Composite soil improved based on waste shells and preparation method

Abstract

The invention belongs to the technical field of soil improvement and waste resource utilization, and particularly relates to composite soil based on waste shell improvement and a preparation method. According to the composite soil, acid soil serves as substrate soil, shell powder prepared from waste shells is added to serve as a unique modifier, and pH value adjustment and structure optimization of soil with different acidification degrees are achieved by precisely controlling the adding concentration of the shell powder. The preparation method comprises the steps of shell powder preparation, soil grouping adjustment, gradient mixing and after-treatment, the process is simple, the cost is low, and raw materials are environmentally friendly. Waste shells such as oysters and freshwater mussels are subjected to resource utilization, soil acidity is effectively neutralized, the ventilation and water retention performance of soil is improved, meanwhile, nutrients such as calcium are provided for plants, the emergence rate and growth quality of the plants in the acid soil are remarkably improved, and good economic and environmental benefits are achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of soil improvement and waste resource utilization, and specifically relates to a composite soil based on waste shell improvement and a preparation method. The application is suitable for agricultural acidification soil treatment, heavy metal pollution repair and crop cultivation. BACKGROUND

[0002] From the perspective of waste shell treatment difficulties, China, as the world's largest aquaculture and consumption country, produces more than 10 million tons of coastal waste shells every year, mainly oyster shells and scallop shells, with a calcium carbonate content of more than 90%. Due to the long natural degradation period of 5-10 years, these shells are currently treated by landfill and disposal: landfill requires a large amount of coastal land, and during the stacking process, bacteria are easy to breed and odors are released, polluting the surrounding soil and groundwater; some discarded shells on the coast will also damage the nearshore habitat of aquatic organisms after being broken by sea waves, becoming a "waste pollution problem" that needs to be solved in coastal areas. How to realize the resource utilization of shells has become an important direction of environmental governance.

[0003] From the perspective of soil health status, China's arable land is facing multiple degradation challenges. First, the acidification problem is serious. Long-term excessive use of chemical nitrogen fertilizer leads to the activation of aluminum and manganese ions in the soil, inhibiting plant root growth and reducing microbial activity. Second, the risk of heavy metal pollution is prominent. Excessive heavy metals such as cadmium and lead threaten food safety through the food chain. Third, the carbon sink capacity is weakened. Unreasonable farming practices such as straw burning and long-term rotary tillage lead to soil organic carbon loss. The average content of soil organic carbon in China's farmland is only 12-15 g / kg, which is much lower than the level in developed countries in Europe and the United States, and weakens the soil carbon sequestration function.

[0004] From the perspective of carbon sink demand and technical defects, under the "double carbon" goal, soil carbon sink as a low-cost and high-potential carbon sequestration approach has attracted much attention, but existing technologies have obvious shortcomings. On the one hand, shell resource utilization is mostly limited to simple crushing and powdering, which only adjusts the soil pH through physical properties, does not optimize the activity of calcium carbonate, and has low improvement efficiency, and does not tap its carbon sequestration potential. On the other hand, soil conditioners have single functions - chemical conditioners can easily cause soil compaction, and biological conditioners cannot solve the problems of heavy metals and carbon sinks, and there is a lack of collaborative technical solutions that can simultaneously achieve "waste utilization-soil repair-carbon sink enhancement". SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provide a composite soil based on waste shell improvement and a preparation method, which solves the problem of soil acidification through acid-base neutralization.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0007] A composite soil based on discarded shell modification, composed of base soil and shell modifier; the base soil is weakly acidic soil with pH value of 5.5-6.0 or strongly acidic soil with pH value of 4.5-5.0; the shell modifier is a powder made by crushing discarded shell.

[0008] Further, the above-mentioned composite soil based on discarded shell modification, the discarded shell is one or two or more of oyster shell, river clam shell, clam shell, and snail shell.

[0009] Further, the above-mentioned composite soil based on discarded shell modification, the mass of the shell modifier accounts for 1% or 3% of the mass of the base soil.

[0010] Preferably, the mass of the shell modifier accounts for 3% of the mass of the base soil.

