Method for regulating and controlling available phosphorus content in soil based on organic carbon-inorganic carbon

Abstract

The invention discloses a method for regulating and controlling the content of available phosphorus in soil based on organic carbon-inorganic carbon, and belongs to the technical field of cultivated land conservation. The preparation method comprises the following steps: firstly, carrying out carbonization treatment on straws to obtain straw biochar; uniformly mixing the basalt powder, the straw biochar and the soil to form mixed soil, and planting crops for cultivation. After the soil is cultivated by the method, the contents of organic carbon and inorganic carbon in the soil are increased, so that the content of available phosphorus is regulated and controlled; and the crop growth condition is good.

Description

Technical Field

[0001] The present invention relates to a method for regulating the available phosphorus content in soil based on organic carbon-inorganic carbon, belonging to the technical field of cultivated land conservation. Background Art

[0002] Yunnan is a major tobacco production base in China. In recent years, due to climate change and farmers' inaccurate soil conservation practices, the style and quality characteristics of tobacco leaves produced there have become unstable, and even weakened. Tobacco quality is influenced by a variety of factors, including climate and soil. Climate is the primary controlling factor, but it's difficult to regulate. Therefore, suitable soil is crucial for high-quality tobacco production.

[0003] The inventors' previous research revealed that the primary obstacle to tobacco-growing soil in Lijiang is low soil phosphorus content, which leads to an imbalance between supply and demand. Excessive nitrate nitrogen stimulates excessive phenolic acid secretion from flue-cured tobacco roots, and the high abundance of slime molds, Desulfobacterium, Methanogenes, Mucor, and SAR bacteria, which are detrimental to the accumulation of chemical components in tobacco leaves. The primary obstacle to tobacco-growing soil in Chuxiong is low soil phosphorus content, which leads to an imbalance between supply and demand and a reduced abundance of Gemmatimonas, which is detrimental to the accumulation of chemical components in tobacco leaves. In other words, soil phosphorus imbalance is the primary obstacle to tobacco leaf chemical composition in both regions. Therefore, regulating the availability of soil phosphorus is expected to effectively improve tobacco leaf quality in both Lijiang and Chuxiong tobacco-growing areas.

[0004] Currently, soil phosphorus levels are primarily regulated through the application of phosphate fertilizers, organic fertilizers, lime, returning straw to the fields, and soil conditioners. While these methods are convenient and fast, in practice, it's difficult to ensure that fertilizers deliver effective phosphorus on demand based on tobacco plant growth, making them less eco-friendly and sustainable. Furthermore, the application of fertilizers doesn't guarantee that all of the fertilizer is available for plant absorption and utilization. Therefore, increasing the amount of phosphorus in the soil that can be absorbed and utilized by plants—that is, available phosphorus—is crucial.

[0005] In addition, conventional soil conservation technologies such as organic fertilizers, biochar, straw application, and crop rotation are generally used to achieve carbon sequestration and emission reduction, which basically increase the content of organic carbon, and rarely mention the increase of inorganic carbon. However, there are differences between organic carbon and inorganic carbon, such as: (1) different sources: organic carbon mainly comes from animal and plant residues, microorganisms and their metabolites; inorganic carbon includes bicarbonate in soil solution, carbon dioxide and calcium carbonate deposited in soil; (2) functional differences: organic carbon focuses more on improving soil biological activity and fertility, and participates in complex biogeochemical cycles; inorganic carbon is more involved in regulating soil chemical properties, such as pH control and mineral nutrition supply; (3) different stability: organic carbon is less stable, is greatly affected by microbial decomposition, and is easy to transform; inorganic carbon is relatively stable, especially calcium carbonate, which is not easily affected by microbial activity.

[0006] In addition, there is no literature mentioning how to simultaneously increase the content of organic carbon and inorganic carbon, and no literature mentioning how to regulate the available phosphorus content in the soil based on organic carbon and inorganic carbon. Summary of the Invention

[0007] [Technical Issues]

[0008] It is difficult to supply effective phosphorus on demand by conventionally applying fertilizer to increase phosphorus content;

[0009] Conventional methods to improve soil properties only focus on increasing the organic carbon content, with little attention paid to the inorganic carbon content.

[0010] [Technical solution]

[0011] To address these issues, the present invention first carbonizes straw to produce straw biochar. Basalt powder, straw biochar, and soil are then mixed to form a mixed soil, which is then planted with crops for cultivation. This method increases the organic and inorganic carbon content in the soil, thereby regulating the available phosphorus content, and promotes good crop growth.

[0012] The first object of the present invention is to provide a method for regulating the available phosphorus content in soil based on organic carbon-inorganic carbon, comprising the following steps:

[0013] The basalt powder, straw biochar and soil are evenly mixed to form mixed soil, and then crops are planted for cultivation.

[0014] In one embodiment of the present invention, the particle size of the straw biochar is below 10 mesh, more preferably 10-100 mesh.

[0015] In one embodiment of the present invention, the preparation method of straw biochar is as follows:

[0016] The straw is heated to 500-550° C. at a heating rate of 5-15° C. / min under a nitrogen atmosphere (nitrogen flow rate of 180-200 mL / min), carbonized at a constant temperature of 2-4 h, cooled, and sieved to obtain the product.

[0017] In one embodiment of the present invention, the pH of the soil is between 6-9.

[0018] In one embodiment of the present invention, the straw is one or more of wheat straw, tobacco straw, rice straw, and corn straw.

