Planting method for improving survival rate of bare-root seedling afforestation in sandy land

Abstract

This invention discloses a planting method to improve the survival rate of bare-root seedlings in sandy areas, belonging to the field of sandy afforestation technology. The planting method is as follows: (1) Afforestation land preparation: the afforestation land is tilled, and then the sandy land is prepared by the pit method before the rainy season; (2) Seedling treatment: 2-3 year old bare-root seedlings are selected for afforestation; before afforestation, the seedling roots are pruned and soaked in water and rooting agent; (3) Planting: dig planting holes and place the seedlings in the planting holes. Then add the substrate, backfill with topsoil and subsoil, cover with soil and water; (4) Cover with film: after transplanting the seedlings, cover the hole with film to retain moisture and compact with soil; (5) Tending: water needs to be replenished in the first year after planting, and water should be replenished every year according to rainfall. Weeds should be removed every year and replanted in spring; (6) Pruning: after planting for 5-6 years, prune the lower dead branches and diseased and weak branches, and retain the crown height ratio of 2:3 to solve the problem of cumbersome tending and high afforestation cost after bare-root seedling afforestation.

Description

Technical Field

[0001] This invention relates to the field of sandy land planting technology, and in particular to a planting method for improving the survival rate of bare-root seedlings in sandy land afforestation. Background Technology

[0002] Desertification is a global environmental problem that seriously threatens human survival and development. Afforestation in sandy areas is one of the effective means of combating desertification, and through reasonable techniques and measures, it can help improve the desert environment. Common afforestation plants in sandy areas include Scots pine, Populus euphratica, Pinus tabuliformis, and Pinus tabuliformis. The soil moisture and organic matter content vary significantly in different parts of sand dunes. Sand dunes are classified into four site conditions based on location: interdune lowlands, lower dune, middle dune, and upper dune. Interdune lowlands consist of fixed aeolian soil with high vegetation cover and good water and fertilizer conditions. The lower dune is also relatively low-lying, with fixed aeolian soil and generally poor water and fertilizer conditions. The middle and upper dunes are higher in elevation, with greater undulation and poorer site conditions. Scots pine is highly adaptable and drought-tolerant, and can be planted in areas where Populus euphratica is unsuitable. Therefore, Scots pine afforestation is usually carried out in the middle and upper parts of sand dunes.

[0003] In afforestation in sandy areas, either container seedlings or bare-root seedlings can be used. Container seedlings have a higher initial cost than bare-root seedlings. Container seedlings are prone to root coiling and root system twisting, which can negatively impact the normal development of the young tree's root system after planting. Bare-root seedlings typically do not have this problem. However, container seedlings generally have a higher survival rate after one year, and their subsequent management and nurturing costs are lower. This is mainly because bare-root seedlings are prone to water loss after planting and have a slow growth period. To ensure survival, they require regular watering during the initial acclimatization period, leading to higher initial nurturing costs. Furthermore, Pinus sylvestris seedlings are susceptible to wind and sand erosion and are prone to lodging, resulting in a low survival rate. Therefore, there is an urgent need for a sandy area afforestation method that combines the initial cost advantages of bare-root seedlings with reduced subsequent management and nurturing costs, thereby improving the survival rate while saving on afforestation costs. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide a transplanting method that improves the survival rate of bare-root seedlings in sandy areas, and to solve the problems of cumbersome post-planting tending and high planting costs associated with bare-root seedlings.

[0005] The present invention solves the above-mentioned technical problems through the following technical solutions:

[0006] A planting method to improve the survival rate of bare-root seedlings in sandy areas, the planting method is as follows:

[0007] (1) Afforestation and land preparation: The afforestation land is reclaimed, and then the sandy land is prepared by pit method before the rainy season;

[0008] (2) Seedling treatment: Select 2-3 year old bare-root seedlings for afforestation; before afforestation, prune the seedling roots and soak them in water for 1-2 days, and then soak the seedling roots in rooting agent for 1-2 hours before planting;

[0009] (3) Planting: Dig planting holes, then mix coarse sand, clay and gel particles in a mass ratio of 1:(1.5-2):(0.2-0.3) to obtain the substrate. Place the seedlings in the planting holes and then add the substrate. Backfill with topsoil and subsoil, cover with soil and water.

