Method for evaluating influence of fulvic acid and different phosphorus application amounts on cotton root system productivity and cotton yield

Abstract

The invention discloses a method for evaluating the influence of fulvic acid and phosphate fertilizer on the productivity and yield of a cotton root system. The method comprises the following steps: step 1, designing five treatments by adopting a random complete block; 2, sampling and analyzing the treated plants; step 3, obtaining the cotton yield and composition factors; 4, evaluating the cotton root system productivity through the root system boll carrying amount and the root system boll forming capacity; 5, measuring the content of non-structural carbohydrates in the cotton root system; 6, measuring the photosynthetic capacity of the cotton; and step 7, carrying out single factor variance analysis and multiple comparison through software, and analyzing the correlation among the cotton yield, photosynthetic ability, root system productivity and root system carbohydrate content so as to evaluate the influence of fulvic acid and phosphate fertilizer on the cotton root system productivity and yield. The invention provides the method for evaluating the influence of fulvic acid and phosphate fertilizer on the productivity and yield of the cotton root system, and the optimal combined application scheme of the phosphate fertilizer and fulvic acid is defined so as to improve the productivity and yield of the cotton root system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of cotton yield increase. More specifically, the present application relates to a method for evaluating the effects of fulvic acid and different phosphorus application amounts on cotton root productivity and cotton yield. BACKGROUND

[0002] Cotton (Gossypium hirsutum L) is the most important economic and fiber crop in Xinjiang Uygur Autonomous Region, China, accounting for 90% of the total cotton yield in the country. The high degree of soil salinization in Xinjiang Uygur Autonomous Region leads to the immobilization of most applied phosphorus fertilizer, making it difficult for cotton to directly absorb and utilize it, which significantly restricts cotton production and highlights the key problem of insufficient available phosphorus in the soil. Excessive application of phosphorus fertilizer not only causes resource waste but also increases the risk of phosphorus loss and leads to water eutrophication. Therefore, there is an urgent need to explore alternative phosphorus fertilizer management measures to ensure high yield and sustainable production of cotton in Xinjiang Uygur Autonomous Region. Numerous studies have shown that reducing inorganic fertilizer inputs and applying organic fertilizer can effectively improve soil nutrient conditions and continuously increase crop yield. However, it is worth noting that existing research has mostly focused on soil biological and physical processes, with insufficient attention to the synergistic relationship between root and aboveground growth.

[0003] Photosynthesis is the basis for crop yield formation. Numerous studies have shown that humus substances can increase crop cell permeability, reduce stomatal opening, reduce water transpiration, and enhance crop water retention. They can also promote plant growth and increase yield by improving photosynthetic capacity, increasing chlorophyll content, and enhancing the activity of ribulose-1,5-bisphosphate carboxylase / oxygenase. Root, as a non-photosynthetic organ and an important organ for absorbing and transporting nutrients from the soil, plays a key role in crop yield through its synergistic relationship with the aboveground part. This relationship refers to the dynamic synergistic mechanism established by plant roots and aboveground parts through photosynthate exchange, signal transduction, and resource allocation, which directly affects plant growth and development and yield formation. Carbohydrate metabolism is the basis for root development, and non-structural carbohydrates such as sucrose and glucose are not only the main storage form of photosynthate but also provide energy for root growth and function. Therefore, clarifying the synergistic relationship between root and aboveground growth helps to elucidate the intrinsic mechanisms of cotton growth and yield formation.

[0004] Humus (HS) is a mixture of weak organic acids formed by the degradation and synthesis of plant and animal residues under the action of microorganisms and under the combined action of various geophysical and chemical factors. Humus can delay the precipitation and crystallization of iron (aluminum, calcium)-phosphate by binding cations and attaching to precipitation and crystallization sites. The formation of humic acid-iron complexes can hinder or delay the formation of ferric phosphate, thereby increasing the solubility of soil phosphorus. Meanwhile, humus can also improve the availability of phosphorus by promoting root growth, increasing root excretion and expression of phosphorus transport proteins. Fulvic acid (FA) is a type of low molecular weight humus that has been shown to improve soil structure and increase nutrient availability, thereby promoting plant growth and yield. The application of fulvic acid and phosphorus fertilizer can significantly increase cotton yield by increasing soil phosphorus availability and enhancing phosphorus uptake by cotton. The application of fulvic acid can reduce phosphorus fixation and increase soil phosphorus availability, thereby increasing crop yield. However, there is still limited research on the synergistic relationship between fulvic acid and phosphorus fertilizer on cotton root-shoot growth, photosynthetic capacity, and root carbohydrate metabolism. SUMMARY

[0005] An object of the present application is to solve at least the above problems and / or drawbacks and to provide at least the advantages stated later.

