Planting method for improving biological activity of citrus orchard soil by interplanting california burclover

Abstract

The invention relates to the technical field of ecological planting, in particular to a planting method for improving the biological activity of citrus orchard soil by interplanting california burclover. The planting method comprises the following steps: (1) sowing california burclover seeds in a citrus garden in late October; (2) when the california burclover enters a branching period, applying a fertilizer; (3) naturally decomposing after the california burclover plant is withered; the california burclover seeds naturally fall into the soil. According to the planting method, the fertility of soil in the citrus orchard can be improved, water and soil are kept, microclimate is adjusted, and environmental pollution is reduced; production cost is reduced, and extra income is increased; the income increase of farmers is promoted. And a basis is provided for ecological and sustainable development of the citrus orchard.

Description

Technical Field

[0001] The present invention relates to the technical field of ecological planting, and particularly relates to a planting method for intercropping alfalfa to improve the soil biological activity in a citrus orchard. Background Art

[0002] As an important fruit production area in the southwest of China, the orchard ecosystem in the western Sichuan Plain and the hilly areas around the basin is facing the dual pressures of climate warming and human intervention. Although the annual precipitation in this area is relatively abundant, natural conditions such as frequent seasonal droughts and weak soil and water conservation ability in hilly terrain, combined with the traditional clean tillage management mode, have led to the aggravation of soil compaction and organic matter loss. To improve soil fertility, farmers increase the input of pesticides and fertilizers to maintain production, which seriously deviates from the policy goal of "reducing the use of chemical fertilizers and pesticides and increasing efficiency". At the same time, the continuous increase in agricultural material costs further compresses the profit space of the orchard, and the existing technical system has fallen into the dilemma of "high investment in ecological restoration and difficult improvement of economic benefits". Therefore, there is an urgent need for a new orchard intercropping model with both ecological adaptability and economic sustainability to achieve the coordinated optimization of soil conservation, pest control, and cost control through variety selection and planting system innovation.

[0003] In recent years, the citrus production in Sichuan has been continuously increasing, but a large area of land in citrus orchards has been left bare and fallow for more than half a year, seriously wasting light and heat resources and being unfavorable for the conservation of soil moisture, which seriously affects the fruit quality and the orchard ecological environment. Leguminous forages are not only a high-quality feed source for animals but also important green manure crops. Different leguminous forages have different effects on orchards. There is an urgent need to solve an ecological planting method that can improve the soil nutrient content in citrus orchards, increase citrus yield, and promote the economic benefits of citrus orchards. Summary of the Invention

[0004] The purpose of the present invention is to provide a planting method for intercropping alfalfa to improve the soil biological activity in a citrus orchard.

[0005] To achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a planting method for intercropping alfalfa to improve the soil biological activity in a citrus orchard, including the following steps:

[0007] (1) In late October, sow alfalfa seeds in the citrus orchard;

[0008] (2) When the alfalfa enters the branching stage, apply fertilizer;

[0009] (3) After the alfalfa plants wither, decompose naturally; the alfalfa seeds falling into the soil grow naturally.

[0010] Preferably, the sowing method in step (1) is broadcasting or drilling;

[0011] Do not sow within a radius of 0.5 to 0.8 m of the vertical projection of the citrus tree crown;

[0012] The sowing depth is 2 to 3 cm.

[0013] Preferably, the seeding rate for sowing in step (1) is 1.0 to 2.0 kg / mu.

[0014] Preferably, the row spacing for strip sowing is 20 to 30 cm.

[0015] Preferably, the fertilizers in step (2) are superphosphate and potassium sulfate;

[0016] The application rate of superphosphate is 10 to 15 kg / mu;

[0017] The application rate of potassium sulfate is 5 to 10 kg / mu.

[0018] The present invention also provides the application of the described planting method in improving the soil nutrient content in a citrus orchard;

[0019] The soil nutrient content includes organic matter content, total phosphorus content, available phosphorus content, available potassium, and total nitrogen content.

[0020] The present invention also provides the application of the described planting method in improving the activity of soil enzymes in a citrus orchard;

[0021] The soil enzymes include invertase and urease.

[0022] The present invention also provides the application of the described planting method in reducing the cadmium content in the soil of a citrus orchard.

[0023] The present invention also provides the application of the described planting method in improving the soil microbial diversity in a citrus orchard.

