Fibrous modular soil for hydroponics and method of making same

Abstract

The application discloses a kind of fibrous module soil for water culture and its preparation method, belong to water culture growth substrate technical field, the fibrous module soil for water culture includes the following mass fraction of raw materials: carbon composite foamed calcined stone 60~75 parts, crop straw 5~10 parts, natural fiber 20~30 parts and adhesive 5~8 parts;The raw material of carbon composite foamed calcined stone includes the foamed calcined stone and carbon source with mass ratio of 100:(8~12).Wherein carbon composite foamed calcined stone as main material, light in quality, will not oppress plant root system, porous structure also makes it have good water absorption and air permeability, guarantee the normal growth of water culture plant, carbon composite can well make up the problem that foamed calcined stone itself is strong in drainage and difficult to lock water, significantly improve the durability of fibrous module soil water retention, while mixing natural fiber and crop straw, improve the overall structural stability.

Description

Technical Field

[0001] This invention belongs to the field of hydroponic growth substrate technology, specifically relating to a fiber module soil for hydroponics and its preparation method. Background Technology

[0002] Hydroponics, as a soilless cultivation technique, mainly meets the growth needs of plants by absorbing minerals and nutrients dissolved in water. Compared with traditional soil cultivation methods, it can provide better control and higher efficiency for plant growth, while reducing the impact on the environment.

[0003] Traditional hydroponic substrates such as perlite, vermiculite, and coconut fiber, while possessing good water retention and aeration properties, still face some challenges in practical applications. For instance, although coconut fiber is an organic and biodegradable hydroponic substrate, its chemical properties and variability can lead to changes in pH and electrical conductivity, thus affecting plant growth. Furthermore, as a natural fiber, coconut fiber degrades rapidly, especially in hydroponic environments, significantly impacting the substrate's durability.

[0004] Therefore, it is of great significance to obtain a hydroponic growth mechanism that is environmentally friendly, has excellent water retention and air permeability, and is sustainable. Summary of the Invention

[0005] The purpose of this invention is to provide a fiber module soil for hydroponics and its preparation method, so as to obtain a hydroponic growth substrate with excellent water retention and air permeability, which is environmentally friendly and sustainable.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a fiber module soil for hydroponics, comprising the following raw materials in parts by weight:

[0008] 60-75 parts of carbon composite foamed stone;

[0009] 5-10 parts of crop straw;

[0010] 20-30 parts natural fiber;

[0011] 5-8 parts of adhesive;

[0012] The raw materials for carbon composite foamed stone include foamed stone and carbon source in a mass ratio of 100:(8-12).

[0013] Preferably, the particle size of the foamed quartz is 4–10 mm.

[0014] By adopting the above technical solution, foamed stone is a lightweight and porous material. Its interior is filled with a fine pore structure, which has good water retention and air permeability. When used as a hydroponic growth substrate, it can not only maintain an appropriate amount of moisture, but also ensure sufficient air circulation around the roots, so that the roots can obtain sufficient oxygen supply. In addition, compared with other hydroponic growth substrates, foamed stone has a lower density and lighter overall weight. During hydroponics, it will not compress the plant roots, and the porous structure is also conducive to the healthy growth of the roots.

[0015] The particle size of foamed pumice plays a crucial role in the growth of hydroponic plants. Larger particle sizes result in higher packing density and fewer pores, hindering root growth. Conversely, smaller particle sizes, while providing good pore structure and aeration, are easily lost due to water erosion during hydroponics, leading to a significant decrease in structural stability. This invention improves the stability of small-particle foamed pumice in hydroponics by directly combining it with natural fibers and crop straw. It also utilizes the pore structure of natural fibers to enhance aeration of the hydroponic substrate, while the nutrients in the crop straw support root growth, thus supporting healthy root development in hydroponic plants.

[0016] While foamed polystyrene has some water retention, it also drains very well over long-term use, drying out quickly. During hydroponics, the substrate easily loses moisture, significantly impacting plant growth and requiring frequent watering to maintain normal growth. Therefore, this invention provides a carbon-composite foamed polystyrene. The carbon composite in the foamed polystyrene also has a porous structure and good water retention. Through the combined action of natural fibers and crop straw, it significantly improves the water retention durability of the resulting fiber module soil, keeping the soil consistently moist during hydroponics and simplifying the process.

