysis and laboratory hyperspectral
Chinese) Manjunatha M V, Oosterbaan R J, Gupta S K, Rajkumar H,
data. Pedosphere, 16, 154-160. Tejada M, Garcia C, Gonzalez J L, Hernandez M T. 2006. Use
Jansen H. 2004. Performance of subsurface drains for reclaiming waterlogged saline lands under rolling topography
of organic amendment as a strategy for saline soil remediation: Influence on the physical, chemical and biological properties
in Tungabhadra irrigation project in India. Agricultural Water Management, 69, 69-82.
of soil. Soil Biology & Biochemistry, 38, 1413-1421. Wang Z, Zhu S, Yu R, Li L, Shan G, You W, Zeng X, Zhang C,
Mokady R S, Bresler E. 1968. Reduced sodium exchange capacity in unsaturated flow. Soil Science Society of America
Zhang L, Song R. 1993. China’s Saline Soils. Science Press, Beijing. (in Chinese)
Proceeding, 32, 436-467. Pilatti M A, Imhoff S, Ghiberto P, Marano R P. 2006. Changes
Yuan B, Li Z, Liu H, Gao M, Zhang Y. 2007. Microbial biomass and activity in salt affected soils under arid conditions.
in some physical properties of Mollisols induced by supplemental irrigation. Geoderma, 133, 431-443.
Applied Soil Ecology, 35, 319-328. Zhang R, Yan H J, Wei Y Q, Shan X Z, Liu J F. 1997. The effect
Qadir M, Qureshi R H, Ahmad N. 1998. Horizontal flushing: a promising ameliorative technology for hard saline-sodic and
of organic matter fertilizer on the reclamation of saline soils. Soil and Fertilizer, 4, 11-14. (in Chinese)
sodic soils. Soil & Tillage Research, 45, 119-131. (Edited by WANG Ning)
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October 2009
2009, 8(10): 1228-1237
Changes in Soil Properties Under the Influences of Cropping and Drip Irrigation During the Reclamation of Severe Salt-Affected Soils TAN Jun-li1, 2, 3 and KANG Yue-hu1 Key Laboratory of Water Cycle and Related and Land Surface Processes, Institute of Geographic Sciences and Natural Resource Research, Chinese Academy of Sciences, Beijing 100101, P.R.China 2 Graduate School, Chinese Academy of Sciences, Beijing 100039, P.R.China 3 College of Civil Engineer and Water Conservancy, Ningxia University, Yinchuan 750021, P.R.China 1
Abstract Reclamation of salt-affected land plays an important role in mitigating the pressure of agricultural land due to competition with industry and construction in China. Drip irrigation was found to be an effective method to reclaim salt-affected land. In order to improve the effect of reclamation and sustainability of salt-affected land production, a field experiment (with reclaimed 1-3 yr fields) was carried out to investigate changes in soil physical, chemical, and biological properties during the process of reclamation with cropping maize and drip irrigation. Results showed that soil bulk density in 0-20 cm soil layer decreased from 1.71 g cm-3 in unreclaimed land to 1.44 g cm-3 in reclaimed 3 yr fields, and saturated soil water content of 0-10 cm layer increased correspondingly from 20.3 to 30.2%. Both soil salinity and pH value in 0-40 cm soil layer dropped markedly after reclaiming 3 yr. Soil organic matter content reduced, while total nitrogen, total phosphorus, and total potassium all tended to increase after cropping and drip irrigation. The quantities of bacteria, actinomycete, and fungi in 0-40 cm soil layer all greatly increased with increase of reclaimed years, and they tended to distribute homogeneously in 0-40 cm soil profile. The urease activity and alkaline phosphatase activity in 0-40 cm soil layers were also enhanced, but the sucrase activity was not greatly changed. These results indicated that after crop cultivation and drip irrigation, soil physical environment and nutrients status were both improved. This was benefit for microorganism’s activity and plant’s growth. Key words: reclamation, drip irrigation, changes of soil properties, salt-affected soil
INTRODUCTION Land used for agriculture is confronted with many pressures with the development of society and the increase in population in China. Moreover, the demand for food and fiber is increasing. Saline soil is an important land resource for agriculture and the area where salt-affected soil is widely distributed is usually abundant in resources of light and heat, and thereReceived 19 May, 2009
fore has great potential to develop agriculture. Soil salinization is one of factors of soil degradation in the world (Qureshi et al. 2008), and it tends to become increasingly serious. It was estimated that there were 99.13 million ha salt-affected soil in China (Wang et al. 1993). The formation of salt-affected soil is not only related to soil parent material, climate, and topography, but also induced by anthropogenic activities particular in improper irrigation and drainage. Inappropriate irrigation leads the ground water table
Accepted 27 August, 2009