[0010] (4) Mulching: After transplanting the seedlings, cover the surface of the planting hole with a layer of plastic film to retain moisture and compact it with soil;

[0011] (5) Nurturing: Watering is required 2-3 times in the first year after planting. Watering should be done every year according to rainfall thereafter. Weeds should be removed every year and replanting should be done in spring.

[0012] (6) Pruning: After 5-6 years of planting, prune away the lower dead branches and diseased and weak branches, and retain a crown height ratio of 2:3.

[0013] Furthermore, the initial planting density is 800-1000 plants per hectare.

[0014] Furthermore, the specific operation during the planting process is as follows: lay a layer of substrate with a thickness of 5-6cm at the bottom of the planting hole, then place the seedling with its roots spread upright in the hole, add another layer of substrate with a depth of 5-6cm, then backfill with topsoil, and finally fill with bottom soil, tamping it down in layers. The planting depth should be such that the original soil mark is 3-4cm higher than the surface of the hole.

[0015] Furthermore, 1.5m x 1.5m grass checkerboard sand barriers were set up in the afforestation area.

[0016] Furthermore, the dimensions of the planting hole are 60cm×60cm×30cm.

[0017] Furthermore, the particle size of the coarse sand is 0.5mm-1mm.

[0018] Furthermore, the preparation process of the gel particles is as follows:

[0019] (1) Sodium carboxymethyl starch is mixed with humic acid and water to prepare a sodium carboxymethyl starch mixed solution; polyvinyl alcohol is dissolved to obtain a 10wt% polyvinyl alcohol solution; poly(N-isopropylacrylamide) is swollen with water for 1-2 hours to obtain a sol; sodium carboxymethyl starch mixed solution, polyvinyl alcohol solution and sol are mixed and polydopamine and glycerin are added and homogenized for 15-20 minutes to obtain a gel solution;

[0020] (2) After adjusting the pH of the gel solution to 5, add glutaraldehyde and calcium carbonate, heat to 45-50℃ and react for 1.5-2h to obtain a gel solution, then freeze at -20℃ for 3-4h and thaw at room temperature. Repeat twice and then spray dry to form particles. Dry under hot air conditions at 40-50℃ until the water content is ≤10% to obtain gel particles.

[0021] Since bare-root seedlings have a high water requirement and need to be protected from wind and sand in the early stages of planting, this invention first mixes coarse sand, clay, and gel particles before planting the seedlings. After planting, watering the seedlings allows the gel particles to absorb water and expand, mixing with the coarse sand and clay to bind and wrap around the seedling roots, thus fixing the seedlings and preventing them from falling over due to wind and sand. It also utilizes the water absorption and release cycle characteristics of the gel particles to reduce the need for watering.

