Effects of Different Soil Amendments on Soil Physical and Chemical Properties, Rice Yield, and Economic Benefits in Low-lying Saline Alkali Land in Northern Shaanxi

doi:10.21203/rs.3.rs-2713554/v1

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Effects of Different Soil Amendments on Soil Physical and Chemical Properties, Rice Yield, and Economic Benefits in Low-lying Saline Alkali Land in Northern Shaanxi

https://doi.org/10.21203/rs.3.rs-2713554/v1

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To explore the effects of different soil modifiers on the improvement of low-lying saline alkali land in Northern Shaanxi, the effects of three soil modifiers (desulfurization gypsum, “Jinfufeng” soil conditioner, and humic acid) on the physical and chemical properties soil, rice yield, and economic benefits were studied and compared through field experiment and indoor analysis. Results show that compared with the blank control, the three soil modifiers could effectively reduce the soil bulk density, improve the physical properties of soil, and reduce the soil pH, and humic acid could also significantly reduce the salt content of surface soil. In addition, the “Jinfufeng” soil conditioner and humic acid had a significant effect on the soil organic matter and total nitrogen contents but no significant effect on the available potassium and phosphorus. Desulfurized gypsum had a significant effect on the soil’s available potassium content but no significant effect on the organic matter and total nitrogen contents and the available phosphorus. The application of soil conditioner could significantly improve the 1000 grain weight and yield of rice, which respectively increased by 10.19–13.59% and 13.54–27.95% compared with the control. The 1000 grain weight and yield of the humic acid modifier treatment were the highest, reaching 23.4 g and 7380 kg•hm^− 2, respectively. The analysis of economic benefits revealed that the application of a modifier could significantly improve the output value and net profit of rice. Among the modifiers, the application of a humic acid modifier could obtain the maximum output value, net profit, and yield investment ratio. Considering the rice quality, the rice yield, and the economic benefits, priority should be given to the application of a humic acid soil modifier to improve the low-lying saline alkali land in Northern Shaanxi.

In recent years, the quantity and quality of cultivated land have been declining with the rapid development of China’s economy. The per capita area of cultivated land in China accounts for only 31% of the world’s per capita area. Cultivated land is the basic carrier of food, and the lack of cultivated land has led to huge risks in China’s food security. Saline-alkali land is the largest land resource reserve in China. According to a survey, the total area of saline-alkali wasteland and saline-alkali land affecting the cultivated land in China exceeds 30 million hm2, including 45.4% of saline soil, 2.5% of alkaline soil, and 52.1% of all kinds of saline-alkali soil [1]. At present, the area of saline-alkali land in Shaanxi Province is approximately 213000 hm², which is mainly distributed in the Yulin area in Northern Shaanxi and the Weinan area in the Guanzhong Plain; the area of heavy and moderate saline-alkali land is approximately 160000 hm², the saline-alkali degree is becoming serious, and the area of heavy and moderate saline-alkali land is increasing [2]. The current saline-alkali land improvement measures mainly include water conservancy improvement measures (e.g., irrigation, leaching, and drainage) [3], chemical improvement measures (e.g., physiological acid fertilizer, gypsum, and conditioner) [4], biological improvement measures (e.g., saline-alkali tolerant forage, crops, and green manure) [5], and agricultural improvement measures (e.g., deep tillage, sand covering, and salt planting)[6].