[0006] To achieve these objects and other advantages of the present application, a method for evaluating the effects of fulvic acid and phosphorus fertilizer on cotton root productivity and yield is provided, comprising: Step one, using randomized complete block design to set up the following five treatments: treatment one is no chemical phosphorus fertilizer, treatment two is 105 kg P2O5 ha -1 , treatment three is 150 kg P2O5 ha -1 , treatment four is 105 kg P2O5 ha -1 + fulvic acid, and treatment five is 150 kg P2O5 ha -1 + fulvic acid; Step two, randomly selecting 5 cotton plants from each treatment at the present budding stage, full flowering stage, boll setting stage, and boll opening stage for plant sampling analysis; Step three, at the time of cotton harvest, selecting 20 consecutive and uniform cotton plants from each plot to obtain cotton yield and constituent factors; Step four, evaluating cotton root productivity by root boll load and root boll setting capacity; Step five, determining the content of non-structural carbohydrates in cotton roots; Step six, determining the photosynthetic capacity of cotton; Step seven, the results of step two-step six are analyzed by software, and the multiple comparisons are carried out by Duncan method, the difference significance test level between treatments is P<0.05, the correlation between the cotton yield, photosynthetic capacity, root productivity and root carbohydrate content is analyzed, which is used to evaluate the influence of different fulvic acid and different phosphate application amount on the photosynthetic capacity, biomass, root productivity and root carbohydrate content of cotton at different growth stages under the treatment of different fulvic acid and different phosphate application amount.

[0007] Preferably, in step two, the sampling of the plants is to define a rectangular parallelepiped soil block of 40 cm x 10 cm x 60 cm with the sampling plant as the center, and the whole cotton plant is completely dug out, and the sampling plant is separated into roots, stems, leaves, flowers and bolls; The root sample of each sampling plant is placed in a 0.25 mm screen and gently washed with running water to remove the soil; After the 105℃ fixation of all sampling plants for 30 min, the plants are baked at 80℃ for 48 h to constant weight, and finally weighed.

[0008] Preferably, in step five, the procedure for determining the non-structural carbohydrate content of the cotton roots includes: 0.5 g of the root sample is taken, 4 mL of 80% ethanol is added, and the mixture is heated at 80℃ water bath for 40 min; After centrifugation at 6000 rpm for 10 min, the supernatant is collected, and the residue is repeatedly extracted with ethanol and centrifuged for 3 times; The combined supernatant is diluted to 10 mL with 80% ethanol, and used for determination of sucrose and hexose content; After the insoluble residue is evaporated to dryness, 2 mL of distilled water is added for dissolution, and the mixture is heated in a boiling water bath (100℃) for 15 min, and then cooled to room temperature. Under the condition of ice water bath, 2 mL of 4.6 M perchloric acid is carefully added, and incubated for 15 min. Then 2 mL of distilled water is added, and the mixture is centrifuged at 6000 rpm for 10 min. The supernatant is transferred to a 25 mL volumetric flask, and the residue is extracted again with 2 mL of 4.6 M perchloric acid. After the combined supernatant is diluted to 25 mL with distilled water, it is used for determination of starch content; The fructose content is determined by the resorcinol method, the glucose content is determined by the glucose oxidase method, and the starch content is determined by the anthrone-sulfuric acid method.

[0009] Preferably, in step six, the photosynthetic capacity of cotton is determined by the assimilation box method at the present bud stage, the flowering stage, the boll setting stage and the boll opening stage, respectively.

[0010] Preferably, in step seven, through correlation analysis, the lint yield is positively correlated with the leaf area index LAI, the photosynthetically active radiation interception rate IPAR, the photosynthetic capacity CAP, the root boll load BLR, the root boll forming capacity BCR, the fructose content and the glucose content, and is significantly negatively correlated with the starch content, the root-shoot ratio R / S and the sucrose content; The starch content is significantly negatively correlated with the LAI, the IPAR, the CAP, the BLR, the BCR, the vegetative organ biomass VB and the reproductive organ biomass RB, but is significantly positively correlated with the root-shoot ratio R / S.

[0011] Preferably, in step seven, through correlation analysis, in the saline-alkali and drought area, the fulvic acid is 105 P2O5ha -1 The FP1 treatment of combined application is the most suitable fertilization mode for cotton production.

[0012] An evaluation method for improving yield in cotton planting in a saline-alkali and drought area.

[0013] The present application at least includes the following beneficial effects: the present application aims to explore the effects of fulvic acid (FA) and different phosphorus application amounts on the photosynthetic capacity, biomass, root productivity and root carbohydrate content of cotton at each growth period, so as to determine the best combined application scheme of phosphorus fertilizer and fulvic acid, and then improve the root productivity and yield of cotton. We assume that the fulvic acid and 105 kgP2O5ha -1 The combined application of phosphorus fertilizer can balance the root-shoot biomass distribution (root-shoot ratio) and the source-sink coordination (leaf area index, root boll load and root boll forming capacity), and finally improve the root productivity and cotton yield.

