CN111248227A

CN111248227A - Modifying agent, preparation method thereof and method for promoting magnesium absorption of underground part of crop

Info

Publication number: CN111248227A
Application number: CN202010078934.2A
Authority: CN
Inventors: 李亚东; 倪红; 汤行春; 杨升; 廖卫芳; 姚伦广; 段鹏飞; 王友平; 汪华
Original assignee: Hubei University; Nanyang Normal University; Institute of Plant Protection and Soil Fertilizer of Hubei Academy of Agricultural Science
Current assignee: Hubei University; Nanyang Normal University; Institute of Plant Protection and Soil Fertilizer of Hubei Academy of Agricultural Science
Priority date: 2020-02-03
Filing date: 2020-02-03
Publication date: 2020-06-09

Abstract

The invention provides a modifier, a preparation method thereof and a method for promoting magnesium absorption of underground parts of crops. The modifier is applied to high-cadmium-polluted acid soil to promote magnesium absorption of the underground part of crops, and the preparation method of the modifier comprises the following steps: mixing a calcium source raw material and a solvent to obtain calcium-containing emulsion; mixing the protein raw material with the calcium-containing emulsion, and uniformly stirring to obtain a mixed solution; and (3) reacting the mixed solution under a heating condition, filtering to obtain a filtrate after the reaction is finished, and concentrating the filtrate to a concentrated solution with the concentration of 20-30%. The method is applied to the acid soil polluted by high-concentration cadmium, can promote the magnesium element absorption of the underground part of the crop, and is beneficial to the generation of nutrient substances in the root system of the crop and the growth of the root system.

Description

Modifying agent, preparation method thereof and method for promoting magnesium absorption of underground part of crop

Technical Field

The invention relates to the technical field of polluted soil treatment, in particular to a modifier, a preparation method and a method for promoting magnesium absorption of an underground part of a crop.

Background

With the rapid development of modern industry and agriculture, the situation of heavy metal pollution of soil is more and more severe, the heavy metal pollution event in China is entering a high-rise period, and the heavy metal pollution is a prominent problem in a plurality of polluted sites. In 2014, "national soil pollution condition survey bulletin" issued by the ministry of environmental protection and the ministry of land resources shows that the point standard exceeding rate of 8 inorganic pollutants of cadmium, mercury, arsenic, copper, lead, chromium, zinc and nickel is respectively 7.0%, 1.6%, 2.7%, 2.1%, 1.5%, 1.1%, 0.9% and 4.8%, wherein cadmium pollution is the most prominent.

Heavy metal pollution of soil is mainly caused by three reasons:

1) the sewage irrigation refers to the irrigation with the sewage which is treated and meets the requirement of irrigation water quality standard as a water source. The sewage irrigation is a double-edged sword, although urban sewage is not only an important fertilizer source but also an important water source of suburban crops, the sewage contains a large amount of heavy metal elements which are not beneficial to the growth of the crops, and particularly in industrial sewage, a plurality of environmental problems can be caused. China is a big agricultural country, and large-area cultivated land and suburb land in cities are polluted by heavy metals to a greater or lesser extent. Moreover, with the rapid development of the industry in China, a large amount of industrial sewage is discharged into a sewer and mixed with domestic sewage without diversion and purification treatment, so that a large amount of heavy metals enter soil in a farmland irrigation area, and serious heavy metal pollution of the soil is caused. According to statistics, the heavy metal pollution area of cultivated land in China accounts for more than 16% of the total cultivated land area, the heavy metal polluted grain reaches astonishing 1200 ten thousand tons every year, the yield of grain is reduced to 1000 ten thousand tons, and the problem is urgently solved.

2) Secondly, China is a big agricultural country and uses a large amount of pesticides and fertilizers every year to promote the rapid development of agriculture. However, fertilizers generally contain a certain amount of heavy metals, and excessive use of fertilizers and pesticides results in an increase in the heavy metal content of soil.