[0019] In one embodiment of the present invention, the particle size of the basalt powder is 200-400 mesh.

[0020] In one embodiment of the present invention, the mass ratio of basalt powder, straw biochar and soil is 0.2-0.8:0.8-1:100.

[0021] In one embodiment of the present invention, the crop is one of tobacco, spider plant, succulent, gardenia, wheat, barley, garlic, and corn.

[0022] In one embodiment of the present invention, fertilization is performed as needed during the cultivation process.

[0023] A second object of the present invention is to provide a method for increasing the availability of phosphorus in soil, the method comprising the following steps:

[0024] The basalt powder, straw biochar and soil are evenly mixed to form mixed soil, and then crops are planted for cultivation.

[0025] A third object of the present invention is to provide a method for improving tobacco leaf quality by increasing the organic carbon-inorganic carbon content in soil, comprising the following steps:

[0026] The basalt powder, straw biochar and soil are evenly mixed to form mixed soil, and then crops are planted for cultivation.

[0027] A fourth object of the present invention is to provide a method for improving tobacco leaf quality based on increasing available phosphorus content, comprising the following steps:

[0028] The basalt powder, straw biochar and soil are evenly mixed to form mixed soil, and then crops are planted for cultivation.

[0029] A fifth object of the present invention is to provide a method for carbon sequestration and emission reduction based on increasing the organic carbon-inorganic carbon content in soil, comprising the following steps:

[0030] The basalt powder, straw biochar and soil are evenly mixed to form mixed soil, and then crops are planted for cultivation.

[0031] The sixth object of the present invention is the application of the method according to the present invention in the field of agriculture.

[0032] In one embodiment of the present invention, the agricultural field includes soil improvement, improvement of crop quality, etc.

[0033] [Beneficial Effects]

[0034] (1) The present invention uses basalt powder combined with straw biochar to reduce soil acidification, and increases the soil available phosphorus (AP), soil inorganic carbon (SIC) and organic carbon (SOC) contents by 17.93-65.77%, 13.83-20.95% and 6.72-14.95% after tobacco grows to maturity.

[0035] (2) The present invention uses an appropriate amount of basalt combined with straw biochar to optimize the supply and demand of soil nutrients, so that the contents of effective Fe, Cu, Zn, exchangeable Ca, and Mg in tobacco after growth to maturity are increased by 4.54-15.09%, 6.63-19.12%, 5.66-40.18%, 9.22-11.18%, and 0.17-4.25%, respectively; at the same time, the abundance of Proteobacteria, Actinomycetes, and Bacteroidetes is increased.

[0036] (3) The present invention uses basalt combined with straw biochar treatment to optimize tobacco leaf quality. Compared with the control treatment of applying tobacco-specific fertilizer alone, the reducing sugar, total sugar and nicotine contents in the tobacco leaves increased by 95.80-116.80%, 54.02-64.86% and 38.22-44.59% after the tobacco leaves reached maturity.

[0037] (4) Under the basalt combined with straw biochar treatment, the total sugar and nicotine content and chemical coordination of tobacco leaves were closer to the standards of high-quality tobacco leaves. It was significantly better than other treatments in terms of biomass, plant height, stem girth, maximum leaf length and effective leaf number. The increase in biomass and effective leaf number was 46.90% and 30% higher than that of the pure biochar treatment, respectively.

[0038] (5) The present invention further improves the yield and quality of tobacco leaves by adding basalt powder to straw biochar to weaken the limitation of phosphorus availability and regulating the availability of K and trace element Fe.

[0039] (6) Compared with biochar alone, the basalt combined with biochar treatment showed varying degrees of reduction in total CO2 and N2O emissions throughout the entire growth period. The reduction in soil CO2 and N2O emissions reached 22.04-72.93% and 3.68-23.40%, respectively. The reduction effect was not linearly related to the amount of basalt added. The 0.6% basalt combined with biochar treatment had the most significant effect on CO2 reduction, while the 0.4% basalt combined with biochar treatment had the best effect on N2O reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Effects of Examples 1-4 on soil pH (a), SIC (b), SOC (c) and TN (d) at different times.

[0041] Figure 2 The effects of Examples 1-4 on the soil available copper (a), exchangeable calcium (b), cation exchange capacity (c), available iron (d), exchangeable magnesium (e) and available zinc (f) contents at different times.

[0042] Figure 3The effects of Examples 1-4 on the relative abundance (%) of bacterial communities at different periods.

[0043] Figure 4 The effects of Examples 1-4 on the relative abundance (%) of fungal communities at different periods.

[0044] Figure 5 This is the effect of Examples 1-4 on the total cumulative emissions of soil CO2 and N2O during the tobacco growth period. DETAILED DESCRIPTION

[0045] The following describes preferred embodiments of the present invention. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0046] Test method:

[0047] 1. Determination of soil physical and chemical indicators:

[0048] Soil pH: The pH of soil samples was measured using a pH meter (FE28, Mettler-Toledo, Switzerland) in a 1:2.5 soil / water (w / v, g / mL) supernatant;

[0049] Soil total carbon (TC) and total nitrogen (TN): 5 mg of air-dried soil passed through a 100-mesh sieve was weighed and packed in a tin boat, and then measured using an elemental analyzer (Vario MICRO cube, Elemental, Germany).