[0017] Preferably, the carbon source is a combination of organic and inorganic carbon sources in a mass ratio of (0.7-0.9):(0.1-0.3).

[0018] Preferably, the organic carbon source includes one or more combinations of citric acid, polyethylene glycol, polyvinyl alcohol, starch, and sucrose.

[0019] Preferably, the inorganic carbon source includes one or more combinations of graphite and carbon fiber.

[0020] By adopting the above technical solution, the carbon source of the present invention uses both organic and inorganic carbon sources. The organic carbon source can be better distributed on the surface of the foamed stone, and then, through calcination, it forms a more complex and uniform pore structure inside the foamed stone. It also decomposes into tiny carbon particles at high temperatures, which become adsorption points for water molecules. This enhances the water absorption and retention capacity of the foamed stone from different aspects, thereby greatly improving the drainage of the foamed stone itself and maintaining the moisture of the roots of the hydroponic fabric. Furthermore, through carbon composite, the organic carbon component can also provide nutrients and habitats for microorganisms, regulate the growth environment of hydroponic plants, and promote plant growth.

[0021] Furthermore, the carbon source of this invention also includes an inorganic carbon source. The addition of the inorganic carbon source can coordinate the thermal expansion performance during the carbon composite process, enabling the organic carbon source to better and more uniformly composite with the foamed stone. By adjusting the thermal expansion performance of carbon, the internal stress caused by roasting is also reduced, the adhesion of carbon is improved, and it will not easily fall off, which also improves the structural stability of the obtained carbon composite foamed stone.

[0022] Preferably, the carbon composite foamed quartz is prepared according to the following method:

[0023] The foamed slag was immersed in a strong acid aqueous solution for 10-15 hours, washed and dried to obtain pretreated foamed slag; the pretreated foamed slag was dispersed in water, a carbon source and an aminosilane coupling agent were added, the temperature was raised to 50-60℃, and the mixture was stirred for 1-2 hours. Finally, after drying and calcination, carbon composite foamed slag was obtained.

[0024] Preferably, the strong acid aqueous solution includes one of hydrochloric acid aqueous solution, nitric acid aqueous solution and sulfuric acid aqueous solution in a mass ratio of 20-30%.

[0025] Preferably, the solid-liquid ratio of the foamed ore to the strong acid aqueous solution is 1:(5-7).

[0026] Preferably, the aminosilane coupling agent includes one or more combinations of γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane and γ-aminopropyltrimethoxysilane; the amount of aminosilane coupling agent added is 6 to 8% of the mass of the pretreated foamed quartz.

[0027] By adopting the above technical solution, the carbon composite foamed stone is pretreated with strong acid beforehand. This removes impurities and contaminants from the surface of the foamed stone, making it purer and improving the bonding force between the organic carbon source and the foamed stone. After acid treatment, the number of active groups on the surface of the foamed stone also increases, promoting chemical bonding with the organic carbon source. Then, under the action of an aminosilane coupling agent, the carbon source and the foamed stone are chemically bonded together. Finally, the carbon source is calcined at high temperature to transform into tiny carbon particles that are composited on the surface of the foamed stone, improving its water retention.

[0028] Preferably, the adhesive is hydroxypropyl methylcellulose.

[0029] By adopting the above technical solution, the present invention uses hydroxypropyl methylcellulose as a binder to participate in the bonding between foamed stone and natural fibers. On the one hand, hydroxypropyl methylcellulose is a non-toxic and biodegradable material. Compared with other binders, it is green and safe for human body and environment, which is in line with the principle of environmental protection, reduces potential pollution to the environment, and will not have a large amount of organic residue that affects plant growth.

[0030] On the other hand, hydroxypropyl methylcellulose has good water retention and hygroscopic properties, which can form a protective film on the surface of each component of the obtained fiber module soil, effectively reducing water evaporation, greatly improving the drainage of foamed stone, and effectively maintaining the water required for hydroponic plant growth. Therefore, it can help provide better growth conditions for plant roots and promote the effective absorption of nutrients.

