Preparation method of water and fertilizer retention type soil conditioner

Abstract

The invention provides a preparation method of a water and fertilizer retention type soil amendment, and belongs to the technical field of soil amendments. Biomass polysaccharide with abundant carboxyl functional groups is combined with metal ions to form a three-dimensional network structure capable of effectively coating soil nutrients; meanwhile, the soil conditioner is endowed with obvious pH responsiveness, and targeted remediation can be performed according to different soil conditions; the biomass-based soil conditioner provided by the invention has excellent water-retaining property and good slow-release performance, can improve the soil moisture content, prolong the retention time of soil moisture, and slowly release inclusions while releasing the system moisture, thereby achieving the effect of improving the soil fertility and realizing the improvement of the water-retaining and fertilizer-retaining capabilities of the soil. Meanwhile, the soil conditioner prepared by the invention can also improve the drought stress resistance of crops.

Description

Technical Field

[0001] The invention belongs to the technical field of soil conditioners, and in particular relates to a method for preparing a water- and fertilizer-retaining soil conditioner. Background Art

[0002] As a non-renewable resource, soil provides habitats and water sources for most of the creatures on Earth and is an important material basis for human survival. However, with the development of society and global climate change, soil has been damaged in various forms. Due to soil erosion, drought, loss of soil organic carbon and other forms of degradation, the net cultivated land area in the world is rapidly decreasing. Heavy rainfall, steep slopes, unscientific land reclamation, crop rotation, and irrational development of hilly and mountainous land have led to soil nutrient loss, resulting in reduced soil productivity and food reserve security. Therefore, it is urgent to repair degraded soil and improve the soil environment.

[0003] The main measures for remediation of degraded soil include plant remediation, animal remediation, soil leaching, soil gas lift, natural degradation, chemical oxidation and application of soil conditioners. Among them, the application of soil conditioners has become a hot topic in the current research on the improvement of degraded soil because of its advantages of low cost, simple operation, improved soil fertility and effective improvement of soil physical and chemical properties. However, traditional soil conditioners still have the following shortcomings: (1) Traditional soil conditioners pay more attention to improving their performance, lack research on the environmental protection of the materials themselves, and the degradation products of the materials during use may cause secondary pollution of the soil; (2) The preparation process of soil conditioners is complicated, the material cost is high, and they cannot be widely promoted and used; (3) The use effect of soil conditioners is single, and it is impossible to make targeted repairs according to different soil environments. In order to solve the problems of the above-mentioned traditional soil conditioners, the development of new soil conditioners with simple preparation methods, environmental protection, multiple functions and wide applicability is an effective way to solve this problem. In addition, the effects of water and fertilizer in the soil complement each other, which is an effective way to synergistically improve the soil environment. Therefore, the use of green and natural biomass materials and the functional combination of water retention and slow release of fertilizers can not only improve the degradation of the soil, improve its physical and chemical properties, and increase the nutrient content of the soil, but also promote the growth of crops and improve crop quality, which has important practical production significance.

[0004] Biomass polysaccharide materials are natural biomacromolecule materials. They are widely used in biology, medicine, food and soil improvement because of their wide sources, low prices, rich active functional groups (such as carboxyl and hydroxyl groups), ability to achieve rapid adsorption of metal ions through coordination or electrostatic interactions, and porous structures of cross-linked networks in three-dimensional grids. Traditional biomass-based hydrogels are prepared by active ion cross-linking. The advantage of this cross-linking is that it can quickly generate gels and shorten the preparation time; however, it will lead to uneven cross-linking of the gel, with tight external cross-linking and relatively loose internal structure, resulting in low swelling rate of the gel and poor reusability, which limits its market application.

