Method for sowing suaeda glauca in saline-alkali soil by covering sand for several times

Abstract

The invention discloses a method for graded sand covering and sowing of suaeda salsa in saline-alkali soil, and relates to the technical field of ecological restoration of saline-alkali soil in arid and semi-arid areas and construction of forage grassland. The method comprises the following steps: sowing suaeda glauca seeds on the ploughed saline-alkali soil; sandy soil is spread on the earth surface after sowing, and the sandy soil spreading is carried out twice, wherein the thickness of the first-time sand spreading is 2-4 cm; the second time of sand covering is conducted within 5-10 days after the first time of sand covering, and the thickness is 1-3 cm; the total thickness of the two times of sand covering is 3-7 cm. According to the method, the emergence rate and the seedling survival rate are effectively increased under the real saline-alkali soil condition, the number of quadrat plants, the coverage degree and the NDVI are remarkably increased when the suaeda glauca is sown according to the method, and the method has the obvious planting advantage on the moderate and severe saline-alkali soil and is suitable for large-scale popularization and application. The method is suitable for large-scale popularization and application in Yellow River basin and similar arid and semi-arid saline-alkali soil

Description

Technical Field

[0001] This invention relates to the field of ecological restoration and forage grassland construction technology for saline-alkali land in arid and semi-arid regions, and more specifically, to a method for multi-stage sand covering and sowing of Suaeda salsa in saline-alkali land. Background Technology

[0002] Saline-alkali land is widespread in the arid and semi-arid regions of northern China, and is one of the important factors restricting regional agricultural production and ecological security. In these areas, the pH of the soil at a depth of 0–20 cm is generally higher than 8.0, and in some areas it can reach above 10.0. The electrical conductivity is generally in the hundreds to thousands of μS / cm, and the content of sodium and chloride ions is high, forming typical soda-type or complex saline-alkali land. The common characteristics of this type of soil are: the easy formation of salt crust and compaction layer on the surface, strong capillary upwelling, and high evaporation, resulting in the continuous accumulation of soluble salts on the surface. These adverse factors severely inhibit plant seed germination and seedling growth, and are key bottlenecks restricting the establishment of forage plants and ecological restoration in saline-alkali land.

[0003] As an annual true halophyte, *Suaeda salsa* exhibits strong adaptability to moderately to severely saline-alkali soils, completing its full life cycle even in environments with a pH close to 10 and high soluble salt content. *Suaeda salsa* plants possess high aboveground biomass and good forage quality, with its aboveground parts containing approximately 80–200 g / kg of crude protein and moderate levels of neutral detergent fiber (NDF) and acid detergent fiber (ADF). It is a potential germplasm with both windbreak and sand-fixing value, as well as forage potential. Therefore, promoting *Suaeda salsa* cultivation in saline-alkali soils is of great significance for enhancing the combined ecological and economic benefits of saline-alkali land.

[0004] In current production practices, Suaeda salsa is mostly established through direct row sowing or broadcasting. For mildly or moderately saline-alkali land, under relatively suitable climatic conditions and with a less severe surface salt crust, direct sowing can achieve a certain plant density and canopy coverage. However, in moderately to severely saline-alkali sandy land, direct sowing presents the following prominent problems: First, the accumulation of surface salts and the formation of salt crusts are severe. Under strong evaporation and capillary uplift, soluble salts accumulate in the topsoil, forming a surface salt crust and a compacted layer. This leads to poor soil aeration, excessively high osmotic pressure, inhibits the water absorption, swelling, and germination of Suaeda salsa seeds, makes seedling emergence difficult, and easily causes seedling burn.

[0005] Secondly, wind erosion and sandstorms damage the germination environment. In arid and semi-arid regions with strong winds, exposed topsoil without sand cover is easily blown away by the wind, fine soil is lost, seeds are blown away or exposed, and germinated seedlings are easily broken, pulled up or buried, leading to missing seedlings, broken rows or even failure of germination in the entire plot.

