Water-culture seedling raising method for rice

Abstract

The invention relates to the technical field of agriculture, and discloses a rice hydroponic seedling raising method which comprises the following steps: paving a watertight water storage film on a flat field to construct a seedbed; laying a layer of seedling raising substrate taking crushed crop straws as a main raw material on the water storage film; sowing rice seeds on the surface of the substrate without covering soil, and adding water into the seedbed to form a continuous shallow water layer; and performing cultivation management on the seedlings. Preferably, accumulated water is drained for water control and seedling hardening 5-7 days before transplanting, and transplanting is completed within 28-35 days after sowing. Compared with the prior art, the closed water balance system is constructed through the water storage film, and the water saving effect is remarkable; the light straw substrate is used for replacing nutrient soil, the process is simplified, and the labor intensity is greatly reduced; homogenized water and fertilizer supply ensures that the seedlings grow neatly and are high in quality; the stress resistance and the transplanting survival rate of the seedlings are remarkably improved through timely water control and seedling hardening.

Description

Technical Field

[0001] The invention relates to the technical field of agriculture, and in particular to a method for hydroponic rice seedling cultivation. Background Art

[0002] As a major global food crop, rice's ultimate yield is closely linked to the quality and quality of its rice seedlings. Strong, well-groomed rice seedlings are the foundation for achieving high and stable yields. Currently, the mainstream method for raising rice seedlings is still traditional soil seedling cultivation, including paddy field and dryland seedling cultivation. However, these traditional methods generally face inherent technical bottlenecks in practical application.

[0003] These methods all rely on open soil seedbeds, resulting in a large amount of water loss through seepage during the seedling raising process, which not only causes a serious waste of water resources, but also in the winter and spring drought seasons or water-scarce areas, the seedling raising work is often seriously restricted due to insufficient water sources. At the same time, the traditional seedling raising process is extremely tedious and labor-intensive, requiring a series of heavy physical labor such as land preparation and bed making, long-distance transportation and laying of thick nutrient soil, and in the later stage, frequent watering is required to maintain the appropriate soil moisture, resulting in low overall production efficiency and difficulty in adapting to the current situation of increasing shortage of agricultural labor. More importantly, due to the uneven physical properties and nutrient distribution of the soil medium itself, there are natural differences in the conditions for the seedling roots to obtain water and fertilizer, which ultimately makes the cultivated seedling population grow uniformly and have serious size differentiation, making it difficult to ensure the population consistency and high yield potential of subsequent field production. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for raising rice seedlings in hydroponics to solve the problems of high water consumption, high labor intensity, uneven seedling quality, severe impact of seasonal drought and complicated production process in the rice seedling raising process in the prior art.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for growing rice seedlings in hydroponics, comprising the following steps:

[0007] a) Seedbed construction: Laying an impermeable water-retention membrane on a pre-selected and leveled site to construct a seedling bed that can effectively prevent water leakage;

[0008] b) substrate laying: evenly laying a layer of seedling raising substrate on the water storage film, wherein the seedling raising substrate is mainly made of crushed crop straw;

[0009] c) Sowing and Water Storage: Pre-treated rice seeds are evenly sown on the surface of the seedling-raising substrate. Water is then added to the seedbed until a continuous shallow layer of water forms on the water-retaining membrane, soaking the bottom of the substrate. In this step, no soil or substrate covering is required after sowing.

[0010] d) Seedling management: Cover the seedbed after sowing to keep it warm and manage water and fertilizer until the seedlings grow to a stage suitable for transplanting.

[0011] As a further optimization of the technical solution of the present invention:

[0012] The seedling-raising substrate is prepared by mixing crop straw crushed material with a rice seedling-strengthening agent or a nitrogen, phosphorus, and potassium compound fertilizer. Specifically, the ratio can be 15-25 kilograms of the rice seedling-strengthening agent or compound fertilizer evenly mixed into every cubic meter of straw crushed material to provide the necessary nutrients for seedling growth in the early stages of raising the seedlings.