[0024] The present invention also provides the application of the described planting method in improving the citrus yield and / or quality.

[0025] The present invention provides a planting method for intercropping alfalfa to improve the soil biological activity in a citrus orchard. The method of the present invention has the following advantages compared with the methods of the prior art:

[0026] (1) Ecological value: By intercropping alfalfa in the citrus orchard, the present invention can improve the soil fertility of the citrus orchard, conserve water and soil, regulate the microclimate, and reduce environmental pollution; alfalfa grows rapidly in spring and has a high vegetation coverage rate, which can significantly inhibit weeds; at the same time, the good vegetation coverage effectively ensures that the soil environment in the orchard is in a relatively stable temperature and humidity, thereby promoting the stability of the orchard ecosystem.

[0027] (2) Economic value: Reducing production costs and increasing additional income. Planting alfalfa reduces the use of herbicides and the cost of weed control in orchards. The cost of herbicides and labor for weed control per mu is reduced by 5 - 30 yuan. The seed yield is 50 - 100 kg / mu. Calculated at 40 - 60 yuan per kilogram of seeds, the seed production can generate an income of 2,000 - 6,000 yuan per mu. The cost investment of alfalfa mainly includes seed cost, fertilizer cost, and labor management cost, with a cost of 500 - 1,500 yuan, and the income per mu is 500 - 5,500 yuan.

[0028] (3) Social value: This technology can effectively promote the agricultural green revolution, improve the utilization efficiency of land resources, increase farmers' income, create new employment opportunities, and promote the popularization of agricultural technologies. The no-tillage cultivation technology of intercropping alfalfa in citrus orchards conforms to the development concepts of green agriculture and sustainable agriculture, helps to promote the transformation of agriculture towards an eco-friendly type. The popularization of this technology can reduce the use of chemical fertilizers and pesticides and reduce the negative impact of agriculture on the environment. Intercropping alfalfa can make full use of the space resources in orchards, improve land utilization rate, achieve "multiple uses of one piece of land", and is especially suitable for areas with limited land resources, helping to ease the contradiction between people and land. The planting and management of this technology are relatively simple, easy for farmers to master, and the popularization threshold is low. In the future, through the demonstration and training of this technology, farmers' ecological awareness and concept of sustainable development can be enhanced. Description of the Drawings

[0029] Figure 1 shows the soil bacterial species composition of different treatments;

[0030] Figure 2 shows the soil fungal species composition of different treatments;

[0031] Figure 3 shows the bacterial diversity index of different treatments;

[0032] Figure 4 shows the fungal diversity index of different treatments. Detailed Implementation Modes

[0033] The present invention provides a planting method for intercropping alfalfa to improve the soil biological activity in citrus orchards, including the following steps:

[0034] (1) In late October, sow alfalfa seeds in the citrus orchard;

[0035] (2) When alfalfa enters the branching stage, apply fertilizers;

[0036] (3) After the alfalfa plants wither, they decompose naturally; the alfalfa seeds that fall into the soil grow naturally.

[0037] In the present invention, the sowing method in step (1) is broadcasting or drilling;

[0038] Do not sow within a radius of 0.5 to 0.8 m of the vertical projection of the citrus tree crown; preferably, do not sow within a radius of 0.5 m of the vertical projection of the citrus tree crown.

[0039] The sowing depth is 2 to 3 cm, preferably 2.5 cm.

[0040] In the present invention, the seeding rate for sowing in step (1) is 1.0 to 2.0 kg / mu, preferably 1.5 kg / mu.

[0041] In the present invention, the row spacing during strip sowing is 20 to 30 cm, preferably 25 cm.

[0042] In the present invention, the fertilizers in step (2) are superphosphate and potassium sulfate;

[0043] The application rate of superphosphate is 10 to 15 kg / mu, preferably 12 kg / mu;

[0044] The application rate of potassium sulfate is 5 to 10 kg / mu, preferably 8 kg / mu.

[0045] In the present invention, the tree age in the citrus orchard is preferably ≥3 years, and the crown closure degree is ≤0.7.

[0046] In the present invention, the suitable climatic conditions for intercropping are preferably an annual average temperature of 16 to 18 °C, an annual precipitation of 800 to 1200 mm, an altitude not exceeding 1500 m, and a frost-free period of more than 280 days.