[0006] Third, the sand-covering method is crude and lacks design tailored to the characteristics of small seeds. Some techniques have proposed using topsoil or sand to cover and suppress salt on saline-alkali land, mainly for the restoration of afforestation of trees or shrubs, often using a soil covering thickness of 8-10 cm or even deeper. While such thick sand-covering measures can reduce surface salt damage to some extent, they do not take into account the characteristics of Suaeda salsa seeds: small size, shallow sowing depth, and weak seedling root system. An excessively thick sand layer significantly increases the emergence distance, making it difficult for small seeds to penetrate the soil layer and reach the surface after germination, resulting in a significant reduction in the actual emergence rate, and even the situation of "soil suppressing and killing seeds". In addition, some techniques only vaguely propose "covering with a layer of sand", without specifying the range of sand covering thickness and its matching relationship with soil salinity and sowing depth, making it difficult to reproduce the effect stably on highly saline-alkali and wind-blown sandy land.

[0007] Fourth, there is a lack of systematic validation based on actual salinity and forage quality. Existing technologies mostly evaluate the effectiveness of sand covering based on indicators such as plant survival, sporadic cover, or individual height. They rarely systematically examine the response relationships between vegetation density, cover, normalized difference vegetation index (NDVI), and forage quality indicators (crude protein, NDF, ADF) under defined salinity gradients. Furthermore, there is a lack of stepwise sand covering and sowing techniques suitable for using *Suaeda salsa* as forage grassland in saline-alkali land. Especially in moderately to severely saline-alkali land with a soil pH of 8.91–10.32 and an electrical conductivity as high as 1545 μS / cm in the 0–20 cm soil layer, how to achieve a certain level of surface cover and forage quality while ensuring seedling emergence remains an unresolved issue with existing technologies.

[0008] In summary, existing technologies for planting Suaeda salsa in saline-alkali land suffer from several problems, including unstable germination without sand covering, difficulty in germination due to thick sand covering in a single application, lack of optimized sand covering thickness design for small seed characteristics, and lack of systematic verification based on real salinity and feed quality indicators. There is an urgent need to provide a new method for multi-stage sand covering and sowing that is simple in structure, moderate in cost, verifiable based on real saline-alkali land data, and suitable for small-grained feed plants.

[0009] In view of this, the present invention is proposed. Summary of the Invention

[0010] The purpose of this invention is to provide a method for sowing Suaeda salsa in stages with sand covering to solve practical problems such as high surface salinity, strong wind erosion, difficulty in germination of small seeds, and difficulty in establishing Suaeda salsa vegetation in moderately to severely saline-alkali land in arid and semi-arid regions.

[0011] This invention is implemented as follows: This invention provides a method for sowing Suaeda salsa in stages with sand covering, which includes the following steps: (1) Sow Suaeda salsa seeds on saline-alkali land after tilling; (2) After sowing, cover the ground with sand. The sand covering is done in two stages: the first sand covering is 2-4 cm thick; the second sand covering is done within 5-10 days after the first sand covering, with a thickness of 1-3 cm; the total thickness of the two sand coverings is 3-7 cm.

[0012] The present invention has the following beneficial effects: This invention employs a phased sand covering method of "first thin covering, then supplementary covering," which lowers the surface layer of high-salt native soil, reducing capillary ascent and salt crust formation. This places the seed germination zone within a low-salt, moisture-retaining sand layer and its interface, effectively improving germination rate and seedling survival rate under actual saline-alkali soil conditions. In contrast, the uncovered control treatment is prone to severe salt crust and compaction, resulting in missing seedlings, broken rows, and large areas of bare land within the sample plots, with persistently low vegetation cover and NDVI.

[0013] Compared to a single application of 8-10 cm thick sand, while a single thick layer enhances salt suppression, it significantly increases the soil layer that seedlings need to penetrate for small-grained Suaeda salsa seeds sown at a depth of 1-2 cm, resulting in excessively long emergence distances and a lower actual germination rate. In this invention, by applying sand in stages, with a total thickness of 3-7 cm, good salt suppression, moisture retention, and wind erosion resistance are maintained. Furthermore, the first layer of sand application retains moderate soil resistance, making seedling emergence easier. The second layer primarily addresses wind erosion and secondary salt crust formation, thus balancing the dual needs of seedling emergence and salt reduction.

