Agricultural Activities Increased Soil Organic Carbon in Shiyang River Basin, a typical inland river basin in China

doi:10.21203/rs.3.rs-4723160/v1

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Agricultural Activities Increased Soil Organic Carbon in Shiyang River Basin, a typical inland river basin in China

https://doi.org/10.21203/rs.3.rs-4723160/v1

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Oasis agriculture is one of the main forms of agriculture in the world. Studying the impact of agricultural practices on soil organic carbon (SOC) within oases can provide valuable insights into the dynamics of carbon input and sequestration in oasis agriculture. It can contribute to the development of well-reasoned agricultural policies. This work took the farmland in a typical inland river basin, Shiyang River Basin, of arid areas as the research object and compared the impact of the leading agricultural activities on the SOC. Samples were collected and their SOC content was determined in the laboratory. This work believes that: (1) In the same inland river basin, the organic carbon of farmland in the upper and middle reaches is significantly higher than that in the lower reaches, and the farmland in the core area of the oasis is higher than that in the marginal area; (2) The SOC content of farmland in the inland river basin is higher than that of woodland and grassland, and agricultural reclamation increases the SOC content in the inland river basin; (3) The abandonment of cultivated land leads to a decrease in SOC, and plastic film mulching has no obvious effect on the content of SOC. The research has clarified the impact of agricultural activities on SOC in arid oasis areas, and quantified the impact of different agricultural activities on SOC. The research can provide new references for understanding the impact of agriculture in arid regions on carbon cycling.

Earth and environmental sciences/Ecology/Agri ecology

Biological sciences/Ecology/Biogeochemistry/Carbon cycle

Soil organic carbon

Shiyang River

Agricultural reclamation

Oasis farmland

Abandon farming

Soil is the largest carbon pool in the terrestrial ecosystem and an important part of the global carbon cycle (Schlesinger, 2000; Amundson, 2002; Lal, 2003, 2004). Two thirds of the global organic carbon are stored in the soil, and the content of SOC is three times that of plant organic carbon and twice that of atmospheric organic carbon (Davidson, 2006). SOC plays an important role in mitigating climate change and food security (Li, 2004). The soil organic carbon (SOC) in agricultural fields is the cornerstone of soil fertility, ensuring crop production and food security, while also influencing climate conditions by regulating greenhouse gas emissions. (Schlesinger, 2000; Amundson, 2001; Lal, 2003, 2004; Zhao, 2018). Soil organic carbon can provide nutrients needed by plants and energy required by microorganisms in the soil, which plays an important role in agricultural production. The change of SOC content is affected by many factors, such as climate and soil conditions (Miller, 2004; Chen, 2020). Temperature and precipitation affect the organic matter in the soil by directly affecting vegetation and microorganisms and further affect the content of SOC. Many scholars also focus on the influence of vegetation types on SOC and the dynamic changes of soil carbon pool after the Grain for Green Project (Ayoubi et al., 2012). Land use/cover change significantly impacts organic carbon storage in ecosystems, especially on agroecosystems (Wang et al., 2016; Gelaw et al., 2014).

The agricultural soil carbon pool is the most active and important soil organic carbon pool (Hobley E U et al., 2016). On the one hand, the agricultural soil will change rapidly and be adjusted in a short time due to strong human interference, which plays an important role in global soil carbon balance. On the other hand, SOC is the core of soil fertility and coordinates soil nutrients and water. It is one of the material foundations for the high yield and stability of crops. It also affects CO₂ emissions and is directly related to climate change (Loveland P et al., 2003). SOC is an important index for evaluating cultivated land quality and an important factor for sustainable development of agriculture.. Cultivated land soil is a complex of human activities. The different biomass of different crop types and the proportion of litter residues entering the soil will impact SOC content. Different agricultural management methods (Davidson, 2006; Lal et al., 2011), such as planting systems, farming methods and fertilization methods, play a vital role in the organic carbon content of agricultural soil. Studies have shown that irrigation, deep tillage or shallow tillage, and the use of different plows will impact on soil carbon pool (Feng et al., 2020). Crop cultivation, irrigation, and other soil management activities significantly impact the quality and quantity of soil carbon, thus affecting the regional and global environment (Lal, 2004). The effects of different tillage methods on SOC depend on the degree of disturbance and the intensity of land management measures (Haddaway et al., 2017).

