Water-saving dry-sowing wet-out irrigation method for increasing yield of cotton in saline-alkali soil

Abstract

The invention relates to the technical field of agricultural water-saving irrigation, and discloses a saline-alkali soil cotton yield-increasing water-saving dry-sowing wet-out irrigation method which comprises the following steps that saline-alkali soil located in an arid or semi-arid area is selected as a cotton planting area, the soil pH value of the saline-alkali soil is 7.5-8.5, and the conductivity of the saline-alkali soil is 3.0-5.0 dS / m; sowing is conducted in a dry sowing mode instead of traditional broad irrigation from winter to spring, and the sowing depth ranges from 2 cm to 5 cm; after sowing, in a cotton seedling emergence period and a seedling vigorous period, proper seedling emergence irrigation amount and drip irrigation frequency are determined according to soil texture, cotton varieties and local climate conditions. Through the precise drip irrigation system and the control center for monitoring soil moisture and salinity in real time, precise application of irrigation water according to needs is achieved. The drip irrigation system can automatically adjust the drip irrigation frequency and the irrigation amount according to different growth stages of cotton and specific soil conditions, it is ensured that water evenly permeates into soil, and evaporation loss is reduced to the maximum extent.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of agricultural water-saving irrigation technology, in particular to a kind of saline-alkali soil cotton yield-increasing water-saving type dry sowing wet emergence irrigation method. BACKGROUND

[0002] In arid and semiarid regions, water scarcity and soil salinization are key issues that constrain the efficiency and sustainable development of cotton planting. The existing irrigation technology mainly relies on winter to spring flooding irrigation method, which aims to flush the salt in the soil with a large amount of fresh water to reduce the degree of soil salinization, thereby creating a more suitable soil environment for cotton seeding and seedling growth. Although this method can alleviate the problem of soil salinization to some extent, it also has many significant drawbacks. First, flooding irrigation requires a large amount of water, which is contrary to the current concept of water-saving agriculture, and is particularly unsustainable in areas where water resources are scarce. Second, excessive irrigation water can lead to the rise of groundwater level, which in turn exacerbates the secondary salinization of soil, forming a vicious cycle and adversely affecting the long-term growth of cotton and the soil ecology. In addition, the traditional irrigation method is relatively rough in regulating soil moisture and salt, and it is difficult to accurately meet the water and salt requirements of cotton at different growth stages, thereby affecting the emergence rate, seedling growth and final yield of cotton. Therefore, the existing irrigation technology has obvious shortcomings in water resource utilization efficiency, soil salinization improvement and precise support for cotton growth.

[0003] Therefore, the present application provides a kind of saline-alkali soil cotton yield-increasing water-saving type dry sowing wet emergence irrigation method to solve the above problems. SUMMARY

[0004] In view of the shortcomings of the prior art, the present application provides a kind of saline-alkali soil cotton yield-increasing water-saving type dry sowing wet emergence irrigation method, which solves the technical problems of water resource waste, soil salinization aggravation and insufficient support for cotton growth in the prior art.

[0005] To achieve the above purpose, the present application is realized by the following technical scheme: a kind of saline-alkali soil cotton yield-increasing water-saving type dry sowing wet emergence irrigation method, comprising the following steps:

[0006] Selecting saline-alkali soil located in arid or semiarid regions as cotton planting area, the soil pH value of the saline-alkali soil is 7.5-8.5, and the conductivity is 3.0-5.0 dS / m;

[0007] Instead of traditional flooding irrigation in winter to spring, dry sowing method is used for sowing, and the sowing depth is 2cm-5cm;

[0008] After sowing, at the cotton seedling stage and the vigorous stage of cotton seedlings, according to the soil texture, cotton variety and local climate conditions, the appropriate seedling irrigation amount and drip irrigation frequency are determined, precise irrigation is carried out through the drip irrigation system laid in the cotton field, the soil is kept in a suitable water and salt state, the cotton seedling emergence and growth are promoted, and the irrigation water use efficiency is improved;

[0009] During the whole cotton growth period, the soil water and salt are monitored in real time through the soil water sensor and the soil salt sensor, the seedling irrigation amount and the drip irrigation frequency are adjusted in time according to the monitoring results, and the soil volume water content is maintained at 15% to 30%, and the soil salt content is controlled between 0.5 and 2.0 g / kg.

