Preparation method of straw-based rice seedling raising substrate

Abstract

The invention provides a preparation method of a straw-based seedling raising substrate, and relates to the field of rice seedling raising. The method comprises the following steps: 1) straw bundle type in-situ innocent treatment: bundling straws, adding urea into straw bundles, adjusting the water content to be 60-70%, and performing mulching fermentation for 20-30 days; (2) preparing straw fibers with strong organic nitrogen mineralization capability, namely disassembling the straws fermented in the step (1), airing the straws until the water content is 25-30%, and grinding the straws by using a high-concentration pulping machine until the diameter is less than 1mm; (3) preparing straw matrix nutrients, namely adding ammonium sulfate, calcium superphosphate and potassium sulfate into the ground straw fibers according to the adding amounts of 1.9%, 1.4% and 0.3% of the mass of a dry basis of the straw fibers, so as to obtain the straw-based seedling raising matrix. Nitrogen, phosphorus and potassium nutrients contained in the substrate can meet the requirements of seedlings for nutrients, slow release and stable supply of the nutrients are achieved, the nutrients are matched with the growth requirements of the seedlings, topdressing is not needed in the whole rice seedling raising process, and therefore the seedling raising cost is further reduced.

Description

A method for preparing straw-based rice seedling substrate Technical Field

[0001] This invention relates to the field of rice seedling cultivation, and in particular to a method for preparing a straw seedling cultivation substrate that uses crop straw as a single raw material, has the ability to continuously supply fast-acting nutrients, and is suitable for machine transplanting. Background Technology

[0002] Crop straw is one of the main products of agricultural production and also a major agricultural waste. It contains abundant macro-elements such as nitrogen, phosphorus, and potassium, as well as micro-elements. It also contains organic energy sources such as cellulose, hemicellulose, lignin, protein, and sugars, making it an important biological resource.

[0003] Straw can be transformed into seedling substrate through processes such as crushing and fermentation, thereby achieving efficient utilization of agricultural waste. Straw seedling substrate has similar water retention and air permeability to peat, and after improvement, it can replace the reliance on peat in conventional seedling cultivation. Currently, research on seedling substrates produced primarily from crop straw focuses on improving the porosity of the substrate and enhancing its water and fertilizer retention capacity. Therefore, various auxiliary materials, such as perlite, vermiculite, biochar, and attapulgite, are added to the prepared straw-based seedling substrate. This inevitably increases the preparation steps and production costs of the straw-based seedling substrate and reduces the amount of straw waste that can be recycled.

[0004] Furthermore, using straw compost as a raw material to produce seedling substrates, the physicochemical properties of the substrate can be improved through processes such as optimizing the composting process and nutrient formulation, resulting in low-cost straw-based seedling substrates that promote root growth and strong seedling development. In the preparation of this type of substrate, crop straw must undergo long-term aerobic composting and maturation before it can be used to produce the seedling substrate. However, during long-term aerobic composting, the dry matter loss rate of the material can reach 50% to 60%, and large amounts of gases such as NH3, CO2, and N2O are emitted. This not only wastes straw resources and pollutes the atmospheric environment but also increases the production cost of straw-based seedling substrates.

[0005] During the rice seedling raising process, proper nutrient management is a key measure to improve the seedling vigor index. In production, fertilizers such as urea are usually applied in the middle and late stages of seedling raising to meet the needs of seedling growth. However, due to the sensitivity of seedlings to nutrients, fertilizer damage such as seedling burn and root damage caused by improper operation is prone to occur.

[0006] Therefore, providing a straw-based rice seedling substrate that uses pure straw as raw material, has low production cost, provides a continuous and stable supply of nitrogen, phosphorus and potassium nutrients, and does not require secondary topdressing has become an urgent technical problem to be solved in this field. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a straw-based rice seedling substrate that uses crop straw as a single raw material, has low production costs, provides a continuous supply of readily available nutrients, and eliminates the need for secondary topdressing, along with its green and low-carbon preparation method.

[0008] Specifically, the above-mentioned objective is achieved through the following technical solution: a method for preparing a straw-based seedling substrate, comprising the following steps: 1) In-situ harmless treatment of straw bales: After rice or wheat harvest, the straw in the field is directly compacted and baleed using a baler to obtain straw bales; the straw bales are stacked in the field or nearby, and an aqueous solution of urea is slowly and evenly added to the straw bales, with the amount of urea added being 0.5% to 1% of the dry weight of the straw, and the moisture content of the stack being 60% to 70%. Then, the stack is covered with a breathable and rainproof covering (such as film, non-woven fabric, etc.) for open-air natural fermentation treatment, with the entire stacking time being 20 to 30 days. During the fermentation process, the temperature of the straw bales rises, reaching a maximum of about 70°C, and the high-temperature fermentation effectively kills some pathogens and weed seeds carried inside the straw.

