CN115024041A

CN115024041A - Method for improving saline-alkali soil of orchard

Info

Publication number: CN115024041A
Application number: CN202210725178.7A
Authority: CN
Inventors: 姜远茂; 姜翰; 冯资权; 彭奥翔; 葛顺峰; 朱占玲
Original assignee: Shandong Agricultural University
Current assignee: Shandong Agricultural University
Priority date: 2022-06-23
Filing date: 2022-06-23
Publication date: 2022-09-09

Abstract

The invention discloses a method for improving saline-alkali soil of an orchard, and belongs to the technical field of soil improvement. The method for improving the saline-alkali soil of the orchard has the advantages of promoting the physicochemical property of the saline-alkali soil and promoting the growth of plants, and the completely pure natural surfactant rhamnolipid is applied to the soil to serve as a direct improver, so that compared with the improver in the prior art, the improver has the advantages of energy conservation, environmental protection, high efficiency, high economy, no toxicity, no pollution, no secondary pollution and the like, can be applied to the soil to promote the physicochemical property of the soil, and also has the effect of promoting the growth of plants, and compared with the condition that rhamnolipid is not applied, the applied rhamnolipid obviously reduces the volume weight, the compactness, the EC value and the pH value of the soil; the biomass index, the root index, the photosynthetic index and the related photosynthetic index are obviously improved, the activities of SOD, POD and CAT enzymes are improved, and the content of Malondialdehyde (MDA), the relative conductivity and the salt damage index are reduced.

Description

Method for improving saline-alkali soil of orchard

Technical Field

The invention belongs to the technical field of soil improvement, and particularly relates to an orchard saline-alkali soil improvement method.

Background

In order to meet the requirement of high yield of apples, the development of saline-alkali soil and the repair of some old orchards with serious secondary salinization are urgent problems. At present, the total area of the global saline-alkali soil is close to 25%, if the salinization continues to develop according to the speed, the united nations food and agriculture organization predicts that almost half of the global soil can be salinized in the coming 2050 year. The saline-alkali soil in China occupies 1/5 of agricultural cultivated land area in China. Wherein, in northeast, most regions in northwest, a small part of Huang-Huai-Hai region has been eroded by saline-alkali, at least comprising 20 provinces, most regions in Xinjiang, river estuarine region, yellow river midstream region and Bohai Bay region overlap with the areas of four main production regions for apple cultivation.

In coastal areas, due to the fact that the water level line is high, salt content gradually rises along with the underground water level, evaporation of water evaporation on the ground is aggravated by heat of dry weather on the ground, and the salt concentration accumulated on the surface of soil is gradually increased. In arid areas, the increase of the application of various fertilizers, the unreasonable development and utilization of soil, the chopping of plants and the unreasonable irrigation all cause the secondary salinization of soil to be serious. Northwest is the dominant producing area of apples in China, but the natural soil contains more calcareous substances, and the highest pH value in the area can reach 8.92 according to investigation. Xinjiang apples are popular in the market recently, but Xinjiang apples serve as important apple producing areas, the structure of a soil layer is not ideal, the proportion of sandy soil is extremely prominent, rainfall in the Aksu area is only 42.4-94.4 mm all the year but evaporation capacity all the year reaches 1980-2602 mm, and secondary salinization is easily caused. In addition to the traditional old brand apple production area, the new apple production area has great development potential, and it is reported that Binzhou will become an important high-acid apple production base nationwide. In 2007, the cultivation area of the high acid apple in Binzhou city has exceeded 1 ten thousand hm2, and has become the largest production base of the high acid apple in China at that time. The coastal cities are located at east of Shandong, belong to plain, and yellow river passes through the coastal cities, so that the coastal cities are subjected to increasingly serious silt impact at sea withdrawal positions and are accompanied with repeated flood tide. Therefore, the water quality is hard, so the saline-alkali content of the soil is higher, and the soil belongs to typical saline-alkali soil. The whole coastal cities are generally saline-alkali soil, and the more serious regions have a lower saline-alkali degree in the northeast and the northwest. According to the saline-alkali survey of the Bin State city, the result shows that the area of the severe saline-alkali area is 1026.72km2, which accounts for 85.56% of the total area (according to the standard, the salt content of the severe saline-alkali area is more than 0.4%).