A large number of studies have focused on the impact on SOC of different agricultural activities, especially in some arid areas (Topa et al., 2021; Xu et al., 2021; Wang et al., 2016). Shiyang River is a typical inland river basin in arid areas, and agriculture is the main industry. At present, the main research focuses on the characteristics of SOC under different natural vegetation, river dissolved organic carbon (DOC) and different geomorphic units and land use patterns (Wan et al., 2019; Zhu et al., 2020). Clarifying the impact of agricultural activities on SOC plays an important role in formulating reasonable agricultural management measures, increasing soil carbon storage and mitigating climate change in inland river basins in arid areas. In this work, soil samples from different agricultural management methods in the upper, middle and lower reaches of Shiyang River Basin were collected, hoping to solve the following problems: (1) Differences in soil organic carbon content between farmland and other land use types; (2) Effects of agricultural activities such as abandoned tillage and plastic film mulching on SOC. The research can provide new insights for the study of the carbon cycle in arid areas.

Shiyang River Basin is located on the north slope of the eastern Qilian Mountains and the east of the Hexi Corridor (Fig. 1). The basin is a complex landscape composed of many landform types, such as fluvial landform and wind-sand landform. The basin belongs to the arid area of Northwest China, with an altitude of 2,000–5,000m, which belongs to continental temperate arid climate with strong solar radiation, long sunshine time and large temperature difference between day and night. The basin is dry and rainy in summer, with 300-600mm annual precipitation and vigorous evaporation of 700-1,200mm. Shiyang River Basin is one of the three inland river basins in the Hexi Corridor, with 41,600 km². Shiyang River originates from the northern slope of Qilian Mountain, and the whole water system is composed of Dajing River, Gulang River, Huangyang River, Zamu River, Jinta River, Xiying River, Dongda River and Xida River from east to west. The flood season is mainly in spring and summer. The temperature rises in spring, and the snow and ice melt in mountainous areas, resulting in a spring flood. Precipitation is concentrated in summer, forming flood peaks. The vertical zonality of vegetation in the basin is obvious, with forest grassland and subalpine shrub meadow vegetation belts in the upper reaches. The middle and lower reaches are mainly bare land with poor vegetation coverage. The soil is mainly composed of calcareous, chestnut, alpine shrub meadow, and desert soil. The soil type in the oasis agricultural belt is oasis irrigation and siltation soil.

The agriculture in the region is mainly production, planting and animal husbandry. Limited by natural conditions in the region, agriculture is distributed along rivers and oases, with a total cultivated land area of 6.25 million acres. The crops in the region are mainly grain crops such as spring wheat and summer corn, and economic crops are mainly cotton, sunflower and fennel. At present, the total population of the basin is 2.27 million, with a population density of 55 people per square kilometer, which is 3.4 times the population density in the Hexi area, and the ecological environment is under great pressure. There is a lack of agricultural water resources in the region, which is generally irrigated agriculture, with irrigation area accounting for 70%, and the source of irrigation water is river diversion. Affected by long-term irrigation, soil salinization is serious. The main types of crops planted are corn, wheat, cotton and vegetables.

3.1 Design of sampling points

In the Shiyang River Basin, Xiyingwugou (M1) was selected as the mountainous area farmland sampling point in the upper reaches. Yangxiaba (O1), Wuwei Basin (O2) and Caiqiqiao (O3) were chosen as oasis farmland sampling points in the middle reaches. Suwu Township (O4), Datan Township (O5) and Xiqu Town (O6) were selected as the oasis marginal area farmland sampling points in the lower reaches. Poplar is selected as the natural vegetation sampling point at the upstream sampling point Xiyingwugou (M1). In Caiqiqiao Town (O3) in the oasis area of the middle reaches, abandoned land, woodland, grassland and farmland abandoned for 2 years were selected to collect samples, and the distance between sampling points should not be the distance between sampling points exceed 100m Desert soil samples were collected downstream of Qingtu Lake (D1).