[0014] The method of this invention for sowing Suaeda salsa significantly increases the number of plants per plot, coverage, and NDVI. The method of this invention has obvious advantages in establishing plants on moderately to severely saline-alkali land.

[0015] Following the sowing and harvesting method of this invention, the aboveground samples of Suaeda salsa exhibited excellent feed quality indicators, demonstrating the advantages of "ecological + feed use." Even in medium-to-high salinity environments, Suaeda salsa maintains relatively high crude protein and moderate crude fiber levels, resulting in good feed quality. Compared to the poor growth, stunted size, and low coverage observed without sand covering, the method of this invention improves vegetation establishment quality while ensuring feed value, achieving the dual goals of "ecological restoration and feed utilization."

[0016] The sowing method provided by this invention is simple, low-cost, and suitable for widespread application. This invention primarily utilizes the low-salinity aeolian sand from the surrounding sand dunes as the covering material, using locally sourced materials without the need for large-scale soil imports or expensive chemical amendments. Land preparation, sowing, and sand covering can all be completed using conventional agricultural machinery in conjunction with manual labor, making construction simple and cost-effective. By employing a multi-stage sand covering method, it can flexibly adapt to different years' rainfall, wind erosion intensity, and salinity fluctuations, making it suitable for large-scale application in the Yellow River basin and similar arid and semi-arid saline-alkali lands. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the process for the multi-stage sand covering and sowing method of the present invention applicable to saline-alkali land Suaeda salsa forage grassland; Figure 2 A schematic diagram illustrating how multiple layers of sand covering promote the establishment of Suaeda salsa in saline-alkali land; Figure 3 This is a schematic diagram of vegetation characteristics in a representative quadrat after sowing Suaeda salsa according to the method provided in Example 1. Figure 4 This is a schematic diagram of the feed quality indicators of Suaeda salsa in a representative plot after sowing according to the method provided in Example 1. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0020] This invention provides a method for sowing Suaeda salsa in stages with sand covering, which includes the following steps: (1) Sow Suaeda salsa seeds on saline-alkali land after tilling; (2) After sowing, cover the ground with sand. The sand covering is done in two stages: the first sand covering is 2-4 cm thick; the second sand covering is done within 5-10 days after the first sand covering, with a thickness of 1-3 cm; the total thickness of the two sand coverings is 3-7 cm.

[0021] This invention addresses the practical problems of high surface salinity, strong wind erosion, difficulty in germination of small seeds, and difficulty in establishing Suaeda salsa vegetation in severely saline-alkali lands in arid and semi-arid regions. It provides a multi-stage sand-covering and sowing method suitable for Suaeda salsa. By changing the sand-covering process from a single thick layer to a combination of two thin layers, this invention ensures salt suppression while coordinating the matching relationship between sand thickness and sowing depth. This improves the water and salt environment of the 0-10 cm root zone, reduces germination resistance, and increases the germination rate, seedling survival rate, and vegetation establishment quality of Suaeda salsa. The method has been validated in real saline-alkali land experiments using vegetation structure and feed quality indicators. The method provided by this invention improves vegetation establishment quality while ensuring feed value, achieving the dual goals of "ecological restoration and feed utilization." The method provided by this invention is simple, low-cost, and suitable for widespread application.

[0022] By controlling the number of sand coverings and their thickness, surface salt damage was significantly reduced, and the seedling emergence environment was improved. The total sand covering thickness was 3-7 cm, which maintained good effects in salt suppression, moisture retention, and wind erosion resistance. In the first sand covering stage, moderate soil resistance was maintained, making it easier for seedlings to emerge. The second sand covering mainly addressed wind erosion and secondary salt crust issues, thus balancing the dual needs of seedling emergence and salt reduction.

[0023] In a preferred embodiment of this invention, the thickness of the first sand covering is 2, 3, 3.5, or 4 cm; this places the seed zone below the sand covering layer or near the boundary between the sand covering and the original soil, reducing salt damage while maintaining a suitable emergence distance. Within 5, 6, 7, 8, 9, or 10 days after the first sand covering, a second sand covering is performed, with a thickness of 1, 2, or 3 cm, depending on the local wind erosion intensity and initial emergence status. After the second sand covering, the sand layer essentially covers the root collar area of ​​the Suaeda salsa seedlings, further weakening capillary ascent and surface salt crust formation, and enhancing windbreak and sand-fixing effects.