[0014] Other advantages, objects and features of the present application will be partly embodied in the following description, and partly understood by those skilled in the art through research and practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 Comparison chart of the effects of fulvic acid combined with phosphorus fertilizer on the lint yield of cotton in 2023 and 2024; Figure 2 Comparison chart of the effects of fulvic acid combined with phosphorus fertilizer on the leaf area index of cotton in 2023 (A, B, C, D) and 2024 (E, F, G, H); Figure 3 Comparison chart of the effects of fulvic acid combined with phosphorus fertilizer on the photosynthetically active radiation interception rate (IPAR, %) of cotton in 2023 (A, B, C, D) and 2024 (E, F, G, H); Figure 4The influence comparison chart of fulvic acid combined with phosphorus fertilizer on cotton photosynthetic capacity (CAP, μmol CO2m -2 s -2 ) in 2023 (A, B, C, D) and 2024 (E, F, G, H); Figure 5 The influence comparison chart of fulvic acid combined with phosphorus fertilizer on cotton root-shoot ratio in 2023 (A, B, C, D) and 2024 (E, F, G, H); Figure 6 The influence comparison chart of fulvic acid combined with phosphorus fertilizer on cotton root boll-forming capacity in 2023 (A, B, C) and 2024 (D, E, F); Figure 7 The influence comparison chart of fulvic acid combined with phosphorus fertilizer on cotton root boll load in 2023 (A, B, C) and 2024 (D, E, F); Figure 8 The influence comparison chart of fulvic acid combined with phosphorus fertilizer on cotton root fructose content in 2023 (A, B, C, D) and 2024 (E, F, G, H); Figure 9 The influence comparison chart of fulvic acid combined with phosphorus fertilizer on cotton root glucose content in 2023 (A, B, C, D) and 2024 (E, F, G, H); Figure 10 The influence comparison chart of fulvic acid combined with phosphorus fertilizer on cotton root sucrose content in 2023 (A, B, C, D) and 2024 (E, F, G, H); Figure 11 The influence comparison chart of fulvic acid combined with phosphorus fertilizer on cotton root starch content in 2023 (A, B, C, D) and 2024 (E, F, G, H); Figure 12 The correlation analysis schematic diagram of cotton lint yield and population photosynthetic capacity, root productivity and root carbohydrate content. DETAILED DESCRIPTION

[0016] The application will be further described in detail below with reference to the accompanying drawings so as to enable those skilled in the art to implement the application according to the description and drawings.

[0017] Embodiment: Cotton roots maintain photosynthesis through nutrient absorption and cooperate with aboveground growth to affect yield. This embodiment mainly discusses the influence of fulvic acid (FA) and phosphorus fertilizer on the relationship between cotton photosynthetic capacity (CAP) and root carbohydrate metabolism. The study sets up 5 treatments through field experiment: no phosphorus fertilizer (CK), 105 kg P2O5ha -1 (P1), 150 kg P2O5ha -1(P2), 105 kg P2O5 ha -1 + fulvic acid (FP1) and 150 kg P2O5 ha -1 + fulvic acid (FP2). The results showed that FP2 treatment exhibited the most significant advantage, which could ensure appropriate leaf area index (LAI) and incident photosynthetically active radiation (IPAR), thereby maintaining higher photosynthetic capacity; compared with FP2, FP1 treatment increased root system boll load (BLR) and root system boll forming capacity (BCR) by 8.1% and 9.3%, respectively, and the contents of sucrose and starch in the root system of FP1 were 6.2%-19.2% and 26.5%-27.9% lower than those of FP2, respectively, while the contents of fructose and glucose were 6.4%-10.8% and 7.2%-8.8% higher than those of FP2, respectively, the biomass of reproductive organs increased by 11.1% and 14.7%, respectively, and the yield was the highest, which increased by 8.5% and 11.0% compared with P2 and FP2, respectively. Comprehensive research showed that in the saline and alkaline drought cotton area, application of FP1 (105 kg P2O5 ha -1 + fulvic acid) might be an appropriate way of phosphorus fertilizer application, and the specific implementation process was as follows: 1. Test site Field experiments were conducted in Alar City (40°32′N, 81°18′E) of Xinjiang Uygur Autonomous Region, China in 2023 and 2024. The region belongs to a warm temperate continental arid climate, with an average annual temperature of 10.7°C and an annual precipitation of 40.1-82.5 mm. The soil used for the test was sandy loam soil, with total nitrogen content of 1.1 g kg⁻¹, available phosphorus of 16.9 mg kg⁻¹, available potassium of 110.5 mg kg⁻¹, available nitrogen of 93.5 mg kg⁻¹, and organic matter content of 6.7 g kg⁻¹.

[0018] 2. Test design The experiment used a randomized complete block design, with five treatments: no chemical phosphorus fertilizer (CK), 105 kg P2O5 ha -1 (P1), 150 kg P2O5 ha -1 (P2), 105 kg P2O5 ha -1 + fulvic acid (FP1) and 150 kg P2O5 ha -1 + fulvic acid (FP2). Each treatment was repeated three times, with a plot area of 92 m 2The cotton variety tested was "Tahe No. 2," sown on April 18, 2023, and April 20, 2024, using drip irrigation under mulch. The planting pattern was a wide-narrow row configuration (66 cm + 10 cm), with a planting density of 220,000 plants per hectare. -1 , plant spacing 7.5 cm.

[0019] All treatments were fertilized with nitrogen fertilizer (urea, 46% nitrogen) at 300 kg ha -1 Potash fertilizer (K2O, containing 52% potassium) 90 kgha -1 The phosphate fertilizer is diammonium phosphate (containing 46% P2O5). The fulvic acid is mineral potassium fulvate (humic acid ≥50%, fulvic acid ≥50%, organic matter ≥60%, potassium oxide ≥10%, pH 8-11), with an application rate of 45 kg ha -1 This mineral-sourced potassium fulvate fertilizer was purchased from Shandong Fengxiang Xiannong Biotechnology Co., Ltd. Because it has a national standard registration number, no additional element testing was performed. All fertilizers were applied via drip irrigation. Field management (irrigation, weeding, etc.) adhered to high-yield cultivation requirements.