The salt and alkali cause the increase of ion concentration in the soil, damage the root system of the plant, destroy the photosynthetic structure of the plant and cause the physiological drought of the plant. Salt often appears in soil along with alkali, at present, only salt or alkali single-component soil is few, the soil with the combination of the salt and the alkali is much, and the damage to plants of the soil is also serious. In the process of alkali stress, the periphery of the root system is affected by high pH, the change of osmotic pressure and salt damage plants together, the osmotic pressure ion balance of the plants is affected, the yield of crops is damaged, the quality is affected, and the economy is reduced, so that the method for improving the orchard saline-alkali soil is provided for solving the problems.

Disclosure of Invention

In view of one or more of the above-mentioned deficiencies in the art or needs for improvement, the present invention provides a method for improving saline-alkali soil in an orchard, which has the advantages of promoting the physicochemical properties of saline-alkali soil and promoting the growth of plants.

In order to achieve the aim, the invention provides an orchard saline-alkali soil improvement method, which comprises the following steps:

s1: uniformly watering the garden soil after seedling setting, and then carrying out first treatment 7 days after seedling revival, wherein the treatment process is as follows: watering the orchard thoroughly, and broadcasting rhamnolipid which has a function of promoting the physicochemical property of saline-alkali soil and the growth of plants according to the volume of water and the concentration of 1-3 g/L;

s2: after primary treatment, the rhamnolipid is watered once every two times, the watering frequency is once every five days, the rhamnolipid is watered for 6 times and 12 times according to the scientific watering amount, and other conditions are kept consistent, and conventional orchard management is carried out.

As a further improvement of the invention, the soil has pH of 8.96, the soil compactness of 1013kpa, the soil bulk density of 1.3g/L and the electrical conductivity of 2.15 ms/cm.

As a further improvement of the invention, the rhamnolipid is a 6FA model rhamnolipid.

As a further improvement of the invention, the rhamnolipid has the concentration of 60g/L, the purity of 80 percent and the pH value of 7 +/-0.5.

As a further improvement of the invention, the plant is a Malus hupehensis seedling.

Generally, compared with the prior art, the technical scheme conceived by the invention has the following beneficial effects:

according to the method for improving the saline-alkali soil of the orchard, the completely pure natural surfactant rhamnolipid is applied to the soil to serve as a direct modifier, compared with the modifier in the prior art, the conditioner has the advantages of energy conservation, environmental protection, high efficiency, strong economy, no toxicity, no pollution, no secondary pollution and the like, can be applied to the soil to promote the physical and chemical properties of the soil, and also has the effect of promoting plant growth, and compared with the condition that the rhamnolipid is not applied, the applied rhamnolipid obviously reduces the volume weight, the compactness, the EC value and the pH value of the soil; the biomass index, the root index, the photosynthetic index and the related photosynthetic index are obviously improved, the activities of SOD, POD and CAT enzymes are improved, and the content of Malondialdehyde (MDA), the relative conductivity and the salt damage index are reduced.

Drawings

FIG. 1 is a bar graph of the test conclusion of the present invention;

FIG. 2 is a bar graph of the test conclusion of the present invention;

FIG. 3 is a bar graph of the test conclusion of the present invention;

FIG. 4 is a bar graph of the test conclusion of the present invention;

FIG. 5 is a bar graph of the conclusion of the test of the present invention.

FIG. 6 is a bar graph of the test conclusion of the present invention;

FIG. 7 is a bar graph of the conclusion of the test of the present invention.

FIG. 8 is a bar graph of the test conclusion of the present invention;

FIG. 9 is a bar graph of the test conclusion of the present invention;

FIG. 10 is a bar graph of the test conclusion of the present invention;

FIG. 11 is a bar graph of the test conclusion of the present invention;

FIG. 12 is a bar graph of the test conclusion of the present invention;

FIG. 13 is a bar graph of the test conclusion of the present invention;

FIG. 14 is a line graph of the conclusion of the test of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Characteristics of soil

The soil is sandy soil, saline-alkali soil is collected at coastal command ports of the Heilu community in Bin, the pH value of the soil is 8.96, the soil compactness is 1013kpa, the soil volume weight is 1.3g/L, the conductivity is 2.15ms/cm, and each basin is filled with 4kg of the soil.

Secondly, determining organic fertilizer and application amount

The rhamnolipid to be tested was a 6FA model rhamnolipid (concentration 60 g/L; purity: 80%; pH 7. + -. 0.5) produced by Seanergiy Biotech Ltd.