[0013] The thickness of the seedling raising substrate on the seedbed is preferably 1.5-2.5 cm. This thickness can provide sufficient attachment and growth space for the rice roots, ensure the permeability of the substrate layer, and facilitate the formation of a lightweight blanket-like seedling.

[0014] The shallow water layer formed on the water-storage membrane preferably has a depth of 1-5 mm, which can ensure that the bottom of the substrate continuously and stably absorbs water while preventing seeds or roots from lacking oxygen due to excessively high water levels.

[0015] After sowing and water storage, a moisturizing film is preferably applied to the surface of the seedbed. When the emergence rate reaches 70% or higher, the film is removed. This effectively maintains a high humidity environment on the substrate surface before emergence, promoting uniform and rapid germination of the seeds.

[0016] During seedling management, it's best to stop adding water to the seedbed and drain any accumulated water 5-7 days before planned transplanting to harden the seedlings. This reduces the free water content in the seedlings and increases their cell sap concentration, significantly enhancing their mechanical strength and resistance to environmental stress.

[0017] In order to ensure the best transplanting effect and survival rate, the rice seedlings cultivated by this method are preferably controlled at a seedling age of 28-35 days at the time of transplanting.

[0018] When carrying out large-scale or standardized seedling raising, after laying the water storage film, first place several standard seedling raising trays on the film, and then lay the seedling raising substrate in these seedling raising trays.

[0019] The crop straw crushed material can be flexibly selected from one or more sources, such as crushed materials of rape straw, corn straw, wheat straw, or common by-products in agricultural production such as rapeseed hulls and wheat husks.

[0020] The impermeable water storage membrane is preferably a polyethylene (PE) agricultural anti-seepage membrane with a thickness of 0.05-0.08 mm. This specification of the membrane has good anti-seepage performance and sufficient mechanical strength.

[0021] The present invention provides a method for growing rice seedlings in hydroponics, which has the following beneficial effects:

[0022] 1. By installing an impermeable water-retention membrane at the bottom of the seedbed, this invention fundamentally blocks water loss through underground seepage, creating a closed water balance system. Water required for seedling cultivation is consumed only in small amounts through evaporation and seedling transpiration, resulting in an extremely high water utilization rate. Compared to traditional seedling raising methods, this method can save over 80% of water, effectively resolving the bottleneck of waterless seedling raising in drought-stricken winter and spring regions.

[0023] 2. This invention eliminates the arduous steps of traditional rice seedling cultivation, including land preparation, nursery plot preparation, and the transportation and laying of large quantities of heavy nutrient soil. Using lightweight straw as the substrate makes the rice seedling blanket extremely lightweight, making it easy to transport and carry. Furthermore, no soil covering is required after sowing, simplifying water and fertilizer management. This reduces the labor time per unit area of rice seedling cultivation by over 90%, making it ideally suited to the current labor shortage in agriculture.

[0024] 3. This method uses a shallow layer of water at the bottom of the seedbed to ensure that all seedling roots have equal and continuous access to water and nutrients, avoiding the uneven size and growth of seedlings caused by uneven rooting depth and nutrient distribution in traditional soil seedling cultivation. This method cultivates uniform and robust seedlings, laying a solid foundation for high yields.

[0025] 4. The present invention uses agricultural waste such as crop straw as the main seedling-raising matrix, providing an effective way to utilize these wastes as resources, reducing environmental pollution caused by burning or random discarding, and meeting the requirements of sustainable development of modern agriculture. DETAILED DESCRIPTION

[0026] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be described in detail below with reference to specific embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] Example 1:

[0028] This embodiment provides a trayless rice hydroponic seedling cultivation method suitable for manual transplanting.

[0029] 1. Prepare the seedling medium: Prepare dry, mold-free corn stalks with a particle size of 0.5-2.0 cm. Evenly mix 20 kg of a commercially available rice seedling-strengthening agent into every 1.0 cubic meter of corn stalks. Spray water on the mixture and stir until the moisture content is such that it can be held in a ball without water seeping through fingers. Then, stack the mixture for later use.