[0024] If only a thin layer of sand is applied once, the sand will be easily blown away by the wind, resulting in a low germination rate and seedling survival rate.

[0025] In a preferred embodiment of the present invention, the total sand covering thickness is 3 cm, 4 cm, 4-6 cm, 5 cm, 5-7 cm, 6 cm, or 7 cm.

[0026] In a preferred embodiment of the present invention, the total thickness of the two sand coverings is 4-6 cm.

[0027] In a preferred embodiment of the present invention, the thickness of the first layer of sand is 3 cm ± 0.5 cm, the thickness of the second layer of sand is 2 cm ± 0.5 cm, and the total thickness of the two layers of sand is 5 cm ± 0.5 cm.

[0028] In a preferred embodiment of the present invention, saline-alkali land refers to saline-alkali land with a soil pH of 8.5–10.3, an electrical conductivity of 200–1500 μS / cm in the 0–20 cm soil layer, and a sodium ion content of 87.71–819.66 mg / kg and a chloride ion content of 263.89–1810.79 mg / kg. Preferably, it is soda saline-alkali land or compound saline-alkali land with a pH of 9.0–10.0 and an average electrical conductivity of 300–1300 μS / cm in the 0–20 cm layer.

[0029] Saline-alkali land includes, but is not limited to: slightly saline-alkali land, moderately saline-alkali land, and severely saline-alkali land.

[0030] The method provided by this invention is particularly suitable for sowing Suaeda salsa in moderately or severely saline-alkali soils.

[0031] In a preferred embodiment of the present invention, the seed density of *Suaeda salsa* is 64–680 seeds / m². For example, the seed densities are 64–100 seeds / m², 104–200 seeds / m², 200–300 seeds / m², 300–400 seeds / m², 350–450 seeds / m², 450–500 seeds / m², 500–550 seeds / m², 550–600 seeds / m², 600–650 seeds / m², and 600–680 seeds / m².

[0032] In a preferred embodiment of the present invention, Suaeda salsa seeds are sown by row sowing or broadcast sowing. When sowing by row sowing, the row spacing is 20-30 cm, the sowing width is 5-10 cm, and the sowing depth is 1-2 cm.

[0033] In a preferred embodiment of the invention, the covering sand is low-salt sand with an electrical conductivity of less than 200 μS / cm. In other embodiments, the electrical conductivity of the covering sand can be selected from nearby low-salt sand, depending on the region where the sand is being covered. As long as the electrical conductivity of the sand is lower than or slightly lower than that of the sowing area, it is acceptable.

[0034] In a preferred embodiment of the present invention, the low-salt sand is local low-salt aeolian sand or river sand.

[0035] In a preferred embodiment of the present invention, low-salt sand is sand with an electrical conductivity of less than 200 μS / cm, a pH of 7.5 to 8.5, and which does not easily form a hard salt crust.

[0036] In a preferred embodiment of this invention, the tillage depth is 10-15 cm. From sowing to emergence, shallow irrigation or sprinkler irrigation is used to conserve soil moisture, depending on the soil moisture condition. Excessive irrigation should be avoided to prevent salt migration. During the seedling stage, noxious weeds should be removed appropriately to avoid early grazing. Before the end of the growing season, mowing or rotational grazing should be implemented as needed. The method of this invention can also be combined with quadrat sampling to periodically measure the density, canopy cover, plant height, and NDVI of Suaeda salsa vegetation. Aboveground samples can be collected at appropriate times to measure crude protein, NDF, ADF, and other feed quality indicators to evaluate the overall effectiveness of the method.

[0037] Shallow tillage helps break up the surface salt crust and compacted layer, remove obstacles such as stones and dead branches, and make the surface basically flat. This step helps loosen the soil, disrupt capillary continuity, provide conditions for subsequent sand covering and salt suppression, and create a good foundation for uniform sowing and sand covering.

[0038] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0039] Example 1 In this embodiment, Suaeda salsa was established by sowing seeds in stages with sand covering in moderately to severely saline-alkali land in Inner Mongolia.