Thirdly, selecting plant species

Taking the Malus hupehensis Rehd as a test material, and counting the low-temperature Malus hupehensis Rehd seeds for 1 month from the beginning in a laminated sand pit dug in a laminating greenhouse in advance. Sowing the sand-stored seeds into a nutrition pot after 1 month, spraying 1/2Hoagland (Hoagland and Arnon1950) nutrient solution, spraying the nutrient solution once or twice a week, normally managing watering for the rest of the week, and maintaining the Malus hupehensis Rehd seedlings. After two months of cultivation, regular and consistent Malus hupehensis Rehd seedlings are selected as test materials. 108 Malus hupehensis seedling plants which are relatively uniform in growth and cannot be corroded by diseases and insect pests are selected, 3 Malus hupehensis seedlings are planted in each pot, and 6 treatment steps are set after potting treatment.

Fourth, the measurement procedure

Measuring the soil compactness at 0d, 30d, 60d and 90d, measuring at the position of 10cm of soil depth by using a soil compactness measuring instrument, avoiding the areas of depression, stone, cracks and the like, randomly measuring in different directions, and repeating for multiple times; and (3) carrying out soil pH and conductivity EC on the same day, determining 5 sampling points by adopting a snake-shaped sampling method according to the area and the shape of the flowerpot, collecting 3 parts of soil by using a quartering method for each sampling point, and then uniformly mixing and bagging for later use. Soil volume weight is measured at 0d, 40d and 80d, random sampling is carried out at different directions by adopting a customized 50 square meter circular knife (the volume is small, the soil sampling amount of potted soil is reduced), the root system of the Malus hupehensis Rehd, the soil pit and the like are avoided, the collected soil is brought back, and the measurement is carried out according to the measurement method.

The relative conductivity was measured at 20d, healthy mature leaves were collected, punched with a punch and repeated several times. Measuring chlorophyll index at 30d, picking off mature and healthy leaves, cleaning, cutting off vein, cleaning, and grinding. The biomass and root system indexes are to collect the whole plant, the damage to the root system is avoided, the plant is brought back by using a soil shaking method, and the plant is decomposed into three parts, namely roots, stems and leaves after being cleaned, and the fresh weight of the plant is respectively called. The root system is firstly placed in deionized water, the root system index is firstly scanned, then all parts are placed in a 105 ℃ oven for water deactivation for 30min, and then the temperature is reduced to 80 ℃ until the plant is completely dried, and the dry weight is called.

Example 1

An orchard saline-alkali soil improvement method comprises the following steps:

s1: uniformly watering the garden soil after seedling setting, and then carrying out first treatment 7 days after seedling revival, wherein the treatment process is as follows: watering the orchard thoroughly, and broadcasting rhamnolipid which has a promoting effect on the physicochemical property of saline-alkali soil and the plant growth according to the volume of water and the concentration of 0 g/L;

Example 2

An orchard saline-alkali soil improvement method comprises the following steps:

s1: uniformly watering the garden soil after seedling setting, and then carrying out first treatment 7 days after seedling revival, wherein the treatment process is as follows: watering the orchard thoroughly, and broadcasting rhamnolipid which has the function of promoting the physicochemical property of saline-alkali soil and the plant growth according to the water volume and the concentration of 1 g/L;

s2: and (3) after primary treatment, the rhamnolipid is watered every two times, the watering frequency is that the rhamnolipid is watered every five days, the rhamnolipid is watered for 6 times and 12 times according to the scientific watering amount, and other conditions are kept consistent, and the orchard management is carried out conventionally.

Example 3

An orchard saline-alkali soil improvement method comprises the following steps:

s1: uniformly watering the garden soil after seedling setting, and then carrying out first treatment 7 days after seedling revival, wherein the treatment process is as follows: watering the orchard thoroughly, and broadcasting rhamnolipid which has the function of promoting the physicochemical property of saline-alkali soil and the plant growth according to the water volume and the concentration of 1.5 g/L;

Example 4

An orchard saline-alkali soil improvement method comprises the following steps:

s1: uniformly watering the garden soil after seedling setting, and then carrying out first treatment 7 days after seedling revival, wherein the treatment process is as follows: watering the orchard thoroughly, and broadcasting rhamnolipid which has the function of promoting the physicochemical property of saline-alkali soil and the growth of plants according to the water volume and the concentration of 2 g/L;

Example 5

An orchard saline-alkali soil improvement method comprises the following steps:

s1: uniformly watering the garden soil after seedling setting, and then carrying out first treatment 7 days after seedling revival, wherein the treatment process is as follows: watering the orchard thoroughly, and broadcasting rhamnolipid which has the function of promoting the physicochemical property of saline-alkali soil and the plant growth according to the water volume and the concentration of 2.5 g/L;

Example 6

An orchard saline-alkali soil improvement method comprises the following steps:

s1: uniformly watering the garden soil after seedling setting, and then carrying out first treatment 7 days after seedling revival, wherein the treatment process is as follows: watering the orchard thoroughly, and broadcasting rhamnolipid which has the function of promoting the physicochemical property of saline-alkali soil and the growth of plants according to the volume of water and the concentration of 3 g/L;

According to examples 1 to 6, the following conclusions are drawn:

CK 3: example 1; y1: example 2; y2: example 3; y3: example 4; y4: example 5; y5: example 6.