Soil conditioner application can improve the soil structure and physical and chemical indexes of saline-alkali soil. The soil conditioner can improve saline-alkali soil and reduce the harm of saline-alkali soil to crops by adjusting the soil acidity, reducing the soil’s salt content, and improving the soil structure [7]. Jiang Zengming et al. [8] analyzed the main characteristics of saline-alkali land and its impact on crop growth, expounded on the role of different soil conditioners in saline-alkali land improvement, and suggested that suitable soil conditioners should be selected in practical application according to different types of saline-alkali land. Wu Zhiqiang et al. [9] studied the application effects of four different soil amendments (quicklime, organic fertilizer, calcium magnesium phosphate fertilizer, and soil conditioner) on rice fields through field experiments. Their results show that the application of soil amendments can not only improve the physical and chemical properties of soil to varying degrees but also significantly improve the yield and output value of rice. A comparison revealed that the yield and output ratio of quicklime treatment was the highest among the four amendments. Wang Hong et al. [10] selected straw biochar, gypsum, and gypsum + organic fertilizer as soil conditioners to improve the saline farmland soil in Inner Mongolia and found that applying biochar and gypsum can significantly improve the physical and chemical properties of saline-alkali soil, reduce the soil pH and salt content, and increase the soil’s available phosphorus, alkali-hydrolysable nitrogen, and organic matter contents. Taking the rice in Dingbian County saline-alkali land as the research object, Shu Kun et al. [11] studied the effect of the amount of “Jinfufeng” soil conditioner on the physical and chemical properties of Dingbian County saline-alkali land soil and the growth of rice. Their results show that the application of soil conditioner in Northern Shaanxi saline-alkali land can significantly reduce the pH and salt content of the surface soil and increase the rice yield. On the basis of the analysis of rice yield and the saline-alkali land improvement effect, the recommended amount is 1500–2000 kg•hm^− 2. The climate in Northern Shaanxi is cold, the temperature difference between day and night is large, and the scale of rice planting is small. Although some studies on the use of soil conditioners have been conducted, few studies on the comparison and selection of different types of soil conditioners exist. Through field experiments in the Duiziliang area of Dingbian County, this study investigated the effects of different soil conditioners on the physical and chemical properties of soil and rice yield in Northern Shaanxi saline-alkali land and analyzed the economic benefits to determine the soil conditioner suitable for Northern Shaanxi saline-alkali land.

Overview of test plots

The test site is located in the Duiziliang area, Dingbian County, Northwest Shaanxi Province (35°31′02″–35°34′01″ N, 110°30′34″–110°33′36″ E). This area is located in the salinized meadow soil area where the alluvial parent material developed on the ancient riverbed. The soil salinization characteristics are obvious because of the flat and low-lying terrain, the large evaporation, the salt ions that gathered with the water flow, the shallow groundwater level, the high salinity, and the poor outflow. The average annual precipitation in this area is approximately 330 mm, which is mainly concentrated in July–September, accounting for 61.34% of the annual precipitation. The annual average evaporation is 2290 mm, the annual average temperature is 7.9 ℃, the annual average sunshine time is 2700–2800 h, the annual average frost-free period is 120–130 days, and the annual average frozen soil depth is approximately 100 cm.

Test materials

The test land is saline-alkali farmland, and the previous crop was corn. The desulfurized gypsum used in the test is the waste desulfurized gypsum produced by Hengshan Coal Power Co., Ltd. of the Shaanxi Yulin Energy Group. This conditioner’s main component is CaSO₄•2H₂O (content is more than 90%), the water content is ≤ 10%, the pH is 8.1, and the application rate of gypsum treatment is 20000 kg•hm^− 2 [12]. The “Jinfufeng” soil conditioner is produced by Inner Mongolia Fufeng Biotechnology Co., Ltd., with a nitrogen (N) content of approximately 16%, an organic matter content of approximately 4%, and a pH of 3.0–4.0, and the amount of “Jinfufeng” soil conditioner is 2000 kg•hm^− 2 [11]. Humic acid was extracted from Shenmu weathered coal by Yulin Dingliyuan Ecological Technology Co., Ltd. The effective humic acid content in the humic acid used in the test is 51%, the pH after water dissolution is 4.7, and the amount of humic acid is 2000 kg•hm^− 2 [13]. The crop tested was rice, and its variety is “Longyou 619,” which is developed by Tianjin Tianlong Seed Science and Technology Co., Ltd. The rice was transplanted manually in early June 2019 at the transplanting density of 18000 plants •hm^− 2. The rice was harvested in mid-October.