[0005] At present, the prior art "Enhanced swelling ratio and water retention capacity for novel super-absorbent hydrogel" records a highly absorbent hydrogel with excellent adsorption performance for removing methylene blue dye, a high water absorption rate of more than 5500g / g and excellent water retention performance. After the swollen hydrogel sample was placed outdoors for 3 days, the water retention rate remained above 60%, indicating that it has excellent water absorption (Qingyun Lv, MinWu, Yong Shen. Enhanced swelling ratio and water retention capacity for novel super-absorbent hydrogel [J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2019, 583: 123972.); the prior art "Cellulose nanocrystals-reinforced core-shell hydrogels for sustained release of fertilizer and "Water retention" records an alginate-coated gelatin-cellulose nanocrystal hydrogel. After using it as a soil conditioner, the water absorption rate of the hydrogel can reach 5580g / g and 6490g / g compared with traditional soil conditioners. The fertilizer retention of gelatin-cellulose nanocrystal hydrogel is manifested as the release of almost all soil nutrients in the system within 72h (Diego M.do Nascimento, Yana L.Nunes, Judith P A Feitosa, etc. Cellulose nanocrystals-reinforced core-shell hydrogels for sustained release of fertilizer and water retention [J]. International Journal of Biological Macromolecules, 2022, 216: 24-31.). The biomass-based soil conditioner prepared by the above technology has greatly improved its water absorption compared with traditional soil conditioners, but due to its expensive raw materials, complex processing methods, single performance, secondary pollution to the soil, and poor applicability, the effect is not ideal in practical applications.Therefore, developing a green, low-cost, multifunctional and widely used soil improvement material remains a difficulty in current research. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a method for preparing a water-retaining and fertilizer-retaining soil conditioner. The biomass-based soil conditioner provided by the present invention has excellent water retention and good sustained-release performance, can improve the water holding capacity of the soil, and slowly release the contents while releasing the water in the system, thereby achieving the effect of improving soil fertility, thereby achieving the improvement of the soil's water and fertilizer retention capabilities.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A method for preparing a water- and fertilizer-retaining soil conditioner comprises the following steps:

[0009] (1) mixing the biomass-based polysaccharide, soil nutrients, ionic crosslinking agent and water, and first homogenizing to obtain a mixed solution I;

[0010] (2) mixing gluconolactone with the mixed solution I, and homogenizing for a second time to obtain a mixed solution II;

[0011] (3) allowing the mixed solution II to stand to obtain a pre-product;

[0012] (4) freeze-drying the pre-product to obtain a soil conditioner.

[0013] Preferably, the mass ratio of the biomass-based polysaccharide, soil nutrients and ionic crosslinking agent is 1:1:1 to 10:1:10.

[0014] Preferably, the biomass-based polysaccharide comprises one or more of sodium alginate, carrageenan, fructose and chitosan.

[0015] Preferably, the soil nutrients include one or more of sodium lignin sulfonate, urea, fulvic acid and humic acid.

[0016] Preferably, the ionic crosslinking agent includes one or more of calcium carbonate, ethylenediaminetetraacetic acid calcium complex ion, magnesium carbonate, barium carbonate, barium sulfate and zinc carbonate.

[0017] Preferably, the rotation speed of the first homogenizer in step (1) is 500-1000 rpm;

[0018] Preferably, the rotation speed of the second homogenizer in step (2) is 300-500 rpm.

[0019] Preferably, the standing temperature in step (3) is 22 to 28° C., and the standing time is 2 to 5 hours.

[0020] Preferably, the freeze-drying temperature is -40 to -60°C, and the freeze-drying time is 24 to 48 hours.

[0021] The invention also provides a water- and fertilizer-retaining soil conditioner.

[0022] The invention also provides an application of a water- and fertilizer-retaining soil conditioner in improving the drought stress resistance of crops.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention uses biomass polysaccharides and metal cross-linking agents as carriers to load soil nutrients to obtain a soil conditioner that can release nutrients over a long period of time, achieve water-fertilizer synergy, reduce fertility loss caused by soil leaching, and enhance the soil's ability to retain water and fertilizer.