[0020] 3. Plant sampling and analysis Five cotton plants were randomly selected from each treatment at the peak bud stage (PSS), peak flowering stage (PFS), peak boll stage (PBS), and boll opening stage (BOS). A 40 cm × 10 cm × 60 cm rectangular soil block was demarcated centered on the sampled plant, and the entire cotton plant was excavated as completely as possible. Plant samples were separated according to their different organs (roots, stems, leaves, flowers, and bolls). Root samples from each sampling point were placed through a 0.25 mm sieve and gently rinsed under running water to remove soil. All plant samples were withered at 105°C for 30 minutes, then dried at 80°C for 48 hours to constant weight, and finally weighed. It should be noted that sampling here is only used for the calculation of subsequent indicators.

[0021] 4. Cotton yield and its components At the time of cotton harvest, 20 consecutive and uniformly growing cotton plants were selected from each plot, and the number of bolls per plant was recorded. The boll shells were air-dried and weighed to calculate the seed cotton yield. The lint cotton yield was obtained after ginning.

[0022] 5. Cotton root productivity Cotton root productivity can be quantified by two key indicators: boll load per root (BLR) and boll forming capacity per root (BCR).

[0023] BLR (g -1 ) = Number of bolls per plant (ha -1 ) / root biomass (kg ha -1 ) × 1000 (1) BCR (gg-1 Biomass of cotton boll (kg ha -1 Biomass of root (kg ha -1 ) x 1000 (2) The formula for calculating root-shoot ratio (R / S) is: R / S = Biomass of root (kg ha -1 Biomass of shoot (kg ha -1 ) (3) 6. Determination of non-structural carbohydrate content in cotton root The determination of non-structural carbohydrate content in cotton root refers to the method of Iqbal et al. The specific steps are as follows: take 0.5 g of root sample, add 4 mL of 80% ethanol, and heat in a water bath at 80°C for 40 min. After centrifugation at 6000 rpm for 10 min, collect the supernatant, and repeat the extraction of the residue with ethanol for 3 times (repeat the incubation and centrifugation steps). The combined supernatant is diluted to 10 mL with 80% ethanol for determination of sucrose and hexose content. After evaporation of the insoluble residue to dryness, 2 mL of distilled water is added for dissolution, and heated in a boiling water bath (100°C) for 15 min. After cooling to room temperature, 2 mL of 4.6 M perchloric acid is carefully added under ice water bath conditions, and incubated for 15 min. Then 2 mL of distilled water is added, and centrifuged at 6000 rpm for 10 min. The supernatant is transferred to a 25 mL volumetric flask, and the residue is extracted again with 2 mL of 4.6 M perchloric acid. After combining the supernatant, it is diluted to 25 mL with distilled water for determination of starch content. The content of fructose is determined by the resorcinol method, the content of glucose is determined by the glucose oxidase method, and the content of starch is determined by the anthrone-sulfuric acid method.

[0024] 7. Determination of photosynthetic capacity of cotton The photosynthetic capacity (CAP) of cotton is determined by the assimilation box method at each growth stage (presenting bud stage, flowering stage, boll setting stage, and boll opening stage). The determination is carried out between 11:00-14:00 on sunny and windless days. The size of the assimilation box is 90 cm x 90 cm x 130 cm, covered with high-transmittance (≥95%) polyester film, and 2 fans are installed in the box to mix the air and balance the temperature. For each determination, 6 cotton plants are selected and covered in the box to ensure air tightness, and gas sampling is performed at the 20th and 60th seconds, respectively. After completing the determination of photosynthetic capacity, the plants in the box are cut off, and the CO2 gas exchange rate is determined at the original position.

[0025] The formula for calculating photosynthetic capacity is as follows: CAP = (D x Ac x V) / (S x At) (4) Where D is CO2 gas concentration; Δc (ppm) is the CO2 concentration difference in the assimilation chamber within a certain time interval (Δt, s); V is the volume of the assimilation chamber; S (m 2 ) is the ground area occupied by plants in the chamber.

[0026] 8、Statistical analysis SPSS22.0 software (IBM, USA) was used for one-way ANOVA, and Duncan's method was used for multiple comparisons. The difference between treatments was tested at the level of P<0.05. All graphs were drawn by Origin (Pro 2024, OriginLab, USA). The correlation between cotton yield, photosynthetic capacity, root productivity and root carbohydrate content was analyzed using the correlation plotting tool of Origin 2024.

[0027] FP1 (105 kg P2O5ha -1 + fulvic acid) is considered to be the appropriate phosphorus fertilizer application method in saline-alkali and drought areas. This treatment showed a comprehensive effect in optimizing photosynthetic parameters, promoting root development and increasing yield. In addition, excessive fertilization can lead to excessive nutrient concentration in soil solution, which can accelerate root aging, reduce the photosynthetic capacity of cotton population, and ultimately cause yield loss.