Use manual auger to collect 0–10 cm, 10–20 cm, 20–30 cm, 30–40 cm, 40–50 cm, 50–60 cm, 60–70 cm, 70–80 cm, 80–90 cm, 90–100 cm soil samples. At each sampling point, sampling is performed at the centre point and 4 positions 2 meters away from the centre point, so each sampling point has five sub-sample positions. Mix 5 sub-samples at each sampling point to obtain a composite sample. A total of 1,327 samples were collected from April to October 2018–2019(Table 1).

Table 1

Basic data for each sampling point
Sampling point	Sample size	Long (°E)	Lat (°N)	Alt (m)	T (°C)	P (mm)	Vegetation species
Sampling point	Sample size	Long (°E)	Lat (°N)	Alt (m)	T (°C)	P (mm)	Natural vegetation	Crop
Xiyingwugou (M1)	217	102°10′	37°53′	2097	7.99	273.52	Populus L.	Maize
Yangxiaba (O1)	113	102°41′	38°01′	1489	10.76	121		Maize
Wuwei Basin (O2)	112	102°42′	38°06′	1467	10.15	186.5		Maize
Caiqiqiao (O3)	440	102°45′	38°13′	1443	11.40	—	Salix matsudana Koidz.	Maize
Suwu Township (O4)	120	103°05′	38°36′	1372	11.1	—		Maize
Datan Township (O5)	120	103°23′	38°79′	1349	11.49	115		Maize
Xiqu Town(O6)	86	103°29′	38°92′	1325	—	—		Maize
Qingtu Lake (D1)	119	103°36′	39°03′	1313	8.8	98.4	Haloxylon ammodendron (C. A. Mey.) Bunge
Note: T: annual temperature; P: annual precipitation; — : not measured.

3.2 Experimental analysis

In the laboratory, soil samples were air-dried, gravel and roots were removed using a 2 mm sieve, and SOC concentration was determined by wet oxidation with dichromate (Zhu et al., 2017).

$$\:{C}_{2}=\frac{0.2\times\:20}{{v}_{1}}$$

Where C₂ is the concentration of ferrous sulfate standard solution; v₁ is the volume of ferrous sulfate consumed.

$$\:C=\frac{({v}_{0}-v)\times\:{C}_{2}\times\:0.03\times\:1000}{M}$$

Where C is organic carbon content, v₀ is the volume of ferrous sulfate consumed by two blanks, v is the volume of ferrous sulfate consumed per sample, and M is sample quality.

3.3. Meteorological data

The automatic weather station (WatchDog 2000 Series Weather Stations) set up near the sample site was used to obtain and record the local temperature and other meteorological data during the sampling period. Precipitation data were obtained from precipitation observation points placed near the soil sampling sites.

4.1 Spatial distribution characteristics of soil organic carbon in Shiyang River farmland

The average SOC content of 0-100 mm farmland decreased gradually from upstream to downstream in Shiyang River Basin: mountainous farmland in the upstream (20.91g/kg) > oasis farmland in the midstream (20.52g/kg) > oasis marginal farmland in the downstream (8.17 g/Kg)(Fig. 2). There was little difference in SOC content between mountainous farmland in the upstream and oasis farmland in the midstream. There was a big difference in SOC content between oasis marginal farmland in the downstream and farmland in the upstream and midstream. The farmland in the upper mountainous area is a rain-fed agricultural area with sufficient rainfall and vegetation types. The accumulation of organic matter is good. At the same time, the sampling point of M1 is located in the piedmont area, where a large amount of fertile soil is accumulated by erosion, the soil is fertile, and the organic carbon content is high. Oasis farmland in midstream is irrigated agriculture with flat terrain and good agricultural management. The soil type is typical oasis irrigation and silting soil, and a large number of crop roots remain in the soil, which increases the input of soil organic matter and has high SOC content. The farmland in oasis marginal farmland downstream lies between Tengger Desert and Badain Jaran Desert, and there are more sand grains in the soil. At the same time, due to less precipitation and large evaporation in the downstream, the growth of plants is limited due to the influence of drought, so the biomass is less, the input of organic matter is less, and the SOC content is lower.