[0010] Preferably, the drip irrigation frequency is divided into two kinds:

[0011] Low-frequency drip irrigation: drip irrigation is carried out once at the cotton seedling stage;

[0012] High-frequency drip irrigation: drip irrigation is carried out once at the cotton seedling stage, and once again at the vigorous stage of cotton seedlings;

[0013] Among them, compared with low-frequency drip irrigation, high-frequency drip irrigation can significantly improve the cotton plant height, dry matter accumulation and yield, and improve the irrigation water use efficiency.

[0014] Preferably, the drip irrigation system includes a drip irrigation pipe laid in the cotton field, a plurality of drippers are arranged on the drip irrigation pipe, the distance between the drippers is 30 to 50 cm, which is adjusted according to the cotton planting density, and the laying depth of the drip irrigation pipe is 10 to 20 cm, so that the irrigation water can uniformly penetrate into the soil, and local waterlogging or drought is avoided.

[0015] Preferably, when drip irrigation is carried out, the water flow speed of drip irrigation is controlled to be 0.5 to 1.5 L / h, and the pressure is 0.1 to 0.3 MPa, so that the water can uniformly penetrate into the soil, and the evaporation loss of water is reduced.

[0016] Preferably, it further includes regularly detecting the root activity during irrigation, determining the root activity by the triphenyl tetrazolium chloride method, and ensuring that the root activity is maintained at a high level to promote the healthy growth of cotton seedlings.

[0017] Preferably, the monitoring frequency of the soil water sensor and the soil salt sensor is once every 2 to 4 hours, the monitoring data is transmitted to the control center in real time through the wireless transmission module, and the control center automatically adjusts the operation parameters of the drip irrigation system according to the preset soil water and salt threshold values.

[0018] Preferably, it further includes timely supplemental irrigation according to the dynamic changes of soil water and salt in the late growth period of cotton.

[0019] Preferably, the emergence irrigation amount is adjusted according to the cotton variety and the initial content of soil salt:

[0020] When the initial content of soil salt is less than 1.0 g / kg, the emergence irrigation amount is 22.5-28.5 mm;

[0021] When the initial content of soil salt is between 1.0-2.0 g / kg, the emergence irrigation amount is 37.5-40.5 mm;

[0022] When the initial content of soil salt is higher than 2.0 g / kg, the emergence irrigation amount is 45.0-50.5 mm.

[0023] The present application provides a kind of saline-alkali soil cotton yield-increasing water-saving type dry sowing wet emergence irrigation method.It has the following beneficial effects:

[0024] 1.The present application realizes the precise application of irrigation water by precise drip irrigation system and real-time monitoring of soil moisture and salt control center.The drip irrigation system can automatically adjust the drip irrigation frequency and irrigation amount according to the specific conditions of soil and different growth stages of cotton,ensure that water penetrates uniformly into soil and minimize evaporation loss.Meanwhile,according to the cotton variety and the initial content of soil salt,the emergence irrigation amount is adjusted,which not only meets the key water requirement period of cotton seedlings growth,but also effectively avoids the overuse of water resources.This method can significantly improve the utilization efficiency of water resources in arid and semiarid areas,enhance the adaptability of cotton planting to water resource shortage environment,effectively alleviate the local water resource shortage problem,and has significant water-saving benefit and environmental friendliness.

[0025] 2.The present application provides a more suitable growth environment for cotton seedlings by optimizing soil moisture and salt state.High-frequency drip irrigation can significantly improve the emergence rate and root activity of cotton,promote the optimization of root length density and distribution range,and reduce the oxidation stress level of root system.In addition,real-time monitoring and dynamic adjustment of soil moisture and salt during the whole cotton growth cycle ensure that cotton can obtain stable water and salt supply at each growth stage,which helps cotton to better absorb nutrients,further promotes the healthy growth of plants,improves the overall growth performance and yield performance of cotton,and significantly improves the growth condition and yield level of cotton in saline-alkali soil,providing an efficient and sustainable irrigation solution for cotton planting in saline-alkali soil. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is the overall flow chart of the present application.

[0027] Figure 2 It is the dynamic diagram of soil volume water content of the present application.

[0028] Figure 3 A soil salinity dynamic diagram of the present application.

[0029] Figure 4 A cotton seedling stage root length density and root activity contrast diagram of the present application.

[0030] Figure 5 A root crown ratio contrast diagram of the present application.

[0031] Figure 6 A cotton seedling stage root system superoxide dismutase and peroxidase activity contrast diagram of the present application.