[0047] The present invention also provides the application of the described planting method in improving the soil nutrient content of the citrus orchard;

[0048] The soil nutrient content includes organic matter content, total phosphorus content, available phosphorus content, available potassium, and total nitrogen content.

[0049] The present invention also provides the application of the described planting method in improving the activity of soil enzymes in the citrus orchard;

[0050] The soil enzymes include invertase and urease.

[0051] The present invention also provides the application of the described planting method in reducing the cadmium content in the soil of the citrus orchard.

[0052] The present invention also provides the application of the described planting method in improving the soil microbial diversity of the citrus orchard.

[0053] The present invention also provides the application of the described planting method in improving the citrus yield and / or quality.

[0054] In the present invention, Medicago hispida can grow naturally during its growth process. When the seeds mature in April or May, the Medicago hispida seeds are collected. The seeds that fall into the soil grow naturally, and the plants decompose naturally and return to the field. The dry grass in the field can also play roles such as suppressing weeds, increasing soil fertility, and maintaining soil and water. This method is very friendly to orchards with extensive management and no mechanical support.

[0055] In the present invention, when Medicago hispida grows to 30 - 40 cm, it is mowed, leaving a stubble of 5 - 10 cm. The cut plants can be placed between the rows of Medicago hispida (avoid placing them on the plants of the subsequent crop) or under the tree canopy, and they decompose naturally and return to the field. After the last mowing is completed at the beginning of April at the end of March, no more mowing is carried out. Then, let the plants grow and bear fruit. After the seeds mature, they are collected. The seeds that naturally fall into the orchard soil wait to germinate and grow again in autumn. In this way, there is plant return to the field in the orchard, which improves soil fertility, and at the same time, it can ensure the continuous growth of Medicago hispida and reduce the sowing cost. This method of "mowing and utilization + leaving seeds for self - sowing" is applicable to orchards with lawn mowers and relatively sufficient labor.

[0056] Medicago hispida blooms from March to April, bears fruit from April to May, withers and dies in the middle and late May. Some pods (seeds) naturally fall into the soil. The seeds germinate from September to October, forming new plants. The growth is relatively slow from October to January of the next year, and it grows rapidly after the spring in February, which is the biennial habit.

[0057] The following combines examples to elaborate in detail on the solution provided by the present invention, but they cannot be understood as limiting the protection scope of the present invention.

[0058] The citrus orchard described in the embodiment of the present invention is located in Shuangshi Village, Qinglian Town, Jiangyou City, Sichuan Province, covering an area of 20 mu. Chunjian Ponkan was planted in September 2019. The experiment was carried out in October 2023. At this time, the tree age of the orchard is 4 years (the crown closure degree ≤ 0.7), with 120 plants planted, the row spacing is 3 m, and the plant spacing is 2.6 m. The vegetative growth of the fruit trees is too strong, and the fruit yield is relatively low. The average fruit yield of Chunjian Ponkan is 8.8 kg / plant, and the overall fruit yield of the orchard is about 1056 kg. The fruit trees are damaged by pests such as rust mites, fruit flies, and aphids. The main weed damage is Alternanthera philoxeroides (Mart.) Griseb. The orchard soil is yellow clay, with soil compaction and low organic matter content. The results of soil nutrient determination show that: pH value is 5.67, organic matter is 12.58 g / kg, total nitrogen is 0.9381 g / kg, total phosphorus is 0.748 g / kg, available phosphorus is 117.98 mg / kg, and available potassium is 316.81 mg / kg.

[0059] The climate conditions in Shuangshi Village, Qinglian Town, Jiangyou City, Sichuan Province are as follows: the annual average temperature is 16 - 18°C, the annual precipitation is 800 - 1200 mm, the altitude does not exceed 1500 m, and it is planted in areas with a frost-free period of more than 280 days. The examples of the present invention were carried out from 2023 to 2024. The average temperature in the two years was 16°C, the annual rainfall was 1000 mm, the altitude was 550 m, and the frost-free period was 290 days.

[0060] The alfalfa mentioned in the examples of the present invention is 'Southern Sichuan' alfalfa, which is sourced from the Sichuan Academy of Grassland Science.

[0061] Example 1

[0062] The experiment adopted a single-factor randomized block design. The experimental plot was divided into 3 treatment groups: the alfalfa group, the clean tillage group (CK1), and the natural grass group (CK2), and each treatment group was replicated 3 times.