As can be seen from fig. 1, the bulk density of soil tends to decrease first and then increase as the rhamnolipid concentration increases. The Y4 treatment was the lowest at both 40d and 80d, which were a 2.22% and 4.41% reduction, respectively, over the CK3 treatment. The impact on volume weight over time appears as: the volume weight of soil with different concentrations of rhamnolipid treatment is reduced at 80d compared with 40 d; the CK3 treatment increased in bulk soil weight at 80d compared to 40 d. 80d to 0d, the rhamnolipid treatment with different concentrations is reduced compared with the soil volume weight of 0d, and the reduction range of Y4 treatment is maximum and is reduced by 2.26%; the volume weight of the soil treated by CK3 is increased by 1.99% compared with that of the soil treated by 0 d.

From fig. 2, it is known that the rhamnolipid reduces the compactness of saline-alkali soil, the soil compactness is in a trend of decreasing first and then increasing along with the increase of the concentration of the rhamnolipid, the soil compactness of the Y4 treatment at 30d, 60d and 90d is the maximum, and the soil compactness is respectively reduced by 9.30%, 19.48% and 31.20% compared with the CK3 treatment, and then the Y5 treatment is performed. The soil compactness treated by CK3 is in an increasing trend along with the time, and the soil compactness at 90d is improved by 25.25 percent compared with that at 0 d; the treatment of other different rhamnolipid concentrations shows a descending trend, the Y4 treatment has the largest descending amplitude, the soil compactness of 90d is reduced by 12.49 percent compared with 0d, and the Y5 treatment is the second.

As can be seen from fig. 3, the application of rhamnolipid can significantly reduce pH in saline-alkali soil, and the pH tends to decrease with the increase of the applied concentration of rhamnolipid. The Y5 treatment was minimal at 30d, 60d, and 90d, which were a 2.37%, 5.61%, 8.90% reduction compared to CK3 treatment, respectively. The pH decreased with time, with the greatest decrease in Y5 treatment at 90d compared to 0d, followed by Y4 treatment, which showed no significant difference at 30 d.

As can be seen from fig. 4, the rhamnolipid can significantly reduce the conductivity in saline-alkali soil, the conductivity has a tendency of decreasing and then increasing with the applied concentration of rhamnolipid, and the conductivity EC of the Y4 treatment at 30d, 60d and 90d is the lowest, and is decreased by 6.07%, 10.80% and 15.24% respectively compared with the CK3 treatment. The conductivity of the Y1 treatment at 30d is higher than that of the CK3 treatment, but the conductivity of the treated soil at different concentrations of rhamnolipid is reduced along with the time, and the conductivity of the treatments at 60d and 90d is lower than that of the CK3 treatment. For a soil conductivity of 90d, the decrease of Y4 treatment was greatest and Y5 was second.

It can be seen that the rhamnolipid with the concentration of 2.5g/L obviously reduces the volume weight, compactness and EC value of soil conductivity of saline-alkali soil, and the rhamnolipid with the concentration of 3g/L obviously reduces the pH value of the soil, but the difference between the rhamnolipid with the concentration of 3g/L and the rhamnolipid with the concentration of 30d, 60d and 90 is not obvious. Therefore, the application concentration of the fertilizer is 2.5g/L, and the improvement effect on the physicochemical property of the saline-alkali soil is optimal.

As can be seen from table 1, the fresh weight of the above-ground parts, the fresh weight of the below-ground parts, the dry weight of the above-ground parts and the dry weight of the below-ground parts tended to increase with the increase in the rhamnolipid concentration. The maximum fresh weight of the overground part is Y5, which is increased by 228.17% compared with CK 3; the maximum fresh weight of underground parts is Y5 treatment, which is improved by 180.39% compared with CK3 treatment; the maximum dry weight of the aerial parts was Y5 treatment, which was 232.14% higher than CK3 treatment; the maximum dry weight of the underground portion was the Y5 treatment, which was 512.5% higher than the CK3 treatment, followed by the Y4 treatment. The plant height, stem thickness and leaf number also increase along with the increase of the rhamnolipid concentration, and the Y5 treatment is the largest and is respectively 1.61 times, 1.75 times and 2.65 times of the CK3 treatment, and then the Y4 treatment. Therefore, the rhamnolipid with different concentrations can increase the biomass of the Malus hupehensis Rehd under the saline-alkali stress, and the effect of the application concentration of 3g/L is most obvious.