[0032] Figure 7 A cotton seedling stage root system catalase activity and malondialdehyde content contrast diagram of the present application.

[0033] Figure 8 A seedling emergence rate contrast diagram of the present application.

[0034] Figure 9 A correlation relationship heat map between all variables of the present application. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the specification of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0036] Please refer to the drawings in the specification of the present application Figure 1 - the drawings in the specification of the present application Figure 9 The present application provides a saline-alkali soil cotton yield-increasing water-saving dry sowing wet emergence irrigation method. The content is as follows:

[0037] 1. Test site and design:

[0038] The field test was carried out in the South Xinjiang Production-Teaching-Recreation Modern Agricultural Training Base of Tarim University (North Latitude 44°32', East Longitude 81°18') in Alar City, Xinjiang Uygur Autonomous Region, China from 2023 to 2024. The research area belongs to a warm temperate, highly continental arid desert climate. The annual evaporation in this area is between 1976.6 mm and 2558.9 mm, while the annual precipitation is between 40.1 mm and 82.5 mm. The 0-20 cm surface soil type is sandy loam, with a pH value of 7.9, an electrical conductivity of 3.9 dS / m, an available phosphorus content of 14.2 mg / kg, an available potassium content of 154 mg / kg, and an available nitrogen content of 174 mg / kg.

[0039] The experiment was designed with a completely randomized design, and six irrigation combination treatments were set up, with local spring irrigation treatment as the control (Table 1). The six irrigation combination treatments included three different emergence water irrigation amounts (W1: 22.5 mm, W2: 37.5 mm, W3: 45.0 mm) and two drip irrigation frequencies (F1: once irrigation, F2: twice irrigation). For the F1 group, drip irrigation was performed once during the seedling stage, while the F2 group was drip irrigated once during the emergence stage and once during the vigorous seedling stage (Table 1). The control treatment was irrigated in March of each year, with an irrigation amount of 225 mm based on the local spring irrigation amount. Each experimental plot had an area of 69 m 2 (4.6 m x 15 m) and was repeated three times. Cotton (variety Tarhe No. 2) was sown using the mulched drip irrigation method on April 14, 2023, and April 15, 2024. The cotton was planted using the wide-narrow row planting method (66 cm + 10 cm), with a planting density of 200,000 plants per hectare and a plant spacing of 11.5 cm. In all treatments, the first irrigation was performed within 48 hours of sowing using drip irrigation, followed by a second irrigation after 9 days. After emergence, field management was carried out according to the conventional field management method.

[0040] Based on the nutrient absorption characteristics of each growth stage of cotton, fertilization was performed using a topdressing method, with the fertilizer amount set as 300 kg / hm 2 (containing 46% nitrogen), 150 kg / hm 2 (containing 46% dihydrate), and 75 kg / hm 2 (containing 60% potassium oxide), which were evenly topdressed during the three important growth stages of the seedling stage, the present budding stage, and the flowering and bolling stage in proportion to irrigation, avoiding nutrient waste and late fertilizer loss. Each plot was irrigated six times per year, with an irrigation amount of 635 m 3 / hm 2 .

[0041] Table 1: 2023-2024 Cotton Field Dry Sowing and Wet Emergence Test Treatments

[0042]

[0043] 2. Soil Sampling and Analysis:

[0044] Soil samples were collected using a 5 cm diameter soil drill at depths of 0-20 cm and 20-40 cm. Sampling was completed within 48 hours after each irrigation. At each sampling point, six soil samples were collected, naturally air-dried, sieved through a 1 mm sieve, and then diluted soil extract was prepared at a soil to water ratio of 1:5. Soil pH was measured using a pH meter (PHS-2F). Soil salt content (SC) was determined using the dry weight method. Soil volumetric water content was determined using the oven drying method.

[0045] 3. Plant Sampling and Analysis:

[0046] The emergence of all cotton plants in each plot was observed and recorded 20 days after cotton planting, and the emergence rate was calculated. Cotton root samples were collected as whole samples to collect as many roots as possible. At the end of the cotton seedling stage (63 days after planting), a rectangular soil pit with a size of 40 cm x 10 cm x 60 cm was excavated for root sampling. Subsequently, the soil sample was packed in a self-sealing bag and sieved through a 1 mm sieve. Fresh roots were manually separated from soil particles, dead roots, and other impurities, then washed, dried, and placed in a root dish with an appropriate amount of water to disperse the roots. The morphological characteristics of the cotton roots were measured by an LD-WinRHIZO plant root scanner.