Experimental design

According to the different types of soil conditioners, four treatments were set up in the field test, namely, no application of soil conditioner (CK), application of desulfurized gypsum (FGD), application of the “Jinfufeng” soil conditioner (SC), and application of humic acid (HA). Each treatment was performed in triplicates, each treatment was ridged and covered with plastic film, and isolation measures between the treatment rooms were taken. Each test area is 80 m² (10 m × 8 m), soil samples were collected from the 0–20, 20–40, and 40–60 cm soil layers in the test plot before the test, and their basic physical and chemical properties were determined. Table 1 presents the detailed data. The management measures in each experimental plot, such as fertilization, pest control, and field irrigation, are consistent. The dosage of urea, diamine phosphate, and potassium chloride is 334, 196, and 96 kg•hm^− 2, respectively. The annual irrigation amount of the experimental field is approximately 15000 m3•hm^− 2, the irrigation water is well water, the total salt amount is 0.23 mg•L^− 1, and the pH is 8.1.

Table 1

Basic soil physical and chemical properties of the test site
Soil layer/ cm	pH	Salt content/ (g ·kg^− 1)	Bulk density/ (g·cm^− 3)	Organic matter/ (g·kg^− 1)	Total nitrogen/ %	Available phosphorus/ (mg·kg^− 1)	Available potassium/ (mg·kg^− 1)
0—20	9.03 ± 0.11	2.97 ± 0.04	1.51 ± 0.08	2.47 ± 0.10	0.26 ± 0.05	0.26 ± 0.03	92.77 ± 3.01
20—40	9.10 ± 0.05	2.10 ± 0.05	1.53 ± 0.05	2.28 ± 0.06	0.43 ± 0.03	0.33 ± 0.05	85.02 ± 2.54
40—60	9.08 ± 0.11	2.22 ± 0.07	1.55 ± 0.10	4.47 ± 0.04	0.37 ± 0.04	0.35 ± 0.04	81.75 ± 2.13

Table 2

Soil bulk density of 0–60 cm soil layer under different soil amendments (g·cm^− 3)
Treatment	Layer
Treatment	0—20 cm	20—40 cm	40—60 cm
CK	1.49 ± 0.04 a	1.53 ± 0.03 a	1.52 ± 0.06 a
FGD	1.45 ± 0.11 b	1.46 ± 0.05 b	1.51 ± 0.04 a
SC	1.42 ± 0.05 c	1.43 ± 0.02 c	1.52 ± 0.02 a
HA	1.41 ± 0.03 c	1.42 ± 0.09 c	1.50 ± 0.05 a
Note: Different lowercase letters in same column indicate significant differences between different treatments at P < 0.05 level;NS indicates no significant effect༛* and ** indicate significant effects at P < 0.05 and P < 0.01 levels, respectively

Table 3

Soil nutrients in 0–60 cm soil layer under different soil amendments
Treatment	Layer/cm	Organic matter/ (g·kg^− 1)	Total nitrogen/ %	Available phosphorus/ (mg·kg^− 1)	Available potassium/ (mg·kg^− 1)
CK	0—20	8.72 ± 0.96 a	0.72 ± 0.24 a	8.6 ± 1.54 a	121 ± 3.68 a
	20—40	8.34 ± 1.06 b	0.71 ± 0.32 b	8.5 ± 1.74 a	106 ± 4.87 b
	40—60	7.61 ± 0.55 c	0.73 ± 0.33 a	7.6 ± 1.56 b	86 ± 5.74 c
FG	0—20	8.83 ± 0.96 a	0.84 ± 0.27 a	8.5 ± 1.19 a	138 ± 6.77 a
	20—40	8.41 ± 0.84 ab	0.71 ± 0.21 b	8.3 ± 1.62 b	115 ± 4.59 b
	40—60	7.85 ± 1.21 b	0.66 ± 0.26 c	8.1 ± 1.54 c	85 ± 5.78 c
SC	0—20	11.8 ± 0.95 a	0.93 ± 0.32 a	8.4 ± 2.02 a	124 ± 9.61 a
	20—40	9.58 ± 1.07 b	0.82 ± 0.31 ab	6.2 ± 1.26 b	105 ± 6.45 b
	40—60	8.62 ± 1.36 c	0.81 ± 0.24 b	6.8 ± 1.30 b	83 ± 5.64 c
HA	0—20	11.3 ± 1.08 a	1.13 ± 0.41 a	8.5 ± 1.68 a	113 ± 8.35 a
	20—40	9.37 ± 1.14 b	0.95 ± 0.38 b	8.1 ± 1.69 ab	106 ± 7.67 b
	40—60	8.35 ± 1.01 b	0.84 ± 0.42 c	7.5 ± 1.58 b	92 ± 8.21 c
Note: Different lowercase letters in same column indicate significant differences between different treatments at P < 0.05 level;NS indicates no significant effect༛* and ** indicate significant effects at P < 0.05 and P < 0.01 levels, respectively