[0040] Overview of the test site The experimental site was located in a typical saline-alkali sandy area in Inner Mongolia, with relatively open terrain and significant wind erosion. Based on the soil physicochemical properties tests of the 0–20 cm soil layer, the soil pH in the study area ranged from 8.91 to 10.32, the electrical conductivity from 194.2 to 1545.0 μS / cm, the sodium ion content from 87.71 to 819.66 mg / kg, and the chloride ion content from 263.89 to 1810.79 mg / kg. Suaeda salsa plots J-1 to J-6 were established within the experimental site, with J-2, J-4, and J-6 representing moderately to severely saline-alkali plots. The average pH of plot J-1 was 10.18, and the average electrical conductivity (EC) was 738.7 μS / cm; the average pH of plot J-2 was 9.54, and the average electrical conductivity (EC) was 423.4; the average pH of plot J-3 was 9.85, and the average electrical conductivity (EC) was 405.7; the average pH of plot J-4 was 10.01, and the average electrical conductivity (EC) was 1316.3; the average pH of plot J-5 was 9.82, and the average electrical conductivity (EC) was 332.0; and the average pH of plot J-6 was 9.43, and the average electrical conductivity (EC) was 599.3.

[0041] Refer to the flowchart for the specific method of multi-stage sand covering and sowing. Figure 1As shown, the process includes, in sequence, the selection of saline-alkali land, shallow tillage and land preparation, sowing of *Suaeda salsa* seeds, first covering with sand, second covering with sand, and seedling emergence and turf establishment management. Specifically, it includes the following steps: (1) Shallow tillage and sowing of Suaeda salsa After the soil thaws in spring, shallow tillage was carried out on three sample plots, J-2, J-4, and J-6, to a depth of approximately 10–15 cm. This broke up the surface salt crust and compacted layer, and removed stones and dead branches larger than 3 cm. After tillage, Suaeda salsa seeds were sown in rows with a spacing of 25 cm, a sowing width of approximately 8 cm, and a sowing depth of about 1.5 cm. After sowing, the soil surface was lightly compacted using a roller to improve seed-soil contact.

[0042] (2) Phased sand covering measures After sowing, local low-salt aeolian sand was used for mulching in each plot. The mulch material had an electrical conductivity of less than 200 μS / cm and a pH of approximately 8.0. Mulching was done in two stages: the first mulch was completed within 1 day after sowing, with a thickness of approximately 3 cm; the second mulch was performed 7 days after the first mulch, based on observations of seedling emergence and wind erosion, with a thickness of approximately 2 cm, for a total thickness of approximately 5 cm. After the second mulch, the mulch layer essentially covered the root collar area of ​​the Suaeda salsa seedlings, and no obvious salt crust appeared on the soil surface. (See the diagram illustrating the staged mulching process for promoting Suaeda salsa establishment in saline-alkali land.) Figure 2 As shown.

[0043] (3) Seedling emergence and turf establishment management From sowing to emergence, shallow irrigation or sprinkler irrigation should be used to conserve soil moisture, depending on soil conditions, to avoid excessive irrigation that could cause salt to migrate upwards. During the seedling stage, noxious weeds should be removed appropriately to prevent early grazing. Before the end of the growing season, mowing or rotational grazing should be implemented as needed. This method can also be combined with quadrat sampling to periodically measure the density, canopy cover, plant height, and NDVI of Suaeda salsa vegetation. Aboveground samples should be collected at appropriate times to measure crude protein, NDF, ADF, and other feed quality indicators to evaluate the overall effectiveness of this invention.

[0044] Comparative Example 1 Shallow tillage and sowing of Suaeda salsa were carried out according to step (1) of Example 1. After that, no sand covering was carried out. Seedling emergence and turf management were carried out in the same way as step (3).

[0045] Comparative Example 2 Shallow tillage and sowing of Suaeda salsa were carried out according to step (1) of Example 1. Then, a thick sand covering was carried out once, with a sand covering thickness of 8cm. The source and conditions of the sand were the same as in Example 1. Then, seedling emergence and turf management were carried out in the same way as step (3).