TABLE 1 Effect of different treatments on Malus hupehensis Rehd biomass

As can be seen from Table 2, the rhamnolipid can improve the root indexes of the Malus hupehensis seedling under the saline-alkali stress, the total root length, the root volume, the number of root tips and the root surface area all tend to increase along with the increase of the concentration of the rhamnolipid, and the maximum indexes are Y5 treatment which is 4.91 times, 5.30 times, 5.36 times and 6.19 times of CK3 treatment respectively, and then Y4 treatment; the largest mean root diameter was Y4 treatment, which was 37.03% higher than CK3 treatment, followed by Y5. Overall performance was best for Y5 treatment and second for Y4 treatment. In conclusion, the application of 3g/L rhamnolipid has the optimal effect on improving the root system index of Malus hupehensis Rehd in saline-alkali stress.

TABLE 2 Effect of different treatments on Malus hupehensis Rehd root systems

As can be seen from Table 3, the content of chlorophyll a, b and a + b increases with the increase of the rhamnolipid concentration during the administration of rhamnolipid, and the content of chlorophyll a, b and a + b reaches the maximum in the Y5 treatment, which is 1.60 times, 1.96 times and 1.72 times of the CK3 treatment. The chlorophyll a/b values were minimal at the Y5 treatment, but were almost no different from the Y4 treatment, which was 18.18% lower than the CK3 treatment.

TABLE 3 Effect of different treatments on chlorophyll of Malus hupehensis leaves

As can be seen from FIG. 5, intercellular CO ₂ Concentration C _i With a decreasing trend of rhamnolipid administration, Y5 treatment was minimal at both 20 and 40d, a 46.11%, 60.26% reduction compared to CK3 treatment, respectively. Intercellular CO extension with experimental time ₂ Concentration C _i The value of (A) is reduced, and CK3 and rhamnolipid treatment at different concentrations are all carried out at 40d compared with intercellular CO at 20d ₂ Concentration C _i Is to be low. Y5 treatment at 40d vs 0d intercellular CO ₂ Concentration C _i Is most reduced, followed by Y4 treatment.

As shown in FIG. 6, the application of rhamnolipid can increase the net photosynthetic rate P of Malus hupehensis seedling under saline-alkali stress _n Net photosynthetic rate P _n With increasing trend of applied concentration, the Y5 treatment was maximal with net photosynthetic rates at 20d and 40d 2.39-fold and 3.44-fold higher than CK3 treatment, respectively. It is noteworthy that the treatment of different concentrations of rhamnolipids at their net photosynthetic rate P of 40d compared to 20d _n Both are rising, only CK3 treatment is falling; y4, Y5 treatment net photosynthetic rate P at 40d vs. 0d _n Increasing, CK3 processing decreases compared to 0 d.

As shown in FIG. 7, it can be seen that the application of rhamnolipids can increase the stomatal conductance G of Malus hupehensis Rehd, which grows under the saline-alkali stress _s There is an increasing trend with increasing rhamnolipid administration concentration. Y5 has the largest treatment, and the porosity conductance G of 20d and 40d _s The times of the treatment are respectively 1.83 times and 2.70 times of the treatment of CK 3. Gas hole conductance G with time _s In an ascending trend, Y5 measures the porosity G at 40d _s Compared with the treatment of Y4, the lifting amplitude is the largest compared with 0d, the two have no obvious difference, and the porosity conductivity of the CK3 treatment is reduced compared with 0 d.

As shown in FIG. 8, the application of rhamnolipid can increase the transpiration rate T of Malus hupehensis seedling growing under saline-alkali stress _r The Y5 treatment was maximal at both 20d and 40d, which were 2.77 and 3.54 times the CK3 treatment, respectively. Treatment of rhamnolipid at different concentrations transpiration rate T at 40d to 0d _r For higher, the maximum lifting amplitude is Y5 treatment, and then Y4 treatment, and the difference between the two treatments is not obvious; the CK3 treatment is the transpiration rate T compared to 0d _r And (3) the process is reduced.

Therefore, the rhamnolipid with different concentrations can improve the chlorophyll index of the Malus hupehensis Rehd under the condition of saline-alkali stress, reduce intercellular carbon dioxide, and improve the net photosynthetic rate, the stomatal conductance and the transpiration rate, and the application concentration is the best at 3 g/L.