3) Industrial activities such as energy exploitation, metal smelting, fuel burning and the like discharge a large amount of waste gas, the waste gas contains a large amount of heavy metals, most of the heavy metals enter the atmosphere in the state of aerosol, and enter the soil through a series of natural sedimentation and precipitation, and statistics show that when fossil fuels are burned, 10% -30% of the heavy metals naturally settle within 10km of the emission source, and enter the atmosphere along with smoke dust and finally enter the soil.

However, in many agricultural areas in China, the cadmium content in the soil is very high due to the influence of sewage irrigation, for example, in Zhang irrigated area of Liaoning, the cadmium content in the soil of some areas is over 7mg/kg, but due to the shortage of farmlands in China, the planting of crops in the soil with high cadmium pollution has to be carried out.

The existing research shows that the cadmium resolution rate of acid soil types such as red soil, yellow soil and the like at different temperatures is over 15 percent and is obviously higher than that of alkaline soil types such as grey desert soil, chestnut calcium soil and the like (less than 10 percent). In addition, according to the test data statistical analysis of 902 ten thousand soil samples of the soil testing formula fertilization in 2005-2011, compared with the second soil general investigation before 30 years, the soil pH of cultivated land in China is reduced by 0.13-1.3, the average reduction is 0.8, and 40% of cultivated land soil in China is below pH 6.5.

Magnesium is one of the essential nutrients for wheat growth and development, and is listed as the fourth most essential nutrient for crops second to nitrogen, phosphorus and potassium. Magnesium is not only a component of chlorophyll, but also an activator of various enzymes, and has important effects on photosynthesis, nitrogen absorption, carbohydrate synthesis and transportation, protein synthesis, fat metabolism, active oxygen metabolism, enzyme activity, gene expression, root activity, stress resistance and other ion absorption of crops. Magnesium also has certain promotion effect on wheat heading, grain number per ear and thousand grain weight, and has great significance on improving wheat yield.

The content of active aluminum in the acid soil is increased, so that aluminum stress is generated, and the absorption of crops to magnesium is influenced. The reason is as follows: the aluminum inhibits the cell division of the meristem of the crop root tip, so that the root system growth is hindered; the ionic radius of aluminum is similar to that of magnesium, and the aluminum competes for exchange sites in apoplast of the root system, so that the exchangeable magnesium is replaced by the aluminum; aluminum inhibits the support on the plasma membrane or competes at the support sites; the excessive aluminum causes the damage of the structure and stability of the cell membrane of the crops, and the magnesium can reduce the poison of the aluminum to the bodies of the crops.

Therefore, it is a very important and realistic problem to promote the absorption of magnesium by crops in cadmium-contaminated acidic soil.

Disclosure of Invention

The invention mainly aims to make up for the defects of the prior art and provides a modifier, a preparation method and a method for promoting the magnesium absorption of the underground part of a crop.

The invention also provides application of the modifier in promoting magnesium absorption of the underground part of crops under the high-cadmium-polluted acid soil, wherein the preparation method of the modifier comprises the following steps: mixing a calcium source raw material and a solvent to obtain calcium-containing emulsion; mixing the protein raw material with the calcium-containing emulsion, and uniformly stirring to obtain a mixed solution; and (3) reacting the mixed solution under a heating condition, filtering to obtain a filtrate after the reaction is finished, and concentrating the filtrate to a concentrated solution with the concentration of 20-30%.

In the above applications, the crop may be selected from wheat.

In the above application, the calcium source raw material may be one or a mixture of at least two selected from quicklime, calcium oxide and slaked lime, preferably quicklime; the solvent may be selected from one of purified water, ultrapure water, distilled water, tap water and deionized water, preferably tap water.

In the above application, the protein material may be selected from protein waste, and the protein waste may be selected from one or a mixture of at least two of plant protein waste, microbial cells, sludge, animal hair, animal hoof and horn, and blood.

In the application, the mass ratio of the calcium source raw material, the solvent and the protein raw material is (10-70): (80-1400): 100.

In the application, the heating temperature is 100-200 ℃, preferably 110-180 ℃, and more preferably 120-160 ℃; the reaction time is 1-8 h, preferably 1.5-6 h, and more preferably 2-5 h.