[0046] Comparative Example 3 This comparative example involves a single thin sand covering. The land was shallowly tilled and the Suaeda salsa was sown according to step (1) of Example 1. Then, a single thin sand covering was applied with a thickness of 3 cm. The source and conditions of the sand were the same as in Example 1. Then, seedling emergence and turf management were carried out in the same manner as step (3).

[0047] Experimental Example 1 This experiment involved quadratic surveys and statistical analysis of vegetation characteristics.

[0048] In July, during the Suaeda salsa growing season, one representative quadrat with good growth performance was selected from each of the three plots J-2, J-4, and J-6, named J-2-3, J-4-2, and J-6-2, with a quadrat area of ​​50 cm × 50 cm. The survey included: the number of Suaeda salsa plants within the quadrat (converted to plants / m²), vegetation cover, average plant height, and NDVI. The average plant height was determined by randomly selecting 5 Suaeda salsa plants in each quadrat, measuring the height, and averaging the results. Vegetation cover was estimated visually, and NDVI was measured using a portable instrument above the center of the quadrat.

[0049] NDVI, or Normalized Difference Vegetation Index, is used to quantitatively measure the growth status, density, and health of vegetation in a region.

[0050] The survey results indicate that: Quadrat J-2-3: vegetation cover was 0.45±0.01, number of Suaeda salsa plants was 170±5 plants / quadrat (equivalent to 680±20 plants / m²), average plant height was 10.6±0.8cm, and NDVI was 0.60±0.02; Quadrat J-4-2: vegetation cover was 0.60±0.03, number of Suaeda salsa plants was 110±4 plants / quadrat (equivalent to 440±16 plants / m²), average plant height was 8.6±0.3 cm, and NDVI was 0.56±0.04; Plot J-6-2: vegetation cover was 0.72±0.08, number of Suaeda salsa plants was 82±2 plants / plot (equivalent to 328±8 plants / m²), average plant height was 12.3±1.1cm, and NDVI was 0.58±0.03.

[0051] Vegetation cover refers to the percentage of the ground area covered by the vertical projection of the aboveground parts (stems, leaves, branches) of all plants in the vegetation.

[0052] Figure 3The results showed that, overall, under the phased sand covering conditions of Example 1, Suaeda salsa exhibited medium plant height, high density, and moderate canopy in the moderately saline-alkali plot (J-2); while in the higher salinity plots (J-4 and J-6), it exhibited higher canopy or higher plant height, respectively, forming a certain spatial structure complementarity. This revealed that the method of the present invention can form stable Suaeda salsa vegetation with a certain canopy under different salinity backgrounds.

[0053] The vegetation cover of the plot (J-1-1) in Comparative Example 1 was 0.22, the number of Suaeda salsa plants was 38 plants / plot (equivalent to 152 plants / m²), the average plant height was 6.8±1.4cm, and the NDVI was 0.32±0.04.

[0054] The vegetation cover of plot J-1-2 in Comparative Example 2 was 0.30, the number of Suaeda salsa plants was 56 plants / plot (equivalent to 224 plants / m²), the average plant height was 7.3±1.1, and the NDVI was 0.38±0.03.

[0055] The vegetation cover of plot J-1-3 in Comparative Example 3 was 0.35, with 76 Suaeda salsa plants per plot (equivalent to 304 plants per m²), an average plant height of 8.1 ± 1.6 cm, and an NDVI of 0.43 ± 0.05.

[0056] In Comparative Example 1 without sand covering, although the same sowing method and sowing amount were used, the seedling emergence was extremely uneven due to the influence of surface salt crust and wind erosion. The number of plants in many plots was low, and the local surface was obviously bare. The vegetation cover and NDVI were significantly reduced compared with the sand covering treatment of this invention.

[0057] In Comparative Example 2, a single thick sand covering was applied immediately after sowing, with a low-salt sand layer of approximately 8 cm thick, significantly thicker than the 5 cm thickness of the method described in this invention. This treatment significantly reduced the surface salt crust, but due to the excessive sand covering thickness, the Suaeda salsa seedlings had difficulty penetrating the sand layer to reach the ground surface, resulting in a lower actual germination rate. The number of seedlings and the coverage of the sample plots were significantly inferior to the multi-stage sand covering treatment.