As can be seen from FIG. 9, the initial fluorescence F ₀ With increasing rhamnolipid concentrations, the effect on the initial fluorescence change amplitude over time was smaller, with Y5 treatment being maximal at 20d, 40d, 1.57 times, 1.50 times higher than CK3 treatment, respectively.The initial fluorescence of rhamnolipid treatment and CK3 treatment at each different concentration was reduced compared to 0d at 40d, but the Y5 treatment had the least reduction in its magnitude at 40d compared to 0d, followed by Y4 treatment; the CK3 process drops most significantly compared to 0 d.

As shown in FIG. 10, the maximum fluorescence F of Malus hupehensis seedling under the saline-alkali stress can be increased by applying rhamnolipid _m And shows an upward trend with increasing rhamnolipid concentration upon administration. The change in maximum fluorescence over time was not great, and the Y5 treatment was maximal at both 20d and 40d, which were 1.44-fold and 1.36-fold respectively greater than the CK3 treatment. The maximum fluorescence of each of the rhamnolipid treatment and the CK3 treatment at 40d is less than the maximum fluorescence of 0d, but the maximum fluorescence of the Y5 treatment is reduced to the minimum, and then the Y4 treatment is carried out; the magnitude of the CK3 processing droop is greatest.

As can be seen from fig. 11, the maximum PS ii light energy conversion rate of the Malus hupehensis seedlings grown under the saline-alkali stress was significantly increased by applying rhamnolipids, and increased with the increase of rhamnolipid concentration, the maximum PS ii light energy conversion rate of the Y5 treatment was the maximum in both 20d and 40d, which were 1.86 times and 1.26 times of that of the CK3 treatment. The influence of the maximum light energy conversion rate of the PS II along with the time is smaller, the maximum light energy conversion rates of the PS II in 40d of the treatment of rhamnolipid with different concentrations and the CK3 treatment are both smaller than 0d, but the reduction amplitude of the Y5 treatment is the minimum, and then the Y4 treatment is carried out; the CK3 process decreases most.

As shown in FIG. 12, the application of rhamnolipid can improve F of Malus hupehensis Rehd seedlings under saline-alkali stress _v /F _m And increasing with rhamnolipid concentration in an ascending trend with time for F _v /F _m The effect of the variation is relatively small. The Y5 treatment was greatest in both 20d and 40d, CK3 treatment F _v /F _m 1.24 times and 1.53 times of the total weight of the composition. Treatment of rhamnolipid at various concentrations at 40d F _v /F _m Are all larger than 0d, only CK3 processes F smaller than 0d _v /F _m . The amplitude of the boost was greatest for the Y5 treatment, followed by the Y4 treatment, and at 40d, there was no significant difference for the Y2, Y3, Y4, Y5 treatments.

Therefore, the rhamnolipid has a remarkable improvement effect on the related photosynthetic indexes of the Malus hupehensis in saline-alkali stress, and the release effect on the related photosynthetic indexes in the saline-alkali stress is the best when the rhamnolipid is applied at the concentration of 3 g/L.

As shown in Table 4, the rhamnolipid can significantly increase the enzymatic activities of SOD, POD and CAT of Malus hupehensis Rehd under the saline-alkali stress; reducing the content of Malondialdehyde (MDA) in plants. Wherein the activities of SOD, POD and CAT enzymes are increased along with the increase of the application concentration of rhamnolipid, and are respectively the maximum of Y5 treatment, 1.49 times, 2.4 times and 1.94 times of CK3 treatment, and then Y4 treatment; the content of Malondialdehyde (MDA) decreased with increasing rhamnolipid concentration, with the lowest treatment of Y5, a 31.67% decrease compared to CK3 treatment, followed by Y4 treatment. Therefore, when the rhamnolipid is applied to the patients with the diseases of SOD, POD and CAT, the effects of increasing the activities of SOD, POD and CAT and reducing Malondialdehyde (MDA) are the most remarkable.

TABLE 4 Effect of different treatments on Malus hupehensis Rehd enzyme Activity and malondialdehyde

As can be seen from fig. 13, the application of rhamnolipid can significantly reduce the relative conductivity of the seedlings of cognac sweet tea under saline-alkali stress. The Y5 treatment was the lowest at 20d, 40d, 60d, and was a 31.46%, 50.19%, 56.71% reduction compared to CK3 treatment, respectively. The treatment with rhamnolipids at different concentrations over time showed a decreasing trend in relative conductivity between 20 and 60d, but the CK3 treatment showed an increasing trend. The Y5 treatment showed the greatest relative conductivity drop at 60d compared to 0d, the Y4 treatment was second, and the CK3 treatment was elevated compared to 0 d. In combination, a rhamnolipid concentration of 3g/L was best applied to reduce the relative conductivity.