Correspondence KANG Yue-hu, Ph D, Professor, Tel: +86-10-64856516, Fax: +86-10-65856516, E-mail: [email protected]
© 2009, CAAS. All rights reserved. Published by Elsevier Ltd. doi: 10.1016/S1671-2927(08)60333-8
Changes in Soil Properties Under the Influences of Cropping and Drip Irrigation During the Reclamation of Severe
be uprised and makes the salts be accumulated on the upper soil layer through capillary rise. This process results in the secondary salinization (Kitamura et al. 2006). Usually, leaching salts in the root zone to the crop tolerance with excess irrigation and drainage are applied for reclamation of salt-affected soils (Qadir et al. 1998; Manjunatha et al. 2004; Feng et al. 2005; Qureshi et al. 2008). Drip irrigation was thought to be an effective method to reclaim salt-affected soil. Many research results showed that the leaching efficiency with drip irrigation was higher than other irrigation methods (Mokady and Brelser 1968; Bresler et al. 1982). The distribution of soil water and salts under drip irrigation is benefit for crop growth. The soil water content in the inner of wetted volume is higher than that in the outer where salts accumulate. The key issue of the salt-affected soils reclamation using drip irrigation is that a reasonable irrigation regime needs to be made to ensure not only the normal crop growth but also surplus water for salts leaching. Recently, Kang et al. (2008) and Jiao et al. (2007, 2008) reported a study of reclamation of heavy-textured severely salt-affected soils by drip irrigation with the soil salinity and bulk density in 0-30 cm soil layer averaged 21 g kg-1 and 1.71 g cm-3, the ground water table was at about 0.6 m during the growing season, and only halophyte plant can grow. By controlling the soil matric potential at 20 cm depth right under the emitter at the range of -5 to -25 kPa, waxy corn and oil-sunflower can grow. They found both waxy maize and oil-sunflower got the highest yield when the soil matric potential was controlled over -5 kPa, and the yields decreased with the decrease of soil matric potential. They also observed that the differences of crop yield and growth among different soil matric potential treatments were decreased with increasing cultivation year. However, the changes in soil properties during the reclamation of such severely salt-affected soils have not been well clarified yet. Therefore, the objectives of the paper are: i) to investigate the changes in soil physical, chemical, and biological properties under the influences of cropping and drip irrigation; and ii) to offer information for better salt-affected soil management.
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MATERIALS AND METHODS Experimental site Field experiments were carried out at Qingtongxia Agriculture Integrated Development Experimental Station, Ningxia Hui Autonomous Region of China. The station (latitude: 37°36´N; longitude: 105°39´E; 1 156 m asl.) is located in the middle part of Qingtongxia irrigation district where the irrigation water is diverted from the Yellow River. It is a typical mid-temperate continental climate. The mean annual temperature is 8.5°C and the mean annual precipitation is 185 mm, most of which occurred in summer. The potential evaporation is about 2 085 mm. The ground water table was at about 0.6 m during the growing season. The terrain slope of experimental site is about 0.8% and there was a 1.0 m width, 0.5 m depth ditch to drain surface water westward 50 m distance from experimental site.
Experimental design The three fields were selected which were reclaimed in 2004 (3 yr), 2005 (2 yr), and 2006 (1 yr), and whose areas were 144, 360, and 250 m2, respectively. And an undisturbed land neighbor to experimental field as the initial condition. Each field was divided into three subsites as three replicates. All fields were planted with waxy corn and applied with drip irrigation and plasticfilm mulching. The matric potential right under the 20 cm depth emitters was controlled at -10 kPa, i.e, when the readings of tensiometer were lower than -10 kPa then drip irrigating was carried out. The amount of the 1st irrigation in three fields was about 35 mm for leaching salt in the upper soil layer. Then tensiometer was uesd to trigger irrigation and 5 mm water was applied at early growth stage every time and 10 mm at later growth stage. Soil texture and field capacity of the tested soils in the 0-90 cm proile are listed in the Table 1. Table 1 Texture and field capacity of tested soils in the 0-90 cm profile Soil layer (cm) Sand (g kg -1) Silt (g kg-1) 0-20 20-40 40-90
346 295 626
618 679 359
Clay (g kg-1)
Field capacity (%)
36 26 15
16.3 20.3 27.5
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The 0-40 cm soil is silt loam textured. Electrical conductivity and pH value of 0-40 cm soil in different reclaimed years before sowing are presented in Table 2.