[0028] Verification example: 1、Cotton lint yield Compared with CK, the two-year lint yield of P1 and P2 treatments increased by 32.1%–45.8% and 42.4%–54.6%, respectively, and the two-year lint yield of FP1 and FP2 treatments increased by 55.5%–66.6% and 38.6%–51.8%, respectively, compared with CK Figure 1 ). In 2023 and 2024, the lint yield of FP2 treatment was significantly lower than that of FP1 by 12.2% and 9.8%, respectively. Compared with P2, the two-year lint yield of FP1 treatment increased by 7.8%–9.2%.

[0029] In Figure 1, different letters represent significant differences between treatments (p<0.05). CK: no phosphorus fertilizer; P1: 105 kg P2O5ha -1 ; P2: 150 kg P2O5ha -1 ; FP1: 105 kg P2O5ha -1 + fulvic acid; FP2: 150 kg P2O5ha -1 + fulvic acid.

[0030] 2、Cotton biomass distribution As the growth period progressed, the biomass of both vegetative and reproductive organs of cotton showed a gradual accumulation trend, with differences between treatments becoming more pronounced during the full boll stage and boll opening. During these stages, the vegetative organ biomass of cotton in the FP1 treatment was 1.2%–2.5% lower and 1.3%–2.4% lower than that of FP2, respectively, over the two years. However, the reproductive organ biomass of cotton in the FP1 treatment was 10.5%–11.8% higher and 13.9%–15.6% higher, respectively. Compared with CK, the biomass of cotton reproductive organs in the P1 and P2 treatments at the boll stage increased significantly by 56.9%–62.1% and 62.7%–72.1%, respectively, and in the FP1 and FP2 treatments by 79.7%–94.6% and 60.8%–71.6%, respectively. The biomass of reproductive organs in the P1 and P2 treatments at the boll opening stage increased significantly by 15.8%–20.5% and 22.7%–26.5%, respectively, and in the FP1 and FP2 treatments by 40.8%–49.2% and 21.2%–26.0%, respectively. The effects of fulvic acid combined with phosphorus fertilizer on the biomass of cotton vegetative organs and reproductive organs (t ha) in 2023 and 2024 were obtained as shown in Table 1. -1 )’s impact.

[0031] Table 1 In Table 1, PSS stands for bud stage, PFS stands for bloom stage, PBS stands for boll stage, and BOS stands for boll opening stage. Data are means (n ​​= 3). Different letters in the same column indicate significant differences (p < 0.05). CK: no phosphate fertilizer; P1: 105 kg P₂O₅ha₄. -1 ;P2: 150 kgP2O5ha -1 FP1: 105 kg P2O5ha -1 + fulvic acid; FP2: 150 kg P2O5ha -1 + Fulvic acid.

[0032] 3. Cotton photosynthetic capacity The leaf area index (LAI) showed a trend of increasing first and then decreasing during the growth process of cotton, reaching a peak at the peak of boll setting (e.g. Figure 2 Analysis of variance showed that the LAI of treatments P1, P2, FP1, and FP2 was significantly higher than that of CK at all growth stages. However, no statistical differences were found between the P2, FP1, and FP2 treatments at peak bud and flowering stages. Compared with P2, the LAI of treatments FP1 and FP2 at peak boll setting increased significantly by 6.2%–7.1% and 6.4%–8.8%, respectively, over the two years. However, no significant differences were found between the FP1 and FP2 treatments.

[0033] Figure 2Among them, A and E are the peak of squaring stage, B and F are the peak of flowering stage, C and G are the peak of bolling stage, D and H are the peak of boll opening stage. Different letters represent significant differences among treatments (p<0.05). CK: no phosphorus fertilizer; P1: 105 kg P2O5 ha -1 ; P2: 150 kg P2O5 ha -1 ; FP1: 105 kg P2O5 ha -1 + fulvic acid; FP2: 150 kg P2O5 ha -1 + fulvic acid.

[0034] The cotton photosynthetic active radiation interception rate (IPAR) increased first and then decreased with the growth process, reaching a peak at the peak of bolling stage (e.g. Figure 3 ). The IPAR of other treatments at each growth stage was higher than that of CK. At the peak of bolling stage, the IPAR of P1 and P2 treatments was significantly increased by 10.9%–11.0% and 12.1%–12.3% respectively compared with CK in two years; the IPAR of FP1 and FP2 treatments was 12.3%–15.3% and 15.4%–15.5% higher than that of CK, respectively. The IPAR of FP1 treatment was significantly higher than that of P2 treatment, but there was no significant difference between FP1 and FP2 treatments.

[0035] Figure 3 Among them, A and E are the peak of squaring stage, B and F are the peak of flowering stage, C and G are the peak of bolling stage, D and H are the peak of boll opening stage. Different letters represent significant differences among treatments (p<0.05). CK: no phosphorus fertilizer; P1: 105 kg P2O5 ha -1 ; P2: 150 kg P2O5 ha -1 ; FP1: 105 kg P2O5 ha -1 + fulvic acid; FP2: 150 kg P2O5 ha -1 + fulvic acid.