Table 4

Effects of different soil amendments on Rice Yield and economic benefits in low-lying saline alkali land in Northern Shaanxi
Treatment	1 000 grain weight/g	Yield (kg·hm^− 2)	Output value (yuan·hm^− 2)	Investment (yuan·hm^− 2)	Net profit (yuan·hm^− 2)	Production investment ratio
CK	20.6	4 076	14 266.0	/	/	/
FGD	22.7	6 450	22 575.0	6 000	2 309.0	1.38
SC	23.1	7 215	25 252.5	5 400	5 586.5	2.03
HA	23.4	7 380	25 830.0	5 000	6 564.0	2.31

Sample collection and processing

After the rice harvest, soil samples were collected from the test area with a soil drill at the following depths: 0–20 cm (surface layer), 20–40 cm (middle layer) and 40–60 cm (deep layer). The total amount of water-soluble salts, pH, bulk density, organic matter, total nitrogen, available phosphorus, and readily available potassium in the soil were determined through indoor tests. The soil pH, the total amount of water-soluble salt, the bulk density, the organic matter, the total nitrogen, the effective phosphorus content, and the available potassium were respectively determined using the potentiometric, mass, ring knife [14], potassium dichromate volumetric, semi-micro Kjeldahl, sodium bicarbonate extraction–molybdenum-antimony resistance spectrophotometry, and flame photometric methods [15]. After maturation, the rice was harvested, and the rice yield was measured in four treatment groups. Representative rice seeds were randomly selected for the measurement and calculation of their 1000–grain weight.

Economic benefit analysis

In 2020, the average purchase price of rice was 3.5 yuan•kg-1, and the comprehensive purchase and application prices of desulfurization gypsum, the “Jinfufeng” soil conditioner, and humic acid were 400, 2700, and 2500 yuan, respectively. We can calculate the output value, the net profit, and the production to investment ratio using the following formula.

Output value = Output × Unit Price (1)

Net profit = (Output value of improver treatment - Output value of control treatment) − Input (2)

Production and investment ratio = (Output value of improver treatment − Output value of control treatment) / Input (3)

Data analysis

The Microsoft Excel 2007 and SPSS 11.4 software were used for data processing statistics and significance analysis.

Ethical approval

All procedures with plants were conducted in accordance with the guidelines and regulation.

Effects of different soil amendments on the physical and chemical properties of saline-alkali soil

Change of soil salt content

Soil salt content is an important indicator of soil salinization. An extremely high soil salt content will cause damage to plants and hinder the normal growth and development of plants, resulting in poor quality and reduced yield. Figure 1 shows that the application of humic acid can significantly reduce the salt content of the surface layer (0–20 cm) of soil, which is 12.43% lower than that of the control. This phenomenon is mainly due to the high cation exchange capacity of humic acid, which can significantly improve the anion adsorption capacity of soil and reduce the salt content of the surface soil after its application. In addition, humic acid can improve the soil aggregate structure, improve the soil porosity, destroy the salt rising conditions, and play a role in salt removal. The variance analysis results show no significant difference in the salt content of the surface soil with desulfurized gypsum and the “Jinfufeng” soil conditioner compared with the control. The soil salt content of the four treatments showed a distribution pattern of high surface layer (0–20 cm), low middle layer (20–40 cm), and high bottom layer (40–60 cm). The salt content of the 0–20 and 20–40 cm soil layers in the test area before rice planting was 2.97 and 2.10 g • kg^-1, respectively, and their average salt content after rice planting was 1.78 and 1.61 g • kg^-1, respectively, indicating that rice planting can significantly reduce the salt content of the soil surface, mainly due to the leaching effect of well water irrigation and the reduction of surface evaporation after rice planting. Moreover, rice has a certain absorption effect on the salt ions in the soil. In addition, rice planting has a significant impact on promoting the formation of soil aggregates and improving the soil structure, which can promote water movement in the soil profile and reduce the occurrence of salt return, significantly reducing the soil salt content after rice planting [16].