[0022] Due to the large temperature difference and humidity variations between day and night in sandy areas, coupled with the poor water retention and rapid evaporation of water in sandy soil, the release rate of traditional water-retaining agents is not compatible with environmental requirements. Therefore, this invention uses sodium carboxymethyl starch, which has high water absorption and salt resistance, as the main material. Simultaneously, polyvinyl alcohol, poly(N-isopropylacrylamide), and polydopamine are used to regulate the properties of the prepared gel particles, achieving dual regulation of humidity and temperature. Poly(N-isopropylacrylamide) undergoes a shrinkage and water release reaction in the high-temperature environment of the daytime, while absorbing water under the low-temperature conditions of the sandy soil at night. Polyvinyl alcohol is a humidity-sensitive substance; it dehydrates and shrinks under low-humidity conditions and absorbs water under high-humidity conditions. Therefore, when poly(N-isopropylacrylamide), polyvinyl alcohol, and sodium carboxymethyl starch are mixed in a certain mass ratio, a water release equilibrium is achieved in the sandy soil environment of high temperature and low humidity during the day and low temperature and high humidity at night, ensuring a stable growth environment for trees and preventing water shortage. Furthermore, this invention incorporates polydopamine and other polymeric materials into the gel particles for cross-linking, enhancing the bonding strength between the gel particles and coarse sand and clay, strengthening the anchoring force of seedling roots, and improving resistance to wind and sand. Simultaneously, due to the rapid natural degradation rate of sodium carboxymethyl starch, the addition of a certain amount of polydopamine for cross-linking slows down the degradation rate of the gel particles, causing the gel to slowly shrink and become ineffective during the vigorous root growth period. During this period, it promotes natural root growth, increases survival rate, and prevents excessive seedling dependence due to the prolonged effectiveness of the gel particles, hindering their adaptation to the environment. The particles of this invention also contain fulvic acid, which not only stimulates root development, improves the initial survival rate of seedlings and shortens the recovery period, but also induces root gravitation, enabling them to quickly take root in sandy soil and further prevent wind and sand erosion. Furthermore, while gel particles bind to the roots after absorbing water, providing moisture and stabilizing the seedling root system, the afforestation process requires seedlings to recover and then rely on their environment for growth. Therefore, this invention uses a mixture of poly(N-isopropylacrylamide), polyvinyl alcohol, sodium carboxymethyl starch, and polydopamine in a specific ratio. This mixture reduces the fixation and water replenishment effect after ensuring seedling survival in the early stages, encouraging the roots to seek water downwards and adapt to the environment. Since gel particles slowly degrade in sandy soil, producing acidic substances, this invention adds trace amounts of calcium carbonate particles to prevent a decrease in pH around the seedling roots, thus preventing localized acidification that could reduce the activity of mycorrhizal microorganisms. Glycerol can be inserted between polymer chains, reducing brittle fracture and improving the structural integrity of the gel particles after water absorption and dehydration cycles, while also maintaining stability during wet-dry cycles.

[0023] Furthermore, the mass ratio of sodium carboxymethyl starch: poly(N-isopropylacrylamide): polydopamine: polyvinyl alcohol is (50-60):(20-30):(1-2):(10-12); the mass ratio of calcium carbonate, humic acid, glycerol to sodium carboxymethyl starch is (0.5-0.6):(1-1.5):(1-1.5):25.

[0024] Furthermore, potassium dihydrogen phosphate can be added in step (1) at a mass ratio of (1-2.5):30 between potassium dihydrogen phosphate and sodium carboxymethyl starch. To prevent nutrient deficiency in bare-root seedlings, potassium dihydrogen phosphate can also be added during the preparation of gel particles to supplement nutrition.

[0025] Beneficial effects:

[0026] This invention uses bare-root seedlings for afforestation in sandy areas. At the same time, it uses a dry-wet cycle formed by gel particles, coarse sand, and clay to dynamically regulate water supply and root guidance, thereby improving the survival rate of bare-root seedlings in the early stage, while reducing the difficulty of tending and management and lowering the cost of afforestation. Detailed Implementation

[0027] The present invention will be described in detail below with reference to specific embodiments:

[0028] Unless otherwise specified, the experimental methods used in the embodiments of this invention are conventional methods. Unless otherwise specified, the materials and reagents used in the embodiments of this invention are commercially available.

[0029] Example 1: Preparation of Gel Particles

[0030] (1) Dissolve 50g sodium carboxymethyl starch in water at 40℃ to make a 10wt% sodium carboxymethyl starch solution, then add 2g humic acid and stir evenly to make a mixed sodium carboxymethyl starch solution.

[0031] 10g of polyvinyl alcohol was also mixed and dissolved with water at 40℃ to obtain a 10wt% polyvinyl alcohol solution.

[0032] 20g of poly(N-isopropylacrylamide) was swollen in cold water for 2 hours to obtain a sol.

[0033] After mixing and stirring the sodium carboxymethyl starch solution, polyvinyl alcohol solution, and sol evenly, 1g of polydopamine and 2g of glycerol were added, and the mixture was homogenized at 10000rpm for 15min to obtain the gel solution.