[0030] 2. Seedbed Construction: Select a flat, dry plot of land and build an approximately 8-cm-high earthen ridge around the perimeter. Lay a 0.06-mm-thick polyethylene agricultural impermeable membrane inside the ridge as a water-retaining membrane, with the edges of the membrane covering and pressing beneath the ridge. Pour a small amount of water into the membrane. Observe and adjust the flatness of the seedbed bottom, ensuring the height error is within 1 cm.

[0031] 3. Laying the substrate and sowing: Evenly lay the seedling substrate prepared in step 1 on the water-retention film, controlling the thickness to 2.0 cm. Select high-quality rice seeds, soak and germinate them, and evenly sow them on the substrate surface at a rate of 0.8 kg per mu of field. Do not cover the seeds with soil or the substrate after sowing.

[0032] 4. Post-sowing Management: After sowing, evenly spray the seedbed with a watering can to ensure the substrate absorbs water and form a shallow layer of water 3 mm deep at the bottom of the water-retention film. Then, lay a layer of moisture-retaining film on the surface of the seedbed and set up a bamboo arch covered with agricultural film. Once the seedling emergence rate reaches 70%, remove the moisture-retaining film and retain the arch.

[0033] 5. Seedling Management: After the seedlings have two leaves and one heart, add water from the side of the seedbed according to the moisture level of the substrate. 7 days before planned transplanting, that is, 25 days after sowing, make a small cut on one side of the water-retaining film to drain the accumulated water in the seedbed and control the water to harden the seedlings.

[0034] 6. Transplanting: On the 32nd day after sowing, dig out the blanket seedlings and transplant them manually.

[0035] Example 2:

[0036] This embodiment provides a tray-type rice hydroponic seedling cultivation method suitable for mechanized transplanting.

[0037] 1. Preparation of seedling medium: Take dried rape straw crushed material and mix it with compound fertilizer with a nitrogen, phosphorus and potassium ratio of 15-15-15, at a ratio of 18 kg of compound fertilizer per 1.0 cubic meter of straw crushed material. Subsequent humidity control treatment is the same as in Example 1.

[0038] 2. Seedbed construction: The seedbed construction process is the same as in Example 1, and the water storage membrane is a polyethylene agricultural anti-seepage membrane with a thickness of 0.08 mm.

[0039] 3. Laying the substrate and sowing: Arrange several standard machine-transplanting trays (580 x 280 x 28 mm) neatly on the water-retention membrane. Fill the trays with the seedling substrate prepared in Step 1 and smooth it out to a thickness of 2.5 cm. Select a high-quality rice variety suitable for machine transplanting. After treatment, evenly sow the seeds on the surface of the substrate in the trays at a standard rate of 1.3 kg per mu (approximately 1.3 kg) per mu (approximately 1.5 acres) of field. Do not cover the seeding trays after sowing.

[0040] 4. Post-sowing management: After sowing, water is added to the seedbed to form a shallow water layer with a depth of 5 mm on the water storage film at the bottom of the seedling tray. The subsequent film covering and film removal management is the same as in Example 1.

[0041] 5. Management during the seedling stage: 5 days before planned transplanting, that is, 23 days after sowing, drain the accumulated water in the seedbed and control the water to harden the seedlings.

[0042] 6. Transplanting: On the 28th day after sowing, the seedling trays with blanket seedlings are transported to the field for mechanized transplanting.

[0043] Example 3:

[0044] This embodiment provides a method for growing rice seedlings in hydroponics using mixed matrix raw materials.

[0045] 1. Preparation of Seedling Medium: Mix ground wheat straw and rapeseed hulls in a 1:1 weight ratio as the primary raw material. Evenly mix 25 kg of a 20:20:20 nitrogen, phosphorus, and potassium compound fertilizer into every 1.0 cubic meter of this mixture. Subsequent humidity control is the same as in Example 1.

[0046] 2. Seedbed construction: The seedbed construction process is the same as in Example 1, and the water storage membrane is a polyethylene agricultural anti-seepage membrane with a thickness of 0.05 mm.