Soil pH change

Soil pH is an important indicator of the soil acid-base status, which directly affects the form and availability of nutrient elements in the soil. An extremely high or low soil pH is not conducive to the absorption of nutrient elements by plant roots [17]. The distribution of the soil pH in the 0–60 cm soil layer under different soil amendments is shown in Figure 2. Each treatment shows a distribution pattern of low surface soil pH and high deep soil pH. The pH of the surface soil treated with CK is high, reaching 8.9. According to the classification standard of soil acidity and alkalinity in China, the soil has reached strong alkalinity, which seriously affects the normal growth of rice. The other three soil amendments can significantly reduce the pH of the surface soil. Compared with the control, the pH of the surface soil treated with FGD, SC, and HA decreased by 5.78%, 4.53%, and 5.55% respectively. The pH of the treatment with the “Jinfufeng” soil conditioner is 3.0–4.0, and that of humic acid is 4.7, which are acidic. These treatments can neutralize with the alkali in the soil and reduce the soil pH. The main components of desulfurized gypsum are CaSO4 and a small amount of CaSO3. After adding desulfurized gypsum to the soil, the Ca²⁺in the gypsum reacted with the free NaHCO₃ and Na₂CO₃ in the soil to generate insoluble CaCO₃ or Ca(HCO₃)², which reduced the soil pH.

Change of soil bulk density

Soil bulk density can reflect the soil compactness, which is an important physical property reflecting soil water, fertilizer, air, heat, and other factors. The saline soil bulk density is generally large, with a compact structure and poor permeability. The saline is difficult to improve and use [18-19]. The results in Table 2 show that the application of a soil conditioner can effectively reduce the soil bulk density, increase the soil porosity, and improve the soil physical properties of the 0–40 cm soil layer, and humic acid has the best effect on improving the soil physical properties among the conditioners. Compared with the control, the FGD, SC, and HA treatments significantly reduced the bulk density of the surface soil by 0.04, 0.07, and 0.08 g•cm^-3, and that of the middle soil by 0.07, 0.10, and 0.11 g•cm^-3, respectively. No significant difference could be observed in the bulk density of the deep soil.

Change of soil bulk density

Soil nutrients are essential nutrients for plants provided by soil, and the important indicators of soil nutrients mainly include soil organic matter, total nitrogen, available phosphorus, and available potassium. The effect of different soil amendments on the soil nutrients in the low-lying saline-alkali soil in Northern Shaanxi is shown in Table 3. Compared with the control treatment, the soil organic matter and total nitrogen contents significantly increased after adding “Jinfufeng” soil amendments and humic acid, and the available potassium content significantly increased after adding desulfurization gypsum. The mechanism is that the “Jinfufeng” soil conditioner and humic acid contain a certain amount of organic matter and nitrogen, so adding them to the soil increases the soil organic matter and total nitrogen contents, but the available phosphorus and available potassium contents are low, so the impact is insignificant. Applying desulfurized gypsum can promote the adsorption of potassium by the soil colloid, thus increasing the exchangeable potassium ions in the soil as well as the available potassium in the soil. Among the treatments, the SC treatment achieved the largest organic matter content at each soil layer depth, with an average value of 10.0 g•kg^-1, which is 21.61%, 19.57%, and 3.37% higher than those achieved by the CK, FGD, and HA treatments, respectively, indicating that the “Jinfufeng” soil conditioner has the most significant effect on the increase of the soil organic matter content. The total nitrogen content achieved by the HA treatment is the highest, with an average value of 0.97 g•kg^-1, which is 35.14%, 32.08%, and 14.02% higher than those achieved by the CK, FGD, and SC treatments, respectively. The soil available potassium is the highest in the FGD treatment, and the average content is 113mg•kg^-1, which is 8.65%, 8.65%, and 9.71% higher than those in the CK, AG, and HA treatments, respectively.

