Preparation method of modified straw for activating residual phosphorus in soil

Abstract

The present invention belongs to the field of materials, and specifically discloses a method for preparing a novel material-modified straw for activating residual phosphorus in soil, comprising the following steps: adding water to alkali lignin and urea, stirring, and then adjusting pH; crushing rice straw after drying; adding crushed straw to an alkali lignin-urea solution after acid-base adjustment, first ultrasonically treating, then stirring to fully mix, and then standing and soaking; filtering the obtained product after soaking, washing with water, and drying to obtain a modified straw for activating residual phosphorus in soil. The modified straw of the present invention has the function of activating residual phosphorus in soil.

Description

Technical Field

[0001] The invention belongs to the field of materials, and particularly relates to a preparation method of a new material for activating residual phosphorus in soil - modified straw. Background Art

[0002] Phosphorus is an essential element for crop growth. According to its form in the soil, it can be divided into ionic, adsorbed, mineral, organic phosphorus compounds and microbial phosphorus. It is reported that about 40% of the world's arable land soils are limited by phosphorus deficiency, which limits crop yields. Phosphorus has become one of the large nutrients that must be invested in agricultural production to achieve high crop yields. However, after phosphate fertilizer is applied to the soil, it is easily adsorbed and fixed by iron and aluminum oxides in the soil, and its utilization rate in the season is only 10%-25%. In agricultural production, the long-term, large-scale and extensive application of phosphate fertilizers in vegetable fields has led to the accumulation of soil phosphorus year by year, and the proportion of effective phosphorus has gradually decreased. In order to increase the amount of phosphorus absorbed by crops, the amount of fertilizer continues to increase, and the residual phosphorus in the soil continues to increase until saturation, increasing the risk of soil phosphorus and toxic and harmful heavy metals being released into the environment, causing agricultural non-point source pollution. The main pathways are leaching, surface runoff, and infiltration.

[0003] In response to the problems existing in current research - the research on phosphorus activation is mainly focused on field trials of grain crops, with fixed test subjects and few types, and there is insufficient research on improving the yield and quality of vegetable crops.

[0004] The mechanism of action of phosphorus activator mainly includes:

[0005] 1. Acid (base) dissolution:

[0006] Low phosphorus conditions induce plant roots to secrete organic acids, which can ionize H+, reduce the pH value in the rhizosphere environment, dissolve some phosphorus-absorbing substrates, and increase the effectiveness of phosphorus. For example, after the acidic groups of lignin are degraded in the soil, they can promote the dissolution of calcium phosphate into effective phosphate.

[0007] 2. Adsorption effect:

[0008] For example, the aforementioned zeolite.

[0009] 3. Ion bridge effect:

[0010] The active groups such as carboxyl and hydroxyl contained in organic acids, lignin and humic acid form ion bridges with phosphorus in the soil solution, and phosphorus is transferred to the root system through the bridging complex. Summary of the invention

[0011] The technical problem to be solved by the present invention is to provide a method for preparing a novel material for activating residual phosphorus in soil, which method has the advantages of being rapid, easy to operate and having a good effect of activating residual phosphorus in soil.

[0012] In order to solve the above technical problems, the present invention provides a method for preparing modified straw for activating residual phosphorus in soil, comprising the following steps:

[0013] 1) Add water to the alkali lignin and urea, stir, and then adjust the pH to 7.0-7.5 to obtain an acid-base adjusted alkali lignin-urea solution;

[0014] The weight ratio of the alkali lignin to urea is 1:0.9-1.1; the dosage ratio of the alkali lignin to water is 50g:(600±60)mL;

[0015] 2) Drying the rice straw and then crushing it to obtain crushed straw with a length of 1 to 3 cm;

[0016] 3) Add the chopped straw obtained in step 2) to the acid-base adjusted alkali lignin-urea solution obtained in step 1) at a material-liquid ratio of 20±2g:100ml, first perform ultrasonic treatment, then stir to fully mix, and then stand and soak for 1±0.2h;

[0017] Note: The ultrasonic treatment time is about 8 to 12 minutes. The purpose of the ultrasonic treatment is to fully mix the chopped straw with the alkali lignin-urea solution; then stir with a magnetic stirrer at room temperature (20 to 30°C) (stirring time is about 8 to 12 minutes) until fully mixed;

[0018] 4) filtering the product obtained after soaking in step 3) and washing with water (using deionized water) to obtain alkali lignin-urea modified straw;

[0019] 5) Dry the alkali lignin-urea modified straw obtained in step 4) and then crush it (it can be crushed by a crusher or a ball mill) to obtain the modified straw (the final modified straw product) for activating residual phosphorus in the soil.