[0047] 3. Laying the substrate and sowing: Evenly spread the seedling substrate prepared in step 1 on the water-retention film, controlling the thickness to 1.5 cm. Sow seeds at a rate of 1.0 kg per mu of field. Do not cover after sowing.

[0048] 4. Post-sowing management: After sowing, water is added to the seedbed to form a shallow water layer with a depth of 1 mm at the bottom of the water storage film. Subsequent film covering and film removal management is the same as in Example 1.

[0049] 5. Management during the seedling stage: 5 days before planned transplanting, that is, 30 days after sowing, drain the accumulated water in the seedbed and control the water to harden the seedlings.

[0050] 6. Transplanting: On the 35th day after sowing, dig out the blanket seedlings and transplant them manually.

[0051] Comparative Example 1:

[0052] Compared with Example 1, the difference lies in that the traditional dry seedling raising method is used: no impermeable water-retaining film is laid; a mixture of sieved farmland soil and well-rotted farmyard manure is used as the nutrient soil for raising seedlings, replacing the straw substrate; after sowing the seeds, a layer of fine soil with a thickness of 0.5 cm is covered on the surface of the seeds; during the seedling management period, watering is required every day or every other day depending on the soil moisture conditions. All other conditions remain the same.

[0053] Comparative Example 2:

[0054] Compared with Example 1, the difference is that in the seedbed construction step, no water-impermeable water storage film is laid, but the seedling raising substrate is laid directly on the leveled soil seedbed. The rest are the same.

[0055] Comparative Example 3:

[0056] Compared with Example 2, the difference is that in the step of laying the seedling raising substrate, a standard seedling raising tray placed on the soil seedling bed is used instead of directly laying the substrate. The rest are the same.

[0057] Comparative Example 4:

[0058] Compared with Example 1, the difference is that the transplanting time of the rice seedlings is extended to the 42nd day after sowing. The rest are the same.

[0059] Test Example 1:

[0060] A comparative test on the consumption of key resources in the seedling raising process was conducted on Examples 1 to 3 and Comparative Examples 1 to 2, in order to quantitatively evaluate the specific effects of the method of the present invention in terms of water saving and labor saving.

[0061] The experimental steps are as follows:

[0062] 1. Total water consumption test:

[0063] For each treatment group of Examples 1 to 3 and Comparative Examples 1 to 2, an independent 10-square-meter seedling raising area was set up and equipped with an independent, calibrated water supply pipeline and water meter. After each treatment group sowed and completed the first watering, the initial reading of each water meter was recorded. During the entire seedling raising period, all subsequent water additions were measured by the corresponding water meter. Before each treatment group entered the water control and seedling hardening stage, the final reading of its water meter was recorded. The total water consumption was obtained by subtracting the initial reading from the final reading, and the final result was expressed in liters per square meter (L / m 2 ) as the unit for recording.

[0064] 2. Total working hours test:

[0065] A stopwatch was used to accurately record the labor time spent at different stages of the seedling raising process for each treatment group. The recorded stages included: seedbed preparation and substrate laying (or nutrient soil laying), sowing and covering (or not covering), and all daily operations related to water management during the entire seedling growth period. The time spent on each stage was accumulated to obtain the total labor time. For ease of comparison, the final result was uniformly converted to hours per 10 square meters (h / 10m 2 ) as the unit for recording.

[0066] The experimental results are shown in Table 1:

[0067] Table 1 Comparative test results of key resource consumption in the seedling raising process

[0068] Treatment group <![CDATA[Total water consumption (L / m 2 )]]> <![CDATA[Total man-hours (h / 10m 2 )]]> Example 1 48.5 0.26 Example 2 51.2 0.29 Example 3 47.9 0.25 Comparative Example 1 285.6 3.15 Comparative Example 2 211.3 0.35

[0069] The test results in Table 1 demonstrate that the rice seedling raising method provided by the present invention offers significant advantages in terms of resource consumption. Compared to Comparative Example 1, which employs a traditional dry rice seedling raising method, Examples 1-3 significantly reduce total water consumption and total labor hours, demonstrating the significant improvement in water and labor savings achieved by the present invention. The data from Comparative Example 2 demonstrates that even with a lightweight substrate similar to that of the present invention, resource consumption, particularly water consumption, remains high if key technical features are missing.