[0025] (2) The biomass polysaccharide used in the present invention has abundant carboxyl functional groups, which can form a three-dimensional network structure when combined with metal ions, thereby achieving effective encapsulation of soil nutrients. At the same time, it gives the soil improver obvious pH responsiveness, and can make targeted repairs according to different soil conditions;

[0026] (3) The present invention adopts an inert metal ion activation crosslinking method to prepare a homogeneous porous water-retaining and fertilizer-retaining biomass-based soil conditioner. Compared with the biomass-based soil conditioner gel prepared by direct crosslinking using ordinary active metal ions, the soil conditioner prepared by the present invention has a uniform texture, rich pores, and a large specific surface area. It can not only accommodate a large number of water molecules and provide abundant adsorption sites for soil nutrients, but also enhance the stability and reusability of the soil conditioner. At the same time, the carbon dioxide generated during the activation of the inert metal ions makes the soil conditioner have a porous internal morphology, which can increase the drug loading rate of the biomass-based soil conditioner and provide the necessary conditions for the water absorption performance of the soil conditioner.

[0027] (4) The biomass polysaccharide-based soil conditioner prepared by the present invention has excellent water retention and good slow-release performance, which can not only effectively improve the water holding capacity of the soil, but also slowly release the contents (i.e., soil nutrients) while releasing the water in the system, thereby achieving the effect of improving soil fertility, thereby improving the water and fertilizer retention capacity of the soil;

[0028] (5) The biomass polysaccharide-based soil conditioner prepared by the present invention is green, cheap, simple to prepare, and reusable, and has great application prospects in improving soil drought, alleviating soil fertility decline, and regulating soil pH. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1The results of the effects of soil conditioners on the maximum water holding capacity of soil measured in comparative experiments 1-3 are shown, wherein CK is a blank control group, and SA / SLS is a soil conditioner group prepared in Example 3;

[0030] Figure 2 The results of the effects of the soil conditioner on the soil water holding capacity within 10 days of application in the soil measured in the comparative experiments 1-3, wherein CK is the blank control group and SAS is the soil conditioner group prepared in Example 3;

[0031] Figure 3 The microstructure diagrams of the soil conditioner prepared in Example 3 under an electron scanning microscope at different magnifications, wherein a is a microstructure diagram at 100 times magnification, and b is a microstructure diagram at 200 times magnification;

[0032] Figure 4 To compare the growth of eggplant seedlings in Experiment 4, a is the morphological picture of eggplant seedlings before applying soil conditioner, and b is the morphological picture of eggplant seedlings after 15 days of extreme drought treatment;

[0033] Figure 5 To compare the growth of pepper seedlings in Experiment 5, a is the morphological picture of pepper seedlings before applying soil conditioner, and b is the morphological picture of pepper seedlings after 15 days of extreme drought treatment;

[0034] Figure 6 The swelling rate results of the soil conditioner measured in comparative test 7, wherein a is the swelling rate change curve of the soil conditioner in different pH buffer solutions; b is the effect of different water absorption times on the swelling rate of the soil conditioner. DETAILED DESCRIPTION

[0035] The present invention provides a method for preparing a water-retaining and fertilizer-retaining soil conditioner, comprising the following steps:

[0036] (1) mixing the biomass-based polysaccharide, soil nutrients, ionic crosslinking agent and water, and first homogenizing to obtain a mixed solution I;

[0037] (2) mixing gluconolactone with the mixed solution I, and homogenizing for a second time to obtain a mixed solution II;

[0038] (3) allowing the mixed solution II to stand to obtain a pre-product;

[0039] (4) freeze-drying the pre-product to obtain a soil conditioner.

[0040] In the present invention, biomass-based polysaccharides, soil nutrients, ionic crosslinking agents and water are mixed and first homogenized to obtain a mixed solution I. In the present invention, the mass ratio of the biomass-based polysaccharides, soil nutrients and ionic crosslinking agents is preferably 1:1:1 to 10:1:10, more preferably 3:1:3 to 7:1:7, and more preferably 5:1:5; the water is preferably deionized water, and the amount of water is preferably 40 to 60 mL, more preferably 45 to 55 mL, and more preferably 50 mL; the biomass-based polysaccharides preferably include one or more of sodium alginate, carrageenan, fructose and chitosan, more preferably carrageenan or chitosan, and more preferably sodium alginate; the soil nutrients preferably include sodium lignin sulfonate , urea, fulvic acid and humic acid, more preferably fulvic acid or humic acid, and more preferably sodium lignin sulfonate; the ionic cross-linking agent preferably includes one or more of calcium carbonate, ethylenediaminetetraacetic acid calcium complex ion, magnesium carbonate, barium carbonate, barium sulfate and zinc carbonate, more preferably ethylenediaminetetraacetic acid calcium complex ion or barium sulfate, and more preferably calcium carbonate; the speed of the first homogenizer is preferably 500-1000rpm, more preferably 700-900rpm, and more preferably 800rpm; the time of the first homogenizer is not specifically limited, and is based on obtaining a uniform mixed solution I.