[0047] Root activity is an indicator for assessing the overall root growth condition. Root activity was determined by the triphenyltetrazolium chloride method. Ten representative cotton plant samples were selected from each plot at the boll opening stage. The cotton plant samples were divided into different organs: roots, stems, leaves, buds, flowers, and bolls. The samples were dried in an oven at 105°C for 30 minutes, and then at 80°C until constant weight to determine the biomass of each organ. The root-shoot ratio was calculated by the ratio of root biomass to aboveground biomass. Cotton root peroxidase activity and catalase activity were determined by spectrophotometry. Root superoxide dismutase activity was determined by the nitro blue tetrazolium photoreduction method. Root malondialdehyde content was determined by the thiobarbituric acid method.

[0048] 4. Calculation:

[0049] Soil desalination rate was used to evaluate the desalination effect of the soil layer, and the calculation method was as follows:

[0050]

[0051] Where S1 is the initial soil salt content (g / kg), and S2 is the soil salt content after irrigation ends (g / kg).

[0052] The calculation method of irrigation water production efficiency (IWPE) (kg / m 3 ) is as follows:

[0053]

[0054] Here, Y represents the seed cotton yield of each treatment (kg / hm 2 ), and I represents the irrigation quota (m / hm 2 ).

[0055] 5. Statistical analysis:

[0056] Data analysis was performed using SPSS Statistics 22.0. One-way analysis of variance (ANOVA) was used to detect significant differences among different treatment groups, followed by Duncan’s multiple range test, with a significance level set at P < 0.05. Graphs were drawn using Origin 2024. To explore the relationship between soil water and salt dynamics, cotton root characteristics, emergence rate, and yield, we used the correlation diagram in Origin 2024 software for correlation analysis.

[0057] 6. Results:

[0058] Temporal and spatial dynamics of soil water content: In the seedling stage, soil volumetric water content increased significantly after each irrigation, and showed similar trends in both study years ( Figure 2 ). For the single irrigation treatment, the peak soil volumetric water content occurred during the emergence stage (April 29 to May 5). Although the water content in the W3F1 treatment was the highest among all treatment groups, it was still lower than the control (CK). The dynamic changes in soil volumetric water content for the two irrigation treatments were more complex, mainly due to the significant increase in drip irrigation frequency. Under the same irrigation quota, the soil volumetric water content in the multiple irrigation treatment (F2) remained higher and had smaller fluctuations than the single irrigation treatment (F1) throughout the seedling stage. The W2F2 and W3F2 treatments maintained relatively high soil water content during the seedling stage (May 8 to May 10), which was significantly higher than the control (CK).

[0059] 7. Temporal and spatial dynamics of soil salt content:

[0060] During the cotton seedling stage, the soil salt content in the 0-40 cm layer (the main root distribution layer during the seedling stage) decreased significantly after each irrigation, and this post-irrigation salt reduction trend showed high consistency in both 2023 and 2024, without significant fluctuations due to minor differences in annual climate (such as seedling stage rainfall) Figure 3 ). For the single irrigation treatment, the lowest salt content occurred during the emergence stage (April 29 to May 5). As the irrigation period ended, the soil salt content gradually stabilized. The dynamic changes in soil salt content for the two irrigation treatments were more complex, mainly due to the significant increase in drip irrigation frequency. For the same irrigation quota, the multiple irrigation (F2) reduced soil salt content during the entire cotton seedling emergence stage compared to the single irrigation (F1).

[0061] 8. Soil desalination rate

[0062] The soil salt content of CK treatment was significantly lower than that of dry sowing and wet emergence treatment before irrigation, and tended to be stable at seedling stage (Table 2). The soil desalination rate of dry sowing and wet emergence treatment was significantly improved, and showed significant difference after irrigation. Under the same irrigation amount, the soil desalination rate of multiple irrigation (F2) treatment was significantly higher than that of single irrigation (F1). The two-year average soil desalination rates of W2F2 and W3F2 treatments were 40.2% and 39.5% higher than those of W2F1 and W3F1 treatments, respectively. For single irrigation treatment, the soil desalination rate increased with the increase of irrigation amount. However, the irrigation amount had no significant effect on the soil desalination rate regardless of the number of irrigations.