In the above application, the concentration method is evaporation by using a multi-effect evaporator; the pH value of the concentrated solution can be 10-14, preferably 11-13.

In the above application, an optional modifier preparation method is as follows: mixing quicklime and water to obtain calcium-containing emulsion; mixing rapeseed cakes with the calcium-containing emulsion, wherein the mass ratio of the quick lime to the water to the rapeseed cakes is 11:100:50, and uniformly stirring to obtain a mixed solution; and reacting the mixed solution at 137 ℃ for 3 hours, filtering to obtain filtrate after the reaction is finished, and evaporating the filtrate by using a multi-effect evaporator to obtain a concentrated solution with the pH value of 12-13 and the concentration of 25-30%.

In the above application, the concentration of Cd in the high-cadmium-polluted acid soil is not less than 4mg/kg, preferably more than 4.8 mg/kg.

The invention provides a method for promoting magnesium absorption of underground parts of crops in acid soil polluted by high cadmium, which comprises the following steps: mixing a calcium source material and a solvent to obtain a calcium-containing emulsion; mixing the protein raw material with the calcium-containing emulsion, and uniformly stirring to obtain a mixed solution; reacting the mixed solution under a heating condition, filtering to obtain a filtrate after the reaction is finished, and concentrating the filtrate to a concentrated solution with the concentration of 20-30%; applying the concentrate to the high-cadmium-contaminated acidic soil to promote magnesium absorption in the high-cadmium-contaminated acidic soil by the underground part of the crop; wherein, the concentration of Cd in the high-cadmium polluted acid soil can be not less than 4mg/kg, preferably more than 4.8 mg/kg.

The method provided by the invention is applied to the acid soil polluted by high-concentration cadmium, can promote the magnesium element absorption of the underground part of the crop, and is beneficial to the generation of nutrient substances in the root system of the crop and the growth of the root system.

Drawings

FIG. 1 shows the amount of magnesium absorbed by the aerial parts of wheat at seedling stage I under different conditions.

FIG. 2 shows the amount of magnesium absorbed by the underground portion of the seedling stage I wheat under different conditions.

FIG. 3 shows the amount of magnesium absorbed by the overground part of wheat at seedling stage II under different conditions.

Figure 4 shows the amount of magnesium absorbed by the underground portion of seedling stage ii wheat under different conditions.

FIG. 5 shows the amount of magnesium absorbed by the aerial parts of the wheat in jointing stage I under different conditions.

FIG. 6 shows the magnesium content absorbed by the underground portion of the jointing I wheat under different conditions.

FIG. 7 shows the amount of magnesium absorbed by the overground part of the jointing II wheat under different conditions.

Figure 8 shows the magnesium content absorbed by the underground portion of the jointing ii wheat under different conditions.

FIG. 9 shows the magnesium content absorbed by the overground part of wheat in different growth stages in Cd0 soil.

FIG. 10 shows the magnesium content absorbed by the underground parts of wheat in different growth stages in Cd0 soil.

FIG. 11 shows the magnesium content absorbed by the overground part of wheat in different growth stages in Cd2 soil.

FIG. 12 shows the magnesium content absorbed by the underground parts of wheat in different growth stages in Cd2 soil.

FIG. 13 shows the magnesium content absorbed by the overground part of wheat in different growth stages in Cd5 soil.

FIG. 14 shows the magnesium content absorbed by the underground parts of wheat in different growth stages in Cd5 soil.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below, and it should be apparent that the described embodiments are some, but not all, embodiments of the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Furthermore, the terms "include" and "have," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.

The invention provides a preparation method of a modifier, which comprises the following steps:

step 1: mixing the calcium source material and the solvent to obtain the calcium-containing emulsion.

In step 1, the calcium source material may be one or a mixture of at least two selected from quicklime, calcium oxide and slaked lime, and is preferably quicklime.

In step 1, the solvent may be selected from one or a mixture of at least two of purified water, ultrapure water, distilled water, tap water and deionized water, preferably tap water.

Step 2: mixing the protein material and the calcium-containing emulsion, and stirring uniformly to obtain a mixed solution.