[0070] The core mechanism of the present invention for achieving efficient water conservation is that a closed water balance system is constructed by laying a water-impermeable water-storage membrane at the bottom of the seedbed. The water-storage membrane physically blocks the vertical downward leakage of water, which is the main way of water loss in traditional seedling cultivation methods, such as Comparative Examples 1 and 2. Water is effectively stored in the shallow water layer formed at the bottom of the seedbed, and is continuously and stably supplied to the roots of the seedlings through the capillary action of the matrix, thereby greatly improving the efficiency of water utilization. Compared with Example 1, the only difference between Comparative Example 2 and Example 1 is whether a water-storage membrane is used, and its water consumption is much higher than that of Example 1. This directly and irrefutably confirms that the water-storage membrane structure is the fundamental reason for achieving the water-saving effect.

[0071] The labor-saving effect of the present invention is derived from the systematic simplification of the entire seedling raising process. First, the use of crushed crop straw as a lightweight seedling raising substrate completely replaces the heavy nutrient soil in Comparative Example 1 that requires a lot of labor to dig, carry and lay. Secondly, the step of not needing to cover the soil after sowing further simplifies the operation. More importantly, due to the presence of the water storage film, daily water management becomes extremely simple, and the operation of frequent and careful observation and watering required in Comparative Example 1 is changed to only regularly adding a small amount of water to the seedbed at one time, which greatly reduces the labor input of daily management. The combination of this series of technical features ultimately makes the total working hours of this method significantly lower than other methods.

[0072] Test Example 2:

[0073] The rice seedling quality and quality comparison tests were conducted on Examples 1 to 3 and Comparative Examples 1, 2, and 4, aiming to quantitatively evaluate the robustness and group uniformity of the rice seedlings cultivated by the method of the present invention through objective physiological indicators.

[0074] The experimental steps are as follows:

[0075] When each treatment group reached its preset transplanting day (set as per their respective settings for Examples 1 to 3 and Comparative Examples 1 to 2, and 42 days after sowing for Comparative Example 4), 100 representative rice seedlings were randomly selected from the seedling raising area of each treatment group as test samples.

[0076] 1. Determination of plant height and uniformity:

[0077] Using a millimeter ruler, measure the vertical height of each of the 100 sample seedlings from the substrate surface to the tip of the highest leaf when the plant is standing naturally. This is known as plant height. After recording all 100 data points, calculate the arithmetic mean, which is the average plant height. Also, calculate the coefficient of variation (CV) based on these 100 plant height data points. This value is used to quantify the uniformity of growth within the seedling population.

[0078] 2. Determination of average dry weight of individual plants:

[0079] The 100 sample seedlings, whose plant heights had been measured, were rinsed with clean water to remove any substrate attached to their roots. The seedlings were then dried in a constant-temperature, forced-air oven at 80°C to a constant weight. The total dry weight of the 100 seedlings was weighed using an analytical balance with an accuracy of 0.001 g and divided by 100 to obtain the average dry weight per plant.

[0080] The experimental results are shown in Table 2:

[0081] Table 2 Comparative test results of seedling quality and quality

[0082] Treatment group Average plant height (cm) Coefficient of variation of plant height (CV,%) Average dry weight per plant (mg) Example 1 15.1 5.8 25.3 Example 2 14.8 6.1 26.1 Example 3 15.3 5.5 25.8 Comparative Example 1 13.9 12.7 19.8 Comparative Example 2 12.5 18.2 16.5 Comparative Example 4 16.5 25.4 18.1

[0083] The test results in Table 2 demonstrate that the rice seedlings cultivated using the present method (Examples 1-3) exhibited excellent physiological performance across all indicators. Compared to Comparative Examples 1 and 2, the rice seedlings from the Example groups not only exhibited a significant advantage in average dry weight per plant, demonstrating stronger individual plants, but also exhibited a significantly lower coefficient of variation in plant height. This directly demonstrates the excellent effectiveness of the present method in ensuring uniform height growth in a rice seedling population. The results from Comparative Example 4, however, showed that despite a higher average plant height, both individual dry weight and population uniformity showed a significant decline.