[0034] (2) After adjusting the pH of the gel solution to 5 with 1 mol / L hydrochloric acid solution, add 0.5 g glutaraldehyde and 1 g calcium carbonate, heat to 50℃ and react for 2 h to obtain a gel solution, then freeze at -20℃ for 4 h and thaw at 25℃. Repeat twice and then spray dry to form particles. The inlet temperature of the spray dryer is set to 160℃ and the outlet temperature is set to 80℃. Dry under hot air at 40℃ until the moisture content is ≤10% to obtain gel particles. The particle size obtained is 3±0.2 mm.

[0035] Example 2: Preparation of Gel Particles

[0036] (1) Dissolve 60g of sodium carboxymethyl starch in water at 40℃ to prepare a 10wt% sodium carboxymethyl starch solution. Then add 3.6g of humic acid and stir evenly to prepare a sodium carboxymethyl starch mixed solution. Dissolve 12g of polyvinyl alcohol in water at 40℃ to obtain a 10wt% polyvinyl alcohol solution. Soak 30g of poly(N-isopropylacrylamide) in cold water for 2 hours to obtain a sol. Mix the sodium carboxymethyl starch mixed solution, polyvinyl alcohol solution, and sol evenly, add 2g of polydopamine and 3.6g of glycerin, and homogenize at 10000rpm for 15 minutes to obtain a gel.

[0037] (2) After adjusting the pH of the gel solution to 5 with 1 mol / L hydrochloric acid solution, 0.5 g glutaraldehyde and 1.44 g calcium carbonate were added. The mixture was heated to 45°C and reacted for 2 h to obtain a gel solution. Then, it was frozen at -20°C for 3 h and thawed at 25°C. This process was repeated twice. After spray drying, the gel particles were formed. The inlet temperature of the spray dryer was set to 160°C and the outlet temperature was set to 80°C. The gel particles were dried under hot air at 50°C until the moisture content was ≤10%. The particle size was 3 ± 0.2 mm.

[0038] Example 3: Afforestation of Pinus sylvestris var. mongolica

[0039] (1) Afforestation and land preparation: The afforestation land is reclaimed, the sand blocks are broken up, and the grass roots are cleaned up. Then, about 40 days before the rainy season, the sandy land is prepared using the pit method. Then, straw and other materials are used to set up 1.5m × 1.5m grass square grid sand barriers.

[0040] (2) Seedling treatment: Select 2-3 year old bare-root seedlings for afforestation. The preferred seedling specifications are seedlings with a height of more than 80cm and a ground diameter of more than 1.5cm. Before afforestation, prune the seedling roots, retain about 25cm of the main root and cut the lateral roots to about 15cm with a 45° angled cut. Then soak the seedlings in water for 1-2 days. Before planting, soak the seedling roots in 100ppm ABT rooting agent for 1-2 hours. The water temperature for soaking is about 20℃. Direct sunlight should be avoided.

[0041] (3) Planting: Mix coarse sand (0.5mm-1mm particle size), clay and gel particles in a mass ratio of 1:1.5:0.3 to obtain the substrate. After digging a 60cm×60cm×30cm planting hole, lay a 5-6cm thick layer of substrate at the bottom of the planting hole, then place the seedling with its roots spread upright in the hole, add another 5-6cm layer of substrate, then backfill with topsoil, and finally fill with subsoil, compacting it in layers. The planting depth should be such that the original soil mark is 3-4cm higher than the surface of the hole. The initial planting density is 800-1000 plants / hectare.

[0042] (4) Mulching: After transplanting the seedlings, water them thoroughly, cover the hole with a layer of plastic film to retain moisture, and press it down with soil to prevent water loss;

[0043] (5) Nurturing: Watering is required 2-3 times in the first year after planting. Watering should be done every year according to rainfall thereafter. Weeds should be removed every year and replanting should be done in spring.

[0044] (6) Pruning: After 5-6 years of planting, prune away the lower dead branches and diseased and weak branches, and retain a crown height ratio of 2:3.

[0045] Comparative Example 1:

[0046] This invention is compared with Example 1, the difference being that the raw materials for preparing the gel particles are different, specifically, no polydopamine is added, and the preparation process is the same as in Example 1.