[0036] The cotton photosynthetic capacity (CAP) increased first and then decreased with the growth process, reaching a peak at the peak of bolling stage (e.g. Figure 4 ). The CAP of other treatments at each growth stage was higher than that of CK. At the peak of flowering stage, the CAP of P1 and P2 treatments was significantly increased by 40.4%–49.1% and 47.0%–56.6% respectively compared with CK in two years; the CAP of FP1 and FP2 treatments was 46.5%–55.4% and 35.7%–45.0% higher than that of CK, respectively. At the peak of bolling stage, the CAP of P1 and P2 treatments was significantly increased by 32.1%–34.8% and 35.5%–41.5% respectively compared with CK; the CAP of FP1 and FP2 treatments was 56.1%–59.2% and 36.7%–42.8% higher than that of CK, respectively. In addition, the CAP of FP1 treatment was significantly higher than that of FP2 treatment, but there was no significant difference between FP1 and P2 treatments.

[0037] Figure 4 Among them, A and E are the full-bud stage, B and F are the full-blooming stage, C and G are the full-boll stage, and D and H are the boll opening stage. Different letters represent significant differences between treatments (p<0.05). CK: no phosphorus fertilizer; P1: 105 kg P2O5 ha -1 ; P2: 150 kg P2O5 ha -1 ; FP1: 105 kg P2O5 ha -1 + fulvic acid; FP2: 150 kg P2O5 ha -1 + fulvic acid.

[0038] 4、 Cotton root productivity During the development of cotton phenological stages, the root-shoot ratio (R / S) showed a gradually decreasing trend (Fig. 2). Figure 5 Compared with CK, the R / S of P1 and P2 treatments at the boll opening stage was significantly reduced by 6.6%–7.1% and 3.3%–7.3%, respectively, and the R / S of FP1 and FP2 treatments was reduced by 3.2%–7.6% and 4.9%–8.1%, respectively. However, there was no significant difference between P2, FP1 and FP2 treatments in two years, and there was no significant difference between P2, FP1 and FP2 treatments at each growth stage.

[0039] Figure 5 Among them, A and E are the full-bud stage, B and F are the full-blooming stage, C and G are the full-boll stage, and D and H are the boll opening stage. Different letters represent significant differences between treatments (p<0.05). CK: no phosphorus fertilizer; P1: 105 kg P2O5 ha -1 ; P2: 150 kg P2O5 ha -1 ; FP1: 105 kg P2O5 ha -1 + fulvic acid; FP2: 150 kg P2O5 ha -1 + fulvic acid.

[0040] Cotton root bolling capacity (BCR) showed a gradually increasing trend (Fig. 3). Figure 6 Compared with CK, the BCR of P1 and P2 treatments at the boll opening stage was significantly reduced by 19.8%–22.4% and 44.3%–47.2%, respectively, and the BCR of FP1 and FP2 treatments was reduced by 56.0%–56.7% and 42.1%–43.9%, respectively. Compared with FP2, the BCR of FP1 treatment at the boll opening stage was significantly reduced by 8.3%–10.3% in two years. At the full-blooming stage and the boll opening stage, there was no significant difference between FP2 and P2 treatments.

[0041] Figure 6Among them, A and D are the flowering stage, B and E are the bolling stage, and C and F are the boll opening stage. Different letters represent significant differences between treatments (p<0.05). CK: no phosphorus fertilizer; P1: 105 kg P2O5 ha -1 ; P2: 150 kg P2O5 ha -1 ; FP1: 105 kg P2O5 ha -1 + fulvic acid; FP2: 150 kg P2O5 ha -1 + fulvic acid.

[0042] The boll load of cotton root system (BLR) showed a gradually increasing trend with the growth process Figure 7 ). Compared with CK, the BLR of P1 and P2 treatments at the boll opening stage was significantly reduced by 9.9%–10.9% and 22.2%–26.9%, respectively, and the BLR of FP1 and FP2 treatments was reduced by 31.0%–37.2% and 23.2%–24.8%, respectively. In 2024, the BLR of FP1 treatment was significantly lower than that of FP2 by 10.0% at the boll opening stage. There was no significant difference between P2 and FP2 treatments at the boll opening stage.

[0043] Figure 7 Among them, A and D are the flowering stage, B and E are the bolling stage, and C and F are the boll opening stage. Different letters represent significant differences between treatments (p<0.05). CK: no phosphorus fertilizer; P1: 105 kg P2O5 ha -1 ; P2: 150 kg P2O5 ha -1 ; FP1: 105 kg P2O5 ha -1 + fulvic acid; FP2: 150 kg P2O5 ha -1 + fulvic acid.

[0044] 5、Cotton root carbohydrate content With the advancement of cotton phenological stages, the contents of root fructose and glucose showed a gradually increasing trend Figure 8 , Figure 9 ), while the contents of sucrose and starch first increased and then decreased, reaching a peak at the bolling stage Figure 10 , Figure 11 ), and the differences between treatments were more significant at the flowering and bolling stages. Compared with CK, the contents of fructose in P1 and P2 treatments at the bolling stage were increased by 4.2%–8.1% and 13.0%–19.2%, respectively, and the contents of glucose were increased by 4.1%–28.0% and 8.5%–34.8%, respectively. The contents of fructose and glucose in FP1 and FP2 treatments were increased by 25.5%–29.0% and 15.1%–16.2%, and 23.1%–44.8% and 14.3%–35.7%, respectively. At the flowering and bolling stages, the contents of root fructose and glucose in FP1 treatment were significantly higher than those in FP2 treatment. Compared with CK, the sucrose contents of P1 and P2 treatments in 2023 and 2024 were reduced by 13.8%–16.7% and 18.4%–20.5%, respectively, and the FP1 and FP2 treatments were reduced by 28.5%–36.0% and 19.1%–19.9%, respectively. The starch contents were reduced by 9.3%–13.6% and 14.3%–23.5%, respectively, and the FP1 and FP2 treatments were reduced by 37.4%–40.0% and 18.4%–25.1%, respectively. At the flowering and boll stages, the sucrose and starch contents of the root system of the FP1 treatment were significantly lower than those of the FP2 treatment.