The highest SOC content in oasis farmland in midstream was at sampling point O2 (24.02g/kg), and the highest SOC content in oasis marginal farmland in downstream was at sampling point O4 (24.02g/kg). Sampling point O2 is located in Wuwei Basin, with flat terrain, surrounding farmland shelterbelts and crops growing well, proper agricultural management measures and high SOC content in farmland. The closer farmland is to the desert area, the lower SOC content is.

The box represents 25–75% percentile, the required line indicates 95th and 5th percentile. The line in the box represents median (50thpercentile), the square in the box represents average value.

4.2 Vertical distribution characteristics of SOC in Shiyang River farmland

The vertical distribution of SOC content in most farmland showed a law of fluctuation and decreasing in Shiyang River Basin (M1, O2, O3, O5, O6). The SOC content in the upper layer (0–20 cm) was significantly higher than that in the lower layer (20–100 cm), and the maximum SOC content appeared in the 0-30cm soil layer. However, SOC in the topsoil (0–20 cm) at sampling points O1 and O4 was lower than that in the lower soil, and the maximum SOC content appeared in 80–90 cm soil layer and 90–100 cm soil layer, respectively (Fig. 3). Because the roots of crops are shallow, they are generally distributed in the surface soil, and a large amount of organic matter is left in the farmland after the crops are harvested, and the surface soil layer has more humus and higher SOC content.With the increase of soil depth, organic matter and microorganisms content reduced, and the SOC content gradually reduced. The reason for this anomaly at sampling points O1 and O4 may be that the crops planted at sampling points are all corn. The agricultural management measures of straw returning to the field and deep ploughing changed the vertical distribution of SOC.

The maximum SOC content in mountainous farmland (M1) was 20.2 g/kg, which appeared in 0–10 cm soil layer, the minimum SOC content was 12.56 g/kg, and it appeared in 90–100 cm soil layer, and the difference between the maximum SOC content and the minimum SOC content was 7.64 g/kg. In oasis farmland (O1, O2, O3) 0-100 cm soil layer, the maximum and minimum SOC content was 6.34 g/kg, 12.5 g/kg and 17 g/kg, respectively the difference increased gradually. The differences between the maximum and minimum SOC content in 0-100 cm soil layer of oasis marginal farmland (O4, O5, O6) were 14.76 g/kg, 1.8 g/kg and 9.47 g/kg, respectively, showing a trend of first decreasing and then increasing, which was smaller than that of oasis farmland in midstream (Fig. 3). This is because agricultural irrigation and human activities in oasis areas have profoundly changed the properties of soil. Agricultural measures such as irrigation and fertilization have significantly improved the fertility of the surface soil layer and increased the SOC content in the surface soil layer. Therefore, the vertical difference of SOC content in 0-100 cm of oasis farmland is large.

5.1 Influences of agricultural reclamation on SOC

The change of land use type is an essential factor leading to the change of SOC pool (Gaillard M J et al.,2018). Under the pressure of population growth and economic and social development, many woodland and grassland have been reclaimed as farmland in Shiyang River Basin. The average SOC content of farmland in 0-100 mm soil layer in the upstream of Shiyang River was 20.24g/Kg, which was obviously higher than that of woodland (12.57g/Kg), and the SOC increase rate was 61.01%. In the midstream, the average SOC content of farmland in 0-100 mm soil layer was 5.04g/Kg, which was higher than that of woodland (4.31g/Kg) and 2.1 times that of grassland (2.39g/Kg). In the downstream, the average SOC content of farmland in 0-100 mm soil layer is 4.1g/Kg, which was higher than that in the downstream desert area (Fig. 4).