[0047] Comparative Example 2:

[0048] This invention is compared with Example 1, the difference being that the raw materials for preparing the gel particles are different, specifically, polyvinyl alcohol is not added, and the preparation process is the same as in Example 1.

[0049] Comparative Example 3:

[0050] This invention is compared with Example 1 in that the raw materials for preparing the gel particles are different. Specifically, poly-N-isopropylacrylamide is not added, and the preparation process is the same as in Example 1.

[0051] Comparative Example 4:

[0052] This invention differs from Example 1 in that the raw materials used to prepare the gel particles are different; specifically, humic acid is not added. The preparation process of the sodium carboxymethyl starch mixed solution is as follows:

[0053] Dissolve 50g of sodium carboxymethyl starch in water at 40℃ to prepare a 10wt% sodium carboxymethyl starch solution.

[0054] The remaining preparation process is the same as in Example 1.

[0055] Comparative Example 5:

[0056] This invention is compared with Example 1 in that the raw materials for preparing the gel particles are different. Specifically, calcium carbonate is not added, and the preparation process is the same as in Example 1.

[0057] Comparative Example 6:

[0058] This invention is compared with Example 1, the difference being the ratio of raw materials used in the preparation of the gel particles. The mass ratio of sodium carboxymethyl starch: poly(N-isopropylacrylamide): polydopamine: polyvinyl alcohol was changed from 50g:20g:1g:10g to 50g:10g:1g:10g.

[0059] Comparative Example 7:

[0060] This invention is compared with Example 1, the difference being the ratio of raw materials used in the preparation of the gel particles. The mass ratio of sodium carboxymethyl starch: poly(N-isopropylacrylamide): polydopamine: polyvinyl alcohol was changed from 50g:20g:1g:10g to 50g:25g:1g:10g.

[0061] Comparative Example 8:

[0062] This invention is compared with Example 1, the difference being the ratio of raw materials used in the preparation of the gel particles. The mass ratio of sodium carboxymethyl starch: poly(N-isopropylacrylamide): polydopamine: polyvinyl alcohol was changed from 50g:20g:1g:10g to 50g:20g:1g:5g.

[0063] Comparative Example 9:

[0064] This invention is compared with Example 1, the difference being the ratio of raw materials used in the preparation of the gel particles. The mass ratio of sodium carboxymethyl starch: poly(N-isopropylacrylamide): polydopamine: polyvinyl alcohol was changed from 50g:20g:1g:10g to 50g:20g:1g:15g.

[0065] Comparative Example 10:

[0066] This invention is compared with Example 1, the difference being the ratio of raw materials used in the preparation of the gel particles. The mass ratio of sodium carboxymethyl starch: poly(N-isopropylacrylamide): polydopamine: polyvinyl alcohol was changed from 50g:20g:1g:10g to 50g:20g:3g:10g.

[0067] Experiment 1:

[0068] The prepared gel particles were subjected to water absorption-release experiments at different temperatures and humidity levels, and the water absorption-release results were measured after 20 water absorption-dehydration cycles, with three replicates for each group. The specific experimental procedures are as follows:

[0069] 1. Set up a daytime sandy environment with a temperature of 35℃ and a relative humidity of 30%; set up a nighttime sandy environment with a temperature of 10℃ and a relative humidity of 70%; weigh 1g (3mm ± 0.2mm) of gel particles (10% water content) prepared in Example 1 and Comparative Examples 1-10, soak them in deionized water at 25℃ for 5 hours, remove them, drain the water, weigh them W1, place them under constant temperature and humidity conditions of 35℃ / 30%RH for 12 hours, weigh them W2, and calculate the water release rate; then place them under constant temperature and humidity conditions of 10℃ / 70%RH for 12 hours, weigh them W3, and calculate the water absorption rate;

[0070] 2. After repeating the above water absorption-release experiment 20 times, the gel particles were soaked in deionized water at a constant temperature of 10℃ / 70%RH for 5 hours to obtain the water absorption weight W after the 20th cycle. 20 Then, place it at 35℃ / 30%RH for 12 hours and weigh it (W). 21 Then calculate the water release rate and water absorption rate.