In step 2, the protein material may include protein waste, and the protein waste may be selected from one or a mixture of at least two of plant protein waste, microbial cells, sludge, animal hair, animal hoof and horn, and blood.

In the step 1 and the step 2, the mass ratio of the calcium source raw material, the solvent and the protein raw material is (10-70): (80-1400): 100.

And step 3: and (3) reacting the mixed solution under a heating condition, filtering after the reaction is finished, and concentrating the filtrate to a concentrated solution with the concentration of 20-30%.

In step 3, the reaction temperature is 100-200 ℃, preferably 110-180 ℃, and more preferably 120-160 ℃.

In the step 3, the reaction time is 1-8 h, preferably 1.5-6 h, and more preferably 2-5 h.

In step 3, the method of concentration is evaporation using a multiple effect evaporator.

In step 3, the pH value of the final product is in the range of 10-14, preferably 11-13.

Examples

Adding 1000kg of pulverized rapeseed cake into a mixing barrel, and using 2m³Dissolving 220kg of quicklime in tap water to prepare lime emulsion, inputting the lime emulsion into a mixing barrel added with rapeseed cakes, uniformly stirring, inputting the uniformly stirred mixture into a reaction kettle by using a pump, introducing 0.2Mpa of water vapor into the reaction kettle, heating to 137 ℃, preserving heat for 3 hours, sampling by using a measuring cylinder, and if the solution is in a turbid state, indicating that the lime slightly soluble in water is not converted into a final product. If precipitation is rapid and the supernatant is a clear liquid, it indicates that the clear liquid has been converted to the final product, i.e., the peptide calcium salt. At this time, use is made of 40m²Filtering with plate-and-frame machine, and concentrating the filtrate with multi-effect evaporator until the filtrate is 20Be⁰The concentration of the peptide calcium salt was determined to be 28% (w/v) by spectrophotometry, and the pH value was determined to be 12.2 by pH paper, and this concentrated solution was the modifier provided in this example, i.e., the peptide calcium salt.

The calcium peptidate prepared in the embodiment is a peptidic substance, and a molecular polymer between protein and amino acid is formed by linking 2 to hundreds of amino acids through peptide bonds. Through detection, the nutritional rice has high nutritional value, is rich in amino acid, has the advantages of good solubility, low viscosity, high concentration, strong fluidity, good thermal stability and the like, and is a usable resource with high value.

Experimental materials: the crop variety is Zheng wheat 103.

Normal soil: the soil to be tested was taken from englery red soil, which is an acid soil, and the physicochemical properties of the acid soil are shown in table 1. Removing the stones and the residue of the mobile crops in the soil by using tweezers, naturally drying, crushing the soil by using a mortar, sieving by using a 2mm sieve, and uniformly mixing for later use.

Table 1: physicochemical properties of acid soil

Total nitrogen (g/kg)	Total phosphorus (g/kg)	Total potassium (g/kg)	pH	Organic matter (g/kg)	Volume weight
						0.65	0.81	0.40	4.5	15.4	1.2

And (3) polluted soil: as the cadmium concentration in most cadmium-polluted soil in China is about 2mg/kg, the polluted soil with the total cadmium concentration of 2mg/kg and 5mg/kg is prepared. Uniformly spraying the standard cadmium stock solution on the standby normal soil to ensure that the total cadmium concentration reaches 2mg/kg and 5mg/kg respectively, fully and uniformly stirring, and filling into a plastic basket. Adding tap water according to 80% of the field water holding capacity, covering and sealing, opening the cover every 3 days for ventilation, aging after 30 days, taking out 3 soil samples for air drying, and sieving by using a 2mm nylon sieve for later use.

0mg/kg, 2mg/kg and 5mg/kg of soil are briefly described below as Cd0, Cd2 and Cd 5.

Compound fertilizer: nitrogen 14-phosphorus 5-potassium 6 type compound fertilizer produced by complete fertilizer industry limited of yellow stone city.