[0031] Furthermore, as a binder, the numerous polar groups contained in hydroxypropyl methylcellulose also help to bond tightly with foamed pebbles, natural fibers, and crop straw, enhancing the overall mechanical strength and stability of the resulting fiber module soil. Some small-sized foamed pebbles will not be washed away by the water flow during hydroponics.

[0032] Preferably, the natural fibers include one or more combinations of coconut fiber, wood fiber and flax fiber.

[0033] Preferably, the crop straw includes one or more of the following: rice straw, wheat straw, corn straw, rapeseed straw, and soybean straw.

[0034] By adopting the above technical solution, on the one hand, the fiber module soil for hydroponics, which is made by mixing natural fibers with crop straw and foamed stone, can greatly improve the overall stability of the fiber module soil. The connection between natural fibers and crop straw can ensure that the small-sized foamed stone particles will not be easily washed away. The fiber module soil is more solid and stable and is not easily compressed and deformed, which improves the ability of the fiber module soil to resist external pressure, ensures that plant roots have enough space to expand, and promotes the healthy growth of hydroponic fabrics.

[0035] On the other hand, natural fibers and crop straw can absorb and store large amounts of water, thereby improving the water retention capacity of the entire fiber module soil and further reducing irrigation frequency. During the process, crop straw also gradually releases essential plant nutrients such as nitrogen, phosphorus, and potassium, becoming a natural fertilizer source available to plants and providing them with additional nutrients. Simultaneously, the presence of organic matter is conducive to establishing a healthy microbial ecosystem, further promoting nutrient cycling.

[0036] Secondly, the present invention provides a method for preparing fiber module soil for hydroponics, comprising the following process steps:

[0037] S1. Sterilize natural fibers and crop straw at high temperature, then dry them for later use;

[0038] S2. Prepare an aqueous solution of 40-50% by mass of the adhesive, mix it with carbon composite foamed stone, natural fibers and crop straw, and finally compress it to obtain fiber module soil.

[0039] The beneficial effects of this invention are:

[0040] 1. The fiber module soil for hydroponics of this invention is a type of hydroponic growth substrate that provides excellent support for plant roots. It uses carbon-composite foamed pumice as the main material. The foamed pumice is lightweight and does not compress plant roots; its porous structure also provides excellent water absorption and aeration, ensuring the normal growth of hydroponic plants. Furthermore, the foamed pumice of this invention is also composited with carbon. The addition of carbon effectively compensates for the inherent problem of poor water retention in foamed pumice, simplifying the cultivation process and significantly improving the water retention durability of the fiber module soil. During hydroponics, the fiber module soil remains moist, which is beneficial for the growth of hydroponic plants.

[0041] 2. This invention also incorporates natural fibers and crop straw mixed with carbon composite foamed aggregate, which connects the tiny foamed aggregate particles, improving the overall stability of the fiber-modified soil. This results in a more robust and stable fiber-modified soil, ensuring sufficient space for plant roots to expand. Furthermore, the natural fibers and crop straw can absorb and store water, enhancing overall water retention and providing a favorable environment for plant growth. Simultaneously, this invention uses hydroxypropyl methylcellulose as a binder, which is environmentally friendly and possesses certain water-retention properties, effectively reducing water evaporation and promoting the effective absorption of nutrients. Detailed Implementation

[0042] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0043] Preparation Example

[0044] Preparation Example 1: A carbon composite foamed sintering stone was prepared according to the following method:

[0045] 100g of foamed abrasive (particle size 4-10mm) was immersed in 600mL of 30% hydrochloric acid aqueous solution for 12h. After washing and drying, pretreated foamed abrasive was obtained. 100g of pretreated foamed abrasive was dispersed in 500mL of water, and 10g of carbon source and 8g of γ-aminopropyltriethoxysilane were added. The carbon source was a mixture of starch and graphite with a mass ratio of 0.8:0.2. The temperature was raised to 60℃ and stirred for 1h. Finally, carbon composite foamed abrasive was obtained after drying and calcination.