[0050] Soil ammonia nitrogen (NH4 + -N), nitrate nitrogen (NO3 - -N): measured using a spectrophotometer (P4 PC, Shanghai Meipuda Co., Ltd., China) in accordance with the environmental industry standard (HJ 634-2012) and the national standard (GB / T 32737-2016);

[0051] Soil available phosphorus (AP): measured using a spectrophotometer (same as above) according to the agricultural industry standard (NY / T 1121.7-2014);

[0052] Soil chlorine (Cl): measured using a continuous flow analyzer (AA3, SEAL Analytical, UK) according to the agricultural industry standard (NY / T 1378-2007);

[0053] Soil available potassium (AK): measured using a flame photometer (A3F, Beijing Puxi General Instrument, China) according to the national standard (NY / T889-2004);

[0054] Soil total phosphorus (TP), total potassium (TK), and nutrient elements (Ca, Mg, Fe, Mn, Cu, Zn, and Mo): Determined according to the method described by Rao De'an et al. (Rao De'an. Research on the restoration technology of flue-cured tobacco continuous cropping soil and its application effect [D]. Jiangnan University, 2021. DOI: 10.27169 / d.cnki.gwqgu.2021.001687.). Soil samples were digested (Multiwave PRO, Anto Paar, Austria) and then analyzed by ICP-OES (Optima 8300, PerkinElmer, USA).

[0055] Soil inorganic carbon (SIC) determination: Take a small amount of soil in a conical flask, add 10mL hydrochloric acid (1mol·L -1 HCl), sealed and placed overnight, the acid-soluble matter was filtered off, washed until neutral, the precipitate was dried until neutral, crushed and passed through a 2 mm sieve, 5.000 g of sample was weighed and placed in a high-temperature resistance furnace (MXX1600-30, Microx, USA), calcined at 1050 ° C in the presence of oxygen for 2 h, cooled and weighed;

[0056] Soil organic carbon (SOC): measured using a spectrophotometer according to industry standards (HJ 615-2011);

[0057] The soil samples at each location were tested three times.

[0058] 2. Determination of chemical composition of tobacco leaves:

[0059] Flue-cured tobacco leaf samples of grade C3F representing the middle leaves in the survey area were selected to determine the chemical composition of the tobacco leaves.

[0060] The specific measurement indicators and methods are as follows:

[0061] Total alkali: Weigh 1.0 g of evenly ground tobacco leaf sample and extract with a mixture of 70% ethanol and 30% water. Centrifuge at 4000 rpm for 15 min, and collect the supernatant. Determine the total alkali content using a continuous flow analyzer according to YC / T 160-2002.

[0062] Total nitrogen: Weigh 0.5 g of evenly ground tobacco leaf sample and add 10 mL of a 4:1 sulfuric acid-hydrogen peroxide mixture into a digestion tube. Digest thoroughly at 300°C, then cool and dilute to 50 mL. Determine total nitrogen using a continuous flow analyzer according to YC / T161-2002.

[0063] Total sugar and reducing sugar: Weigh 0.5g of evenly ground tobacco leaf powder, transfer it to a filter paper tube, and soak in 80°C hot water for 30 minutes. After extraction, clarify and filter to obtain a sample solution. Determine the total sugar and reducing sugar using a continuous flow analyzer according to YC / T 159-2002.

[0064] Potassium: Weigh 0.5 g of evenly ground tobacco leaf sample, ash it in a muffle furnace (550°C) to constant weight, transfer the ash into a beaker, and add an appropriate amount of 2 mol·L -1 Dissolve dilute nitric acid in agitated, heated solution until completely dissolved. After cooling, dilute to 50 mL with water and shake well to obtain the sample solution. Measure using a continuous flow analyzer according to YC / T 217-2007.

[0065] The raw materials used in the embodiment are:

[0066] Soil: Surface soil was collected from tobacco fields along the Jinsha River (adjacent to the G353 Highway), bagged, and transported to the laboratory. Air-dried indoors, roots and rocks were removed, and the soil was passed through a 5 mm sieve and mixed thoroughly for use as potting soil. The soil is alluvial soil from the Jinsha River. Basic physical and chemical properties are: pH 7.07, total carbon 14.09 g / kg, total phosphorus 0.85 g / kg, available phosphorus 35.43 mg / kg, total potassium 9.51 g / kg, and available potassium 174.49 mg / kg.

[0067] Tobacco seedlings: Yunyan 87 tobacco seedlings are grown using floating seedling cultivation. The seedling cultivation cycle is 2 months and is completed by tobacco farmers at the seedling cultivation center in Hongyan Village, Shigu Town, Yulong County. After the seedlings are grown, they are transported to the sunroom of the Dongyu Campus of Jiangnan University. Seven-leaf, one-heart tobacco seedlings with similar growth characteristics are selected and transplanted within 1-2 days.

[0068] Basalt powder: Basalt was purchased from the Shijiazhuang Mineral Products Factory in Hebei Province. The purchased basalt was washed and dried, crushed, and passed through a 300-mesh sieve for later use. Basic physical and chemical properties are as follows: pH 8.34, total phosphorus 175.00 g / kg, total potassium 36.05 g / kg, total calcium 234.30 g / kg, total magnesium 5.28 g / kg, total iron 0.2 g / kg, total manganese 1.02 mg / kg, total copper 5.28 mg / kg, and total zinc 1.37 mg / kg.

[0069] Flower pot: Made of polypropylene (PP) material with a diameter of 38 cm, a bottom diameter of 32 cm, and a height of 25 cm. The volume is 25L, with 6 drainage holes at the bottom. Each pot can hold 25kg of soil.