[0058] The results of the comprehensive embodiments and comparative examples show that the present invention, through the "3 cm + 2 cm" layered sand covering method, achieves a higher seedling emergence rate and better vegetation establishment effect under similar saline-alkali background, and also performs well in terms of feed quality.

[0059] Experiment Example 2 This experiment was conducted to determine the feed quality.

[0060] During the mid-to-late growing season, representative aboveground plant samples were collected from six Suaeda salsa plots, J-1 to J-6. After drying and pulverizing, the crude protein content (in g / kg) and the contents of neutral detergent fiber (NDF) and acid detergent fiber (ADF) were determined. Figure 4The results showed that the crude protein content of *Suaeda salsa* in the six sample plots ranged from 79.27 to 210.14 g / kg, with an average of approximately 124.30 ± 52.25 g / kg; the NDF content ranged from 17.31 to 33.23%, and the ADF content ranged from 8.35 to 19.73%. Specifically, the crude protein content in sample plots J-2, J-4, and J-6 was 113.50 ± 5.68, 79.27 ± 3.96, and 164.83 ± 8.24 g / kg, respectively. This indicates that under the phased sand covering method of this invention, *Suaeda salsa* can still maintain a high crude protein content and a moderate crude fiber level in moderately to severely saline-alkali soils, demonstrating good forage potential.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for multi-stage sand covering and sowing of Suaeda salsa in saline-alkali land, characterized in that, It includes the following steps: (1) Sow Suaeda salsa seeds on saline-alkali land after tilling; (2) After sowing, cover the ground with sand. The sand covering is done in two stages: the first sand covering is 2-4 cm thick; the second sand covering is done within 5-10 days after the first sand covering, with a thickness of 1-3 cm; the total thickness of the two sand coverings is 3-7 cm.

2. The method for multi-stage sand covering and sowing of Suaeda salsa in saline-alkali land according to claim 1, characterized in that, The total thickness of the two sand coverings is 4-6 cm.

3. The method for multi-stage sand covering and sowing of Suaeda salsa in saline-alkali land according to claim 2, characterized in that, The thickness of the first layer of sand is 3 cm ± 0.5 cm, the thickness of the second layer of sand is 2 cm ± 0.5 cm, and the total thickness of the two layers of sand is 5 cm ± 0.5 cm.

4. The method for multi-stage sand covering and sowing of Suaeda salsa in saline-alkali land according to claim 1, characterized in that, The saline-alkali land refers to saline-alkali land with a soil pH of 8.5-10.3, an electrical conductivity of 200-1500 μS / cm, and a sodium ion content of 87.71-819.66 mg / kg and a chloride ion content of 263.89-1810.79 mg / kg in the 0-20 cm soil layer.

5. The method for multi-stage sand covering and sowing of Suaeda salsa in saline-alkali land according to claim 4, characterized in that, The density of Suaeda salsa seeds sown is 64–680 seeds / m².

6. The method for multi-stage sand covering and sowing of Suaeda salsa in saline-alkali land according to claim 5, characterized in that, Suaeda salsa seeds can be sown by row sowing or broadcast sowing. When sowing by row sowing, the row spacing should be 20-30 cm, the sowing width should be 5-10 cm, and the sowing depth should be 1-2 cm.

7. The method for multi-stage sand covering and sowing of Suaeda salsa in saline-alkali land according to claim 1, characterized in that, The covered sand is low-salt sand with an electrical conductivity of less than 200 μS / cm spread on the ground surface.

8. The method for multi-stage sand covering and sowing of Suaeda salsa in saline-alkali land according to claim 7, characterized in that, The low-salt sandy soil mentioned is local low-salt aeolian sand or river sand.

9. The method for multi-stage sand covering and sowing of Suaeda salsa in saline-alkali land according to claim 7, characterized in that, The low-salt sandy soil is sandy soil with an electrical conductivity of less than 200 μS / cm, a pH of 7.5 to 8.5, and which does not easily form a hard salt crust.

10. The method for multi-stage sand covering and sowing of Suaeda salsa in saline-alkali land according to claim 1, characterized in that, The tillage depth is 10-15cm. From sowing to emergence, water should be used for shallow irrigation or sprinkler irrigation to conserve soil moisture, depending on the soil moisture condition.

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