Effects of different soil amendments on rice yield and economic benefits

The 1000-grain weight of rice can reflect the grain size and plumpness of rice and is an important basis for testing the quality of rice and predicting the field yield. Table 4 shows that the application of soil conditioner can improve the 1000-grain weight and yield of rice. Compared with the control, the 1000-grain weight and yield of rice increased by 10.19%–13.59% and 13.54%–27.95%, respectively, after applying soil amendments. Among them, the 1000-grain weight and yield of the HA treatment are the largest, reaching 23.4 g and 7380 kg • hm^-2, respectively. In addition, the analysis of the economic benefits revealed that the application of modifiers can improve the output value and net profit of rice. Among the treatments, the HA treatment obtained the largest output value, net profit, and output to investment ration, which are 25830.0 yuan •hm^-2, 6564 yuan•hm^-2, and 2.31 yuan, respectively. Compared with the FGD and SC treatments, the output to investment ratio of the HA treatment increased by 67.01% and 13.68%, respectively. In comprehensive consideration of the rice quality and yield and the economic benefits, a humic acid soil conditioner should be preferentially selected to improve the low-lying saline-alkali land in this area.

Excessive soil salt content will hinder the normal growth and development of rice and lead to water absorption difficulties and physiological drought, damage the normal metabolism, inhibit photosynthesis and respiration, and affect the formation of leaf green protein [13]. Soil acidity and alkalinity are among the important factors affecting the availability of soil nutrients. Extremely high or low pH is not conducive to the absorption of soil nutrients by rice [17]. The test area is low-lying, with a large evaporation capacity, salt ions gather with the water flow, and the underground water level is shallow, with high salinity and poor outflow. The soil salinization characteristics are obvious. The pH of the topsoil is 9.03, and the total amount of water-soluble salt is 2.97 g•kg^-1, which seriously affects the growth and development of rice. The three soil amendments selected in this experiment can significantly reduce the pH of the surface soil, and the reduction range of each treatment is 4.53%–5.57% compared with the control. The humic acid soil amendments significantly reduced the salt content of the surface soil, and the salt content of the surface soil is 12.43% lower than that of the control. Zhou Yang [20] found through the study on the effect of desulfurization gypsum and humic acid on improving saline-alkali soil that the combined application of desulfurization gypsum and humic acid can significantly reduce the soil pH and salt content. In addition, some studies discovered that the “Jinfufeng” soil conditioner can effectively reduce the soil pH [11], which is basically the same as the results of this study. Soil bulk density can reflect soil compactness. This study found that applying a soil conditioner in saline-alkali soil can effectively reduce the soil bulk density and improve the soil’s physical properties. Among the three soil conditioners, humic acid has the best effect on improving the soil bulk density. Humic acid dissolves in water and forms hydrophilic colloid. Under the action of plant roots, humic acid coagulates with the calcium ions in the soil to form a soil aggregate structure, reducing the soil bulk density and increasing the soil porosity [21]. Wang Yan [22] took the salinized meadow soil in the Horqin area as the research object, tested the influence of different improvement measures on the soil bulk density of different salinized degrees, and found that humic acid can adjust the soil texture, reduce the soil bulk density, and improve the soil physical structure to a certain extent, which is basically the same as the results of this study.