[0070] Tobacco fertilizer: purchased from Yunnan Yunzhiye Biotechnology Co., Ltd.; the basic composition is as follows: total nutrients ≥ 45%, N:P2O5:K2O = 15:15:15, it is a high-concentration compound fertilizer with a high nitrate nitrogen content and can be used as a base fertilizer and topdressing;

[0071] Wheat straw raw material: purchased from Henan Neixiang County Senmiao Energy Saving Technology Co., Ltd.;

[0072] Composting straw: Crush wheat straw (1-2 cm), mix it with composting agent and urea, adjust the moisture content to about 60%, and place the mixture in an environment with a temperature of 45-55°C and a humidity of 60-70%. When the straw color becomes noticeably darker, the texture becomes loose and brittle, the C / N ratio drops below 25:1, and the microbial activity weakens, the straw is fully composted.

[0073] Straw biochar: Wheat straw raw material was placed in a closed oxygen-limited drawer carbonization furnace for carbonization. First, nitrogen was passed through for 30 minutes to expel the air. Under the protection of N2 flow (200 mL / min), the temperature was increased to 500°C at a rate of 10°C / min and carbonized at a constant temperature for 2 hours. The product was cooled and crushed, passed through a 10-mesh sieve, and dried at 65°C to constant weight to obtain straw biochar.

[0074] The basic properties of wheat straw raw material, decomposed straw, straw biochar, and decomposed straw + straw biochar (mass ratio 1:1) are as follows:

[0075] Table 1 Basic properties of wheat straw with different carbon forms

[0076]

[0077] Potting method:

[0078] Transplant the seedlings (about 60 days old). Dig a pond before planting with a diameter of 30 cm and a depth of 15 cm. Pour 3 L of rooting water into each pond. Transplant and cover the pots with film when the rooting water is about to fall. There are 4 plants in each pot. When the seedling-returning period is over, remove the weaker plants. Leave one plant in each pot. The row spacing × plant spacing = 60 cm × 50 cm. Remove the film and add soil 35-40 days after planting. When the seedling-returning period is over, remove the weaker plants. Leave one plant in each pot. The row spacing × plant spacing = 60 cm × 50 cm.

[0079] Example 1 CSC4

[0080] A method for simultaneously increasing the available phosphorus and inorganic carbon contents in soil comprises the following steps:

[0081] 100 g of basalt powder, 225 g of straw biochar, and 25 kg of soil were mixed evenly to form mixed soil;

[0082] The mixed soil was placed in a flowerpot, and tobacco seedlings were transplanted. Fertilizer (a tobacco-specific fertilizer solution with a mass concentration of 3%, 1 L / plant) was applied at 15 and 40 days; and cultivation was continued.

[0083] Example 2CSC2

[0084] The amount of basalt powder in Example 1 was adjusted to 50 g; the other ingredients remained the same as in Example 1.

[0085] Example 3CSC6

[0086] The amount of basalt powder in Example 1 was adjusted to 150 g; the other ingredients remained the same as in Example 1.

[0087] Example 4CSC8

[0088] The amount of basalt powder in Example 1 was adjusted to 200 g; the other parameters remained the same as in Example 1.

[0089] Comparative Example 1CSC0

[0090] The amount of basalt powder in Example 1 was adjusted to 0 g; the other contents remained the same as in Example 1.

[0091] Samples were taken for testing during the rooting stage (40 days), vigorous growth stage (70 days), and maturity stage (120 days) of tobacco seedlings. The test results are as follows:

[0092] Table 2 Physical and chemical properties of soil

[0093]

[0094] Table 2 shows the test results of soil physical and chemical properties. It can be seen from Table 2 that during the flue-cured tobacco growth period, the soil pH of each treatment first increased and then decreased. Compared with the 40th day, the soil pH of the basalt combined with biochar treatment increased by 0.02-0.15 units on the 120th day, while the pH of the biochar treatment alone decreased by 0.23 units. The SIC content of the CSC2, CSC4, and CSC6 treatments was significantly higher than that of the CSC0 treatment at all stages (P<0.05). Compared with CSC0, the SIC content of the CSC2, CSC4, CSC6, and CSC8 treatments increased significantly on the 120th day, by 13.83%, 20.95%, 17.39%, and 19.76%, respectively. This is because the silicates in the basalt react with soil carbonate (CO2+H2O) to produce HCO3 - , which increases the alkalinity of the soil. Basalt releases a large amount of alkaline cations, which can increase the soil's ability to sequester CO2. Therefore, the addition of basalt significantly increased the SIC of tobacco-growing soils. The SOC content of each treatment soil gradually decreased with the growth period of flue-cured tobacco. Compared with the biochar treatment alone, the soil SOC increased significantly under the basalt combined with biochar treatment on the 120th day, with an increase ranging from 6.72-14.95%. Due to the enhanced activity of soil microorganisms leading to the decomposition of organic matter and the fixation of nutrients by basalt, the basalt combined with biochar resulted in more organic carbon accumulation in the soil compared with pure biochar application. Compared with the 40th day, the TP reduction in the soil under the CSC0 treatment was 1.27g·kg on the 120th day. -1, while soil TP reductions in the CSC2, CSC4, CSC6, and CSC8 treatments were 1.05-, 1.06-, 1.13-, and 1.19-fold higher than those in the CSC0 treatment, respectively. Compared to the CSC0 treatment, AP content increased by 17.93%, 16.68%, 41.43%, and 65.77% in the CSC2, CSC4, CSC6, and CSC8 treatments on day 120, respectively. This is due, on the one hand, to the increasing demand for phosphorus during the root extension phase, peaking during the growth phase, and a decrease in soil AP uptake during the maturity phase. On the other hand, the alkaline components in basalt (such as calcium and magnesium) neutralize soil acidity, reducing the fixation of phosphorus with metal ions such as aluminum and iron, increasing phosphorus availability and promoting tobacco uptake. In summary, compared with biochar alone, basalt combined with biochar during the tobacco maturity phase mitigated soil acidification, promoted phosphorus transformation, and significantly increased soil SIC, SOC, and AP content.

