A method for measuring field water holding capacity of seedling raising medium

Abstract

The present invention discloses a method for determining the field water holding capacity of a seedling raising substrate, which includes four steps: natural water content determination, bulk density determination, and field water holding critical point determination and calculation. In the whole process of the present invention, it is not necessary to take the original soil, but the original soil is made by immersion sedimentation until the structure of the seedling raising substrate is stable, thereby avoiding the destruction of the original soil structure in the process of taking the original soil with a ring knife. In the method of the present invention, the outer wrapping layer of the substrate is cloth, and even if the substrate forms an impermeable layer, gravity water can be smoothly drained away through the small holes on the cloth. The method of the present invention proposes a new method for judging the critical point of field water holding capacity, which drains water by draining gravity water with cotton thread, and the moisture content of the substrate can be distinguished by the speed of water droplets sliding down the drainage cotton thread and the speed of increase of water droplets hanging on the lower end of the cotton thread. This method can more simply and conveniently judge the critical point of field water holding capacity, is simple to operate, and produces accurate results.

Description

Technical Field

[0001] The invention relates to a determination method, in particular to a method for determining the field water holding capacity of a seedling raising matrix. Background Art

[0002] Field water holding capacity refers to the relatively stable soil water content (soil water potential or soil water suction reaches a certain value) that the soil profile can maintain after sufficient irrigation or precipitation on land with deep groundwater and good drainage, allowing water to fully infiltrate and preventing its evaporation, over a certain period of time.

[0003] Common methods for determining field water holding capacity include the field test method and the knife ring method. The field test method produces reliable results, but is labor-intensive and time-consuming, especially in saline-alkali areas where poor soil permeability makes field testing more difficult. The knife ring method is simpler and easier to perform than the field test method, making it more widely adopted and providing more reliable values.

[0004] The seedling-raising matrix is ​​generally made of a mixture of soil and other substances (such as rice husks, straw, etc.). There is no ready-made seedling-raising matrix in the wild, and it is not suitable for the plot irrigation method. The matrix structure is loose, and the thickness of the filling when in use is relatively thin. It has the characteristics of looseness and unstable structure. As a result, it is impossible to directly use a ring knife to obtain the complete original soil for the determination of the field water holding capacity of the seedling-raising matrix, and it is not suitable for the common ring knife method. Even if a thicker matrix soil layer is artificially filled and then sampled with a ring knife, its structural instability will inevitably cause certain damage to the internal structure of the matrix during the sampling process, and 100% original soil cannot be obtained. In addition, the water withdrawal process of the ring knife method must ensure that the ring knife and the soil structure inside it are stable. Under the condition that the bottom of the matrix in the ring knife is not supported, the matrix will inevitably slide out of the ring knife; after adding a supporting bottom plate, the water withdrawal is not smooth, which will lead to inaccurate and distorted measured data. Therefore, the determination of the field water holding capacity of the seedling-raising matrix cannot be achieved by using conventional measurement methods. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for determining the field water holding capacity of a seedling culture medium, so as to solve the above-mentioned technical problems existing in the existing methods.

[0006] The technical solution of the present invention is a method for determining the field water holding capacity of a seedling raising substrate, comprising four steps of determining natural water content, determining bulk density, and determining and calculating field water holding capacity;

[0007] S1 Determination of natural moisture content: weigh the seedling raising substrate with a balance, dry the seedling raising substrate, and weigh the dried seedling raising substrate with a balance;

[0008] S2 Bulk density is measured: take 3 ring knife covers and prick them with small holes, spread a filter paper with the same diameter as the ring knife cover inner diameter in each cover, then place the ring knife on the filter paper, paste the ring knife and the ring knife cover to fix, and seal the gap between the ring knife and the ring knife cover, weigh the weight of 3 groups of ring knives, ring knife covers and filter paper respectively on a balance, fill the 3 ring knives with matrix and slightly above the ring knife edge, then cut off the seedling raising matrix above the ring knife close to the ring knife edge with a soil cutter blade, weigh the weight of each group of ring knives, ring knife cover, filter paper and matrix, put 3 ring knives, ring knife cover, filter paper and matrix assembly into a container, slowly fill water in the container to the position that the water surface is 2 millimeters below the ring knife edge, soak for 24 hours, measure the height of the matrix surface and the ring knife edge after soaking sedimentation with a ruler;