[0063] Table 2 Desalination rate of 0-40 cm soil layer under different water emergence treatment

[0064]

[0065]

[0066] 9. Root length density, root activity and root-shoot ratio:

[0067] For the same irrigation quota, the root length density under multiple irrigation (F2) was always higher than that under single irrigation (F1) (A, B). Figure 3 The root length densities of W2F2 and W3F2 treatments were 162.5% and 65.3% higher than those of W2F1 and W3F1 treatments, respectively. Compared with the control (CK), the root length densities under W2F2 and W3F2 treatments increased by 204.4% and 198.2% in two years, respectively. For single irrigation treatment, the two-year average root length density of W3F1 treatment was significantly higher than that of CK by 80.6%. No significant difference was observed between W1F1, W2F1 and CK treatments in 2024. Similarly, no significant difference was found between W2F2 and W3F2 treatments.

[0068] Under the same irrigation amount, the root activity of cotton under multiple irrigation (F2) was always higher than that under single irrigation (F1) (C, D). Figure 4 The root activities of W2F2 and W3F2 treatments were 60.9% and 24.6% higher than those of W2F1 and W3F1 treatments, respectively. Compared with CK, the root activities under W2F2 and W3F2 treatments increased by 76.6% and 68.4% in two years, respectively. For single irrigation treatment, the root activity showed an upward trend with the increase of irrigation amount, and was significantly higher than that of CK. However, the root activity of W3F2 treatment was significantly lower than that of W2F2 in 2024.

[0069] Under the same irrigation quota, the root-shoot ratio of cotton under multiple irrigation (F2) was lower than that under single irrigation (F1) (E, F). Figure 5(A, B) The root-to-shoot ratios of the W2F2 and W3F2 treatments were 51.2% and 36.3% lower than those of the W2F1 and W3F1 treatments, respectively. Compared with the control (CK), the root-to-shoot ratios decreased by 10.6% and 2.7% over two years under the W2F2 and W3F2 treatments, respectively. For a single irrigation, the root-to-shoot ratio of cotton decreased significantly with increasing water volume at emergence, showing a sequence of W3F1 > W2F1 > W1F1. However, no statistically significant difference was observed between the W2F2 and W3F2 treatments.

[0070] 10. Root antioxidant enzyme activity:

[0071] Under the same irrigation quota, the root peroxidase activity of cotton under single irrigation (F1) was higher than that under multiple irrigation (F2). Figure 6 (A, B) In the W2F1 and W3F1 treatments, the peroxidase activity in cotton roots was 23.2% and 46.5% higher than that in the W2F2 and W3F2 treatments, respectively. For a single irrigation, peroxidase activity showed a decreasing trend with increasing water volume at emergence. However, there were no significant differences among the W2F2, W3F2, and CK treatments.

[0072] For a single irrigation treatment, the activity of root superoxide dismutase decreased with increasing water volume at emergence, with the W1F1 treatment reaching the peak activity value. Figure 6 (C, D) There was no significant difference between the W1F1 and CK treatments. Compared with W2F2, the superoxide dismutase activity in cotton roots under the W2F1 treatment was significantly increased by 18.0% and 17.8% in 2023 and 2024, respectively.

[0073] Under the same irrigation quota, the malondialdehyde (MDA) content in cotton roots after multiple irrigations (F2) is lower than that after a single irrigation (F1). Figure 7 (A, B) In the W2F2 and W3F2 treatments, the malondialdehyde (MDA) content in cotton roots was 51.2% and 34.9% lower than that in the W2F1 and W3F1 treatments, respectively. For a single irrigation, the MDA content showed a decreasing trend with increasing water volume at emergence, with the highest peak content observed in the W1F1 treatment. Compared to the control (CK), the MDA content in the W1F1 treatment increased by 92.2% and 91.3% in 2023 and 2024, respectively. However, there were no significant differences among the W2F2, W3F2, and CK treatments.

[0074] The highest root catalase activity was observed in the W3F1 treatment. Figure 7C, D), significantly increased by 77.6% and 78.5% compared with W3F2 and CK, respectively. For single irrigation treatment, the cotton root catalase activity under W2F1 and W1F1 treatments significantly decreased by 65.9% and 65.6% compared with W3F2, respectively. However, there was no significant difference among W2F2, W3F2 and CK treatments.