[0095] Table 3 Effects of treatments at different stages on the growth of flue-cured tobacco

[0096]

[0097] Note: Lowercase letters represent significant differences (P<0.05)

[0098] Table 3 shows the effects of various treatments on flue-cured tobacco growth at different stages. As can be seen from Table 3, at maturity, the CSC4 treatment significantly outperformed the other treatments in biomass, plant height, stem girth, and number of effective leaves. The increases in biomass and effective leaf number were particularly significant (46.90% and 30% higher than those in the CSC0 treatment, respectively). The biomass, plant height, and number of effective leaves of all treatments increased significantly from the vigorous growth stage to the mature stage. Stem girth increased significantly from the root extension stage to the vigorous growth stage, with no significant differences between the treatments. In summary, the CSC4 treatment had the most significant overall promoting effect on flue-cured tobacco growth and development, while the CSC2 treatment showed an advantage in maximum leaf width.

[0099] Table 4 shows the effects of different treatments on the chemical composition of tobacco leaves at day 120. As can be seen, there were significant differences in the total chemical composition of the tobacco leaves among the treatments, with the order CSC4 > CSC2 > CSC8 > CSC6 > CSC0. This indicates that adding basalt can increase the total chemical composition of tobacco leaves within a certain range, with CSC4 being the most effective. There were no significant differences in total nitrogen and potassium content among the treatments, ranging from 2.82-3.10% and 2.11-2.27%, respectively, both meeting the standards for high-quality tobacco leaves. Nicotine content in the tobacco leaves ranged from 2.02-2.27% across all treatments, meeting the standards for high-quality tobacco leaves. Clearly, the addition of biochar and varying proportions of basalt had little effect on nitrogen and potassium content. Furthermore, compared to the CSC0 treatment, nicotine content increased by 7.23%, 12.21%, 4.99%, and 1.42% in the CSC2, CSC4, CSC6, and CSC8 treatments, respectively, suggesting that basalt addition may help increase nicotine content in tobacco leaves. The total sugar content of tobacco leaves in the CSC4 treatment was 18.86%, meeting the standard for high-quality tobacco leaves. With the exception of the CSC4 treatment, the total sugar content in tobacco leaves in the CSC2 treatment was significantly higher than in the other treatments (P < 0.05). Its total sugar content fell 0.38 percentage points short of the standard threshold for high-quality tobacco leaves, which is 1.13 times the total sugar content in tobacco leaves in the CSC0 treatment. The reducing sugar content in tobacco leaves in the CSC2 treatment was significantly higher than in the other treatments, with its reducing sugar content falling 0.58% short of the standard threshold for high-quality tobacco leaves. Furthermore, compared to CSC0, nicotine content increased by 25.20%, 13.04%, 14.32%, and 10.62% in treatments CSC2, CSC4, CSC6, and CSC8, respectively, indicating that the addition of basalt improves tobacco leaf sweetness. In summary, the CSC4 and CSC2 treatments demonstrated significant improvements in tobacco leaf quality, with the CSC4 treatment, in particular, approaching high-quality tobacco leaf standards in terms of total sugar content, nicotine content, and chemical compatibility. Furthermore, total nitrogen content in tobacco leaves from all treatments exceeded the standard threshold, with the CSC6 treatment exhibiting the smallest deviation from the standard. Given that the difference between the two sugars, the sugar-to-alkali ratio, and the alkali-to-nitrogen ratio are closely correlated with tobacco leaf smoking quality, it is likely that all treatments possessed good sensory qualities.

[0100] Table 4 Effects of different treatments on the chemical composition of tobacco leaves on day 120

[0101]

[0102] Figure 1 The effects of Examples 1-4 on soil pH (a), SIC (b), SOC (c) and TN (d) at different times are shown; Figure 1It can be seen that during the flue-cured tobacco growth period, soil pH in all treatments initially increased and then decreased. Compared to day 40, soil pH in the basalt combined with biochar treatment increased by 0.02-0.15 units at day 120, while the pH in the biochar treatment alone decreased by 0.23 units. Compared to biochar alone, the basalt combined with biochar treatment increased soil pH and reduced soil acidification during the tobacco maturity period, significantly increasing soil SIC and SOC contents by 13.83-20.95% and 6.72-14.95% respectively. Compared to the biochar treatment alone, soil TN decreased in the basalt combined with biochar treatment at days 40 and 70. However, the combined basalt and biochar treatment had no significant effect on TN at day 120 during the tobacco maturity period.