[0041] In the present invention, gluconolactone is mixed with the mixed solution I, and a second homogenization is performed to obtain a mixed solution II. In the present invention, the addition amount of the gluconolactone is preferably 30-60% of the mass of the ionic crosslinker, more preferably 40-50% of the mass of the ionic crosslinker, and more preferably 45% of the mass of the ionic crosslinker; the rotation speed of the second homogenization is preferably 300-500rpm, more preferably 350-450rpm, and more preferably 400rpm; the time of the second homogenization is not specifically limited, and is based on obtaining a uniform, bubble-free mixed solution II.

[0042] In the present invention, the mixed solution II is allowed to stand to obtain a pre-product. In the present invention, the standing temperature is preferably 22 to 28°C, more preferably 24 to 26°C, and more preferably 25°C; the standing time is preferably 2 to 5 hours, more preferably 3 to 4 hours, and more preferably 3.5 hours; the standing is preferably carried out in a silicone mold.

[0043] In the present invention, the pre-product is freeze-dried to obtain a soil conditioner. In the present invention, the freeze-drying temperature is preferably -40 to -60°C, more preferably -45 to -55°C, and more preferably -50°C; the freeze-drying time is preferably 24 to 48 hours, more preferably 30 to 45 hours, more preferably 35 to 40 hours, and even more preferably 37 hours.

[0044] The present invention also provides a biomass polysaccharide-based soil conditioner prepared by the above preparation method.

[0045] In the present invention, the soil conditioner is in the form of a gel.

[0046] The invention also provides application of the soil conditioner in improving the drought stress resistance of crops.

[0047] In the present invention, the soil conditioner can be used as base fertilizer and topdressing fertilizer; the application methods when used as base fertilizer or topdressing fertilizer include mixing application, hole application and furrow application.

[0048] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0049] Example 1

[0050] A method for preparing a water- and fertilizer-retaining soil conditioner comprises the following steps:

[0051] (1) Carrageenan, urea and barium sulfate in a mass ratio of 1:1:1 were added to 40 mL of deionized water and mixed, and a first homogenization treatment was performed at a speed of 500 rpm for 2 h to obtain a uniformly dispersed mixed solution I;

[0052] (2) adding 30% of the mass of barium sulfate gluconolactone and performing a second homogenization treatment at a speed of 300 rpm for 0.2 h to obtain a uniform, bubble-free mixed solution II;

[0053] (3) Pour the mixed solution II into a mold and allow to crosslink for 2 h at 22 °C to obtain a pre-product;

[0054] (4) Freeze-drying the pre-product at -40°C for 24 hours to obtain a soil conditioner.

[0055] Example 2

[0056] A method for preparing a water- and fertilizer-retaining soil conditioner comprises the following steps:

[0057] (1) chitosan, fulvic acid and ethylenediaminetetraacetic acid calcium complex ion in a mass ratio of 10:1:10 were added to 60 mL of deionized water and mixed, and a first homogenization treatment was performed at a speed of 1000 rpm for 1.5 h to obtain a uniformly dispersed mixed solution I;

[0058] (2) adding 60% of the mass of EDTA-calcium complex ion gluconolactone, and performing a second homogenization treatment at a speed of 500 rpm for 0.8 h to obtain a uniform, bubble-free mixed solution II;

[0059] (3) Pour the mixed solution II into a mold and place it at 28°C for 5 hours to crosslink and obtain a pre-product;

[0060] (4) Freeze-drying the pre-product at -60°C for 48 hours to obtain a soil conditioner.