The increase of SOC may be due to the decrease of tillage intensity (Puget & Lal, 2005; Rahmati et al., 2020) or the increase of carbon input, such as directly through fertilizer and crops and indirectly through mineral fertilizer (Dong et al., 2018; Yang et al., 2018; Yu et al., 2020). Carbon sequestration in agricultural soil is considered an important way to slow down greenhouse gas emissions and global climate change. The SOC content is mainly determined by the input and output of organic matter. The main sources are animals and plants, microbial residues and root exudates, and the main production includes erosion and decomposition, which is in the process of constant change. The transformation of natural vegetation into farmland in the Mediterranean region leads to a huge loss of SOC (Seddaiu et al., 2013; Aguilera et al., 2013, 2018), contrary to the SOC change trend observed in an inland river basin in the arid regions. Oasis agricultural area in Shiyang River Basin is a typical irrigated agricultural area with a large amount of agricultural fertilizer input. Straw returning to the field will be adopted to maintain soil fertility in the basin, so agricultural reclamation obviously increases SOC content in the Shiyang River basin.

The box represents 25–75% percentile, the required line indicates 95th and 5th percentile, and the point indicates outliers. The line in the box represents median (50thpercentile), the square in the box represents average value.

5.2 Influences of abandoned land on soil organic carbon

Due to the migration of labor force caused by urbanization, land fertility declined, water resources were insufficient, and a large amount of farmland was abandoned (Deng et al., 2016; Romero-Díaz et al., 2017). The oasis agricultural area in Shiyang River Basin is limited by water resources, and a large number of lands that cannot be irrigated or whose soil fertility is declining have been abandoned, or vegetation restoration projects have been carried out in recent years (Wang et al., 2019). Comparing SOC content of abandoned land, farmland and natural grassland in typical oasis irrigation agricultural area of Shiyang River Basin, it was found that SOC content of abandoned land was 3.57 g/kg, which was lower than that of farmland (5.04 g/kg) and woodland (4.31 g/kg) and higher than that of grassland (2.86 g/kg). SOC content of abandoned land decreased by 29.1% compared with that of farmland (Fig. 5). After abandoned land, vegetation restoration is not carried out, which leads to a sudden decrease in surface and underground biomass, a decrease in organic matter entering the soil, and a decrease in carbon input, making the SOC content of abandoned land significantly lower than that of farmland. Woodland has a strong carbon sequestration capacity, and a large number of animal and plant residues directly enter the soil, so the SOC of forest land is obviously higher than that of abandoned land. The root system of grassland plants is shallow, the carbon input of animal and plant residues and artificial carbon input are less, the abandoned land has a short time, and the accumulated carbon before abandonment is not completely decomposed, so the SOC content of grassland is obviously lower than that of abandoned land.

The soil of abandoned land has undergone a process of self-recovery, and these agricultural soils and vegetation are developing towards their natural composition (Kalinina et al., 2011; Nicodemus et al., 2013; Novara et al., 2013). Without interference from human activities, it takes a long time for natural vegetation to be restored. In this process, the carbon content in the soil will gradually increase, which will help to reduce the concentration of CO₂ in the atmosphere (Novara et al., 2012). Comparing the abandoned land with different abandonment periods in other regions, it can be found that SOC content increases with the increase of abandonment period (Table 2). Studies in the Mediterranean area have proved that when the farmland is abandoned, the natural vegetation resettlement will increase the carbon storage in the soil, especially when the abandoned farmland is ultimately succeeded as woodland (Zethof et al., 2019). In the study area, because the abandonment period is only two years, the natural vegetation has not been completely restored, and the abandoned soil is in the process of self-repair, so the SOC content is obviously lower than that of farmland.