[0009] Determination of field water holding capacity of S3 substrate: select 3 pieces of soft and thin cloth, sew a 10 cm cotton thread in the center, weigh the same mass of substrate and put it into the cloth, place the 10 cm cotton thread on the outside and let it droop naturally, tie the cloth mouth with a tie, put the 3 cloth packages into the container, slowly pour water along the container wall until the cloth packages are completely submerged, soak for 24 hours, wait until the substrate and cloth fully absorb water, and the substrate sedimentation is stable, then hang the cloth packages above the sink, so that the cotton threads under all the wrapped cloths droop naturally, observe the water droplets at the end of the cotton thread every half an hour, when there are no hanging water drops on the cotton thread, it can be determined that the gravity water of the substrate has all dripped clean, at this time the substrate has just reached the field water holding capacity, take 3 portions of about 15 g of substrate from each package, and determine the mass field water holding capacity by the drying method;

[0010] The S4 calculation process is as follows:

[0011] (1) Calculate the mass water content W1 based on the natural dry weight m1 and oven-dried weight m2 of the matrix in S1. The calculation formula is:

[0012] (2) Based on the weight of the ring knife, ring knife cover, filter paper m3, the natural dry weight of the ring knife, ring knife cover, filter paper and substrate m4, the volume of the ring knife V1, the height of the ring knife H1, the height H2 of the substrate surface and the ring knife edge after soaking and settling, and the water content of the substrate W1, the dry bulk density ρ of the substrate after soaking and settling is calculated; the calculation formula is:

[0013] (3) Calculate the mass field capacity W based on the weight m5 of the matrix in the field capacity state, the weight after drying m6, and the dry bulk density ρ in S3. m and volumetric field capacity W v :

[0014] Quality Field Capacity:

[0015] Volumetric field capacity: W v =ρ×W m .

[0016] In the aforementioned method for determining the field water holding capacity of a seedling culture medium, in S2, three ring knife covers are used to poke holes with a distance of 0.5 cm to 1 cm between the holes; and the ring knife covers are glued and fixed with transparent tape.

[0017] In the aforementioned method for determining the field water holding capacity of a seedling raising substrate, in S3, the cloth opening is tied tightly with a tie, and the four corners of the cloth are aligned when tying. The internal substrate is supported in the center, with the top thicker and the bottom smaller. The center point of the stitching is exactly at the lowest point of the entire cloth-wrapped substrate sphere, ensuring that during the water withdrawal process, the outflowing gravity water just drips through the lowest point and the 10 cm cotton thread.

[0018] In the aforementioned method for determining the field water holding capacity of a seedling raising substrate, in S3, when the substrate is placed in the cloth, a mineral water bottle with the bottom sawed off is used as a model. The mineral water bottle with the lid removed is placed upside down on a cup, with the center of the cloth aligned with the center of the bottle mouth. A 10 cm cotton thread is hung from the bottle mouth, and an appropriate amount of substrate is placed.

[0019] Beneficial effects of the present invention: Compared with the prior art, the method of the present invention has the following advantages:

[0020] (1) The present invention innovatively solves the problem that conventional methods cannot be used to determine the field water holding capacity of loose soil. During the entire process, there is no need to take the original soil. Instead, the original soil is made by immersing and settling it into the seedling medium structure, thus avoiding the damage to the original soil structure and the poor water withdrawal that may cause errors during the process of taking the original soil with a ring knife.

[0021] (2) The substrate of the present invention is wrapped in a cloth. Even if the substrate forms an impermeable layer, gravity water can be drained away smoothly through the small holes in the cloth. If a circular knife or other sealed container is used as in conventional methods, the impermeable layer may prevent gravity water from being completely drained away, resulting in data distortion.

[0022] (3) The method of the present invention proposes a new method for determining the critical point of field water holding capacity. Water is drained by draining gravity water through cotton thread. The moisture content of the substrate can be determined by the speed of water droplets sliding down the cotton thread and the speed at which the water droplets hanging from the lower end of the cotton thread increase. When the speed of water droplets sliding down the cotton thread is faster, it indicates that there is more gravity water in the substrate; when there are no water droplets sliding down the cotton thread and there are no water droplets hanging from the lower end of the cotton thread, it indicates that the substrate is at the field water holding capacity. This method can more easily and conveniently determine the critical point of field water holding capacity, is simple to operate, and provides accurate results. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a picture of soaking the substrate in water in the method of the present invention;

[0024] Figure 2This is a picture of the matrix in the ring knife after being immersed for 24 hours;

[0025] Figure 3 This is a picture of the cloth bag being drained;

[0026] Figure 4 for Figure 3 An enlarged schematic diagram of . DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the examples, but they are not intended to limit the present invention.

[0028] An embodiment of the present invention: A method for determining the field water holding capacity of a seedling raising substrate, comprising four steps: determining natural water content, determining bulk density, and determining and calculating a critical point of field water holding capacity.