[0061] Example 3

[0062] A method for preparing a water- and fertilizer-retaining soil conditioner comprises the following steps:

[0063] (1) Sodium alginate, sodium lignin sulfonate and calcium carbonate in a mass ratio of 5:1:5 were added to 50 mL of deionized water and mixed, and a first homogenization treatment was performed at a speed of 800 rpm for 2.5 h to obtain a uniformly dispersed mixed solution I;

[0064] (2) adding 50% of the mass of calcium carbonate gluconolactone and performing a second homogenization treatment at a speed of 400 rpm for 0.5 h to obtain a uniform, bubble-free mixed solution II;

[0065] (3) Pour the mixed solution II into a mold and allow to crosslink for 3 h at 25°C to obtain a pre-product;

[0066] (4) The pre-product was freeze-dried at -50°C for 40 h to obtain a soil conditioner (SAS).

[0067] Example 4

[0068] A method for preparing a water- and fertilizer-retaining soil conditioner comprises the following steps:

[0069] (1) fructose, humic acid and zinc sulfate in a mass ratio of 4:1:4 were added to 50 mL of deionized water and mixed, and a first homogenization treatment was performed at a speed of 700 rpm for 1.5 h to obtain a uniformly dispersed mixed solution I;

[0070] (2) adding 40% of the mass of zinc sulfate gluconolactone and performing a second homogenization treatment at a speed of 350 rpm for 0.5 h to obtain a uniform, bubble-free mixed solution II;

[0071] (3) Pour the mixed solution II into a mold and place it at 24°C for 4 hours for crosslinking to obtain a pre-product;

[0072] (4) Freeze-drying the pre-product at -45°C for 30 hours to obtain a soil conditioner.

[0073] Comparative Example 1

[0074] (1) Sodium alginate and calcium carbonate in a mass ratio of 5:5 were added to 50 mL of deionized water and mixed, and a first homogenization treatment was performed at a speed of 800 rpm for 2.5 h to obtain a uniformly dispersed mixed solution I;

[0075] (2) adding 50% of the mass of calcium carbonate gluconolactone and performing a second homogenization treatment at a speed of 400 rpm for 0.5 h to obtain a uniform, bubble-free mixed solution II;

[0076] (3) Pour the mixed solution II into a mold and allow to crosslink for 3 h at 25°C to obtain a pre-product;

[0077] (4) Freeze-drying the pre-product at -50°C for 40 hours to obtain a soil conditioner.

[0078] Comparative test 1

[0079] The soil conditioners prepared in Example 3 (SAS) and Comparative Example 1 were mixed with soil at a ratio of 1:100 (w / w), stirred evenly, and applied to farmland soil in Luocheng, Guangxi by mixing, and natural soil without any conditioner was used as a blank control group. The maximum water holding capacity of the soil after 32 hours of application of different soil conditioners and the soil water content after 10 days of static treatment were measured respectively. The soil water content in farmland soil was determined by the ring knife method. The operating steps were referred to "NY / T 1121.22-2010 Soil Testing Part 22: Determination of Soil Field Water Holding Capacity-Ring Knife Method" to determine the field water holding capacity (maximum water holding capacity) of the test soil, specifically:

[0080] (1) Using a volume of 100cm 3 Use a ring knife to collect farmland soil in Luocheng, Guangxi. When collecting, avoid stones, crop roots or debris. After collecting, bring the ring knife back to the room, put it into a flat-bottomed container with the hole cover facing down and the non-hole cover facing up, slowly add water, keep the water level 2mm lower than the upper edge of the ring knife, and soak for 24 hours.

[0081] (2) At the same soil layer as the soil sample to be measured, take some soil samples from the farmland of Luocheng, Guangxi, remove larger stones or debris, air-dry, grind, and pass through a 2 mm mesh sieve. Place the samples in a ring cutter with a bottom cover without holes, tap and compact the soil to keep the soil surface flat and 2 mm above the edge of the ring cutter. Cover the soil with a piece of filter paper slightly larger than the outer diameter of the ring cutter mouth and place it on a water platform.