1. The fertilizing method comprises the following steps: respectively applying peptide calcium salt in normal soil and polluted soil, and adding compound fertilizer as a control group. The normal soil is filled with 4 kg/pot of soil, the polluted soil is filled with 2 kg/pot of soil, the nitrogen content of each pot is 0.33g/kg, 6.25g of compound fertilizer and 10g of peptide calcium salt and 4.5g of potassium dihydrogen phosphate are calculated and applied.

The physicochemical properties of the home-made peptide calcium salt are shown in table 2.

Table 2: physicochemical Properties of self-made peptide calcium salt

Nitrogen (%)	Potassium (mg/kg)	Calcium (g/kg)	pH	Protein (%)	Phosphorus (g/kg)	Coarse ash (%)
							9.57	212	63.87	12.2	59.8	0.35	18.1

2. The sample processing method comprises the following steps: respectively planting wheat seeds in wet normal soil and contaminated soil, applying compound fertilizer or peptide calcium salt + potassium dihydrogen phosphate for treatment, and sampling four times when the wheat seeds are cultured for 58 days, 108 days, 129 days and 144 days to obtain a seedling stage I, a seedling stage II, an elongation stage I and an elongation stage II. Gently digging out wheat plants, keeping root hairs complete, collecting root soil and non-root soil, air-drying, grinding, and sieving with a 100-mesh nylon sieve for later use.

3. Determination of the experiment

(1) Reagent for experiment

The content of magnesium in wheat is measured according to flame atomic absorption spectrometry in GB 5009.241-2017 & lt & gt determination of magnesium in food safety national standard food.

The magnesium standard solution is a national standard sample GSB 04-1735-2004.

The main reagents used in the experiment are shown in table 3.

Table 3: main reagent for experiment

Primary reagent	Molecular formula	Purity of	Manufacturer(s)
				Nitric acid	HNO₃	Super grade pure	Group of traditional Chinese medicines
Hydrochloric acid	HCl	Super grade pure	Group of traditional Chinese medicines
				Perchloric acid	HClO₄	Super grade pure	Group of traditional Chinese medicines
Cadmium standard stock solution	Cd(NO₃)₂		Quality control of Chinese medicine

The water used is UP water made by an ultrapure water meter and reaches the second-level water specified in GB/T6682.

Nitric acid solution (5+ 95): nitric acid and ultrapure water are measured according to a volume ratio of 1:19, 20mL of nitric acid and 380mL of pure water are generally added into a 500mL polyethylene plastic washing bottle, and the mixture is uniformly mixed for later use.

Hydrochloric acid solution (1+ 1): weighing hydrochloric acid and ultrapure water according to the volume ratio of 1:1, and uniformly mixing for later use. The amount used was small, and the flask was placed in a 100mL volumetric flask.

1% nitric acid solution: 5mL of nitric acid is weighed into a 500mL polyethylene plastic washing bottle, the volume is adjusted to 500mL by ultrapure water, and the mixture is shaken up for standby.

Magnesium standard intermediate (10 mg/L): accurately sucking 1mL of magnesium standard solution into a 100mL volumetric flask by using a pipette, metering the volume to the scale by using a nitric acid solution (5+95), and shaking up.

Magnesium standard series solution: accurately sucking 0mL, 0.25mL, 0.5mL, 0.75mL, 1mL, 1.25mL and 1.5mL of magnesium standard intermediate solution (10mg/L) into a 50mL colorimetric tube, metering the volume to 50mL scale by using a nitric acid solution (5+95), and mixing uniformly. The mass concentrations of magnesium in the magnesium standard series solution are 0mg/L, 0.1mg/L, 0.2mg/L, 0.3mg/L, 0.4mg/L, 0.5mg/L and 0.6mg/L respectively.

(2) Treatment of wheat

When in sampling, the whole pot of plants and the soil are taken out together, and the soil is beaten by a wooden hammer to soften the soil block, so that the single wheat plant can be taken out completely. Collecting the loosened and dropped non-root soil, and filling the soil into a self-sealing bag for later use. The firmest part between the overground part and the underground part of the wheat is pinched and continuously and slowly twisted, so that the single wheat plant is completely taken out. And shaking the soil attached to the wheat roots or poking the soil into a self-sealing bag by hands to serve as root soil for later use. And filling the redundant soil into the flowerpot for later use, and washing the wheat clean by slow water flow.