[0103] Figure 2 The effects of Examples 1-4 on the soil's available copper (a), exchangeable calcium (b), cation exchange capacity (c), available iron (d), exchangeable magnesium (e), and available zinc (f) contents at different times are shown. Figure 2 It can be seen that the decrease in soil CEC content was not significant under any of the treatments. The available Fe content in the soil showed an increasing trend across the different treatments. Compared with CSC0, the available Fe content in the CSC2 treatment at maturity increased most significantly (P < 0.05), reaching 15.09%. Overall, the available Cu and Zn content in the soils of most treatments showed an initial increase followed by a decrease during the flue-cured tobacco growth cycle. Compared with CSC0, the available Cu and Zn content in the CSC2 treatment at maturity increased most significantly (P < 0.05), reaching 19.12% and 40.18%, respectively. Overall, the available Ca and Mg content in the soils of most treatments showed an initial decrease followed by an increase during the flue-cured tobacco growth cycle. Compared with CSC0, the available Mg content in the CSC2 and CSC6 treatments at maturity increased most significantly (P < 0.05), reaching 4.25% and 5.43%, respectively. The available Ca content in the CSC2 and CSC4 treatments at maturity increased most significantly (P < 0.05), reaching 11.18% and 9.22%, respectively. This can be attributed to the rich content of phosphorus, potassium, calcium, magnesium, iron, and copper in basalt, which replenishes nutrients needed by the soil, improves soil structure, and enhances nutrient retention. Furthermore, biochar and basalt may influence the availability of trace elements through adsorption, complexation, and ion exchange. The alkaline components in basalt and biochar may increase the availability of trace elements such as Fe, Ca, and Mg. The decline in Cu and Zn in the late growth period may be related to factors such as tobacco absorption and mineralization of nutrients in root exudates.

[0104] Figure 3 The effects of Examples 1-4 on the relative abundance (%) of bacterial communities at different times are shown in Table 1. Figure 3The relative abundance of Proteobacteria in the bacterial communities showed an overall trend of increasing first and then decreasing across the tobacco growth cycle under the different treatments. Compared to the biochar-only treatment, the relative abundance of Proteobacteria increased by 1-5% in the biochar-plus-basalt treatment. The relative abundance of Actinobacteria also showed an increasing-then-decreasing trend across all treatments. Compared to the CSC0 treatment, the relative abundance of Actinobacteria increased by 1% and 2%, respectively, in the CSC2 and CSC4 treatments at day 120, while it decreased in the CSC6 and CSC6 treatments. The relative abundance of Firmicutes also showed a decreasing-then-increasing trend across all treatments. Compared to day 40, Firmicutes decreased by 16% and 20%, respectively, in the CSC2 and CSC4 treatments at day 120, significantly exceeding the 8%, 4%, and 7%, respectively, observed in the CSC6, CSC8, and CSC0 treatments. Compared to day 40, the relative abundance of Acidobacteria increased by 1-3% in the biochar combined with basalt treatment at day 120. Compared to the biochar alone treatment, the relative abundance of Acidobacteria remained unchanged or slightly decreased (1%) in the biochar combined with basalt treatment at day 120. Compared to day 40, the relative abundance of Chloroflexus increased by 6%, 5%, and 4% in the CSC4, CSC6, and CSC8 treatments at day 70, respectively, exceeding the 2% observed in the CSC0 treatment. Compared to the biochar alone treatment, the relative abundance of Chloroflexus remained unchanged or decreased (1%) in the biochar combined with basalt treatment at day 120. The relative abundance of Bacteroidetes decreased first and then increased across the flue-cured tobacco growth cycle under the different treatments. Compared to day 40, the relative abundance of Bacteroidetes decreased by 1-4% in the biochar combined with basalt treatment, while it decreased by 5% in the biochar alone treatment. Compared to the biochar alone treatment, the relative abundance of Bacteroidetes increased (1%) in the biochar combined with basalt treatment at day 120. With the exception of CSC8, the relative abundance of Gemmatimonads in all treatments showed an initial increase followed by a decrease. Compared to the biochar-only treatment, the relative abundance of Gemmatimonads in the biochar plus basalt treatment remained unchanged or increased slightly (1%) on day 120. The relative abundance of Myxomycetes remained stable at approximately 1% across all treatments throughout the entire growth period.

[0105] Figure 4 The effects of Examples 1-4 on the relative abundance (%) of fungal communities at different times are shown in Table 1. Figure 4As can be seen, the relative abundance of Ascomycetes significantly increased under all treatments at day 120 compared to day 40. Compared to CSC0, the relative abundance of Ascomycetes increased by 1-5% under treatments CSC2, CSC4, and CSC6, while it decreased by 2% under CSC8. The relative abundance of Basidiomycetes decreased continuously throughout the growth period under the biochar treatment alone, while the biochar combined with basalt treatment showed an initial increase followed by a decrease. Compared to CSC0, the relative abundance of Basidiomycetes increased by 1% under CSC4 at day 120, while it decreased in the other treatments (2-3%). Overall, the relative abundance of Myxomycetes showed an initial increase followed by a decrease in all treatments, with the exception of CSC8. Compared to CSC0, the relative abundance of Myxomycetes remained unchanged or decreased (by 1%) under treatments CSC2, CSC4, and CSC6, while it increased by 1% under CSC8. With the exception of CSC8, the relative abundance of SAR bacteria ranged from 1-2% throughout the growth period under all treatments. Compared with the CSC0 treatment, the relative abundance of SAR bacteria decreased by 1% in the CSC2, CSC4, and CSC6 treatments, while it increased by 2% in the CSC8 treatment on day 120. The relative abundance of Mucor species increased in all treatments, reaching approximately 1% on day 120.