Agronomic practices Before sowing, 225 kg ha -1 compound fertilizer (monoammonium phosphate: 18% N, 46% P2O5, 1.5% SO42-) and 150 kg ha-1 K2SO4 fertilizer were uniformly sprinkled to each field as base fertilizer. During the waxy corn growth stage, total 300 kg ha-1 urea and 75 kg ha -1 dipotassium hydrogen phosphate were topdressed to the fields accompanying with drip irrigation. All experimental fields were ploughed with a tractor and were raised beds. Each bed was 0.4 m wide and 0.15 m high, and the distance between two bed centers was 0.8 m. One row of waxy corn (Zea mays L. ceratina Kulesh., variety Zhongnuo 1) was sowed on every bed tops manually with a 0.2-m interval. The drip tapes, with the emitters spaced 0.2 m apart and the emitter discharge of 0.75 L h-1, were placed on the center of the bed. Then, a white polyethylene film with 0.038 mm thickness was covered over the beds. Each field had an individual drip irrigation and fertilization system.
Soil sampling and analysis After corn harvesting, soil samplers in 0-5, 5-10, 1020, and 20-40 cm layers were taken for analysis soil microflora, enzymes activities, and soil nutrients at each subsite on the ridge between two corns. A mixed sample of three soil cores was taken at each subsite. The corresponding soil samples were taken on the undisturbed land, then the soils were stored in a refrigerator at 4°C until the microorganisms count experiment was completed within one week. The surplus soils were airdried and sieved 1 mm completely, and then a portion of soil was separated with quartering method and sieved
0.15 mm. The former sample was used to measure soil enzyme activities, electrical conductivity (EC), and pH; the latter was used to determine soil organic matter, total nitrogen, total phosphorus, and total potassium. The EC and pH were determined using EC meter and pH meter, respectively, suspension was made with a ratio of 1:5 soil and water. Total nitrogen was determined by Kjeldahl’s method. Soil samplers were digested with H2SO4-HClO4 to measure total phosphorus with molybdenum-antimony anti-spectrophotometric method. Total potassium was measured with the method of alkali fusion and flame photometer. Soil organic matter was measured by dichromate oxidation with heating. Urease, sucrase, and alkaline phosphatase activities were measured by spectrophotometer method described by Guan (1986). The counts of soil microorganisms were measured by the method of dilution plate count and bacteria were cultured in beef-protein medium, actinomycetes in Gaoshi 1 medium and fungi in Czapek’s medium. Soil bulk density and saturated water content were determined gravimetrically using a 100-cm3 ring.
Statistics The treatments were run as one-way analysis of variance (ANOVA) with SAS ver. 8.0. The ANOVA was performed at α = 0.05 level of significance to determine if significant differences existed among treatment means.
RESULTS Physical properties Bulk density As shown in Fig.1, soil bulk density of 0-5, 5-10, and 10-20 cm soil layer with cropping and drip irrigation treatments decreased significantly on
Table 2 Electrical conductivity (EC) and pH value of 0-40 cm soil in different reclaimed years before sowing Reclaimed years Unreclaimed 1 yr 2 yr 3 yr
EC (ds m-1)
pH value
0-5 cm
5-10 cm
10-20 cm
20-40 cm
0-5 cm
5-10 cm
10-20 cm
8.84 4.51 5.56 3.23
6.16 4.17 4.99 2.37
5.59 3.91 4.33 3.03
3.59 3.76 4.38 2.79
8.53 8.27 8.21 8.23
8.59 8.27 8.34 8.32
8.48 8.25 8.30 8.68
20-40 cm 8.41 8.18 8.43 8.57
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Changes in Soil Properties Under the Influences of Cropping and Drip Irrigation During the Reclamation of Severe
the reclaimed fields as compared with the unreclaimed land. The decrease was averagely 0.29, 0.24, and 0.32 g cm -3 for 0-5, 5-10, and 10-20 cm soil layer, respectively. Moreover, soil bulk density of upper soil layers tended to continuously decrease with the reclaimed years although there was no significant difference. However, as for 20-40 cm soil layer, bulk density tended to increase with the reclaiming years. It didn’t change for 40-90 cm soil layer. The results indicated that the upper soil gradually became loose and the amount of porosity increased as influenced by cropping and drip irrigation. This was in favor for soil microorganisms and crop growth. Saturated water content Saturated soil water content of 0-5 and 5-10 cm soil layer increased markedly through cropping and drip irrigation (Table 3). Moreover, saturated soil water content of 5-10 cm soil layer tended to increase with the increase of cropping years, which was 18.6% at natural land, 25.6% at the 1st cropping year, 28.8% at the 2nd cropping year, and 29.4% at the 3rd cropping year. It showed that the porosity of 0-10 cm soil increased significantly after cropping and drip irrigation.