[0046] Preparation Example 2, a carbon composite foamed stone, differs from Preparation Example 1 only in that the amount of carbon source added is 8g; and the amount of γ-aminopropyltriethoxysilane added is 6g.

[0047] Preparation Example 3, a carbon composite foamed stone, differs from Preparation Example 1 only in that the amount of carbon source added is 12g.

[0048] Preparation Example 4, a carbon composite foamed stone, differs from Preparation Example 1 only in that the carbon source is a mixture of starch and graphite in a mass ratio of 0.9:0.1.

[0049] Preparation Example 5, a carbon composite foamed stone, differs from Preparation Example 1 only in that the carbon source is a mixture of starch and graphite in a mass ratio of 0.7:0.3.

[0050] Preparation Example 6, a carbon composite foamed stone, differs from Preparation Example 1 only in that the amount of carbon source added is 5g.

[0051] Preparation Example 7, a carbon composite foamed stone, differs from Preparation Example 1 only in that the amount of carbon source added is 15g.

[0052] Preparation Example 8, a carbon composite foamed stone, differs from Preparation Example 1 only in that an equal amount of starch is used to replace the carbon source obtained by mixing starch and graphite in a mass ratio of 0.8:0.2.

[0053] Preparation Example 9, a carbon composite foamed stone, differs from Preparation Example 1 only in that the carbon source obtained by mixing starch and graphite in a mass ratio of 0.8:0.2 is replaced with an equal amount of graphite.

[0054] Example

[0055] Example 1: A fiber module soil for hydroponics is prepared according to the following process steps:

[0056] S1. Sterilize natural fibers and crop straw at high temperature, then dry them for later use;

[0057] S2. Prepare an aqueous solution of 6 parts hydroxypropyl methylcellulose with a mass fraction of 50%, mix it with 70 parts carbon composite foamed stone prepared in Preparation Example 1, 25 parts coconut shell fiber and 8 parts rice straw, and finally compress it to obtain fiber module soil.

[0058] Example 2: A fiber module soil for hydroponics is prepared according to the following process steps:

[0059] S1. Sterilize natural fibers and crop straw at high temperature, then dry them for later use;

[0060] S2. Prepare a 50% aqueous solution of 5 parts hydroxypropyl methylcellulose, mix it with 60 parts carbon composite foamed stone prepared in Preparation Example 1, 20 parts coconut shell fiber and 10 parts rice straw, and finally compress it to obtain fiber module soil.

[0061] Example 3: A fiber module soil for hydroponics is prepared according to the following process steps:

[0062] S1. Sterilize natural fibers and crop straw at high temperature, then dry them for later use;

[0063] S2. Prepare an aqueous solution of 50% by mass of 8 parts of hydroxypropyl methylcellulose, mix it with 75 parts of carbon composite foamed stone prepared in Preparation Example 1, 30 parts of coconut shell fiber and 5 parts of rice straw, and finally compress it to obtain fiber module soil.

[0064] Example 4, a fiber module soil for hydroponics, differs from Example 1 only in that an equal amount of carbon composite foamed stone prepared in Example 2 is used to replace the carbon composite foamed stone prepared in Example 1.

[0065] Example 5, a fiber module soil for hydroponics, differs from Example 1 only in that an equal amount of carbon composite foamed stone prepared in Example 3 is used to replace the carbon composite foamed stone prepared in Example 1.

[0066] Example 6, a fiber module soil for hydroponics, differs from Example 1 only in that an equal amount of carbon composite foamed stone prepared in Example 4 is used to replace the carbon composite foamed stone prepared in Example 1.

[0067] Example 7, a fiber module soil for hydroponics, differs from Example 1 only in that an equal amount of carbon composite foamed stone prepared in Example 5 is used to replace the carbon composite foamed stone prepared in Example 1.

[0068] Example 8, a fiber module soil for hydroponics, differs from Example 1 only in that an equal amount of carbon composite foamed stone prepared in Example 8 is used to replace the carbon composite foamed stone prepared in Example 1.