[0082] (3) Take out the circular knife containing the original soil sample that has been fully saturated with water and soaked for 24 hours in step (1) from the soaking container, remove the lid with holes at the bottom, and place the circular knife on the circular knife containing the air-dried sample covered with filter paper (i.e., the circular knife placed on the horizontal platform in step (2)). Align the edges of the two circular knives and press them with a 2 kg weight to ensure full contact for 8 hours.

[0083] (4) After 8 hours of water infiltration, take 15 g of the original soil from the upper ring cutter, put it into an aluminum box (m0) with a constant weight, and weigh it immediately (m1); dry it at 105°C to a constant weight, take it out and put it into a dryer to cool to room temperature, weigh it (m2), and calculate the moisture content according to formula (1):

[0084]

[0085] In formula (1), X is the field water holding capacity of the soil, in g / kg; m0 is the mass of the dried empty aluminum box, in g; m1 is the mass of the aluminum box and the sample before drying, in g; and m2 is the mass of the aluminum box and the sample after drying, in g.

[0086] The operation steps for determining the soil moisture content in farmland soil are as follows: 0.5g of freeze-dried soil conditioner is fully mixed with 50g of dry farmland soil and then put into a nylon mesh bag, and the total weight of the soil and the nylon mesh bag is measured as W0. Sufficient water is added to make the soil saturated with water, and then the nylon mesh bag is hung in a cool and ventilated place for 10 days, and the total weight of the soil and the nylon mesh bag is measured every day W1. The soil moisture content W (%) is calculated by formula (2).

[0087] W(%)=(W1-W0) / W0×100% Formula (2)

[0088] In formula (2), W is the soil moisture content, in %; W0 is the total weight of dry farmland soil and nylon bags, in g; W1 is the total weight of farmland soil and nylon bags with different moisture contents, in g.

[0089] Figure 1 , Figure 2The results show that the maximum water holding capacity of the blank control group without any soil conditioner is 558.56 g / kg, the maximum water holding capacity of the soil after 32 hours of application of the soil conditioner (SAS) prepared in Example 3 is 639.47 g / kg, and the maximum water holding capacity of the soil after 32 hours of application of the soil conditioner prepared in Comparative Example 1 is 590.76 g / kg. By comparison, it can be seen that compared with the blank control group, the maximum water holding capacity of the soil after the application of the soil conditioner (SAS) prepared in Example 3 is increased by 14.48%; after standing for 10 days in a ventilated place at room temperature, the soil moisture content of the soil conditioner prepared in Example 3 is 17.13%, the soil moisture content of the soil conditioner prepared in Comparative Example 1 is 13.42%, and the soil moisture content of the blank control group is 3.42%. It can be seen that compared with the blank control group, the soil conditioner prepared in Example 3 can increase the soil moisture content by 400.88%.

[0090] Comparative test 2

[0091] The soil conditioners prepared in Example 3 (SAS) and Comparative Example 1 were mixed with soil at a ratio of 1:100 (w / w), stirred evenly, and applied to forest soil in Harbin, Heilongjiang Province by a mixing application method, and natural soil without any conditioner was used as a blank control group. The soil water content of the soil was measured before application of the soil conditioner and after application of the soil conditioner for 32 hours and 10 days.

[0092] The specific determination method is the same as that of comparative experiment 1.

[0093] Figure 1 , Figure 2 The results show that the maximum water holding capacity of the blank control group without any soil conditioner is 693.5 g / kg, the maximum water holding capacity of the soil after 32 hours of application of the soil conditioner (SAS) prepared in Example 3 is 771.1 g / kg, and the maximum water holding capacity of the soil after 32 hours of application of the soil conditioner prepared in Comparative Example 1 is 703.53 g / kg. By comparison, it can be seen that compared with the blank control group, the maximum water holding capacity of the soil after the application of the soil conditioner (SAS) prepared in Example 3 is increased by 11.19%; after standing for 10 days in a ventilated place at room temperature, the soil moisture content of the soil conditioner prepared in Example 3 is 32.63%, the soil moisture content of the soil conditioner prepared in Comparative Example 1 is 28.01%, and the soil moisture content of the blank control group is 20.01%. It can be seen that compared with the blank control group, the soil conditioner prepared in Example 3 can increase the soil moisture content by 63.07%.