Fig. 1 Soil bulk density in the 0-90 cm soil profile in different reclaimed years. The error bars are LSD (P 0.05).
Table 3 Saturated water content of 0-5 and 5-10 cm in different reclaimed years Reclaimed years Unreclaimed 1 yr 2 yr 3 yr
Saturated water content (%) 0-5 cm 21.9 c 28.6 b 31.4 a 31.0 ab
Same letters are not significantly different at P
5-10 cm 18.6 25.6 28.8 29.4 0.05. The same as below.
b a a a
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Chemical properties Soil salinity On the unreclaimed salt-affected land, a mass of salts accumulated in soil surface, and it reduced linearly with soil depth. After cropping and drip irrigation, soil salts at all sampled layers significantly decreased, especially in 0-5 cm soil layer, in which the salts reduced from 10.45 ds m-1 on natural land to 1.65, 3.49, and 0.94 ds m -1 on the 1st, 2nd, and 3rd cropping year’s fields, respectively (Fig.2). Electrical conductivity of field of the 2nd yr was higher than that of the 1st yr, which might be attributed to the fact that the harvesting date of the 2nd yr was earlier than that of the 1st yr. Moreover, the salts tended to distribute homogeneously in 0-40 cm soil profile through crop cultivation and drip irrigation. It showed that these measures could inhibit the salts buildup in the root zone and the effect became more significant with the increase of reclaimed years. Soil pH in water The soil pH value in 0-40 cm soil layers on the natural land was higher than 8.8. It significantly decreased through cropping and drip irrigation (Fig.3). On the field of reclaimed for 3 yr, the soil pH value in 0-40 cm soil layers decreased below 8.5. This showed that alkalinity of soil reaction decreased markedly after cropping and drip irrigation and the soil environment was suitable for crop production. Soil organic matter Compared with natural land, the content of soil organic matter in 0-40 cm layers tended to decrease after cropping and drip irrigation (Fig.4). Particular in 0-5 cm, it was averagely reduced by 2.02 g kg-1. Nevertheless, soil organic matter brought back to rise at the 3rd reclaimed year. That may be related to two reasons. On one hand, soil organic matter was quickly decomposed and mineralized duo to the disturbance of tillage in the 1st 2 yr; on the other hand, the crop root and debris were decomposed and the new organic matters were formed in the soil with the increase of cropping years. Total nitrogen The content of total nitrogen in 0-40 cm soil layers gradually increased with the increase of reclaimed years (Fig.5). It was only about 0.33 g kg-1 on natural land, 0.35 g kg-1on 1 yr , 0.46 g kg-1 on 2 yr, and 0.6 g kg-1 on 3 yr reclaimed land. The main reason may be that the initial nitrogen content was very low on the unreclaimed land, and therefore it was greatly sensitive to nitrogen fertilization and increased quickly.
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Fig. 2 Electrical conductivity of 0-40 cm soil in different reclaimed years before sowing and harvest.
Fig. 3 Soil pH value of 0-40 cm soil in different reclaimed years before sowing and harvest.
Fig. 4 Soil organic matter content of 0-40 cm soil in different reclaimed years.