As shown in FIG. 14, the salt damage index of Malus hupehensis seedling in saline-alkali stress can be reduced by applying rhamnolipid, and the salt damage index is reduced along with the increase of the concentration of rhamnolipid. The Y5 treatment was the lowest among its 30d, 60d, 90d, and was reduced by 35.56%, 59.15%, 69.83% compared to CK3, respectively. The Y5 treatment is the only treatment with the salt damage indexes decreasing in the order of 30d, 60d and 90d, the Y4 treatment has the salt damage index decreasing in the 60d compared with 30d, but the salt damage index increasing in the 90d compared with 60d, and the CK3, Y1, Y2, Y3 and Y4 treatments are all continuously increasing. The salt damage index of the Y5 treatment is reduced to the maximum extent compared with 0d, and then the Y4 treatment is carried out; the salt damage index of 90d is larger than 0d, and CK3 is larger than Y1 is larger than Y2 is larger than Y3 in the sequence from large to small in the other treatments, and in sum, the effect of reducing the salt damage index of the Malus hupehensis Rehd tea is the best when the rhamnolipid concentration is 3 g/L.

The rhamnolipid can improve the alkaline soil environment, and the results of the examples 1-6 show that the soil conductivity, the volume weight and the compactness tend to be reduced firstly and then increased along with the increase of the concentration of the rhamnolipid, and the concentration of the rhamnolipid is the lowest when the rhamnolipid is applied, namely the rhamnolipid is applied at the concentration of 2.5 g/L; the pH of the soil is in a descending trend, and the application concentration is 3g/L minimum. The reason for this is probably that the rhamnolipid with too high concentration increases soluble substances in the soil, the concentration of rhamnolipid also increases in the soil, the conductivity of the soil is improved, and when the soil is dry, redundant rhamnolipid is not dissolved out of the soil along with water, so that the volume weight and the compactness of the soil are increased. The existing research shows that when the concentration of rhamnolipid reaches the middle critical micelle value of soil, the concentration is increased to improve the dissolving efficiency very little, so that the soluble salt ion eluted by applying 3g/L of rhamnolipid is slightly more than 2.5g/L, which causes the treatment of pH slightly lower than 2.5g/L, and the difference is not significant. This is why the conductivity, bulk weight, compactness, pH optimum application concentration are not uniform. The influence of soil characteristics over time is not obvious, the unit weight and compactness of saline-alkali soil without the application of rhamnolipid are in an increasing trend, and besides the characteristic of soil is difficult to improve the characteristics in a short time, the critical micelle concentration of the rhamnolipid is increased due to the temperature rise of the soil caused by the warming of weather, so that the effect is not obvious as before.

The results of examples 1 to 6 show that rhamnolipid has a good effect of relieving Malus hupehensis Rehd under the condition of saline-alkali stress, and the biomass increase is most remarkable under the application concentration of 3 g/L. The reason is that under the alkaline condition, the rhamnolipid is more likely to form the existing form of micelle rather than the vesicle state, and has good effect on improving the leaching saline-alkali of the physical structure of the soil. When the concentration of the rhamnolipid in the soil reaches a critical micelle, the rhamnolipid in the soil is solubilized, and the salt is dissolved in the rhamnolipid solution and discharged out of the soil, so that the overall property of the soil is improved; in addition, the rhamnolipid is used as a surfactant synthesized by microorganisms, has the characteristics of environmental protection, no toxicity and the like, and has the characteristic of stimulating plant growth when being applied as a fertilizer additive and an auxiliary agent.

The root system of the plant has a close and inseparable relationship with the overground part as the directly contacted organs in the soil, and can absorb moisture and inorganic salt and secrete various hormones to regulate the growth of the plant. According to the results of examples 1-6, the total root length, the root volume, the number of root tips and the root surface area are in positive correlation with the increase of the rhamnolipid application concentration, and each index is the largest at the application concentration of 3 g/L. The rhamnolipid reduces the soil salt concentration and improves the growth of the root system of the Malus hupehensis Rehd, the growth of the plant root system is inhibited under the high salt concentration, and the growth of the plant root system is promoted under the low salt concentration.