[0029] S1 Determination of natural moisture content: weigh the seedling raising substrate with a balance, dry the seedling raising substrate, and weigh the dried seedling raising substrate with a balance;

[0030] S2 Bulk Density Determination: Take three ring knife covers and poke them with small holes using a red-hot needle, with a spacing of 0.5 to 1 cm between the holes. Place a piece of filter paper with the same diameter as the inner diameter of the ring knife cover inside each cover. Place the ring knife on the filter paper and secure the ring knife to the ring knife cover with transparent tape. The gap between the ring knife and the ring knife cover should be sealed to facilitate subsequent handling and prevent the gap between the ring knife cover and the ring knife from digging into the seedling medium and affecting the accuracy of the test results. Weigh each set of ring knife, ring knife cover, and filter paper using a balance. Fill the three ring knife covers with medium to slightly above the ring knife edge. Then, use a soil cutter blade, placed against the ring knife edge, to remove the remaining medium above the ring knife edge. Weigh each set of ring knife, ring knife cover, filter paper, and medium. Place the three ring knives, ring knife cover, filter paper, and medium assembly in a container. Slowly fill the container with water until the water level is 2 mm below the ring knife edge. Let it soak for 24 hours. Measure the height of the medium surface above the ring knife edge after soaking and settling with a ruler.

[0031] Determination of the field water holding capacity of the S3 matrix: Select three pieces of soft, thin cloth of appropriate size and sew a 10-cm cotton thread through the center. Weigh equal amounts of matrix and place them inside the cloth. Place the 10-cm cotton thread outside, allowing it to hang naturally. Secure the cloth with a cable tie. Align the four corners of the cloth, with the matrix inside serving as the center support, making the top thicker and the bottom narrower. The center of the thread should be at the lowest point of the entire cloth-wrapped matrix sphere. This ensures that during the drainage process, the outflowing gravity water drips through the lowest point and the 10-cm cotton thread. To ensure that the matrix shape after bundling meets the experimental requirements, use a mineral water bottle with the bottom sawed off as a model. Place the uncapped mineral water bottle upside down on a cup, aligning the center of the cloth with the center of the bottle opening and the 10-cm cotton thread hanging from the bottle opening. Add the appropriate amount of matrix. Place three cloth packages in a container, and slowly pour water along the container wall until the cloth packages are completely submerged. Soak for 24 hours. After the substrate and cloth have fully absorbed water and the substrate has settled steadily, hang the cloth packages above the sink. When hanging, keep each cloth package 5 cm apart to prevent the cloth packages from exchanging water with each other. Allow the cotton thread under all the wrapped cloths to droop naturally, and observe the water droplets at the end of the cotton thread every half an hour. When there are no water droplets hanging on the cotton thread, which usually takes about 3 hours, it can be determined that all the gravity water in the substrate has dripped cleanly. At this time, the substrate has just reached the field water holding capacity. Take 3 portions of about 15g of substrate from each package and determine the mass field water holding capacity by the drying method;

[0032] The S4 calculation process is as follows:

[0033] (1) Calculate the mass water content W1 based on the natural dry weight m1 and oven-dried weight m2 of the matrix in S1. The calculation formula is:

[0034] (2) Based on the weight of the ring knife, ring knife cover, filter paper m3, the natural dry weight of the ring knife, ring knife cover, filter paper and substrate m4, the volume of the ring knife V1, the height of the ring knife H1, the height H2 of the substrate surface and the ring knife edge after soaking and settling, and the water content of the substrate W1, the dry bulk density ρ of the substrate after soaking and settling is calculated; the calculation formula is:

[0035] (3) Calculate the mass field capacity W based on the weight m5 of the matrix in the field capacity state, the weight after drying m6, and the dry bulk density ρ in S3. m and volumetric field capacity W v :

[0036] Quality Field Capacity:

[0037] Volumetric field capacity: W v =ρ×W m .

[0038] In order to verify the effectiveness of the method of the present invention, three experiments were conducted using the method of the present invention, and the data of the three experiments are as follows.

[0039] 1. Natural mass moisture content test

[0040] Table 1 Natural moisture content test data

[0041]

[0042] 2. Bulk density test

[0043] Table 2 Statistical data of bulk density test

[0044]

[0045] 3. Quality field water holding capacity

[0046] Table 3 Experimental data of mass field water holding capacity

[0047]

[0048]

[0049] Control group experiment:

[0050] The following control group experiment was conducted with reference to the Technical Specifications for Soil Analysis.

[0051] S1: Take 3 pieces of disposable hard plastic and poke small holes in the bottom with a needle.

[0052] S2: Place the punctured plastic cup into the container and add the seedling substrate into the container until it is 1 cm higher than the top of the disposable cup.

[0053] S3: Pour water into the container until the substrate is just covered, and soak for 24 hours.

[0054] S4: After the soaking is completed, take out the three plastic cups containing the substrate, use a soil cutter to cut off the seedling substrate that is higher than the disposable cup, and use a soil cutter to wipe the substrate outside the disposable cup.