[0045] Figure 8 Among them, A and E are the full-bud stage, B and F are the full-blooming stage, C and G are the full-boll stage, and D and H are the full-boll stage. Different letters indicate significant differences between treatments (p<0.05). CK: no phosphorus fertilizer; P1: 105 kg P2O5ha -1 ; P2: 150 kg P2O5ha -1 ; FP1: 105 kg P2O5ha -1 + fulvic acid; FP2: 150 kg P2O5ha -1 + fulvic acid.

[0046] Figure 9 Among them, A and E are the full-bud stage, B and F are the full-blooming stage, C and G are the full-boll stage, and D and H are the full-boll stage. Different letters indicate significant differences between treatments (p<0.05). CK: no phosphorus fertilizer; P1: 105 kg P2O5ha -1 ; P2: 150 kg P2O5ha -1 ; FP1: 105 kg P2O5ha -1 + fulvic acid; FP2: 150 kg P2O5ha -1 + fulvic acid.

[0047] Figure 10 Among them, A and E are the full-bud stage, B and F are the full-blooming stage, C and G are the full-boll stage, and D and H are the full-boll stage. Different letters indicate significant differences between treatments (p<0.05). CK: no phosphorus fertilizer; P1: 105 kg P2O5ha -1 ; P2: 150 kg P2O5ha -1 ; FP1: 105 kg P2O5ha -1 + fulvic acid; FP2: 150 kg P2O5ha -1 + fulvic acid.

[0048] Figure 11In the figure, A and E are at the bud stage, B and F are at the flowering stage, C and G are at the boll stage, and D and H are at the boll opening stage. Different letters indicate significant differences among treatments (p < 0.05). CK: no phosphate fertilizer; P1: 105 kg P2O5 ha -1 ; P2: 150 kg P2O5ha -1 FP1: 105 kg P2O5ha -1 + fulvic acid; FP2: 150 kg P2O5ha -1 + Fulvic acid.

[0049] 6. Correlation analysis between cotton yield and photosynthetic capacity, root productivity and root carbohydrate content The results of the correlation analysis between cotton yield and various indicators are as follows: Figure 12 Lint yield was positively correlated with leaf area index (LAI), photosynthetically active radiation interception (IPAR), photosynthetic capacity (CAP), root boll load (BLR), root boll forming capacity (BCR), fructose content, and glucose content, and significantly negatively correlated with starch content, root-to-shoot ratio (R / S), and sucrose content. Starch content was significantly negatively correlated with LAI, IPAR, CAP, BLR, BCR, vegetative biomass (VB), and reproductive biomass (RB), but was significantly positively correlated with root-to-shoot ratio (R / S).

[0050] Figure 12 Correlation analysis between cotton lint yield and population photosynthetic capacity, root productivity, and root carbohydrate content. Correlation coefficients range from 1.0 (red) to −1.0 (blue). * and ** indicate significant differences at p < 0.05 and p < 0.01, respectively. LAI: leaf area index; IPAR: photosynthetically active radiation interception; CAP: photosynthetic capacity; R / S: root-to-shoot ratio; BCR: boll-bearing capacity; BLR: boll-bearing capacity; VB: vegetative biomass; RB: reproductive biomass; LY: lint yield.

[0051] From the above verification example, it can be seen that in saline-alkali arid areas, fulvic acid (FA) and 105 kg P2O5ha -1Combined fertilization (FP1) is the most suitable fertilization method for cotton production. The FP1 treatment formed a more coordinated source-sink relationship by improving root productivity and enhancing cotton photosynthetic capacity, ultimately achieving increased yield. At the same time, FP1 promoted the utilization of sucrose and starch in the cotton roots. This efficient utilization of root carbohydrates is crucial to coordinating the growth relationship of roots, crowns, and reproductive organs, thereby significantly improving the ability to distribute photosynthetic products to the biomass of reproductive organs, manifested as higher root boll load (BLR) and root boll capacity (BCR), which helps to form yield. On the contrary, excessive fertilization (P2 and FP2) will lead to root aging, decreased photosynthetic capacity, and ultimately yield loss. Therefore, FP1 (105 kg P2O5ha -1 + fulvic acid) is a suitable phosphorus fertilizer application method for coordinating the above-ground and underground growth of cotton, improving root productivity and group photosynthetic capacity, and achieving increased cotton production in saline-alkali arid areas.

[0052] The above solution is only an illustration of a preferred embodiment, but is not limited thereto. When implementing the present invention, appropriate replacements and / or modifications can be made according to user needs.