[0084] The fundamental reason the present invention is able to cultivate uniform and strong seedlings lies in its unique water and fertilizer supply mechanism. By installing an impermeable water-retention membrane at the bottom of the seedbed, a homogenized shallow water layer is formed, evenly distributing all water-soluble nutrients throughout the entire seedbed. The roots of each seedling can uniformly and continuously absorb the water and nutrients they need for growth from this shared nutrient reservoir. This equitable supply fundamentally eliminates the "microenvironmental differences" caused by uneven distribution of soil particles, pores, and nutrients in traditional soil seedling cultivation (such as Comparative Example 1), thereby ensuring synchronized and balanced growth of the seedling population. However, in Comparative Example 2, due to the lack of a water-retention membrane to lock in water, uneven water penetration resulted in some seedlings suffering from drought stress and others from waterlogging, leading to severe growth differentiation. The extremely high coefficient of variation and low dry weight of the seedlings further demonstrate the crucial role of the water-retention structure in the present invention in cultivating strong seedlings.

[0085] In addition, the integrity of the technical solution of the present invention is also crucial to achieving the desired effect. The data of Comparative Example 4 warns that although this method can efficiently cultivate strong seedlings, it must be combined with an appropriate transplanting age. When the seedlings are too old, the high-density seedling population will be severely differentiated due to fierce competition for light and nutrients. Some dominant plants will grow too tall (manifested as increased plant height), while a large number of weak plants will turn yellow or even die due to insufficient nutrients, resulting in a decrease in the accumulation of dry weight in the population and a sharp increase in the coefficient of variation. This shows that transplanting within 28-35 days is a necessary condition for achieving the beneficial effects of the present invention, ensuring that the seedlings are put into field production when both individual quality and population quality reach their peak.

[0086] Test Example 3:

[0087] The rice seedlings cultivated in Examples 1 to 3 and Comparative Examples 1 to 4 were subjected to a comparative test on their field performance after transplantation, in order to evaluate the final application effect of the rice seedlings cultivated by the method of the present invention in actual field production, with the transplant survival rate as the core measurement indicator.

[0088] The experimental steps are as follows:

[0089] 1. Select a paddy field with uniform fertility and consistent irrigation and drainage conditions as the experimental field.

[0090] 2. When each treatment group reached its preset transplanting date, 200 representative clumps of rice seedlings were selected from each treatment group. For Example 2 and Comparative Example 3, which used tray-type seedling cultivation, each clump consisted of one seedling; for the other groups using non-tray-type seedling cultivation, each clump contained 3-5 seedlings.

[0091] 3. Transplant all selected seedlings into the experimental field on the same day according to the local conventional plant spacing and set clear separation marks for each treatment group.

[0092] 4. After transplanting, uniform field management was carried out on the entire experimental field to ensure that the water and fertilizer conditions of all treatment groups were completely consistent.

[0093] 5. Ten days after transplanting, examine and count the number of surviving clumps in each treatment group. Survival was determined by green heart leaves and no signs of wilting or death. Calculate the transplant survival rate for each group based on the number of surviving clumps and the total number of transplanted clumps (200).

[0094] The experimental results are shown in Table 3:

[0095] Table 3 Comparative test results of field survival rate after transplanting

[0096] Treatment group Transplant survival rate (%) Example 1 97.5 Example 2 98 Example 3 96.5 Comparative Example 1 91.5 Comparative Example 2 84 Comparative Example 3 86.5 Comparative Example 4 72.5

[0097] The test results in Table 3 demonstrate that the rice seedlings cultivated using the present method (Examples 1-3) exhibited extremely high survival rates after transplanting into the field, significantly outperforming all control examples. This result fully demonstrates the reliability and superiority of the present method in practical production applications, providing a solid seedling-stage foundation for high and stable rice yields.