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Changes in Soil Properties Under the Influences of Cropping and Drip Irrigation During the Reclamation of Severe
Ratio of C to N Table 2 shows that ratio of C to N of different soil layers had a decreasing tendency with the number of years since the 1st reclaimed year. The average ratios in 0-40 cm soil of the undisturbed saltaffected land, the 1st, 2nd, and 3rd yr were 6.05, 4.82, 3.35, and 3.26, respectively. It indicated that the increasing rate of nitrogen exceeded that of carbon after reclamation. In order to preserve the sustainability and stability of salt-affected soil ecosystem, more organic matter should be added to this ecosystem. Total phosphorus As seen from Fig.6, compared with the natural salt-affected land, the total phosphorus content did not change in 5-40 cm soil layer except increase in 0-5 cm soil layer on the field of reclaimed 1
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yr. Obviously it increased in the whole 0-40 cm soil layers at the end of the 2nd and the 3rd reclaimed year. The former increased 0.24, 0.18, 0.05, and 0.15 g kg-1 respectively, and the latter increased 0.24, 0.15, 0.16, and 0.15 g kg-1, respectively. Total potassium From Fig.7, it could be seen that the change of total potassium content was not as significant as the changes of total nitrogen and total phosphorus. At the end of the 1st and 2nd reclaimed year, only in 0-5 cm soil layer, the total potassium c o n t e n t i n c r e a s e d b y 1 . 6 9 a n d 1 . 5 3 g k g -1, respectively. At the end of the 3rd reclaimed year, the total potassium content in 0-5, 5-10, 10-20, and 20-40 cm soil layers all increased and by 3.03, 1.96, 1.03, and 1.53 g kg-1, respectively.
Fig. 5 Soil total nitrogen content of 0-40 cm soil in different reclaimed years.
Fig. 6 Soil total phosphorus content of 0-40 cm soil in different reclaimed years.
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Fig. 7 Soil total potassium content of 0-40 cm soil in different reclaimed years.
Table 3 Ratio of C to N in 0-40 cm soil at different reclaimed years Soil depth (cm)
Reclaimed years Unreclaimed 1 yr 2 yr 3 yr
0-5
5-10
10-20
20-40
9.60 a 5.72 b 4.01 b 3.58 b
7.58 a 5.30 ab 4.14 b 3.44 b
6.06 a 5.61 a 3.52 a 3.23 a
4.78 4.09 2.90 3.15
a a a a
Biological properties Soil microflora On the undisturbed salt-affected land, the colony forming unit (CFU) of bacteria was very few, and it was only 1.05 × 107 count g-1 dry soil in 05 cm soil layer and about 0.02 × 107 count g-1 dry soil in 5-40 cm soil layers. After cultivation for 1 yr, the CFU of bacteria in 0-5, 5-10, 10-20, and 20-40 cm soil layers increased by 9.9, 171, 342, and 8.8 times, respectively (Table 4). After cultivation for 2 and 3 yr , the CFU of bacteria in corresponding layers increased by 1.3, 426, 47, and 54 times, and 3, 465, 603, and 592 times, respectively. This indicated that the soil environment was improved and it was more favor for bacteria to grow after reclamation. In addition, the distribution of bacteria in 0-40 cm soil profile tended to be homogeneous.
Taking one with another, the CFU of actinomycete in 0-40 cm soil increased with the increase of reclaiming years. At the 3rd reclaimed year, the CFU of actinomycete in 0-5, 5-10, 10-20, and 20-40 cm soil layers greatly increased and the increment were 27.9 × 10 3, 18.1 × 103, 31.6 × 103, and 27.5 × 103 count g-1 dry soil, respectively. Moreover, the differences in CFU of actinomycete among soil layers decreased. The CFU of fungi in 0-40 cm soil layers on the unreclaimed salt-affected land was rather few. After reclamation, it significantly increased. Compared with the unreclaimed salt-affected land, the CFU of fungi in 0-5 cm soil layer increased by 28, 67, and 103 times on the 1, 2, and 3 yr reclaimed land respectively. Moreover, The CFU of fungi in 5-40 cm soil layer also greatly increased, and gradually tended to that in the surface layer. Enzyme activities The urease activity in every soil layer of 0-40 cm all gradually increased with the reclaiming years. It was about higher 30.1, 15.7, 14.1, and 6.3 g NH4+-N g-1 dry soil h-1 in 0-5, 5-10, 10-20, and 20-40 cm soil layers at the 3rd reclaiming year than that on the original salt-affected land (Table 4). Alkaline phosphatase activity in 0-40 cm soil layer
Table 4 The quantity of bacteria, actinomycete and fungi in 0-40 cm soil in different reclaimed years Soil depth (cm) 5-5 5-10 10-20 20-40
Bacteria (× 107 count g-1 dry soil) Unreclaimed 1.05 0.02 0.02 0.02
a a a a
Actinomycete (× 103 count g-1 dry soil)
Fungi (× 10 count g-1 dry soil)
1 yr
2 yr
3 yr
Unreclaimed
1 yr
2 yr
3 yr
Unreclaimed
1 yr
2 yr
3 yr
11.4 a 4.37 a 7.20 a 0.20 a
2.39 a 10.8 a 1.0 a 1.12 a
3.86 a 11.8 a 12.7 a 12.1 a
1.41 b 0.36 a 0.74 b 1.21 ab
7.63 b 3.94 a 0.26 b 0b
9.72 b 22.5 a 12.4 b 16.5 ab
29.3 a 18.5 a 32.3 a 28.7 a
0.75 c 0a 0a 0a
21.9 bc 46.1 a 5.25 a 1.57 a
51.0 ab 50.5 a 13.4 a 42.3 a
78.1 18.7 14.2 20.5
a a a a
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Changes in Soil Properties Under the Influences of Cropping and Drip Irrigation During the Reclamation of Severe
also gradually increased. After 3 yr cultivation, Alkinine phosphatase activity in 0-5, 5-10, 10-20, and 20-40 cm soil layer increased by 10.5, 4.4, 2.3, and 2.7 times, respectively. Sucrase activity didn’t change greatly. However, the differences among different soil layers gradually became small. On the original salt-affected land, the ratio of sucrase activity in 0-5 cm soil layer to that in 20-40 cm soil layer was 2.5. On the 1st year reclaimed land, it hardly changed. On the 2nd and 3rd year, the ratios both decreased, which were 0.7 and 0.8 respectively.