[0011] Further, the above-mentioned composite soil based on discarded shell modification, the particle size of the shell modifier is 80 mesh.

[0012] The preparation method of the above-mentioned composite soil based on discarded shell modification, comprising the following steps:

[0013] 1) Shell modifier preparation: weigh one or two or more discarded shells, crush them into fine powder with a pulverizer, and get the shell modifier for standby;

[0014] 2) Soil grouping: measure the pH value with pH paper, and select weakly acidic soil with pH value of 5.5-6.0 and strongly acidic soil with pH value of 4.5-5.0 respectively;

[0015] 3) Gradient preparation: take weakly acidic soil with pH value of 5.5-6.0 or strongly acidic soil with pH value of 4.5-5.0, add shell modifier according to mass percentage, mix well with a shovel, and ensure that the shell modifier is evenly distributed in the soil.

[0016] Further, the above-mentioned preparation method pours water into the obtained composite soil, and the amount of water added is based on the standard of soil saturation without water accumulation.

[0017] Compared with the prior art, the present application has the following beneficial effects:

[0018] 1. Resource recycling: converting aquaculture processing waste shell into efficient soil modifier, reducing solid waste pollution, and realizing "waste into treasure".

[0019] 2. Improved effect precision: For different acidification degree of soil (pH 4.5-6.0), 1% and 3% concentration of shell powder is used to realize directional adjustment of pH value, and at the same time, improve soil physical structure, and enhance water and fertilizer retention capacity.

[0020] 3. Nutrient supply optimization: Calcium elements in shell powder can be slowly released, solving the problem of calcium loss in acid soil, and promoting plant root development and seedling growth.

[0021] 4. Process economic and environmentally friendly: No high temperature treatment or complex additives are required in the preparation process, the equipment is low in dependence, and the cost only comes from raw material collection and basic crushing, which is easy to scale up. DETAILED DESCRIPTION

[0022] Example 1

[0023] (I) Preparation of composite soil based on waste shell improvement

[0024] 1) Preparation of shell improver: Take 500g of mixed waste oyster shells and river clam shells, crush them into fine powder with a crusher for 3-5 minutes, sieve (80 mesh) to remove impurities, and there is no obvious particle feeling, and obtain the shell improver for standby;

[0025] 2) Soil grouping and adjustment: Take 10 kg of natural soil, and measure the pH value to be 5.8 with pH paper, as group A soil; take 2 kg of group A soil, add white vinegar in multiple times and stir, measure the pH value every 5 mL of white vinegar added, and finally adjust to pH 4.7, to obtain group B soil;

[0026] 3) Gradient preparation: Take 200g of group A soil in three portions, respectively, and add 0g, 2g and 6g of shell improver (corresponding to 0%, 1% and 3% concentration) in turn, and mix well by shovel, and the mixing should be free of local clumping to ensure uniform distribution of the improver in the soil, and each group is repeated three times in parallel, and group B soil is treated in the same way, to obtain 18 portions of composite soil;

[0027] 4) Post-treatment: Put the 18 portions of composite soil into pots with a diameter of 10 cm and a height of 10 cm, and pour water into each pot of composite soil until a small amount of water seeps into the bottom of the pot, and the amount of water added is based on the standard of soil saturation and no water accumulation, to ensure uniform moisture of the composite soil, and stand for 1 hour until the water is evenly distributed.

[0028] (II) Verification of application effect

[0029] Sow 10 seeds of Brassica campestris per pot, and place them in a room temperature of 20-25°C, and water daily to keep the soil moist, and observe continuously for 8 days. The results show that:

[0030] (1) Weak acid group composite soil (A group) played a role in bud improvement and auxiliary growth. Bud improvement (Table 1): the average germination rate of 3% group was 73.3%, which was 33.3% higher than that of 0% group and 10% higher than that of 1% group; and the bud was the fastest, with obvious bud on the first day (A3%-1, 1; A3%-2, 3; A3%-3, 6), which was 2-3 days earlier than 0% group into the concentrated bud period, indicating that 3% shell modifier just neutralized the "slightly excessive acidity" in the soil, so that the seed germination had no acid barrier. And the average plant height of 3% group was 4.85 cm, higher than that of 0% group (4.63 cm) and 1% group (4.50 cm), and the only "leaf obviously wide" morphological advantage appeared - this is the direct manifestation of more sufficient nutrient absorption of seedlings after soil acidity optimization, which proves that 3% shell modifier not only "can improve acidity", but also makes the improved soil environment just adapt to the growth needs of the plant, rather than simply "neutralize acidity".