[0009] The preferred straw bales are regular straw bales with a density of 180-210 kg / m³. Too low a density is not conducive to the compaction and baling of straw, while too high a density will result in poor air permeability in the straw bales, thus affecting fermentation and making it difficult to add urea and water.

[0010] Adding urea to the stack in this step serves two purposes: first, to adjust the carbon-to-nitrogen ratio of the straw bales, allowing microorganisms to multiply rapidly during fermentation, thereby raising the temperature of the straw bales to kill pathogens and weed seeds; second, the added nitrogen provides the necessary nitrogen for seedling growth during the later stages of seedling cultivation.

[0011] 2) Preparation of straw fiber with strong organic nitrogen mineralization capacity: After the straw bales that have undergone harmless treatment in step 1 are disassembled, they are dried until the moisture content is 25% to 30%. The straw fibers are then ground to a diameter of less than 1 mm using a high-consistency pulping machine to obtain straw fiber with strong organic nitrogen mineralization capacity.

[0012] Conventional straw seedling substrate production processes typically employ mechanical chopping. Straw pulping is used to break down the straw before it's fed into a pulping tank, where water is added to create a slurry for papermaking or other straw-based packaging materials. This process results in a relatively low concentration of straw raw materials (4%–8%). This step, however, utilizes pulping technology to treat fermentation products with a moisture content of 25%–30%, which is more conducive to the decomposition of straw cellulose and hemicellulose.

[0013] 3) Preparation of nutrients in straw substrate: Using the straw fiber obtained in step 2 as the base material, ammonium sulfate fertilizer, superphosphate and potassium sulfate are added to the straw fiber at amounts of 1.9%, 1.4% and 0.3% of the dry weight of the straw fiber, respectively, to finally obtain a complete nutrient straw seedling substrate for rice.

[0014] This application improves the surface structure and physical properties of straw by optimizing the straw composting cycle and the crushing method of its products, thereby making the physical properties and water and fertilizer retention capacity of the straw seedling substrate suitable for the growth of seedling roots. Simultaneously, by adding appropriate proportions of nitrogen, phosphorus, and potassium elements during the preparation of the straw seedling substrate, a straw seedling substrate that sustainably supplies readily available nitrogen, phosphorus, and potassium nutrients is prepared, ensuring a continuous and stable release of these nutrients to meet the needs of seedling growth without the need for secondary fertilization. Specifically, compared with existing rice straw-based seedling substrates, this invention has the following advantages: 1. The straw harmless treatment in this invention does not require dismantling the straw bales, and the entire composting process does not require turning the pile (conventional aerobic fermentation requires dismantling the straw bales and then using mechanical equipment such as straw catchers for multiple turnings, thus increasing the cost of straw harmless treatment). Furthermore, it eliminates the need for a dedicated fermentation workshop, reducing the cost of straw harmless treatment by more than 50%, and achieving simplified "in-situ" harmless treatment of straw in the field.

[0015] 2. In this invention, the straw crushing method is pulping, which, compared to mechanical chopping, effectively breaks down the surface structure of the straw, improves the mineralization of organic nitrogen, and enhances the supply of nutrients. Furthermore, it increases the specific surface area of ​​the straw, transforming straw fibers into highly absorbent nutrient carriers. Smaller particle sizes result in larger specific surface areas, which is more conducive to the release of nitrogen, phosphorus, and potassium nutrients. Through straw pulping, the particle size of the seedling substrate is precisely controlled, thereby optimizing the substrate's porosity, aeration, and water retention, creating an excellent physical environment for the seedling roots.

[0016] 3. The nitrogen, phosphorus, and potassium nutrients contained in the straw seedling substrate prepared by this invention can meet the nutrient requirements of rice seedlings, achieving slow release and stable supply of nutrients, which matches the growth needs of rice seedlings (see Table 3 of the examples). No topdressing is required throughout the entire rice seedling raising process, thereby further reducing seedling raising costs. Attached Figure Description

[0017] Figure 1 is a schematic diagram of temperature changes during the fermentation process of straw bales.

[0018] Figure 2 shows the comparison results of the seedling raising effect of straw seedling substrates with different nutrient contents. Detailed Implementation

[0019] The present invention will now be described in detail with reference to specific embodiments. The illustrative embodiments and descriptions herein are used to explain the invention, but are not intended to limit it. Unless otherwise stated, the experimental methods disclosed in this invention employ conventional techniques in this field, and the reagents and raw materials used in the embodiments are commercially available.