[0106] Figure 5 The effects of Examples 1-4 on the total cumulative emissions of soil CO2 and N2O during the tobacco growth period. Figure 5 It can be seen that during the entire growth period, compared with CSC0, the total CO2 emissions under the CSC2, CSC4, CSC6 and CSC8 treatments decreased by 22.04%, 31.20%, 72.93% and 36.55%, respectively, and the total N2O emissions decreased by 11.70%, 23.40%, 5.32% and 3.68%. Among them, the CSC6 treatment had the greatest CO2 emission reduction intensity, and the CSC4 treatment had the greatest N2O emission reduction intensity. In summary, the following findings were made: (1) The basalt combined with biochar treatment showed varying degrees of emission reduction effects on both CO2 and N2O emissions during the entire growth period. This indicates that the combined treatment of basalt and biochar has a positive effect on reducing greenhouse gas emissions; (2) The emission reduction effect is not linearly related to the amount of basalt added. The CSC6 treatment had the most significant CO2 emission reduction, while the CSC4 treatment had the best N2O emission reduction effect. This suggests that there is a more optimal basalt addition between the two, which can minimize greenhouse gas emissions while not affecting or even improving crop growth. (3) Biochar itself has the functions of absorbing nutrients, improving soil structure, and increasing microbial activity, indirectly affecting greenhouse gas emissions through these mechanisms. When used in combination with basalt, it may affect CO2 and N2O emissions by affecting soil carbon and nitrogen cycles and microbial processes.

[0107] Comparative Example 2NPK

[0108] Mix 20g of tobacco fertilizer and 25kg of soil to form mixed soil;

[0109] The mixed soil was placed in a flowerpot, and tobacco seedlings were transplanted. Fertilizer (a tobacco-specific fertilizer solution with a mass concentration of 3%, 1 L / plant) was applied at 15 and 40 days; and cultivation was continued.

[0110] Comparative Example 3NPKC

[0111] 20g of tobacco fertilizer, 365g of wheat straw raw material and 25kg of soil were mixed evenly to form mixed soil;

[0112] The mixed soil was placed in a flowerpot, and tobacco seedlings were transplanted. Fertilizer (a tobacco-specific fertilizer solution with a mass concentration of 3%, 1 L / plant) was applied at 15 and 40 days; and cultivation was continued.

[0113] Comparative Example 4 NPKD

[0114] Mix 20g of tobacco fertilizer, 585g of decomposed straw and 25kg of soil to form mixed soil;

[0115] The mixed soil was placed in a flowerpot, and tobacco seedlings were transplanted. Fertilizer (a tobacco-specific fertilizer solution with a mass concentration of 3%, 1 L / plant) was applied at 15 and 40 days; and cultivation was continued.

[0116] Comparative Example 5NPKB

[0117] Mix 20g of tobacco fertilizer, 325g of straw biochar, and 25kg of soil to form a mixed soil.

[0118] The mixed soil was placed in a flowerpot, and tobacco seedlings were transplanted. Fertilizer (a tobacco-specific fertilizer solution with a mass concentration of 3%, 1 L / plant) was applied at 15 and 40 days; and cultivation was continued.

[0119] Comparative Example 6NPKDB

[0120] Mix 20g of tobacco fertilizer, 162.5g of decomposed straw, 162.5g of straw biochar, and 25kg of soil to form mixed soil;

[0121] The mixed soil was placed in a flowerpot, and tobacco seedlings were transplanted. Fertilizer (a tobacco-specific fertilizer solution with a mass concentration of 3%, 1 L / plant) was applied at 15 and 40 days; and cultivation was continued.

[0122] Samples were taken for testing during the rooting stage (40 days), vigorous growth stage (70 days), and maturity stage (120 days) of tobacco seedlings. The test results are as follows:

[0123] Table 5 shows soil physical and chemical indicators. As can be seen from Table 5, soil pH showed a decreasing trend across the tobacco growth cycle under different treatments. Wheat straw with different carbon forms did not affect or increased soil pH during maturity. The NPKB treatment maintained significantly higher pH values ​​at days 70 and 120, 0.15 and 0.18 units higher than the NPK treatment, respectively. Soil TN content decreased due to nitrogen absorption by tobacco. Compared with the control, which only received tobacco-specific fertilizer, application of straw with different carbon forms significantly increased soil TN content at day 70. The NPKC treatment had higher soil TN content than the other treatments (P < 0.05). With the exception of the NPKC treatment, there were no significant differences in TN content across the other treatments at day 120. Soil TP content decreased across all treatments over the tobacco growth cycle, but remained relatively stable. Soil AP content gradually decreased. Compared with the NPK treatment, soil AP increased by 46.16%, 64.61%, 105.61%, and 55.33% under the NPKC, NPKD, NPKB, and NPKDB treatments, respectively, at 120 days. Among them, the NPKB treatment significantly increased soil AP content by 1.38-fold and 2.05-fold at 70 and 120 days, respectively, compared with the NPK treatment (P < 0.05).