DISCUSSION AND CONCLUSION There are several obstacles for crop production in saltaffected soil such as poor fertility, low activity of soil organisms, high salinity, and osmotic potential. The changes of environment induced by irrigation and other agronomic practices received more and more attentions (Ilyas et al. 1997; Barbiéro et al. 2001; Herrero and Pérez-Coveta 2005; Pilatti et al. 2006; Alvarez-Rogel et al. 2007). In this study, soil bulk density of 0-20 cm soil layer reduced quickly at the 1st 3 yr of reclamation and the soil becomes loose and could hold more water and air. Then aeration condition in the root zone would be improved. The result could be verified by the increase of soil saturated water content. It improved from 21.9% in 0.1 m soil of undisturbed saline land to 30.2% of the 3rd yr field. The soil bulk density of 0-20 cm soil changed from 1.71 g cm-3 on the undisturbed saline land to 1.44 g cm-3 on the 3rd year field. Akhter et al. (2004) also observed that soil bulk density decreased from an average value of 1.62 to 1.53 g cm-3 in the upper 0.2 m soil through planting Kallar grass 5 y and soil porosity increased from 38.9 to 42.8%. Soil bulk density of 20-40 cm layer tended to increase by 0.1-0.2 g cm-3 after 2 and 3 reclaimed years. The
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reason was that the upper soil was tilled and became loose, while the soils in the deeper soil layers were impacted during the mechanical tillage. On the other hand, frequent drip irrigation could leach some fine soil particles to the deeper soil layers and made soils of these layers more compact. Soil aeration was a problem to discuss when soil matric potential was controlled above -10 kPa. For only soil matric potential of 0.2 m depth right under the emitter was above -10 kPa and those of outer of the wet volume were below -10 kPa. Addtionally, Jiao et al. (2007, 2008) reported that waxy corn and oil-sunflower were got the highest yield when soil matric potential of 0.2 m depth right under the emitter was -5 kPa at the same experimental site. It indicated that the effect of soil areation on corn growth was not significant when soil matric potential was -5 kPa in this study. At the same time, average salinity of 0-40 cm soil was dropped from 8.8 ds m-1 in undisturbed land to 2.24 ds m-1 in the 3rd yr field. In addition, the soil pH values in the root zone were reduced after reclamation from 8.88 to 8.36 correspondingly. The results were similar with those of Shi et al. (2006), who reported that soil EC and soil pH values steadily decreased after reclamation in coastal saline lands. Soil C and N are two essential elements in the soil ecosystem. Soil organic matter in the 0-40 cm soil reduced at the 1st 2 yr, and then increased at the 3rd yr. Total nitrogen content increased with the increase of reclaimed years. It indicated that total nitrogen content depended on the nitrogen fertilizer greatly. Changes of soil organic matter and total nitrogen caused changes of ratio of C to N. The ratio of C to N declined with the increase of reclaimed years from 6.05 in undisturbed salt-affected land to 3.26 in the 3rd yr field. To preserve the sustainability and stability of salt-affected soil ecosystem, adding organic matter such as farmyard manure, green manure, and crop residual should be required (Zhang et al. 1997; Tejada et al. 2006; Li et al.