[0055] S5: Place the disposable cup containing the seedling medium on the air-dried soil to drain for 8 hours.

[0056] S6: Take three portions of about 15g of matrix from each cup of dehydrated matrix and use the drying method to determine the matrix mass moisture content.

[0057] Table 4 Comparative test quality field water holding capacity experimental data

[0058]

[0059] From the comparison of Table 3 and Table 4, it can be seen that the average field water holding capacity measured by the method of the present invention is 42.10%, while the average field water holding capacity measured by referring to the "Soil Analysis Technical Specifications" is 42.62%, and the difference between the two is only 0.52%. This shows that the method of the present invention can effectively and accurately measure the field water holding capacity.

Claims

1. A method for determining the field water holding capacity of a seedling raising medium, characterized in that: It includes four steps: natural water content determination, bulk density determination, field water holding capacity determination and calculation; S1 Determination of natural moisture content: weigh the seedling raising substrate with a balance, dry the seedling raising substrate, and weigh the dried seedling raising substrate with a balance; S2 Bulk density is measured: take 3 ring knife covers and prick them with small holes, spread a filter paper with the same diameter as the ring knife cover inner diameter in each cover, then place the ring knife on the filter paper, paste the ring knife and the ring knife cover to fix, and seal the gap between the ring knife and the ring knife cover, weigh the weight of 3 groups of ring knives, ring knife covers and filter paper respectively on a balance, fill the 3 ring knives with matrix and slightly above the ring knife edge, then cut off the seedling raising matrix above the ring knife close to the ring knife edge with a soil cutter blade, weigh the weight of each group of ring knives, ring knife cover, filter paper and matrix, put 3 ring knives, ring knife cover, filter paper and matrix assembly into a container, slowly fill water in the container to the position that the water surface is 2 millimeters below the ring knife edge, soak for 24 hours, measure the height of the matrix surface and the ring knife edge after soaking sedimentation with a ruler; Determination of field water holding capacity of S3 substrate: select 3 pieces of soft and thin cloth, sew a 10 cm cotton thread in the center, weigh the same mass of substrate and put it into the cloth, place the 10 cm cotton thread on the outside and let it droop naturally, tie the cloth mouth with a tie, put the 3 cloth packages into the container, slowly pour water along the container wall until the cloth packages are completely submerged, soak for 24 hours, wait until the substrate and cloth fully absorb water, and the substrate sedimentation is stable, then hang the cloth packages above the sink, let the cotton threads under all the cloth packages droop naturally, observe the water droplets at the end of the cotton threads every half an hour, when there are no hanging water drops on the cotton threads, it is determined that the gravity water of the substrate has all dripped clean, at this time the substrate has just reached the field water holding capacity, take 3 portions of about 15 g of substrate from each cloth package, and determine the mass field water holding capacity by the drying method; The S4 calculation process is as follows: (1) Calculate the mass water content based on the natural dry weight m1 and oven-dried weight m2 of the matrix in S1 , the calculation formula is ; (2) According to the weight of the ring knife, ring knife cover, filter paper m3, the natural dry weight of the ring knife, ring knife cover, filter paper and matrix m4, the ring knife volume , ring knife height H1, the height between the substrate surface and the ring knife edge after immersion and sedimentation H2, the substrate mass water content Calculate the dry bulk density of the matrix after immersion and sedimentation The calculation formula is: ; (3) According to the matrix weight m5, weight after drying m6, dry bulk density in field water holding capacity state in S3 , calculate the mass field capacity W m and volumetric field capacity W v : Quality Field Capacity: , Volumetric field capacity: .

2. The method for determining the field water holding capacity of a seedling raising substrate according to claim 1, wherein: In S2, three ring knife covers are used to poke small holes, with the distance between each hole being between 0.5 cm and 1 cm; and the ring knife and the ring knife cover are fixed with transparent tape.

3. The method for determining the field water holding capacity of a seedling raising substrate according to claim 1, wherein: In S3, the cloth opening is tied tightly with a cable tie. The four corners of the cloth are aligned when tying. The internal matrix is ​​supported in the center, and the top is thicker and the bottom is smaller. The center point of the stitching is exactly at the lowest point of the entire cloth-wrapped matrix sphere, ensuring that during the water withdrawal process, the outflowing gravity water just drips through the lowest point and the 10 cm cotton thread.

4. The method for determining the field water holding capacity of a seedling raising substrate according to claim 1, wherein: In S3, when filling the cloth with the matrix, use a mineral water bottle with the bottom sawed off as a model. Place the mineral water bottle with the lid removed upside down on the cup, with the center of the cloth aligned with the center of the bottle mouth. Let a 10 cm cotton thread hang down from the bottle mouth, and then put an appropriate amount of matrix.

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