[0124] Table 5 Soil physical and chemical indicators

[0125]

[0126] Table 6 shows the effects of different treatments on the chemical composition of tobacco leaves at day 120. As can be seen, nicotine and potassium content in tobacco leaves did not differ significantly among the treatments, ranging from 1.57-1.68% and 2.20-2.26%, respectively, meeting the standards for high-quality tobacco leaves. Total nitrogen content in tobacco leaves treated with NPK reached 5.52%, significantly exceeding the threshold for high-quality tobacco leaves. Total nitrogen content in tobacco leaves treated with NPKD, NPKDB, and NPKB ranged from 2.55-3.19%, also meeting the standards for high-quality tobacco leaves. Total sugar content in tobacco leaves treated with NPKB was significantly higher than that in the other treatments (P < 0.05). Its total sugar content was 1.74 percentage points below the threshold for high-quality tobacco leaves, but was 1.42 times that of the NPK treatment. Reducing sugar content in tobacco leaves did not differ significantly among the NPKD, NPKB, and NPKDB treatments, but was significantly higher than that in the NPK and NPKC treatments (P < 0.05). The study found that straw treatments with different carbon forms significantly increased the total sugar and reducing sugar content of tobacco leaves, while reducing total nitrogen content, bringing the leaves to or near the quality standard. Specifically, straw biochar treatment achieved high-quality tobacco leaf standards for total nitrogen, nicotine, and potassium, while also achieving a total sugar content of 16.24%, approaching the quality standard threshold.

[0127] Table 6 Effects of different treatments on the chemical composition of tobacco leaves on day 120

[0128]

[0129] Table 7 shows the soil organic carbon components. As can be seen, soil TC and SOC contents showed a decreasing trend across all treatments over the growing period. Compared to day 70, SOC decreased by 0.09-0.17% in the different carbon forms of straw treatments at day 120, with the NPK treatment showing the greatest decrease (0.17%). This reduction was 1.32-fold and 1.74-fold higher in the NPKB and NPKDB treatments, respectively. Furthermore, SOC content in the NPKB treatment was higher than in the other treatments at both stages (P < 0.05). MBC content varied significantly among the treatments. Compared to the NPK treatment, MBC content in the NPKD, NPKB, and NPKDB treatments increased significantly by 50.04%, 75.07%, and 141.74%, respectively, at day 120. Clearly, the NPKDB treatment had the greatest effect in increasing MBC. This may be due to the fact that the mature straw introduced a greater number of active microorganisms, and the adsorption and protective effects of biochar further promoted microbial proliferation. ROC (readily oxidizable organic carbon) in soil was significantly reduced under NPK and NPKC treatments at day 120 compared to day 70, while changes were minimal under the other treatments. At day 70, soil ROC content did not change significantly under the different treatments. At day 120, compared with NPK, straw treatments with different carbon forms increased ROC by 45.59%, 68.01% (P < 0.05), 100.01% (P < 0.05), and 72.06% (P < 0.05), respectively. Soil POC and DOC content did not change significantly under the different treatments at both days 70 and 120. Clearly, among the active soil organic carbon components, MBC and ROC were the most sensitive to the addition of exogenous straw with different carbon forms. This may be because POC is a more stable organic carbon component than MBC, ROC, and DOC, and therefore responds more slowly to changes. DOC is the most active and sensitive organic carbon component in soil. Although the addition of exogenous straw with different carbon forms increases its content, the increased absorption and consumption of DOC by MBC also leads to no significant changes in DOC content throughout the flue-cured tobacco growth period and across different treatments. Compared with tobacco fertilizer alone, straw treatment with different carbon forms significantly increased soil SOC accumulation during maturity, while having no significant effect on soil DOC and POC content. In particular, the application of straw biochar and mature straw significantly increased soil ROC and MBC content.

[0130] Table 7 Soil organic carbon components

[0131]

[0132] Although the present invention has been disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for regulating the available phosphorus content in soil based on organic carbon-inorganic carbon, characterized in that: The steps include: The basalt powder, straw biochar and soil are evenly mixed to form mixed soil, and then crops are planted for cultivation.

2. The method according to claim 1, characterized in that The mass ratio of basalt powder, straw biochar and soil is 0.2-0.8:0.8-1:

100.

3. The method according to claim 1, characterized in that The preparation method of straw biochar is as follows: The straw was heated to 500-550°C at a heating rate of 5-15°C / min under a nitrogen atmosphere and carbonized at a constant temperature for 2-4 hours, cooled, and sieved to obtain straw biochar.

4. The method according to claim 3, characterized in that The straw is one or more of wheat straw, tobacco straw, rice straw and corn straw.

5. The method according to claim 1, characterized in that The soil pH is between 6-9.

6. A method for increasing the availability ratio of phosphorus in soil, characterized in that: The steps include: The basalt powder, straw biochar and soil are evenly mixed to form mixed soil, and then crops are planted for cultivation.

7. A method for improving tobacco leaf quality by increasing the organic carbon-inorganic carbon content in soil, characterized in that: The steps include: The basalt powder, straw biochar and soil are evenly mixed to form mixed soil, and then crops are planted for cultivation.

8. A method for improving tobacco leaf quality based on increasing available phosphorus content, characterized in that: The steps include: The basalt powder, straw biochar and soil are evenly mixed to form mixed soil, and then crops are planted for cultivation.

9. A method for carbon sequestration and emission reduction based on increasing the organic carbon-inorganic carbon content in the soil, characterized in that: The steps include: The basalt powder, straw biochar and soil are evenly mixed to form mixed soil, and then crops are planted for cultivation.

10. Use of the method according to any one of claims 1 to 9 in the agricultural field.

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