[0071] Saturated water absorption rate = (W1 - W0) / W0 × 100%;

[0072] Daytime water release rate = (W1-W2) / (W1-W0)×100%;

[0073] Nighttime water absorption rate = (W3 - W2) / W0 × 100%;

[0074] Water absorption rate after 20 cycles = (W) 20 -W0) / W0×100%;

[0075] Water release rate after 20 cycles = (W) 20 -W 21 ) / (W 20 -W0)×100%;

[0076] Water absorption retention rate = (Water absorption rate after circulation / Saturated water absorption rate) × 100%;

[0077] The results are shown in Table 1:

[0078] Table 1

[0079]

[0080] Data analysis shows that:

[0081] 1. Based on the comparison of Example 1 and Comparative Examples 1-3, it can be seen that the addition of polydopamine, polyvinyl alcohol, and poly(N-isopropylacrylamide) can adjust the water absorption and release rates of the gel particles. Furthermore, the specific combination of various composite polymers can slow down the degradation rate of the gel, maintaining a high water retention rate of 80%. For example, Comparative Example 1 shows that polydopamine can affect the degradation rate of sodium carboxymethyl starch, leading to a significant decrease in water absorption performance after multiple cycles. Comparative Examples 2 and 3 show that polyvinyl alcohol can affect the humidity response, resulting in a significant decrease in water absorption at night, while poly(N-isopropylacrylamide) itself can affect the temperature response, leading to a significant decrease in water release performance.

[0082] 2. Fulvic acid has no significant effect on the water absorption and release of gel particles, but mainly affects the growth of seedlings. Calcium carbonate has little effect on the water absorption and release performance of gel particles in the early stage. However, the gel performance decreases after 20 cycles because the gel particles degrade after 20 cycles. The pH buffering performance of calcium carbonate alleviates this phenomenon.

[0083] 3. Comparative Examples 6-10 all involve adjustments to the proportions of polymeric raw materials. Reducing the amount of poly(N-isopropylacrylamide) decreases the water absorption and temperature-sensitive response of the gel particles, resulting in a lower water release rate. Conversely, excessive amounts increase the water release rate, leading to excessively rapid water release. Reducing the amount of polyvinyl alcohol decreases the humidity response and water absorption, while excessive amounts increase water absorption but result in insufficient water release, affecting the soil environment around the seedlings and hindering their independent growth. Increasing the amount of polydopamine significantly improves gel performance, but it also prolongs the gel degradation time, leading to prolonged adhesion between the seedling roots and the gel, making it difficult for the seedlings to adapt to the harsh sandy environment. Furthermore, excessive polydopamine has a bactericidal effect, which can inhibit the activity of microorganisms around the roots.

[0084] Experiment 2:

[0085] The afforestation experiment of Pinus sylvestris was conducted in Jinjisha Village, Dongkeng Town, Jingbian County, Yulin City. The area is at an altitude of approximately 1150 m, with an aridity index of 1.6. According to statistical analysis over many years, the average annual temperature is 10.4 ℃, the absolute maximum temperature is 38 ℃, the absolute minimum temperature is -27 ℃, the average January temperature is -10.5 ℃, and the average July temperature is 28.4 ℃. Winters are dominated by northwesterly winds, with an average wind speed of 2.5 m / s and a maximum wind speed of 17 m / s. The average number of days with strong winds is 132 per year, and the number of days with sandstorms is 142, reaching a maximum of 40 days, mainly concentrated in March to June. Annual precipitation is 406.4 mm, concentrated in July to September, accounting for approximately 70% of the total annual precipitation. The frost-free period is 130-155 days. Natural disasters are frequent, with droughts and strong winds occurring occasionally.

[0086] The experimental site was a newly transformed sandy land with aeolian soil covered by about 25 cm of yellow cotton soil. The soil was alkaline, low in organic matter, and had poor water and fertilizer retention, but excellent irrigation conditions. The experimental plots were set up in small beds of 19m × 2m, with each bed spaced 3m apart. Each bed was planted with 50 Pinus sylvestris var. mongolica spp. trees, and the planting holes were 60cm × 60cm × 30cm. Each experimental group used 6 small beds, totaling 300 trees, and a total of 12 experimental groups were set up.