Selecting three wheat plants with similar growth vigor and good development from the wheat plants taken out of each pot as representative samples, drying the taken wheat samples, and drying the samples to constant weight by using a vacuum drying oven at a set temperature of 105 ℃.

Separating each wheat sample into seedlings and roots, grinding the seedlings by a bean grinder, filling the seedlings into a self-sealing bag for later use, continuously turning and shearing the roots by scissors until the roots are thin and powdery, and filling the roots into the self-sealing bag for later use.

(3) And (5) performing a wet digestion method.

Each sample was weighed on an electronic balance, and seedlings and roots were weighed into three groups of 0.3000g (+ -0.0003 g) in 6 250mL Erlenmeyer flasks, 10mL nitric acid and 0.5mL perchloric acid were added, respectively, and the small funnel was closed. The solution was carried out in a fume hood, and the flask was placed on a high-temperature graphite hot plate, the temperature was adjusted to 150 ℃ and heated for about 2 hours, at which stage dense brown gas was collected in the flask. The temperature was then adjusted to 180 ℃ and heated for about 4 hours, at which stage the brown gas in the flask gradually faded. And then the temperature is adjusted to 220 ℃, brown gas in the conical flask can be gradually faded, and the phenomenon of white smoke can occur at the bottle mouth. Part of liquid in the bottle can boil, and attention is paid to no need of evaporating the liquid to dryness, a small amount of nitric acid is continuously dripped in the midway, and the amount of the visible liquid in the bottle is not required to exceed 5mL, so that the digestive juice is convenient to transfer. When the digestive juice is colorless and transparent or slightly yellowish, the digestion end point is reached.

(4) The experimental data processing method comprises the following steps:

transferring the digestive juice to a 10mL colorimetric tube, rinsing the conical flask into the colorimetric tube by using 1% nitric acid, and finally fixing the volume to the scale. The sample solution in the 10mL colorimetric cylinder is diluted because the concentration of magnesium ions is too high.

And (3) sucking 1mL of sample liquid into a 50mL colorimetric tube by using a liquid transfer gun, then metering the volume to 50mL scale by using a nitric acid solution (5+95), and measuring the content of magnesium.

The magnesium content of the sample was determined using an atomic absorption spectrophotometer.

4. Analysis of Experimental data

(1) Magnesium content of wheat at different growth stages

FIG. 1 shows the magnesium content absorbed by the overground part of the wheat at seedling stage I under different conditions, and FIG. 2 shows the magnesium content absorbed by the underground part of the wheat at seedling stage I under different conditions.

As shown in fig. 1 and 2, the magnesium content of wheat to which the peptide calcium salt was applied was gradually increased, while the magnesium content of wheat to which the compound fertilizer was applied was gradually decreased, as the cadmium concentration was increased. As shown in FIG. 2, in the soil of Cd0 and Cd2, the underground part of wheat to which the compound fertilizer was applied was significantly higher in magnesium content than the underground part of wheat to which the peptide calcium salt was applied, but the difference between them was significantly reduced by the Cd5 concentration. Probably because the compound fertilizer is acidic, the organic acid secretion of the wheat root is promoted, and the magnesium in the soil is promoted to be converted into an easily absorbed state, so that the wheat of the compound fertilizer group absorbs more magnesium than the peptide calcium salt group. The method has the advantages that the cadmium concentration is increased, the magnesium element absorption of wheat is inhibited under the stress action of the cadmium element, and the magnesium element absorbed by the underground parts of the peptide calcium salt group wheat in the Cd2 soil and the Cd5 soil is almost not influenced, so that the peptide calcium salt has passivation effect on the cadmium element, the absorption of the cadmium element by the wheat is inhibited, the increase of the cadmium element concentration in the soil is caused, and the influence on the magnesium element absorption by the wheat is not increased.

It can be easily seen that the magnesium content of the underground part in the wheat in the seedling stage I is generally higher than that of the overground part, and the magnesium content of the peptide calcium salt group is in a state of increased adversity no matter the underground part or the overground part under the concentration of Cd5, which shows that the peptide calcium salt has a better effect in the high-concentration cadmium polluted environment in the seedling stage I compared with the compound fertilizer.