Table 2

The influence of abandonment period on SOC
Research area	Abandonment period(year)	Before	After	SOC		Reference
Research area	Abandonment period(year)	Before	After	Abandoned farmland	Farmland	Reference
Shiyang River basin (101°41′~102°04′E, 37°30′~37°52′N)	2	Maize	Nitraria tangutorum	3.97 g/kg	5.04 g/kg	This study
Loess Plateau: Huining (104°29'-105°31'E, 35°24'- 36°26'N)	5–10	apricot trees	Grassland	7.07 g/Kg	6.62 g/Kg	Cao et al., 2020
Italy: Pantelleria (36°44′N, 11°57′E)	15	grape	Grassland	25.1g/Kg	21.9 g/Kg	Novara et al., 2014
	35	grape	Grassland	25.5 g/Kg	21.9 g/Kg
Spain: Andalucía (36°50′N, 4°34′W)	30	cereals and olies	Cistusspp Genista umbellata Ulex parviflorus	20.4 g/kg	7.9 g/kg	Trigalet, Gabarrón-Galeote, Van Oost, & van Wesemael 2016
Cyprus: Troodos	27 27–57	Grape Grape	Garrigue Grape	1.1% 1.2%	1.0% 1.0%	Djuma et al., 2020
Spain:	100			7%	1.0%	Romer-Díaz et al., 2017

5.3 Influences of plastic film mulching on SOC

Lack of precipitation and irrigation water are the main limiting factors for increasing crop yield in semi-arid areas. Plastic film mulching can reduce the limitation of water resources by increasing soil temperature and reducing soil water evaporation (Liu et al., 2014). To study the influences of plastic film mulching on soil organic carbon content in farmland, continuous sampling was carried out in the main growing period of crops in the farmland with plastic film mulching and without plastic film mulching in Datan Township in the downstream of Shiyang River Basin. The results showed that the average SOC content of farmland covered with plastic film and farmland without plastic film was 4.33 g/Kg at 0-100 m, and the SOC content of the soil was not significantly changed by the plastic film in the arid inland river basin (Fig. 6a). Plastic film mulching reduced soil moisture evaporation but prevented some animal and plant residues from entering the soil. At the same time, due to the heat preservation effect of plastic film, it increased soil microbial biomass (Li et al., 2004; Wang et al., 2014; Hai et al., 2015), soil enzyme activity (Gan et al., 2013) and nitrogen mineralization effectiveness (Zhang et al., 2012), which accelerated the decomposition of organic substances in the soil. Plastic film mulching promoted the development of crop roots and increased the underground biomass of soil (Flanagan, Sharp, & Letts, 2013), but microbial mineralization of soil organic carbon offset this part of carbon input (Wang et al., 2016).

Compared with plastic film mulching, SOC content changed more strongly without plastic film mulching (Fig. 6b). SOC content fluctuated wildly in the vertical section of 0-100 cm soil layer in farmland without plastic film mulching. The difference between maximum SOC content (30–40 cm) and minimum SOC content (90–100 cm) was 4.65 g/Kg. SOC content in the vertical section of 0–80 cm soil layer in plastic film mulching farmland showed a fluctuating and decreasing trend. The abnormal high value appeared in the 80–100 cm soil layer, which may be affected by deep organic matter. The difference between the maximum SOC content (0–10 cm) and the minimum SOC content (60–70 cm) was 1.6 g/Kg. Plastic film mulching can keep the soil warm and reduce the evaporation of soil water (Yang et al., 2015), which enhances soi lstability and improves the stability of soil carbon pool (Wang et al., 2016).

5.4 Suggestions on agricultural management in inland river basin

Agricultural reclamation leads to different characteristics of carbon pool changes in different regions (Wang et al., 2014). The results showed that agricultural planting in the inland river basin in arid areas significantly increases the SOC content in the mountainous area of the upstream and the marginal desert area of the downstream. Compared with woodland, SOC content in the oasis agricultural area in the midstream decreased, but SOC content increased obviously compared with grassland. However, forests and natural grasslands play an irreplaceable role in maintaining ecosystem balance and biodiversity (Lu et al., 2018; Sun et al., 2018). Therefore, straw returning to field measures should be taken for farmland to increase carbon input and soil carbon storage, and forests and natural grasslands in uncultivated areas should be protected and managed.