[0087] At the end of March 2024, an afforestation experiment was conducted using three-year-old bare-root Pinus sylvestris seedlings (2 cm in diameter and 90 cm in height) without setting up sand barriers.

[0088] Before transplanting, trim the roots of the seedlings, keeping the main root about 25cm and the lateral roots about 15cm, with a 45° angled cut. Then soak them in water for 1 day. Before planting, soak the roots of the seedlings in 100ppm ABT rooting agent for 1 hour. The water temperature should be about 20℃. Avoid direct sunlight.

[0089] The specific cultivation process for Example 1 and Comparative Examples 1-10 is as follows:

[0090] Mix coarse sand (approximately 0.5mm in diameter), clay, and gel granules in a mass ratio of 1:1.5:0.3 to obtain a substrate. Lay a 5cm thick layer of substrate at the bottom of the planting hole, then place the seedling with its roots extended upright in the hole. Add another 6cm layer of substrate, then backfill with topsoil, and finally fill with subsoil, compacting each layer in one layer. The planting depth should be such that the original soil mark is 4cm above the surface of the hole. After watering thoroughly, cover the hole with a plastic film to retain moisture and compact it with soil to prevent water loss.

[0091] The specific cultivation process for the control group is as follows:

[0092] Mix coarse sand (approximately 0.5mm in diameter), clay, and gel granules in a mass ratio of 1:1.5:0.3 to obtain a substrate. Lay a 5cm thick layer of water-retaining agent at the bottom of the planting hole. The water-retaining agent has a water absorption rate of 300-500g / g times, a specification of 50 mesh, and its main components are polyacrylate and polyacrylamide copolymer. Then, place the seedling with its roots extended upright in the hole, then backfill with topsoil, and finally fill with subsoil, compacting it in layers. The planting depth should be such that the original soil mark is 4cm above the surface of the hole. After watering thoroughly, cover the hole with a layer of plastic film to retain moisture and compact it with soil to prevent water loss.

[0093] The soil, water, and fertilizer management conditions were the same in the experimental plots, with watering only once in mid-May. Statistical surveys were conducted in June and July to record the survival rate and lodging rate. Lodging was defined as seedlings tilting at an angle greater than 15 degrees. The data are shown in Table 2.

[0094] Table 2

[0095]

[0096] Data analysis shows that:

[0097] 1. The survival rate and lodging rate of Pinus sylvestris var. mongolica using the gel particles prepared in Example 1 were significantly higher than those of the comparative group or control group. A comparison with Comparative Example 1 and Comparative Example 10 shows that while polydopamine can anchor the root system of seedlings and prevent them from lodging during wind and sand erosion, excessive polydopamine leads to a decrease in the survival rate in the later stages. This is because polydopamine reduces the activity of microorganisms around the roots and delays gel degradation. When the gel's water absorption and retention capacity decreases, the seedlings' ability to adapt to the environment is reduced, and they fail to establish roots independently.

[0098] 2. Comparisons 2, 8, and 9 are comparisons of polyvinyl alcohol, while comparisons 3, 6, and 7 are comparisons of poly(N-isopropylacrylamide). Polyvinyl alcohol can utilize humidity to regulate the water absorption and release properties of gel particles, while poly(N-isopropylacrylamide) uses temperature regulation. When the added ratio is inappropriate, the water absorption and release regulation becomes unstable, resulting in insufficient water absorption at night and reduced water release during the day. Repeated alternation of wet and dry conditions leads to reduced root anchoring ability and low seedling survival rate.

[0099] 3. Fulvic acid can promote root growth and induce root gravitation, enabling it to quickly take root in sandy soil and allow the roots to autonomously find water sources. Calcium carbonate, on the other hand, balances the pH imbalance caused by the degradation of gel particles around the roots, which has a particularly serious impact on the survival rate in the later stages.

[0100] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention. Technical aspects, shapes, and structures not described in detail in this invention are all well-known technologies.