Fig. 3 shows the magnesium content absorbed by the overground part of the seedling stage ii wheat under different conditions, and fig. 4 shows the magnesium content absorbed by the underground part of the seedling stage ii wheat under different conditions.

As shown in FIGS. 3 and 4, in contrast to the seedling stage I, in the seedling stage II, as the cadmium concentration increases, FIG. 3 is opposite to FIG. 4. Namely, the data difference value between the magnesium content of the overground part of the wheat in the peptide calcium salt group and the overground part of the wheat in the compound fertilizer group is obviously reduced, and the magnesium content of the underground part of the wheat in the peptide calcium salt group is obviously higher than that in the compound fertilizer group.

FIG. 5 shows the amount of magnesium absorbed by the overground part of the wheat in jointing stage I under different conditions, and FIG. 6 shows the amount of magnesium absorbed by the underground part of the wheat in jointing stage I under different conditions.

As shown in FIGS. 5 and 6, in the jointing stage I, except that the magnesium content of the underground part of the Cd5 soil is higher than that of the compound fertilizer group, the magnesium content of the wheat in the peptide calcium salt group is lower than that of the wheat in the compound salt group. The tendency of magnesium content of the overground part and the underground part along with cadmium concentration is similar, namely, the peptide calcium salt group has a slow increasing tendency, and the compound fertilizer group has a descending tendency.

Fig. 7 shows the magnesium content absorbed by the overground part of the jointing stage ii wheat under different conditions, and fig. 8 shows the magnesium content absorbed by the underground part of the jointing stage ii wheat under different conditions.

As shown in fig. 7 and 8, in the jointing stage ii, the magnesium content absorbed by wheat tends to increase with the increase of the cadmium concentration in both the peptide calcium salt group and the compound fertilizer group. In addition, the magnesium content of the overground part of the wheat in the peptide calcium salt group in the Cd5 soil is lower than that of the compound fertilizer group, and the magnesium content absorbed by the wheat in the peptide calcium salt group is higher than that of the compound salt group in other cases

(2) Magnesium content of wheat in soils of different cadmium concentrations

FIG. 9 shows the magnesium content absorbed by the overground part of wheat in different growth periods in Cd0 soil, and FIG. 10 shows the magnesium content absorbed by the underground part of wheat in different growth periods in Cd0 soil.

As shown in FIGS. 9 and 10, analysis of the line graphs for trend observation and comparison revealed that the magnesium content of wheat in the peptide calcium salt group was significantly superior to that of wheat in the compound fertilizer group, except for the magnesium content of the aerial and underground parts of wheat in seedling stage II. In other growth periods, the magnesium content of the wheat in the peptide calcium salt group is not superior to that of the wheat in the compound salt group.

Under the concentration of Cd0, along with the growth of wheat, the magnesium content of wheat in the compound fertilizer group is found to show the trend of descending first and then rising no matter the overground part or the underground part; the magnesium contents of the overground part and the underground part of the wheat in the peptide calcium salt group are different from the trend, the difference between the magnesium contents of the seedling stage I and the seedling stage II is not large, and the magnesium content of the wheat in the peptide calcium salt group is obviously reduced in the jointing stage I.

FIG. 11 shows the magnesium content absorbed by the overground part of wheat in different growth periods in Cd2 soil, and FIG. 12 shows the magnesium content absorbed by the underground part of wheat in different growth periods in Cd2 soil.

As shown in figure 11, under the concentration of Cd2, the magnesium content of the overground part of the wheat in the compound fertilizer group is higher than that of the wheat in the peptide calcium salt group, and the magnesium content of the overground part of the wheat has no obvious trend of rising and falling along with the growth of the wheat.