[0053] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and exemplary embodiments. They can be applied to a variety of fields suitable for the present invention. Further modifications will be readily apparent to those skilled in the art. Therefore, the present invention is not limited to the specific details and illustrations shown and described herein without departing from the general concept defined by the claims and their equivalents.

Claims

1. A method for evaluating the effects of fulvic acid and phosphate fertilizer on cotton root productivity and yield, characterized in that: include: Step 1: Use a randomized complete block design to set up the following five treatments: treatment 1 is no phosphate fertilizer application, treatment 2 is 105 kgP2O5 ha -1 Phosphate fertilizer, treatment three was to apply 150 kg P2O5ha -1 Phosphate fertilizer, treatment 4 was 105 kg P2O5ha -1 Phosphate fertilizer +45 kg ha -1 Fulvic acid, treatment five: 150 kg P2O5 + 45 kg·ha⁻¹ fulvic acid; Step 2: Randomly select 5 cotton plants from each treatment at the peak budding stage, peak flowering stage, peak boll setting stage, and boll opening stage for plant sampling analysis; Step 3: When harvesting cotton, 20 consecutive and uniformly growing cotton plants were selected from each plot to obtain cotton yield and components; Step 4: Evaluate cotton root productivity by root boll-bearing capacity and root boll-forming capacity; Step 5, measuring the content of non-structural carbohydrates in cotton roots; Step 6: measuring the photosynthetic capacity of cotton; Step 7. The results of steps 2 to 6 were subjected to one-way analysis of variance using software, and the Duncan method was used for multiple comparisons. The significance test level of differences between treatments was P < 0.

05. The correlation between cotton yield, photosynthetic capacity, root productivity and root carbohydrate content was analyzed to evaluate the effects of different fulvic acid and different phosphorus application rates on the photosynthetic capacity, biomass, root productivity and root carbohydrate content of cotton at different growth stages.

2. The method for evaluating the effects of fulvic acid and different phosphorus application rates on cotton root productivity and cotton yield according to claim 1, wherein: In step 2, the plant sampling is carried out by demarcating a 40 cm × 10 cm × 60 cm rectangular block of soil with the sampling plant as the center, completely digging out the entire cotton plant, and separating the sampling plant according to roots, stems, leaves, flowers, and bolls; The root samples of each sampled plant were placed in a 0.25 mm sieve and gently rinsed with running water to remove the soil; All sampled plants were sterilized at 105℃ for 30 min, dried at 80℃ for 48 h to constant weight, and finally weighed.

3. The method for evaluating the effects of fulvic acid and different phosphorus application rates on cotton root productivity and cotton yield according to claim 1, wherein: In step 5, the process for determining the non-structural carbohydrate content of cotton roots includes: Take 0.5 g of root sample, add 4 mL of 80% ethanol, and heat in an 80°C water bath for 40 min; After centrifugation at 6000 rpm for 10 min, the supernatant was collected, and the residue was repeatedly extracted with ethanol and centrifuged three times; The combined supernatant was diluted to 10 mL with 80% ethanol for sucrose and hexose content determination; After the insoluble residue was evaporated to dryness, 2 mL of distilled water was added to dissolve it, and the mixture was heated in a boiling water bath (100°C) for 15 min. After cooling to room temperature, 2 mL of 4.6 M perchloric acid was carefully added in an ice-water bath and incubated for 15 min. Subsequently, 2 mL of distilled water was added and the mixture was centrifuged at 6000 rpm for 10 min. The supernatant was transferred to a 25 mL volumetric flask, and the residue was extracted again with 2 mL of 4.6 M perchloric acid. The supernatants were combined and the volume was made up to 25 mL with distilled water for starch content determination. The fructose content was determined by the resorcinol method, the glucose content was determined by the glucose oxidase method, and the starch content was determined by the anthrone-sulfuric acid method.

4. The method for evaluating the effects of fulvic acid and different phosphorus application rates on cotton root productivity and cotton yield according to claim 1, wherein: In step six, the photosynthetic capacity of cotton was measured using an assimilation chamber method at the peak budding stage, peak flowering stage, peak boll setting stage and boll opening stage of cotton.

5. The method for evaluating the effects of fulvic acid and different phosphorus application rates on cotton root productivity and cotton yield according to claim 1, wherein: In step seven, through phase relationship analysis, lint yield was positively correlated with leaf area index (LAI), photosynthetically active radiation interception rate (IPAR), photosynthetic capacity (CAP), root boll bearing rate (BLR), root boll forming capacity (BCR), fructose content, and glucose content. Lint yield was significantly negatively correlated with starch content, root-to-shoot ratio (R / S), and sucrose content. Starch content was significantly negatively correlated with LAI, IPAR, CAP, BLR, BCR, vegetative organ biomass VB and reproductive organ biomass RB, but was significantly positively correlated with the root-to-shoot ratio R / S.

6. The method for evaluating the effects of fulvic acid and different phosphorus application rates on cotton root productivity and cotton yield according to claim 1, wherein: In step 7, through correlation analysis, in saline-alkali arid areas, the humic acid and 105kg P2O5ha -1 Phosphate fertilizer application (FP1 treatment) is the most suitable fertilization method for cotton production.

7. The evaluation method according to any one of claims 1 to 6, characterized in that: Application in increasing yield in cotton cultivation in saline-alkali arid areas.

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