[0020] The raw materials and equipment involved in the example: the straw field baler is a Lovol MF3045, purchased from Weichai Lovol Smart Agriculture Technology Co., Ltd.

[0021] The high-consistency pulping machine, model GMM-600, was purchased from Weifang Derui Biotechnology Co., Ltd.

[0022] The straw crusher, model SFSP50, was purchased from Changzhou Yuanjian Machinery Co., Ltd.

[0023] Urea, ammonium sulfate, superphosphate, and potassium sulfate fertilizers were all purchased from Stanley Fertilizer Co., Ltd.

[0024] The substrate is a special substrate for rice seedling cultivation, purchased from Taicang Lvfeng Agricultural Resources Development Co., Ltd.

[0025] Unless otherwise specified, all raw materials used in the following examples were purchased through commercial channels.

[0026] Example 1: In-situ harmless treatment of straw in bales

[0027] In August 2025, the location was an experimental field of the Jiangsu Academy of Agricultural Sciences. After wheat harvest, the straw bale fermentation group directly compacted and baleed the field straw using a baler, forming square straw bales with a density of approximately 200 kg / m³ (in practice, a baling density of 180-210 kg / m³ can achieve the fermentation purpose), each bale weighing approximately 100 kg. These bales were placed in a nearby field area, and urea, dissolved in water, was slowly and evenly added to the bales at a rate of 1% of the straw's dry weight. The moisture content of the pile was adjusted to 60%, and the bales were covered with breathable and rainproof non-woven fabric. The entire fermentation process took 45 days, with turning the pile at 7 and 20 days of fermentation.

[0028] Meanwhile, using conventional aerobic fermentation as a control, the straw bales were disassembled and then covered with film for fermentation, with other steps being the same as the straw bale fermentation group.

[0029] Thermometers were inserted into the straw bales, and the temperatures of the straw bales and the straw piles undergoing conventional aerobic fermentation were measured at 9:00 AM and 5:00 PM daily during fermentation. The results are shown in Figure 1. It can be seen that the temperature of the straw bales remained above 55℃ for more than 15 days during fermentation, indicating that the fermentation process of the straw bales achieved harmlessness. Furthermore, compared with conventional aerobic fermentation, the temperature fluctuation during the straw bale fermentation process was smaller, and the temperature was significantly higher in the later stages of fermentation. It is generally believed that a fermentation temperature above 55℃ for more than 7 days can effectively kill pathogens contained within the agricultural waste. However, the high-temperature sterilization process is not conducive to the conversion of nutrients in the straw; therefore, the optimal fermentation time is determined to be 20-30 days.

[0030] Example 2: Seedling Raising Effect of Straw Substrate with Different Fermentation Cycles. In Example 1, straw samples were collected before fermentation and at 10, 20, 30, and 40 days after fermentation (straw bale fermentation group). After being crushed, the samples were used as seedling raising substrates to observe the seedling raising effect of straw substrates with different fermentation cycles. This example uses japonica rice as an example, the variety is Nanjing 46, the sowing rate is 120g / tray, and the seedling raising time is 20 days. At the end of the seedling raising period, the biomass, plant height, and stem diameter of the seedlings were measured, and the results are shown in Table 1.

[0031] Table 1. Seedling quality of straw substrates with different fermentation cycles

[0032] As can be seen from the test data in Table 1, the fresh weight, dry weight, plant height, and stem diameter of seedlings fermented for 20 days and 30 days were all higher than those fermented for 10 days and 40 days, and the differences were significant (P<0.05). This indicates that the product of straw fermentation time of 20-30 days is suitable as a raw material for seedling substrate, while straw fermented for less than 20 days and more than 30 days is not suitable as a raw material for seedling substrate.

[0033] Example 3: Preparation of Straw Fiber with Strong Organic Nitrogen Mineralization Capacity and its Seedling Raising Effect. In this example, after wheat harvest, wheat straw was baled in place and fermented under a film for 20 days (the specific baling and fermentation steps are the same as in Example 1) for harmless treatment. Then, some of the harmless-treated straw bales were unpacked and dried until the moisture content was <30%. The dried straw was then ground to a diameter of less than 1 mm using a high-consistency grinding mill to obtain straw fiber with strong organic nitrogen mineralization capacity. The grinding mill mainly processes the straw through the friction and grinding action between a high-speed rotating grinding disc and a fixed grinding disc. In this example, the grinding parameters were: straw moisture content 25%–30%, fine-tooth grinding disc used, and the grinding disc gap set to 0.5–0.8 mm.