[0063] Select alfalfa seeds with plump grains and no pests and diseases, sun the seeds for 2 days, and sow them on October 25th. The sowing method is broadcasting, and the sowing depth is 2 cm. Do not sow within a radius of 0.5 m of the vertical projection of the citrus tree crown. The seeding rate is 2 kg / mu.

[0064] After sowing, keep the soil moist to promote seed germination and emergence. After emergence, water in a timely manner according to the weather conditions and soil moisture to avoid drought. Alfalfa has strong nitrogen-fixing ability and generally does not require topdressing with nitrogen fertilizer. Phosphorus and potassium fertilizers can be topdressed once when it just enters the branching stage, applying 12 kg of superphosphate and 8 kg of potassium sulfate per mu. Alfalfa has fewer pests and diseases. Pay attention to controlling pests such as aphids and prodenia litura, and high-efficiency and low-toxic pesticides can be selected for control. When the alfalfa plant height reaches 30 - 40 cm, mow it, leaving a stubble height of 8 cm. The cut plants are placed between the rows of alfalfa or under the citrus tree basin. After the last mowing is completed at the beginning of April at the end of March, do not mow anymore. Let the plants grow and bear fruit later. After the seeds mature, collect the alfalfa seeds. The seeds that naturally fall on the orchard soil will wait to germinate and grow again in autumn.

[0065] For CK1, manually weed to ensure that there is no vegetation under the orchard trees and no sowing is carried out either.

[0066] For the CK2 group, no sowing is carried out and no weeding is done, allowing the weeds under the orchard to grow naturally.

[0067] Example 2

[0068] Record the sowing time, emergence time, and the time of each phenological period of Medicago hispida Gaertn. After the lawn is formed, measure the natural height of the plants in each plot 5 times with a tape measure, and calculate the average height and plant height (vertical height). In April 2024, investigate the community height (since Medicago hispida Gaertn. has prostrate stems instead of erect growth, this height is used to measure the height of the plants in their natural prostrate state), coverage, soil temperature, and humidity of the plants in each treatment. The results are shown in Tables 1 - 2.

[0069] Table 1 Observation results of the phenological periods of Medicago hispida Gaertn. growing in the citrus orchard

[0070]

[0071] Table 2 Growth conditions of plants and soil temperature and humidity conditions in citrus orchards of different groups

[0072] Group Plant height (cm) Natural height of community (cm) Coverage (%) Soil temperature (°C) Soil humidity (%) Alfalfa group 138.33±4.36c 28.00±0.29b 100.00±0.00a 18.83±0.20cd 46.03±1.27ab CK1 <![CDATA 0.00 ±0.00e]]> 0.00±0.00c 0.00±0.00f 20.17±0.09a 37.33±2.39c CK2 25.60±3.53e 22.67±3.06b 83.33±1.67e 19.50±0.15b 38.60±0.56c

[0073] Note: Different lowercase letters indicate significant differences.

[0074] As can be seen from Tables 1 - 2, Medicago hispida Gaertn. grows well in the citrus orchard and can complete the entire growth period normally. In April 2024, the plant height (vertical height), community height, coverage, soil humidity, and temperature of the Medicago hispida Gaertn. group were investigated in the orchard. The results showed that Medicago hispida Gaertn. can grow up to 138.33 cm; in the natural grass - growing CK2 group, there are mainly Oxalis corniculata, Chrysanthemum indicum, Galinsoga parviflora, Alternanthera philoxeroides, etc., with an average height of 25.6 cm, and the vegetation coverage of the Medicago hispida Gaertn. group is higher than that of the CK2 group. The soil temperature of the Medicago hispida Gaertn. group is lower than that of the CK1 and CK2 groups, and the soil humidity of the Medicago hispida Gaertn. group is greater than that of the CK1 and CK2 groups.

[0075] The relatively low and ground - covering characteristics of Medicago hispida Gaertn. help to effectively inhibit weeds and effectively ensure that the orchard soil is in good and stable temperature and humidity conditions.

[0076] Example 3

[0077] During the full - bloom period of Medicago hispida Gaertn., cut the grass in a 1×1 m quadrat in each plot at a height of 5 - 10 cm from the ground, weigh the fresh weight of the plants in the small quadrat, measure the SPAD (an index reflecting chlorophyll content), and determine the dry weight after drying to a constant weight. Powder the dried grass samples to measure the contents of crude protein, crude fat, acid detergent fiber (ADF), neutral detergent fiber (NDF), and ash. The crude protein is determined by the Kjeldahl method; the fiber is determined by the sulfuric acid digestion method; the crude fat is determined by the Soxhlet extraction method; the crude ash is determined by the crucible heating method; the chlorophyll is measured with a chlorophyll meter. The test results are shown in Table 3.