Soil nutrient is one of the important indicators in evaluating soil productivity. After adding the “Jinfufeng” soil conditioner and humic acid, the soil organic matter and total nitrogen contents significantly increased, and after adding desulfurized gypsum, the available potassium content significantly increased. Xie Shiqi et al. [23] studied the effects of soil amendments on soil nutrients and bacterial communities and found that the application of soil amendments improves the soil pH; the organic matter, available phosphorus, alkali-hydrolyzable nitrogen, and available potassium contents; the exchangeable calcium and magnesium; and the catalase and sucrase activities to varying degrees. Han Jianhong et al. [24] found that after applying humic acid to the topsoil of the saline-alkali land in Baotou, Inner Mongolia for 80 days, the soil’s available potassium, available nitrogen, and organic matter significantly increased, while the available phosphorus content was 6.0% lower than that of the control. Zhou Yang [20] found that using desulfurized gypsum and humic acid to improve saline-alkali soil can significantly increase the organic matter, total nitrogen, and available potassium contents in the surface soil. Compared with the results of the studies above, the use of humic acid and soil conditioners to increase the soil organic matter and total nitrogen contents is the same as the results of this study, while the use of soil conditioner to increase the content of the available phosphorus in soil is quite different from the results of this study, which may be related to the different nutrient contents of the soil conditioners used in the experiments.

The yield and quality of rice are direct reflections of the saline-alkali soil improvement effect. The application of soil conditioners can significantly improve the 1000-grain weight and yield of rice. Compared with the control, the 1000-grain weight and yield of rice with a soil conditioner increased by 10.19%–13.59% and 13.54%–27.95%, respectively. Among the treatments, the 1000-grain weight and yield of rice with the application of humic acid are the largest, which is consistent with the research results in the relevant literature. Desulfurized gypsum, which is the most common saline-alkali soil modifier, can reduce the soil pH, improve the soil’s physical and chemical properties, increase soil aeration and water retention, improve the soil microbial growth and reproduction environment, and promote rice growth [25]. The “Jinfufeng” soil conditioner is acidic and contains a certain amount of organic matter. When applied to saline-alkali soil, this conditioner can change the composition of soil colloid ions, adjust the soil acidity and alkalinity, improve the soil structure, and increase the supply of plant nutrients, thus achieving the purpose of improving saline-alkali soil [26]. Humic acid is a weak acid and negatively charged colloid that plays a very good role in regulating the acidity and alkalinity of soil. When combined with soil, humic acid plays a role in salt removal and absorption. Meanwhile, humic acid contains organic matter and trace elements that are necessary for plant growth, providing necessary supplements for crop growth and development and increased crop yield [13].

(1) The three soil modifiers could effectively reduce the soil bulk density, improve the physical properties of soil, and reduce the soil pH, and humic acid could also significantly reduce the salt content of surface soil.

(2) The “Jinfufeng” soil conditioner and humic acid had a significant effect on the soil organic matter and total nitrogen contents but no significant effect on the available potassium and phosphorus. Desulfurized gypsum had a significant effect on the soil’s available potassium content but no significant effect on the organic matter and total nitrogen contents and the available phosphorus.

(3) The application of soil conditioner could significantly improve the 1000 grain weight and yield of rice, which respectively increased by 10.19%–13.59% and 13.54%–27.95% compared with the control. The 1000 grain weight and yield of the humic acid modifier treatment were the highest, reaching 23.4 g and 7380 kg•hm^-2, respectively.

(4) The analysis of economic benefits revealed that the application of humus acid can significantly improve the output value and net profit of rice, and the application of humic acid treatment has obtained the largest output value, net profit, and output to investment ratio. Considering the rice quality and yield and the economic benefits, the recommendation it to give priority to the use of a humic acid soil conditioner to improve the low-lying saline-alkali land in Northern Shaanxi.

Acknowledgements

This work was supported by Shaanxi Province key research and development Plan - key industrial chain project(Research and development and demonstration of key technologies for soil improvement and restoration in salinized grain fields, 2022ZDLNY02-04).

Author contributions statement

Zhe Pang wrote the main manuscript. Juan Li , Qilong Wang, and Jianglong Shen conceived the study, experimentation and analysed the data.

Data Availability Statement

All data and material generated or used during the study appear in the submitted article.

Additional information

Competing interests

The authors declare no competing interests.

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Effects of Different Soil Amendments on Soil Physical and Chemical Properties, Rice Yield, and Economic Benefits in Low-lying Saline Alkali Land in Northern Shaanxi

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Abstract

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Introduction

Materials And Methods

Overview of test plots

Test materials

Experimental design

Sample collection and processing

Economic benefit analysis

Data analysis

Results And Analysis

Discussion

Conclusion

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References

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