[0034] Meanwhile, some of the straw bales that have undergone harmless treatment are unpacked and dried to a constant weight. Then, a straw crusher is used to crush the straw into particles with a diameter of less than 1 mm (the crusher mainly crushes the straw through impact and shearing action using high-speed rotating hammers or blades). The crushed straw is then used directly as a seedling substrate for seedling cultivation.

[0035] Using crushed straw as a control, the seedling raising effect and effective nitrogen release of the ground straw fiber were compared. The seedling raising method was the same as in Example 2, and the quality of the seedlings raised under different treatments is shown in Table 2.

[0036] Table 2. Quality of seedlings grown from straw products produced by different straw crushing methods

[0037] The statistical results in Table 2 show that, compared with crushed straw, milled straw used for seedling cultivation can increase the number of seedlings, plant height, stem diameter, and fresh weight per 100 plants, with significant differences (P<0.05). Moisture was added to the milled straw fibers and crushed straw particles to achieve a moisture content of 70%, and the mixtures were incubated at 30℃ for 15 days. Samples were collected and the effective nitrogen release was measured at 0, 5, 10, and 15 days of incubation. The results are shown in Table 3.

[0038] Table 3 Effective nitrogen release status of straw products from different crushing methods

[0039] As can be seen from Table 3, compared with the straw crushing treatment, the effective nitrogen release of the straw after grinding increased during the cultivation process. This indicates that the surface structure of the ground straw is more conducive to the mineralization of organic nitrogen and the release of effective nitrogen.

[0040] Example 4 The preparation of a complete nutrient straw seedling substrate involved using straw fiber (straw fiber with strong organic nitrogen mineralization ability) obtained by grinding in Example 3 using a high-concentration mill as the base material. Ammonium sulfate fertilizer (a fertilizer containing ammonium sulfate), superphosphate, and potassium sulfate (the nitrogen, phosphorus, and potassium contained in these three components are the three most important nutrients necessary for rice seedling growth, and the nitrogen, phosphorus, and potassium content in conventional straw and fermented straw cannot meet the needs of seedling growth) to prepare straw seedling substrates with different nutrient contents. The fertilizer addition amounts for low-nutrient straw seedling substrates were 0.9%, 0.7%, and 0.1% of the dry weight of straw fiber, for medium-nutrient substrates they were 1.9%, 1.4%, and 0.3%, and for high-nutrient substrates they were 2.7%, 2.1%, and 0.5%. The seedling effect of straw seedling substrates with different nutrient contents was compared with straw seedling substrates without added fertilizer and conventional commercial substrates as controls. The rice variety was Nanjing 46, and the seedling results are shown in Table 4 and Figure 2.

[0041] Table 4. Seedling quality of straw seedling substrates with different nutrient contents

[0042] Table 4 shows that, compared with straw seedling substrates with different nutrient contents, the straw seedling substrate with medium nutrient content produced the highest levels of all indicators for seedlings, and the differences between treatments were statistically significant. Furthermore, among the three straw seedling substrates with different nutrient contents, only the medium nutrient content substrate produced seedlings of superior quality compared to conventional commercial substrates; therefore, it was chosen as the final nutrient addition scheme for the seedling substrate.

Claims

1. A method for preparing a straw-based seedling substrate, characterized in that, The specific steps are as follows: 1) Straw bale in-situ harmless treatment: Bundle the straw, add urea to the straw bale, adjust the moisture content to 60%-70%, cover and ferment for 20-30 days to obtain straw fermentation products; the mass of urea added is 0.5%-1% of the dry weight of the straw; 2) Preparation of straw fiber with strong organic nitrogen mineralization ability: Disassemble the straw fermentation product obtained in step 1) and dry it to a moisture content of 25%-30%, and grind it with a grinder to a diameter of less than 1 mm to obtain straw fiber; 3) Straw substrate nutrient preparation: Add ammonium sulfate, superphosphate and potassium sulfate to the straw fiber obtained in step 2), with the addition amounts being 1.9%, 1.4% and 0.3% of the dry weight of the straw fiber, respectively, to obtain the straw-based seedling substrate.

2. The method for preparing straw-based seedling substrate according to claim 1, characterized in that, Step 1) The density of the straw bales is 180-210 kg / m³.

3. The method for preparing straw-based seedling substrate according to claim 1, characterized in that, Step 1) The straw bales are wheat straw bales or rice straw bales.

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