[0069] Example 9, a fiber module soil for hydroponics, differs from Example 1 only in that an equal amount of carbon composite foamed stone prepared in Example 9 is used to replace the carbon composite foamed stone prepared in Example 1.

[0070] Comparative Example

[0071] Comparative Example 1, a fiber module soil for hydroponics, differs from Example 1 only in that an equal amount of carbon composite foamed stone prepared in Preparation Example 6 is used to replace the carbon composite foamed stone prepared in Preparation Example 1.

[0072] Comparative Example 2, a fiber module soil for hydroponics, differs from Example 1 only in that an equal amount of carbon composite foamed stone prepared in Preparation Example 7 is used to replace the carbon composite foamed stone prepared in Preparation Example 1.

[0073] Comparative Example 3, a fiber module soil for hydroponics, was prepared according to the following process steps:

[0074] S1. Sterilize natural fibers and crop straw at high temperature, then dry them for later use;

[0075] S2. Prepare a 50% aqueous solution of 6 parts hydroxypropyl methylcellulose, mix it with 70 parts foamed stone, 10 parts graphite, 25 parts coconut fiber and 8 parts rice straw, and finally compress it to obtain fiber module soil.

[0076] Comparative Example 4, a fiber module soil for hydroponics, differs from Example 1 only in that an equal amount of foamed stone is used to replace the carbon composite foamed stone prepared in Preparation Example 1.

[0077] Comparative Example 5, a fiber module soil for hydroponics, differs from Example 1 only in that the amount of foamed stone added in Preparation Example 1 is 50 parts.

[0078] Comparative Example 6, a fiber module soil for hydroponics, differs from Example 1 only in that the amount of foamed stone added in Preparation Example 1 is 80 parts.

[0079] Comparative Example 7, a fiber module soil for hydroponics, differs from Example 1 only in that it does not contain rice straw.

[0080] Comparative Example 8, a fiber module soil for hydroponics, differs from Example 1 only in that an equal amount of styrene-butadiene polymer is used instead of hydroxypropyl methylcellulose.

[0081] Comparative Example 9, a fiber module soil for hydroponics, differs from Example 1 only in that it does not contain coconut fiber.

[0082] Performance testing methods

[0083] The fiber module soil obtained in the examples and comparative examples for hydroponics was cut into samples with dimensions of 100cm×20cm×7cm. Peppers (Sprinter FL green bell peppers) were grown hydroponically for 84 days. Natural light was used throughout the experiment. The fertilizer used included a concentrated mixture of 160ppm (16-4-17, 15.5-0-0, 10-0-0), pH 6.3, and EC of approximately 1200μS / cm.

[0084] Record the average fresh fruit weight (g) after the experiment.

[0085] The experimental results are shown in Table 1:

[0086] Table 1 Fresh Weight of Chili Peppers

[0087]

[0088] According to Table 1, and in conjunction with Examples 1, 8, and 9, it can be seen that the hydroponic effect of Examples 8 and 9 is lower than that of Example 1. The reason is that the carbon source in Example 8 does not include an inorganic carbon source. Therefore, during the preparation of carbon composite foamed stone, the thermal expansion coefficient of the carbon particles formed by the organic carbon source is different from that of the foamed stone, which makes it difficult for the carbon particles to be composited and reduces the performance of the formed carbon layer, thus reducing the water retention capacity and the hydroponic effect. In Example 9, the carbon source does not include an organic carbon source, so the bonding force between the carbon source and the foamed stone is significantly reduced, the adhesion of the carbon layer is reduced, and it is easy to fall off during use, losing the water retention effect, and the hydroponic effect is lower.

[0089] Based on Example 1 and Comparative Examples 1-4, it can be seen that the hydroponic effect of Comparative Examples 1-4 is lower than that of Example 1. This is because the amount of carbon source added in Comparative Example 1 is reduced, leading to a decrease in the carbon layer content on the surface of the foamed stone, which in turn reduces water retention. This results in poor regulation of the root growth environment for hydroponic plants and a decrease in the overall stability of the fiber module soil, thus reducing the hydroponic effect. In Comparative Example 3, no carbon source was added for compounding with the foamed stone, resulting in a more significant performance decline. In Comparative Example 2, the amount of carbon source added was increased. After calcination and compounding, excessive carbon source occupies the pores of the foamed stone, reducing its air permeability and water absorption, and also encroaching on the root growth space, affecting the growth and development of hydroponic plants. In Comparative Example 3, the carbon source and foamed stone were directly mixed. Direct mixing could not improve the overall stability of the fiber module soil, nor could it achieve uniform distribution among the foamed stone, nor could it directly act on the interior of the foamed stone to improve its internal water retention, thus leading to a decrease in hydroponic performance.