[0094] Comparative test 3

[0095] The soil conditioners prepared in Example 3 (SAS) and Comparative Example 1 were mixed with soil at a ratio of 1:100 (w / w), stirred evenly, and applied to alkaline soil in Daqing, Heilongjiang Province by a mixing application method, and natural soil without any conditioner was used as a blank control group. The soil water content of the soil was measured before application of the soil conditioner and after application of the soil conditioner for 32 hours and 10 days.

[0096] The specific determination method is the same as that of comparative experiment 1.

[0097] Figure 1 , Figure 2 The results show that the maximum water holding capacity of the blank control group without any soil conditioner is 560.57 g / kg, the maximum water holding capacity of the soil after 32 hours of application of the soil conditioner (SAS) prepared in Example 3 is 669.5 g / kg, and the maximum water holding capacity of the soil after 32 hours of application of the soil conditioner prepared in Comparative Example 1 is 590.67 g / kg. By comparison, it can be seen that compared with the blank control group, the maximum water holding capacity of the soil obtained by the application of the soil conditioner prepared in Example 3 is increased by 19.43%; after standing for 10 days in a ventilated place at room temperature, the soil moisture content of the soil obtained by the application of the soil conditioner (SAS) prepared in Example 3 is 20.63%, the soil moisture content of the soil obtained by the application of the soil conditioner prepared in Comparative Example 1 is 16.79%, and the soil moisture content of the blank control group is 6.79%. It can be seen that compared with the blank control group, the soil conditioner prepared in Example 3 can increase the soil moisture content by 203.83%.

[0098] Comparative test 4

[0099] Eight groups of eggplant seedlings with similar growth were selected, and the seedlings were transplanted into pots with a length, width and height of 7 cm × 7 cm × 8 cm, and the soil conditioner (SAS) prepared in Example 3 was applied, and a blank control group was set up. The flower pots were watered once until the soil reached the maximum water holding capacity of 693.5 g / kg, and then placed in a sunny place for an extreme drought test (this test was conducted in Harbin, with an average sunshine of 7.72 h and a solar radiation of 140-160 kcal / cm 2 ; In the extreme drought test, the soil moisture was initially added to the maximum water holding capacity, and no water was added subsequently) to observe the subsequent growth changes of the seedlings.

[0100] Seedling growth Figure 4 As shown, on the 15th day after the water supply was stopped, the vitality of the eggplant seedlings in the blank control group was significantly lower than that of the plants treated with the soil conditioner (SAS) prepared in Example 3 of the present application. Compared with the nearly complete withering of the blank group, the stems and leaves of the treated group only showed varying degrees of water shortage. Compared with the blank control group, the growth time of the eggplant seedlings treated with the soil conditioner (SAS) prepared in Example 3 of the present application was extended to 15 days.

[0101] Comparative test 5

[0102] Several groups of pepper seedlings with similar growth were selected, and the seedlings were transplanted into pots with a length, width and height of 7 cm × 7 cm × 8 cm, and the soil conditioner (SAS) prepared in Example 3 was applied, and a blank control group was set up. The flower pots were watered once until the soil reached the maximum water holding capacity of 693.5 g / kg, and then placed in a sunny place for an extreme drought test (this test was conducted in Harbin, with an average sunshine of 7.72 h and a solar radiation of 140-160 kcal / cm 2 ; In the extreme drought test, the soil moisture was initially added to the maximum water holding capacity, and no water was added subsequently) to observe the subsequent growth changes of the seedlings.

[0103] Seedling growth conditions Figure 5 As shown, at 15 days of the extreme drought experiment, the pepper seedlings in the blank group completely withered, while the plants treated with the soil conditioner (SAS) prepared in Example 3 of the present application were slightly wilted compared to the initial state, but the whole plant was upright. Compared with the blank control group, the growth time of the pepper seedlings treated with the soil conditioner prepared in Example 3 of the present application was extended to 15 days.