[0098] The reason why the present invention can ensure a high transplant survival rate is that the cultivated rice seedlings have strong environmental adaptability and stress resistance. The key to obtaining this characteristic lies in the water control and seedling hardening before transplanting of the technical solution of the present invention. By draining the accumulated water in the water storage membrane before planned transplanting, a short-term, controllable drought stress environment is artificially created for the rice seedling root system. This process can effectively reduce the water content in the rice seedling body, increase the cell sap concentration, and promote the stems and leaves to become tougher and stronger. At the same time, it stimulates the growth vitality of the root system, so that the rice seedlings show stronger tolerance when facing mechanical damage and drastic changes in the field environment during transplanting. The rice seedlings of Comparative Examples 2 and 3 lack this process and have weaker qualities. They have a long seedling hardening period after transplanting and a high mortality rate. This strongly proves the importance of the water control and seedling hardening step for improving the survival rate.

[0099] In addition, the extremely low survival rate of Comparative Example 4 proves that even if a superior cultivation method is adopted in the early stage, if the suitable transplanting age is ignored, the final effect will still be greatly reduced. When the rice seedlings grow beyond the optimal window period of 28-35 days, the nutrients in its body are consumed in a large amount, the root activity begins to decline, and yellowing occurs in some base leaves, and the overall structure is in the aging stage. After transplanting, such over-age rice seedlings, their rooting, turning green and tillering abilities are all seriously degraded, and are difficult to adapt to the new growth environment, causing the survival rate to decline sharply. Therefore, the suitable transplanting age defined by the present invention, combined with unique rice seedling raising method and hardening process, jointly constitutes a complete technical system ensuring the high survival rate of rice seedlings.

[0100] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for growing rice seedlings in hydroponics, characterized in that: The following steps are involved: a) Seedbed construction: laying an impermeable water-retention membrane on a flat surface to construct a seedling bed; b) substrate laying: evenly laying a layer of seedling raising substrate with crop straw crushing as the main raw material on the water storage film; c) sowing and water storage: evenly sowing rice seeds on the surface of the seedling raising substrate, adding water to the seedbed after sowing to form a continuous shallow water layer on the water storage film, and there is no need to cover the seeds with soil or substrate after sowing; d) Seedling management: Cultivate and manage the seedlings until they are suitable for transplanting.

2. The rice hydroponic seedling cultivation method according to claim 1, characterized in that: The seedling raising matrix is prepared by mixing crop straw crushed material and rice seedling strengthening agent or compound fertilizer in a ratio of 15 to 25 kilograms per cubic meter of straw crushed material.

3. The rice seedling cultivation method in hydroponics according to claim 1 or 2, characterized in that: The laying thickness of the seedling raising substrate is 1.5 to 2.5 centimeters.

4. The rice seedling cultivation method in hydroponics according to claim 1, characterized in that: The depth of the shallow water layer is 1 to 5 mm.

5. The rice hydroponic seedling cultivation method according to claim 1, characterized in that: Step c) further includes: A layer of moisturizing film is flatly covered on the surface of the seedbed, and the moisturizing film is uncovered after the emergence rate reaches more than 70%.

6. The method for growing rice seedlings in hydroponics according to claim 1, characterized in that: The seedling management in step d) includes draining the accumulated water in the seedbed by destroying the water storage membrane or draining water from it 5 to 7 days before the planned transplanting, and controlling the water supply to harden the seedlings.

7. The method for growing rice seedlings in hydroponics according to claim 1, characterized in that: The transplanting age of the rice seedlings is 28 to 35 days.

8. The method for growing rice seedlings in hydroponics according to claim 1, characterized in that: In step b), the seedling raising substrate is laid in a plurality of seedling raising trays placed on a water storage membrane.

9. The method for growing rice seedlings in hydroponics according to claim 1, characterized in that: The crop straw crushed material is selected from crushed materials of rape straw, corn straw, wheat straw, or at least one of rapeseed hulls and wheat hulls.

10. The method for growing rice seedlings in hydroponics according to claim 1, characterized in that: The water storage membrane is a polyethylene agricultural anti-seepage membrane with a thickness of 0.05 to 0.08 mm.