Table 5 Activities of urease, alkaline phosphatase, and sucrase in 0-40 cm soil in different reclaimed years Soil depth (cm) 0-5 5-10 10-20 20-40
Urease activity (g NH4+-N g -1 dry soil h -1) Unreclaimed 3.86 2.10 3.21 2.80
b b b b
Alkaline phosphatase activity (g Ph(OH) g-1 dry soil h -1)
1 yr
2 yr
3 yr
Unreclaimed
5.81 b 4.26 b 2.33 b 3.22 b
7.40 b 7.31 b 5.27 b 3.04 b
33.97 a 17.80 a 17.28 a 9.10 a
25.59 b 18.95 c 24.18 c 18.40 b
1 yr 192.78 ab 76.71 ab 45.60 bc 19.07 b
Sucrase activity (g Glu g-1 dry soil h-1)
2 yr
3 yr
Unreclaimed
1 yr
89.22 b 47.89 bc 54.66 ab 22.92 b
293.76 a 101.65 a 79.27 a 67.63 a
36.13 a 58.91 a 21.02 a 14.44 a
25.36 a 42.86 a 26.27 a 9.42 a
2 yr 21.92 23.83 15.38 31.72
3 yr a a a a
29.45 29.50 37.93 34.66
a a a a
© 2009, CAAS. All rights reserved. Published by Elsevier Ltd.
1236
2006). Soil microorganisms in salt-affected soil are restrained by high salinity inducing osmotic stress (Yuan et al. 2007). In general, quantities of different kinds of microorganisms in salt-affected soil are very fewer than those in non-saline soils, which increased markedly through cropping and drip irrigation. In salt-affected soil, there were less fungi than bacteria and actinomycete in the 0-40 cm soil. With the increase of reclaimed year, except for the enhancement of the amount of bacteria, actinomycete and fungi, their distribution on the profile of 0-40 cm soil became even. Lin et al. (2006) observed that the bacteria, actinomycete, and fungi increased by 2.3, 4.3, and 71 times through planting Suaeda salsa L. in coastal saline soil. The main reasons were attributed two aspects: The decrease in soil salinity and the improvement in soil fertility created a relatively good environment for microbial growth and reproduction after cropping and drip irrigation; the root exudation and other organic material such as root debris in the soil offered “food” for microorganisms. Enzyme activity is an important indicator for evaluation of soil biological activity. Soil enzymes are catalyzer for many reactions and play an important role in the conversion of energy and cycles of nutrients. The improvements of the activities of urease and alkaline phosphatase not only occurred in the 0-20 cm soil but also in the 20-40 cm soil after cropping and drip irrigation. At the mean time, the activities of urease and alkaline phosphatase of 0-20 cm soil increased with the increase of reclaimed years. However, the activity of sucrase in 0-10 cm soil reduced with the increase of the number of cultivated years. That of 10-40 cm soil increased to some extent after reclaimed 2 and 3 yr. The conclusions in this study were based on only 3 yr of data sets. To assess the sustainability of the measurements of water and salt regulation in arid region, further researches should be carried out.
Acknowledgements This work was financially supported by the Chinese Academy of Sciences Action Plan for the Development of Western China (KZCX2-XB2-13), the Chinese Academy of Sciences Knowledge Innovation Project (KSCX2-YW-N-080), and the Project for 100 Outstanding Young Scientists supported by Chinese Academy of
TAN Jun-li et al.
Sciences.