[0078] Table 3 Yield and nutritional component analysis of Medicago hispida Gaertn.

[0079]

[0080] Table 3 shows that in April 2024, the fresh yield of alfalfa detected was 1568.50 kg / mu, and the content of each nutrient component was high after drying.

[0081] Example 4

[0082] Collect soil samples of 0 - 20 cm in each experimental group at the full-bloom stage of alfalfa, and use the five-point method for mixed sampling. After the samples are air-dried, they are sieved. Measure the pH value, organic matter, total nitrogen, total phosphorus, available phosphorus, and available potassium content of the soil in each plot. The pH value is measured using a pH meter, the organic matter is measured using the external heating method with potassium dichromate, the total nitrogen is measured using the Kjeldahl method, the total phosphorus is measured using the molybdenum-antimony anti-colorimetric method, the available phosphorus is measured using the molybdenum-antimony anti-colorimetric method, and the available potassium is measured using a flame photometer. The results are shown in Table 4. Before treatment refers to before planting.

[0083] Table 4 Soil nutrient content of different treatments

[0084]

[0085] Table 4 shows that planting alfalfa increased the soil pH value by 4.1% compared with before planting, the organic matter by 7.2%, the total nitrogen by 9.6% (p < 0.05), the total phosphorus by 23.67% (p < 0.05), the available phosphorus by 56.33% (p < 0.05), and the available potassium by 28.47% (p < 0.05). For CK1 under clean tillage treatment, each index decreased compared with before planting, but the difference was not significant. In the CK2 group with natural grass growth, the content of total nitrogen, total phosphorus, available phosphorus, and available potassium also increased compared with before planting. Among them, the available phosphorus and available potassium increased by 21.57% (p < 0.05) and 31.84% (p < 0.05) respectively. The increase in available phosphorus was not as much as that in the alfalfa group. Except that the increase in available potassium was higher than that in the alfalfa group, the increase in other indexes was lower than that in the alfalfa group. It can be seen that alfalfa can significantly improve the nutrient content of the citrus orchard soil.

[0086] Example 5

[0087] Collect soil samples of 0 - 20 cm in each experimental group at the full-bloom stage of alfalfa, and use the five-point method for mixed sampling. After the samples are air-dried, they are sieved. Measure the cadmium content in the soil samples of each plot. The test results are shown in Table 5. Before treatment refers to before planting. The detection of cadmium content is measured using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry).

[0088] Table 5 Effects of different treatments on cadmium content in citrus orchard soil

[0089] Group Total cadmium content mg / kg Before treatment 0.145 Alfalfa group 0.137 CK1 0.172 CK2 0.167

[0090] Table 5 shows that the cadmium content in the soil of the alfalfa group decreased by 5.5% compared with that before treatment, while the cadmium content in the soil of the CK1 group with clean tillage and the CK2 group with natural grass growth increased compared with that before treatment. This indicates that alfalfa can significantly reduce the cadmium content in citrus orchards.

[0091] Example 6

[0092] Soil enzymes are active substances secreted by plant roots and their residues, soil animals and their remains, and microorganisms in the soil. They are one of the most active organic components in soil components and important substances participating in soil metabolism. Among them, soil invertase and urease are biological activity indicators characterizing the cycling status of soil C, N and other nutrients and soil properties, and have been applied to evaluate the cycling and transformation of soil nutrients and the effects of various agricultural measures and fertilizer applications.

[0093] Soil samples of 0-20 cm were collected from each experimental group during the full-bloom stage of alfalfa, and mixed sampling was carried out by the five-point method. After the samples were air-dried, they were sieved. The contents of invertase and urease in the soil samples of each plot were measured. The test results are shown in Table 6. Before treatment refers to before planting. The detection of invertase was determined by the biochemical colorimetric method (DNS method); the detection of urease was determined by the indophenol blue colorimetric method.