As shown in FIG. 12, when the magnesium content of underground part of wheat under Cd2 concentration is observed, the magnesium content of wheat in the peptide calcium salt group shows that the value of seedling stage I is lower than that of seedling stage II, the value of seedling stage II is higher than that of jointing stage I, and the value of jointing stage I is lower than that of jointing stage II, thus showing the trend of increasing first, then decreasing and then increasing; the magnesium content of the underground part of the wheat of the compound fertilizer group shows a descending trend between a seedling stage I and an elongation stage I, and the elongation stage I shows an ascending trend between an elongation stage II.

FIG. 13 shows the magnesium content absorbed by the overground part of wheat in different growth periods in Cd5 soil, and FIG. 14 shows the magnesium content absorbed by the underground part of wheat in different growth periods in Cd5 soil.

As shown in FIG. 13, the magnesium content of the overground part of the wheat of the compound fertilizer group under the Cd5 concentration is generally higher than that of the wheat of the peptide calcium salt group, and the magnesium content of the overground part has no particularly obvious trend of rising and falling along with the growth of the wheat.

As shown in FIG. 14, the magnesium content of the underground part of wheat in the peptide calcium salt group is generally higher than that of the wheat in the compound fertilizer group.

Through the research on the influence effect of the peptide calcium salt on the absorption of magnesium element by wheat in the acid soil, the following conclusion is reached:

only in the case of 5mg/kg cadmium concentration, the magnesium content of the part of the wheat underground to which the peptide calcium salt is applied is higher than that of the wheat to which the compound fertilizer is applied, and in other cadmium concentrations, the magnesium content of the wheat to which the peptide calcium salt is applied is lower in the parts above and below the ground. The effect of the peptide calcium salt on the absorption of magnesium ions by the wheat roots is particularly obvious in a high-concentration cadmium environment.

Because the peptide calcium salt is an organic fertilizer rich in calcium element, under the condition that the calcium concentration of crops is increased due to a saturated transportation mechanism, the crops generally need to absorb more calcium element and less magnesium element; and because of the existence of a large amount of cadmium element in the environment with high cadmium concentration, the absorption of magnesium is also inhibited.

Thus, it is theorized that the amount of magnesium ions absorbed by the wheat of the peptide calcium salt group should be lower than that of the wheat of the complex salt group, and the experiment with Cd5 shows that the underground part of the wheat can maintain a higher magnesium content in the case of the application of the peptide calcium salt than in the case of the application of the compound fertilizer.

As mentioned in the background, the activated aluminum is more in acid soil, and the existence of the activated aluminum and cadmium ions in the soil is easy to poison the root system of crops. And the large amount of magnesium stored in the root system is beneficial to the biochemical reaction in the root system, promotes the generation of nutrient substances, such as vitamin A, vitamin C and the like, is also beneficial to the biosynthesis of DNA and RNA, and can stabilize the ribosome configuration necessary for the protein synthesis in the root system.

Therefore, the peptide calcium salt has obvious advantages for crops planted in the acid soil polluted by high-concentration heavy metal, and has obvious practical significance for agricultural development in China.

In conclusion, the peptide calcium salt prepared by the embodiment can promote the absorption of crops on magnesium element when being applied to the acid soil polluted by high-concentration cadmium, and is beneficial to the generation of nutrient substances in the root systems of the crops.

It should be noted that the above embodiments are only examples, and those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be construed as the protection scope of the present invention.

Claims

1. The application of the modifying agent in promoting magnesium absorption of the underground part of crops under the high-cadmium-polluted acid soil is characterized in that the preparing method of the modifying agent is as follows:

mixing a calcium source raw material and a solvent to obtain calcium-containing emulsion;

mixing a protein raw material with the calcium-containing emulsion, and uniformly stirring to obtain a mixed solution;

reacting the mixed solution under a heating condition, filtering to obtain a filtrate after the reaction is finished, and concentrating the filtrate to a concentrated solution with the concentration of 20-30%;

the protein raw material comprises protein waste, and the protein waste is selected from one or a mixture of at least two of plant protein waste, microbial thallus, sludge, animal hair, animal hoof and horn and blood.

2. Use according to claim 1, wherein the crop plants are selected from wheat.

3. The use of claim 1, wherein the concentration of Cd in the high-cadmium-polluted acidic soil is not less than 4mg/kg, preferably more than 4.8 mg/kg.