[0104] Based on the results of comparative test 4 and comparative test 5, it can be seen that the soil conditioner prepared by the present invention can effectively prolong the growth time of pepper and eggplant under extremely drought conditions and improve the ability of crops to resist drought stress.

[0105] Comparative test 6

[0106] The soil conditioner (SAS) prepared in Example 3 and a conventional soil conditioner (both of which are not commercially available products) were applied to alkaline soil in Daqing, Heilongjiang, and the soil moisture content was measured on the same day. The specific application amount and the measurement results of the conventional soil conditioner are shown in Table 1.

[0107] Table 1 Effects of different soil conditioners on soil water holding capacity

[0108] Soil conditioner Addition amount (wt%) Water content increase (%) Sodium alginate / lignin hydrogel 0.5 4.48 Corn stover-based cellulose 0.5 12.8 Amorphous Silica 0.5 0.83 Hemlock biochar 0.5 6.5 Example 3 Soil conditioner obtained 0.5 19.43

[0109] Note: The moisture content is determined by the ring knife method. The specific operation method is the same as that of comparative test 1. The Heilongjiang Daqing alkaline soil with an initial moisture content of 560.57 g / kg is used as a control to calculate the moisture content increment.

[0110] Comparative test 7

[0111] Take 0.5g of the soil conditioner (SAS) prepared in Example 3 and place it in 30mL of buffer solution with pH values ​​of 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, and 10.0, without stirring. Every 15 minutes, use an 80-mesh filter with a diameter of 5cm to take out the soil conditioner in the buffer solution, place it in a watch glass, and measure it by weighing. When the reading of the analytical balance is stable, measure the mass of the swollen soil conditioner. And calculate its swelling rate according to formula (3). At the same time, measure the influence of different water absorption times of the soil conditioner on its swelling rate. The measurement results are as follows: Figure 6 shown.

[0112] Q=(W q -W0) / W0×100% Formula (3)

[0113] Where W0 is the mass of the initial soil conditioner, g; W q is the mass of the soil conditioner after swelling, g; Q is the swelling rate, %.

[0114] Depend on Figure 6 It can be seen that in a buffer solution with a pH value of 4.0 to 10.0, the swelling rate of the soil conditioner can reach 1184.78 to 2891.75%; when the water absorption is repeated 10 times, its swelling rate can reach 8552.67%.

[0115] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a water- and fertilizer-retaining soil conditioner, characterized in that: The steps include: (1) mixing the biomass-based polysaccharide, soil nutrients, ionic crosslinking agent and water, and first homogenizing to obtain a mixed solution I; (2) mixing gluconolactone with the mixed solution I, and performing a second homogenization to obtain a mixed solution II; (3) allowing the mixed solution II to stand to obtain a pre-product; (4) freeze-drying the pre-product to obtain a soil conditioner.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the biomass-based polysaccharide, soil nutrients and ionic crosslinking agent is 1:1:1 to 10:1:

10.

3. The preparation method according to claim 2, characterized in that: The biomass-based polysaccharide includes one or more of sodium alginate, carrageenan, fructose and chitosan.

4. The preparation method according to claim 2, characterized in that: The soil nutrients include one or more of sodium lignin sulfonate, urea, fulvic acid and humic acid.

5. The preparation method according to claim 2, characterized in that: The ionic crosslinking agent includes one or more of calcium carbonate, ethylenediaminetetraacetic acid calcium complex ion, magnesium carbonate, barium carbonate, barium sulfate and zinc carbonate.

6. The preparation method according to claim 1, characterized in that: In step (1), the rotation speed of the first homogenizer is 500 to 1000 rpm; in step (2), the rotation speed of the second homogenizer is 300 to 500 rpm.

7. The preparation method according to claim 1, characterized in that: The standing temperature in step (3) is 22 to 28° C., and the standing time is 2 to 5 hours.

8. The preparation method according to claim 1, characterized in that: The freeze-drying temperature is -40 to -60°C, and the freeze-drying time is 24 to 48 hours.

9. A soil conditioner obtained according to the preparation method according to any one of claims 1 to 8.

10. Use of the soil conditioner according to claim 9 in improving the drought stress resistance of crops.

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