[0094] Table 6 Effects of Different Treatments on Enzyme Activity in Citrus Orchard Soil

[0095]

[0096]

[0097] Table 6 shows that after planting alfalfa in the citrus orchard, the invertase in the soil increased by 65.39% (p < 0.05) compared with that before planting, and the urease increased by 3.38%; compared with the CK1 group with clean tillage treatment, the invertase was 47.22% higher and the urease was 25.93% higher; compared with the CK2 group with natural grass growth, the invertase was 33.98% higher and the urease was 31.90% higher. This indicates that alfalfa can significantly improve the activities of invertase and urease in citrus orchards.

[0098] Example 7

[0099] Soil samples of 0-20 cm were collected from each experimental group during the full-bloom stage of alfalfa, and mixed sampling was carried out by the five-point method. After mixing, plant residues, gravel and other impurities were removed. To prevent sample contamination, the soil samples were disinfected with 75% alcohol before and after each sampling. The samples were put into a sterilized bag and brought back to the laboratory with an ice box, and stored in a -80°C refrigerator for the extraction of soil microbial DNA and subsequent determination. The high-throughput sequencing technology of 16S rRNA and ITS rRNA genes was used to detect soil bacterial diversity and fungal diversity. The results are as Figures 1-4 shown.

[0100] Example 8

[0101] After planting alfalfa in the citrus orchard, the use of herbicides in the citrus orchard decreased in 2023. The cost of herbicides and manual weeding per mu was reduced by 15 yuan. The seed yield was 82 kg / mu. Calculated at 50 yuan per kilogram of seeds, the seeds generated an income of 4,100 yuan per mu. The cost input of alfalfa mainly includes seed cost, fertilizer cost, and labor management cost. The production cost is 800 yuan, and the income per mu is 3,300 yuan.

[0102] The alfalfa treatment group's citrus yield in 2023 was 2,880 kg, which was 23.4% higher than the 2,334 kg of the CK1 citrus yield under clean tillage; and 43.28% higher than the 2,010 kg of the CK2 citrus yield under natural grass growth.

[0103] As can be seen from the above embodiments, the present invention provides a planting method for intercropping alfalfa to improve the soil biological activity in a citrus orchard. The method of the present invention has the following advantages compared with the methods of the prior art: (1) Ecological value: Intercropping alfalfa in the citrus orchard can improve the soil fertility of the citrus orchard, conserve water and soil, regulate the microclimate, and reduce environmental pollution. (2) Economic value: Reduce production costs and increase additional income. (3) Social value: This technology can effectively promote the green revolution in agriculture, improve the utilization efficiency of land resources, increase farmers' income, create new employment opportunities, and promote the popularization of agricultural technology. It provides a basis for the ecological planting and sustainable development of citrus orchards.

[0104] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A planting method for intercropping alfalfa to improve the soil biological activity in a citrus orchard, characterized in that It includes the following steps: (1) In late October, sow alfalfa seeds in the citrus orchard; (2) When the alfalfa enters the branching stage, apply fertilizers; (3) After the alfalfa plants wither, decompose naturally; the alfalfa seeds that fall into the soil grow naturally.

2. The planting method according to claim 1, characterized in that The sowing method described in step (1) is broadcasting or drilling; Do not sow within a radius of 0.5 - 0.8 m of the vertical projection of the citrus tree crown; The sowing depth is 2 - 3 cm.

3. The planting method according to claim 2, characterized in that, The seeding rate for sowing described in step (1) is 1.0 - 2.0 kg / mu.

4. The planting method according to claim 2, characterized in that, The row spacing for drilling is 20 - 30 cm.

5. The planting method according to claim 1, characterized in that The fertilizers described in step (2) are superphosphate and potassium sulfate; The application rate of superphosphate is 10 - 15 kg / mu; The application rate of potassium sulfate is 5 - 10 kg / mu.

6. Application of the planting method according to any one of claims 1 - 5 in improving the soil nutrient content of the citrus orchard; The soil nutrient content includes organic matter content, total phosphorus content, available phosphorus content, available potassium, and total nitrogen content.

7. Application of the planting method according to any one of claims 1 - 5 in improving the activity of soil enzymes in the citrus orchard; The soil enzymes include invertase and urease.

8. Application of the planting method according to any one of claims 1 - 5 in reducing the cadmium content in the soil of the citrus orchard.

9. Application of the planting method according to any one of claims 1 - 5 in improving the soil microbial diversity of the citrus orchard.

10. Application of the planting method according to any one of claims 1 - 5 in improving the citrus yield and / or quality.

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