References Akhter J, Murray R, Mahmood K, Malik K A, Ahmed S. 2004. Improvement of degraded physical properties of a salinesodic soil by reclamation with Kallar grass (Leptochloa fusca). Plant and Soil, 258, 207-216. Alvarez-Rogel J, Jiménez-Cárceles F J, Roca M J, Ortiz R. 2007. Changes in soils and vegetation in a Mediterranean coastal salt marsh impacted by human activities. Estuarine, Coastal and Shelf Science, 73, 510-526. Barbiéro L, Valles V, Régeard A, Cheverry C. 2001. Residual alkalinity as tracer to estimate the changes induced by forage cultivation in a non-saline irrigated sodic soil. Agricultural Water Management, 50, 229-241. Bresler E, McNeal, B L, Carter, D L. 1982. Saline and Sodic Soils: Principles-Dynamics-Modeling. Springer-Verlag, Berlin Heidelberg. Feng Z, Wang X, Feng Z. 2005. Soil N and salinity leaching after the autumn irrigation and its impact on groundwater in Hetao Irrigation District, China. Agricultural Water Management, 71, 131-143. Guan S. 1986. Enzyme in Soils and Their Study Methods. China Agriculture Press, Beijing. pp. 260-313. (in Chinese) Herrero J, Pérez-Coveta O. 2005. Soil salinity changes over 24 years in a Mediterranean irrigated district. Geoderma, 125, 287-308. Ilyas M, Qureshi R H, Qadir M A. 1997. Chemical changes in a saline-sodic soil after gypsum application and cropping. Soil Technology, 10, 247-260. Jiao Y, Kang Y, Wan S, Liu W, Dong F. 2007. Effect of soil matric potential on waxy corn growth and irrigation water use efficiency under mulch drip irrigation in saline soils of arid areas. Agricultural Research in the Arid Areas, 25, 144151. (in Chinese) Jiao Y, Kang Y, Wan S, Sun Z, Liu W, Dong F. 2008. Effect of soil matric potential on the distribution of soil salt under drip irrigation on saline and alkaline land in arid regions. Transactions of the CSAE, 24, 53-58. (in Chinese) Kang Y, Wan S, Jiao Y, Tan J, Sun Z. 2008. Saline soil salinity and water management with tensiometer under drip irrigation. In: Symposia on the Fifth Annual Meeting of Agricultural Land and Water Engineering of Chinese Society of Agricultural Engineering. pp. 124-131. Kitamura Y, Yano, T, Honna T, Yamamoto S, Inosako K. 2006. Causes of farmland salinization and remedial measures in the Aral Sea Basin-Research on water management to prevent secondary salinization in rice-based cropping system in arid land. Agriculture Water Management, 85, 1-14.
© 2009, CAAS. All rights reserved. Published by Elsevier Ltd.
Changes in Soil Properties Under the Influences of Cropping and Drip Irrigation During the Reclamation of Severe
1237
Li X, Li F, Bhupinderpal S, Cui Z, Zed R. 2006. Decomposition of maize straw in saline soil Biol. Fertilizer Soils, 42, 366-
Qureshi A S, McCornick P G, Qadir M, Aslam Z. 2008. Managing salinity and waterlogging in the Indus Basin of Pakistan.
370. Lin X Z, Chen K S HE P Q, Shen J H, Huang X H. 2006. The
Agricultural Water Management, 95, 1-10. Shi Z, Cheng J L, Huang M X, Zhou L Q. 2006. Assessing
effects of Suaeda salsa L. planting on the soil microflora in coastal saline soil. Acta Ecologica Sinica, 26, 801-807. (in
reclamation levels of coastal saline lands with integrated stepwise discriminant analysis and laboratory hyperspectral
Chinese) Manjunatha M V, Oosterbaan R J, Gupta S K, Rajkumar H,
data. Pedosphere, 16, 154-160. Tejada M, Garcia C, Gonzalez J L, Hernandez M T. 2006. Use
Jansen H. 2004. Performance of subsurface drains for reclaiming waterlogged saline lands under rolling topography
of organic amendment as a strategy for saline soil remediation: Influence on the physical, chemical and biological properties
in Tungabhadra irrigation project in India. Agricultural Water Management, 69, 69-82.
of soil. Soil Biology & Biochemistry, 38, 1413-1421. Wang Z, Zhu S, Yu R, Li L, Shan G, You W, Zeng X, Zhang C,
Mokady R S, Bresler E. 1968. Reduced sodium exchange capacity in unsaturated flow. Soil Science Society of America
Zhang L, Song R. 1993. China’s Saline Soils. Science Press, Beijing. (in Chinese)
Proceeding, 32, 436-467. Pilatti M A, Imhoff S, Ghiberto P, Marano R P. 2006. Changes
Yuan B, Li Z, Liu H, Gao M, Zhang Y. 2007. Microbial biomass and activity in salt affected soils under arid conditions.
in some physical properties of Mollisols induced by supplemental irrigation. Geoderma, 133, 431-443.
Applied Soil Ecology, 35, 319-328. Zhang R, Yan H J, Wei Y Q, Shan X Z, Liu J F. 1997. The effect
Qadir M, Qureshi R H, Ahmad N. 1998. Horizontal flushing: a promising ameliorative technology for hard saline-sodic and
of organic matter fertilizer on the reclamation of saline soils. Soil and Fertilizer, 4, 11-14. (in Chinese)
sodic soils. Soil & Tillage Research, 45, 119-131. (Edited by WANG Ning)
© 2009, CAAS. All rights reserved. Published by Elsevier Ltd.