Claims

1. A planting method for improving the survival rate of bare-root seedling afforestation in sandy land, characterized by, The planting method is as follows: (1) Afforestation and land preparation: The afforestation land is reclaimed, and then the sandy land is prepared by pit method before the rainy season; (2) Seedling treatment: Select 2-3 year old bare-root seedlings for afforestation; before afforestation, prune the seedling roots and soak them in water for 1-2 days, and then soak the seedling roots in rooting agent for 1-2 hours before planting; (3) Planting: Dig planting holes, then mix coarse sand, clay and gel particles in a mass ratio of 1:(1.5-2):(0.2-0.3) to obtain the substrate. Place the seedlings in the planting holes and then add the substrate. Backfill with topsoil and subsoil, cover with soil and water. (4) Mulching: After transplanting the seedlings, cover the surface of the planting hole with a layer of plastic film to retain moisture and compact it with soil; (5) Nurturing: Watering is required 2-3 times in the first year after planting. Watering should be done every year according to rainfall thereafter. Weeds should be removed every year and replanting should be done in spring. (6) Pruning: After 5-6 years of planting, prune away the lower dead branches and diseased and weak branches, and retain a crown height ratio of 2:3; The preparation process of the gel particles is as follows: (1) Sodium carboxymethyl starch was mixed with humic acid and water to prepare a sodium carboxymethyl starch mixed solution; polyvinyl alcohol was dissolved to obtain a 10wt% polyvinyl alcohol solution; poly(N-isopropylacrylamide) was swollen with water for 1-2 hours to obtain a sol; A mixture of sodium carboxymethyl starch solution, polyvinyl alcohol solution, and sol was added to polydopamine and glycerin and homogenized for 15-20 minutes to obtain a gel solution. (2) After adjusting the pH of the gel solution to 5, add glutaraldehyde and calcium carbonate, heat to 45-50℃ and react for 1.5-2h to obtain a gel solution, then freeze at -20℃ for 3-4h and thaw at room temperature. Repeat twice and then spray dry to form particles. Dry under hot air conditions at 40-50℃ until the water content is ≤10% to obtain gel particles. The mass ratio of sodium carboxymethyl starch, poly(N-isopropylacrylamide), polydopamine, and polyvinyl alcohol is (50-60):(20-30):(1-2):(10-12).

2. The planting method for improving the survival rate of bare-root seedlings in sandy areas according to claim 1, characterized in that, The initial planting density is 800-1000 plants per hectare.

3. The planting method for improving the survival rate of bare-root seedlings in sandy areas according to claim 2, characterized in that, The specific operation during the planting process is as follows: lay a layer of substrate with a thickness of 5-6cm at the bottom of the planting hole, then place the seedling with its roots spread upright in the hole, add another layer of substrate with a depth of 5-6cm, then backfill with topsoil, and finally fill with bottom soil, tamp it down in layers, and plant the seedling with the original soil mark 3-4cm higher than the surface of the hole.

4. The planting method for improving the survival rate of bare-root seedlings in sandy areas according to claim 3, characterized in that, Set up 1.5m x 1.5m grass grid sand barriers in the afforestation area.

5. The planting method for improving the survival rate of bare-root seedlings in sandy areas according to claim 4, characterized in that, The coarse sand has a particle size of 0.5mm-1mm.

6. The planting method for improving the survival rate of bare-root seedlings in sandy land according to claim 5, characterized in that, The dimensions of the planting hole are 60cm × 60cm × 30cm.

7. The planting method for improving the survival rate of bare-root seedlings in sandy areas according to claim 1, characterized in that, The mass ratio of calcium carbonate, humic acid, glycerol and sodium carboxymethyl starch is (0.5-0.6):(1-1.5):(1-1.5):

25.

8. A planting method for improving the survival rate of bare-root seedlings in sandy areas according to claim 7, characterized in that, In step (1), potassium dihydrogen phosphate may also be added, with the mass ratio of potassium dihydrogen phosphate to sodium carboxymethyl starch being (1-2.5):

30.

9. A planting method for improving the survival rate of bare-root seedlings in sandy areas according to claim 8, characterized in that, The bare-root seedlings are Pinus sylvestris.

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