[0090] Based on Examples 1, 5, and 6, it can be seen that the hydroponic effect of Comparative Examples 5 and 6 is lower than that of Example 1. This is because Comparative Example 5 reduced the amount of carbon composite foamed pumice added, resulting in decreased air circulation and water absorption within the resulting fiber module soil, thus reducing its support for the hydroponic plant roots and affecting their growth, leading to a decline in the hydroponic effect. Comparative Example 6 increased the amount of carbon composite foamed pumice added, but the large-particle substrate material compresses the plant roots, affecting their natural and healthy growth, and consequently impacting the hydroponic plant's growth.

[0091] Combining Examples 1 and Comparative Examples 7-9, it can be seen that the hydroponic effect of Comparative Examples 7-9 is lower than that of Example 1. This is because Comparative Example 7 did not add crop straw, which reduces the structural support of the foamed pumice and decreases the additional nutrient supply to the plant roots from the resulting fiber-modified soil, leading to a significant decrease in the final fruit fresh weight. Comparative Example 8 used a conventional adhesive, which, while enhancing structural stability, has lower water retention and absorption than hydroxypropyl methylcellulose (HMC), failing to further compensate for the poor water retention of the foamed pumice, thus reducing the hydroponic effect. Furthermore, HMC is a natural and environmentally friendly material. Comparative Example 9 did not add natural fibers, resulting in a significant decrease in the overall stability of the fiber-modified soil. The plant roots lacked sufficient space to expand, the bonding force of the foamed pumice particles decreased, making them easily eroded by water flow during hydroponics, thus reducing their support for the plant roots.

[0092] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0093] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A fibrous modular soil for hydroponics, characterized in that, The raw materials include the following parts by weight: 60-75 parts of carbon composite foamed stone; 5-10 parts of crop straw; 20-30 parts natural fiber; 5-8 parts of adhesive; The raw materials for the carbon composite foamed stone include foamed stone and carbon source in a mass ratio of 100:(8-12); The carbon source is a combination of organic and inorganic carbon sources in a mass ratio of (0.7–0.9):(0.1–0.3). The organic carbon source includes one or more combinations of citric acid, polyethylene glycol, polyvinyl alcohol, starch, and sucrose; The inorganic carbon source includes one or more combinations of graphite and carbon fiber; The carbon composite foamed quartz was prepared according to the following method: The foamed slag was immersed in a strong acid aqueous solution for 10-15 hours, washed and dried to obtain pretreated foamed slag; the pretreated foamed slag was dispersed in water, a carbon source and an aminosilane coupling agent were added, the temperature was raised to 50-60℃, and the mixture was stirred for 1-2 hours. Finally, after drying and calcination, carbon composite foamed slag was obtained. The adhesive is hydroxypropyl methylcellulose; The method for preparing the fiber module soil for hydroponics includes the following process steps: S1. Sterilize natural fibers and crop straw at high temperature, then dry them for later use; S2. Prepare an aqueous solution of 40-50% by mass of the adhesive, mix it with carbon composite foamed stone, natural fibers and crop straw, and finally compress it to obtain fiber module soil.

2. The fibrous modular soil for hydroponics according to claim 1, characterized in that, The particle size of the foamed quartz is 4-10 mm.

3. The fiber module soil for hydroponics according to claim 1, characterized in that, The natural fibers include one or more combinations of coconut fiber, wood fiber, and flax fiber.

4. The fiber module soil for hydroponics according to claim 1, characterized in that, The crop straw includes one or more of the following: rice straw, wheat straw, corn straw, rapeseed straw, and soybean straw.

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