[0020] As an improvement of the preparation method of the modified straw for activating residual phosphorus in soil of the present invention:

[0021] In the step 1), the pH is adjusted using 0.1 M sodium hydroxide and glacial acetic acid.

[0022] As a further improvement of the preparation method of the modified straw for activating residual phosphorus in soil of the present invention:

[0023] The drying in step 2) is to dry the rice straw at 50±5°C for 12±1 hours (moisture content ≤ 10.5%);

[0024] The drying in step 5) is to dry the alkali lignin-urea modified straw at 50±5° C. for 24±2 hours.

[0025] As a further improvement of the preparation method of the modified straw for activating residual phosphorus in soil of the present invention:

[0026] The pulverization in step 5) is performed until the particles pass through a 100-mesh sieve.

[0027] As a further improvement of the preparation method of the modified straw for activating residual phosphorus in soil of the present invention:

[0028] The filtration in step 4) is as follows: the mixture is filtered through a 30-mesh filter (stainless steel filter).

[0029] The invention utilizes the coupling of alkali lignin and urea with straw to form modified straw.

[0030] The method of the present invention is characterized in that the adsorption capacity of the modified straw is utilized to physically modify the shredded straw, thereby expanding the adsorption area and adsorbing urea and alkali lignin in the solution at the same time, so as to achieve the purpose of obtaining a functional material for activating residual phosphorus in the soil. The method of the present invention is simple, rapid, efficient, and widely applicable to soil types, and has broad application prospects. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0032] Example 1: A method for preparing a novel material for activating residual phosphorus in soil, comprising the following steps:

[0033] 1) Take a 1000mL beaker, weigh 50g of alkali lignin and 50g of urea, add them into the beaker, then add 600mL of distilled water, stir with a glass rod to make it completely dissolved, and prepare an alkali lignin-urea solution; use 0.1M sodium hydroxide and glacial acetic acid to control the alkali lignin-urea solution to make its pH = 7.0-7.5; obtain the alkali lignin-urea solution after acid-base adjustment;

[0034] 2) Take 500 g of rice straw, dry it in an oven at 50° C. for 12 hours (moisture content ≤ 10.5%), and then cut it into 1-3 cm pieces using a crusher.

[0035] 3) Take 20 g of the chopped straw obtained in step 2) and add it to 100 mL of the acid-base adjusted alkali lignin-urea solution obtained in step 1), first treat it with ultrasound for 10 min (so that the chopped straw is fully mixed with the alkali lignin-urea solution); then stir it with a magnetic stirrer at room temperature for 10 minutes until it is fully mixed, and let it stand and soak for 1 hour.

[0036] 4) Pass the obtained product after soaking in step 3) through a 30-mesh stainless steel filter, and wash the sample with deionized water for 3 times until the eluent becomes clear; and obtain alkali lignin-urea modified straw.

[0037] 5) The alkali lignin-urea modified straw obtained in step 4) is placed in an oven at 50° C. for 24 hours for drying, and then crushed by a pulverizer or a ball mill and passed through a 100-mesh sieve to obtain the modified straw as the final product.

[0038] Experiment 1: The modified straw obtained in Example 1 was tested according to the national standard for bio-organic fertilizer "Bio-organic fertilizer" (NY884-2012), and the results are shown in Table 1 below:

[0039] Table 1 Composition of the modified straw (mass %)

[0040]

[0041] The modified straw of the present invention mainly relies on physical treatment to change the size of the straw block, increase its adsorbable area and thus improve the adsorption capacity. It has a good adsorption effect on urea and lignin, has a higher nitrogen content ratio, is beneficial to increase the soil microbial community structure, and thus promotes the mineralization of organic phosphorus.

[0042] Experiment 2: Add the modified straw to the soil and analyze the available phosphorus forms in the soil.

[0043] The details are as follows:

[0044] According to modified straw: soil = 0.1% (weight %), the modified straw prepared in Example 1 was added to the soil, and samples were taken at the time described in Table 2 below. The water-soluble P in the soil was tested according to GB 11893-89. The results are shown in Table 2 below:

[0045] Table 2 Dynamic changes of soil water-soluble P (mg / kg)

[0046] Addition amount 0d 1d 3d 7d 15d 0 20.4 13.0 14.3 16.1 15.0 0.1％ 22.6 19.3 21.1 21.5 15.6

[0047] Compared with the case without modified straw material, after adding 0.1% modified straw into the soil, the water-soluble P in the soil increased by 4%-48%. Therefore, it can be proved that the modified straw of the present invention can be used to activate the residual phosphorus in the soil.