Chlorophyll is a central pigment in photosynthesis, and its index reveals a large degree of salt tolerance of plants. The compound stress of salt and alkali can make iron, manganese, copper and other ions in the plant body generate disorder and even precipitate. The photosynthetic index can be used as an important reference index for researching the stress resistance of the plant in the saline-alkali environment, and the fluorescence index can reflect the influence of the stress on the photosynthesis of the plant. The results of examples 1-6 show that the application of rhamnolipid chlorophyll a, b and a + b is obviously improved; chlorophyll a/b is decreased. The untreated Malus hupehensis Rehd has low chlorophyll content, and can inhibit chlorophyll production at high salt concentration. The results of examples 1 to 6 show the variation trend of intercellular carbon dioxide concentration, net photosynthetic rate, transpiration rate and porosity with saline-alkali concentration. The results of examples 1 to 6 show that: administration of 3g/L rhamnolipid pairs F ₀ Fm, PS II maximum light energy conversion rate, F _v /F _m The lifting effect is optimal. F ₀ Is the fluorescence yield in the completely open state of PS II, F ₀ The content of the chlorophyll is related to that of the chlorophyll, the chlorophyll is increased, and the F0 is increased. Fm is the fluorescence yield of the complete off-state of the reaction center of PS II, and the application of rhamnolipid improves Fm. Maximum light energy conversion rate of PS II、F _v /F _m An increase in (b) indicates that photoinhibition is alleviated.

MDA is the most harmful substance produced after plants are subjected to oxidation, SOD, POD and CAT enzyme play a role in reducing damage of cell membranes, and the three substances can remove MDA, active oxygen or other harmful substances produced in cells. SOD, POD and CAT enzymes can increase the content of plants when the plants are subjected to saline-alkali stress, and play a great role in protecting the plants and resisting stress. The test result shows that the MDA content of Malus hupehensis Rehd is obviously reduced by applying 3g/L rhamnolipid, because the pH of saline-alkali soil is reduced by the rhamnolipid; the EC value of the soil is reduced, and the MDA content in the plant is reduced. The rhamnolipid of 3g/L is applied, and the activity of SOD, POD and CAT enzymes of the Malus hupehensis Rehd is remarkably improved by reducing the alkalinity of the soil. In conclusion, the application of the rhamnolipid improves the resistance of the Malus hupehensis Rehd under the saline-alkali stress, which may be that the rhamnolipid obviously improves the flow of water and salt in soil, and then has an improvement effect on the environment of the soil with water, the salt and alkali run off along with the movement of the water, and the alkali of the residual small amount of salt stimulates the Malus hupehensis Rehd seedling to improve the enzyme activity and reduce the malonaldehyde.

The relative conductivity can represent the damage to the cell membrane to a certain extent, the concentration of salt determines the relative conductivity, and the more salt, the greater the conductivity. The relative conductivity of the plants is large, indicating that they are less resistant. The relative conductivity measured in examples 1 to 6 was decreased with the concentration of rhamnolipid applied, and the conductivity was the lowest at 3g/L of rhamnolipid, indicating the highest resistance of Malus hupehensis Rehd at this concentration.

The salt damage index is a reference index for evaluating the salt tolerance of fruit trees, the larger the index is, the more serious the damage to plants is, and the results of examples 1 to 6 show that the salt damage index of the seedlings of the Malus hupehensis Rehd which is treated by rhamnolipid is obviously reduced and shows a descending trend along with the increase of the concentration. The rhamnolipid with the concentration of 3g/L is used for reducing the salt damage index most obviously, and the stress of the growth of the Malus hupehensis Rehd is relieved.

In conclusion, the rhamnolipid has obvious effects of reducing active manganese in manganese-toxicity soil and promoting the growth of Malus hupehensis Rehd, and the application concentration is 2.0 g/L-3.0 g/L, so that the effect is optimal.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. The method for improving the saline-alkali soil of the orchard is characterized by comprising the following steps:

2. The method for improving the saline-alkali soil for the orchard according to claim 1, wherein the pH of the soil is 8.96, the compactness of the soil is 1013kpa, the volume weight of the soil is 1.3g/L, and the conductivity is 2.15 ms/cm.

3. The method for improving the saline-alkali soil of the orchard as claimed in claim 1, wherein the rhamnolipid is a 6FA model rhamnolipid.

4. The method for improving saline-alkali soil for orchards according to claim 1, wherein the rhamnolipid has a concentration of 60g/L, a purity of 80%, and a pH of 7 ± 0.5.

5. The method for improving saline-alkali soil for orchards according to claim 1, wherein the plant is a seedling of Malus hupehensis Rehd.