Due to the limitation of water resources and the requirement of ecological environment protection, a large amount of farmland has been abandoned or Grain for Green Project (Cao et al., 2011; Han et al., 2017). In a short period of time, direct abandonment will lead to the decrease of SOC content, which makes a large amount of carbon stored in soil decompose and release into the atmosphere. Grain for Green Project will accelerate the restoration process of soil and natural vegetation, increase SOC content, and then play a role in improving the environment and mitigating climate change (Hu, 2014; Liu et al., 2017; Zhang et al., 2018). From the research results of this paper, it can be concluded that the average SOC content of woodland is obviously higher than that of grassland. Therefore, attention should be paid to the ecological restoration project of abandoned land in the Shiyang River Basin. The afforestation project should be carried out to increase the soil carbon pool reserves, reduce the carbon emission from soil to air mitigate global warming.

In the same inland river basin, the organic carbon of oasis farmland in the midstream and upstream was obviously higher than that in the downstream, and the farmland in the core area of the oasis was higher than that in the marginal area. Through the comparative sampling study of farmland, woodland, grassland and desert in the Shiyang River Basin, the research method of replacing time with space proves that agricultural reclamation increases SOC in Shiyang River Basin. Comparing the abandoned land and farmland with the two years' abandonment period, it was found that SOC content of abandoned land decreased by 29.1% compared with farmland, and the abandonment period was an important factor affecting the change of SOC pool. By comparing SOC of farmland with or without plastic film mulching, it was found that there was no obvious difference in SOC content between them, but with plastic film mulching, the stability of soil was improved within 100 mm, which enhanced the stability of soil carbon pool.

This study provides evidence for the influences of agricultural activities on SOC in arid areas. In the arid inland river basin, agricultural management plays an extremely important role in increasing SOC, so returning straw to the field management should be actively promoted and green manure should be applied to improve SOC content. Ecological restoration projects should be carried out after abandoned farming to maintain the carbon storage in the soil.

Conflict of Interest Statement

The authors declare no conflicts of interest.

Author Contribution

Guofeng Zhu and Qinqin Wang conceived the idea of the study; Wenhao Zhang, Siyu Lu and Ling Zhao analyzed the data; Dongdong Qiu, Longhu Chen and Rui Li were responsible for field sampling; Qinqin Wang, Yuanxiao Xu and Enwei Huang participated in the experiment; Yinying Jiao, Yuhao Wang and Gaojia Meng participated in the drawing; Qinqin Wang wrote the paper; Xiaoyu Qi and Wentong Li checked and edited language. All authors discussed the results and revised the manuscript.

Acknowledgments:

This research was financially supported by the National Natural Science Foundation of China(42371040, 41971036), Key Natural Science Foundation of Gansu Province(23JRRA698), Key Research and Development Program of Gansu Province(22YF7NA122), Cultivation Program of Major key projects of Northwest Normal University(NWNU-LKZD-202302), Oasis Scientific Research achievements Breakthrough Action Plan Project of Northwest normal University(NWNU-LZKX-202303).

Data Availability

The data that support the findings of this study are available on request from the corresponding author, soil organic carbon data are not publicly available due to privacy or ethical restrictions.

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Agricultural Activities Increased Soil Organic Carbon in Shiyang River Basin, a typical inland river basin in China

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Abstract

Figures

1. Introduction

2. Study area

3. Data and methods

3.1 Design of sampling points

3.2 Experimental analysis

3.3. Meteorological data

4. Results

4.1 Spatial distribution characteristics of soil organic carbon in Shiyang River farmland

4.2 Vertical distribution characteristics of SOC in Shiyang River farmland

5. Discussion

5.1 Influences of agricultural reclamation on SOC

5.2 Influences of abandoned land on soil organic carbon

5.3 Influences of plastic film mulching on SOC

5.4 Suggestions on agricultural management in inland river basin

6. Conclusions

Declarations

Conflict of Interest Statement

Author Contribution

Acknowledgments:

Data Availability

References

Additional Declarations

Supplementary Files

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