[0048] Example 2: Another rice straw source different from that of Example 1 was prepared according to the method described in Example 1, and the rest was the same as Example 2. The modified straw product prepared by this scheme was tested in the manner described in Experiment 1, 0.5% was added to the soil and the available phosphorus form of the soil was analyzed, and the rest was referred to Experiment 2.

[0049] Note: The source of the soil used is different from that of Experiment 2.

[0050] The results are as follows:

[0051] Table 3 Composition of modified straw

[0052]

[0053] Table 4 Dynamic changes of soil water-soluble P (mg / kg)

[0054] Addition amount 0d 1d 3d 7d 15d 0 20.2 12.8 13.5 15.7 13.5 0.5％ 23.7 20.5 23.1 20.5 18.1

[0055] Compared with the soil without modified straw material, the addition of 0.5% modified straw into the soil increased the water-soluble P in the soil by 17%-60%.

[0056] Comparative Example 1-1: Change the "50 g alkali lignin and 50 g urea" in Example 1 to "70 g alkali lignin and 30 g urea", and the rest is the same as Example 1.

[0057] Comparative Example 1-2: The "50 g alkali lignin and 50 g urea" in Example 1 is changed to "30 g alkali lignin and 70 g urea", and the rest is the same as Example 1.

[0058] Comparative Example 1-3: The use of urea is eliminated, that is, "50 g alkali lignin and 50 g urea" in Example 1 is changed to "50 g alkali lignin". The rest is the same as Example 1.

[0059] Comparative Example 2: The pH adjustment in step 1) is omitted, that is, the pH is about 11 at this time, and the rest is the same as Example 1.

[0060] Comparative Example 3: "Rice straw" was replaced with plant straw as described in Table 5 below, and the rest was the same as Example 1.

[0061] All the comparative examples described above were tested in the manner described in Experiment 2 (the soil used was the same as the soil in Experiment 2), and the comparison with Example 1 is described in Table 5 below.

[0062] Table 5 Dynamic changes of soil water-soluble P (mg / kg)

[0063]

[0064] The disadvantages of Comparative Examples 1-1 to Comparative Examples 1-3 compared to Example 1 are that they lack an accurate ratio of alkali lignin and urea, which leads to an unbalanced nutrient concentration in the soil, an uncoordinated nutrient ratio such as C / N, and affects the soil microbial community structure.

[0065] Finally, it should be noted that the above examples are only some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by a person skilled in the art should be considered as the protection scope of the present invention.

Claims

1. A method for preparing modified straw for activating residual phosphorus in soil, characterized in that The following steps are involved: 1) Add water to the alkali lignin and urea, stir, and then adjust the pH to 7.0-7.5 to obtain an alkali lignin-urea solution after acid-base adjustment; The weight ratio of the alkali lignin to urea is 1:0.9-1.1; the dosage ratio of the alkali lignin to water is 50g:(600±60)mL; 2) Drying the rice straw and then crushing it to obtain crushed straw with a length of 1 to 3 cm; 3) Add the chopped straw obtained in step 2) to the acid-base adjusted alkali lignin-urea solution obtained in step 1) at a material-liquid ratio of 20±2g:100ml, first perform ultrasonic treatment, then stir to fully mix, and then stand and soak for 1±0.2h; 4) filtering the product obtained after soaking in step 3) and washing with water to obtain alkali lignin-urea modified straw; 5) Drying the alkali lignin-urea modified straw obtained in step 4) and then crushing it to obtain the modified straw for activating residual phosphorus in soil.

2. The method for preparing modified straw for activating residual phosphorus in soil according to claim 1, characterized in that: In the step 1), the pH is adjusted using 0.1 M sodium hydroxide and glacial acetic acid.

3. The method for preparing modified straw for activating residual phosphorus in soil according to claim 1 or 2, characterized in that: The drying in step 2) is to dry the rice straw at 50±5°C for 12±1 hours; The drying in step 5) is to dry the alkali lignin-urea modified straw at 50±5° C. for 24±2 hours.

4. The method for preparing modified straw for activating residual phosphorus in soil according to claim 3, characterized in that: The pulverization in step 5) is performed until the particles pass through a 100-mesh sieve.

5. The method for preparing modified straw for activating residual phosphorus in soil according to claim 4, characterized in that: The filtering in step 4) is as follows: passing the mixture through a 30-mesh filter.

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