[0031] (2) The 3% shell modifier in the strong acid group composite soil (B group) played a role in acid relief and survival guarantee. Bud improvement (Table 1): the average germination rate of 3% group was 50%, that of 1% group was 46.7%, and that of 0% group was 40%; the survival rate of 3% group was 100%, that of 1% group was 40%, and that of 0% group was 20%, indicating that 3% shell modifier could neutralize the excessive acidity in strong acid soil, making the soil change from unsuitable for germination to stable germination, which is the only shell powder ratio that can guarantee the growth of seedlings in strong acid soil. Growth stability: the seedlings in 3% group grew more vigorously, and although the average plant height was the same as that in 1% group on the 8th day, there was no "wilting and stagnation" phenomenon. Compared with 0% group, 3% shell modifier improved the acidity and provided a basic environment for the continuous growth of seedlings.

[0032] Table 1 Plant growth table

[0033] Group Shell flour ratio Soil pH Average germination rate Average survival rate Average plant height (8th day) A0 0% 5.5-6.0 40.0% 100.0% 4.63 cm A1 1% 5.5-6.0 63.3% 100.0% 4.50 cm A3 3% 5.5-6.0 73.3% 100.0% 4.85 cm B0 0% 4.5-5.0 40.0% 20.0% 3.50 cm B1 1% 4.5-5.0 46.7% 40.0% 4.00 cm B3 3% 4.5-5.0 50.0% 100.0% 4.00 cm

[0034] In summary, 3% shell modifier is the most suitable addition amount, which can effectively neutralize the excessive acidity of different acid soils (weak acid and strong acid), eliminate the inhibition of acidity on seed germination and seedling growth, achieve the highest germination rate, the best plant height and the best growth effect, and is better than 0% (no improvement) and 1% (insufficient improvement), which fully achieves the core goal of the experiment "improving soil acidity by shell powder and promoting plant growth".

Claims

1. A composite soil improved from waste seashells, characterized in that, The composite soil consists of base soil and shell amendment; the base soil is weakly acidic soil with a pH of 5.5-6.0 or strongly acidic soil with a pH of 4.5-5.0; the shell amendment is powder made from crushed waste shells.

2. The composite soil based on waste seashells as described in claim 1, characterized in that, The discarded shells are one or more of the following: oyster shells, freshwater mussel shells, clam shells, and snail shells.

3. The composite soil based on waste seashells as described in claim 1, characterized in that, The shell amendment accounts for 1% or 3% of the mass of the substrate soil.

4. The composite soil based on waste seashells as described in claim 3, characterized in that, The shell amendment accounts for 3% of the mass of the substrate soil.

5. The composite soil based on waste seashells as described in claim 1, characterized in that, The shell conditioner has a particle size of 80 mesh.

6. A method for preparing composite soil based on waste seashells as described in any one of claims 1-5, characterized in that, Includes the following steps: 1) Preparation of shell conditioner: Weigh one or more types of waste shells, crush them into fine powder using a pulverizer, and obtain shell conditioner for later use; 2) Soil grouping: pH values ​​were measured using pH test paper, and weakly acidic soils with a pH value of 5.5-6.0 and strongly acidic soils with a pH value of 4.5-5.0 were screened out respectively; 3) Gradient preparation: Take weakly acidic soil with a pH of 5.5-6.0 or strongly acidic soil with a pH of 4.5-5.0, add shell soil conditioner according to the corresponding mass percentage, and mix thoroughly with a shovel to obtain composite soil.

7. The preparation method according to claim 6, characterized in that, Pour water into the resulting composite soil, adding water until the soil is saturated but not waterlogged.