[0075] 11. Cotton emergence rate, yield and irrigation water production efficiency:

[0076] Under the same irrigation quota, the cotton emergence rate under multiple irrigation (F2) was significantly higher than that under single irrigation (F1) Figure 8 ). For single irrigation treatment, the cotton emergence rate under W3F1 treatment was significantly higher than that under W1F1 and W2F1 treatments, while no significant difference was found between W1F1 and W2F1 treatments. The emergence rate under W2F2 treatment was the highest, but there was no statistical difference between W2F2 and CK treatments in 2024.

[0077] Different irrigation methods had significant effects on cotton boll number and seed cotton yield, but had no significant effect on boll weight (Table 3). For single irrigation treatment, boll number and seed cotton yield significantly increased with the increase of emergence water amount. However, under multiple irrigation treatment, emergence water amount had no significant effect on boll number and seed cotton yield. Under the same irrigation quota, boll number and seed cotton yield under multiple irrigation (F2) were significantly higher than those under single irrigation (F1). Compared with W2F1, the cotton boll number under W2F2 treatment increased by 22.8% and 23.8% in 2023 and 2024, respectively. The seed cotton yield under W2F2 treatment was the highest, which significantly increased by 22.5% and 24.5% in 2023 and 2024, respectively, compared with W2F1. However, there was no significant difference in cotton boll number and seed cotton yield among W2F2, W3F2 and CK treatments. In addition, the irrigation water production efficiency of all dry sowing and wet emergence treatments was higher than that of the control (CK). Similarly, W2F2 treatment showed the highest irrigation water production efficiency, which significantly increased by 58.3% and 55.8% in 2023 and 2024, respectively, compared with CK. Compared with W3F2 treatment, the irrigation water production efficiency of W2F2 treatment increased by 3.4% and 4.0% in 2023 and 2024, respectively.

[0078] Correlation analysis Figure 9) indicated that soil volumetric water content, root activity and root length density were positively correlated with cotton emergence rate. Soil salt content was negatively correlated with cotton emergence rate, root length density and root activity. Cotton seed yield was significantly positively correlated with emergence rate, soil volumetric water content, root length density, root activity and cotton boll number, while it was significantly negatively correlated with root / shoot ratio, root peroxidase, root superoxide dismutase and root malondialdehyde content. In addition, in the attached figures of the specification Figure 9 , the correlation coefficient ranges from 1.0 (red) to -1.0 (blue). * and ** indicate significant differences at the probability level of p < 0.05 and p < 0.01, respectively. ER represents emergence rate; SWC represents soil volumetric water content; SSC represents soil salt content; RLD represents root length density; RV represents root activity; R / S represents root / shoot ratio; POD represents root peroxidase activity; SOD represents root superoxide dismutase activity; MDA represents root malondialdehyde content; CAT represents root catalase activity; BN represents cotton boll number; BW represents cotton boll weight; CY represents seed cotton yield.

[0079] Table 3 Cotton yield and water use efficiency under different irrigation methods

[0080]

[0081] 12. Effect of dry sowing and wet emergence water management on soil water and salt dynamics and desalination rate:

[0082] Soil water content is a key environmental factor affecting cotton emergence and growth. Insufficient soil water cannot meet the normal water requirement of seedling growth, thereby hindering cotton growth. On the contrary, excessive soil water will reduce soil temperature, which has an adverse effect on cotton emergence. Dry sowing and wet emergence water management has a significant effect on soil water and salt dynamics, which is mainly attributed to its unique operation process: dry sowing is followed by directional irrigation to promote emergence. In this study, W2F2 and W3F2 treatments maintained a relatively high soil water content, which was significantly higher than that of the control (CK), mainly due to the increase in drip irrigation frequency during the vigorous growth stage of seedlings. Controlling drip irrigation frequency can maintain the stability of soil water content in the sowing layer, reduce the drastic fluctuation of water, and provide a continuously humid microenvironment for seed germination. Under high temperature and strong evaporation conditions, a higher irrigation frequency can offset the loss of evaporation. In addition, by avoiding pre-sowing flooding or excessive irrigation, controlling the water quantity and frequency of drip irrigation can effectively reduce the initial soil water content. Subsequent controlled irrigation helps to maintain a suitable water content in the root zone for a longer period of time compared to excessive irrigation. This is mainly because the evaporation rate of the dry surface layer is slower than that of completely saturated soil.

[0083] Excessive salt content in soil can affect seed germination and delay cotton seedling growth, while appropriate water and salt conditions can promote cotton growth. In this study, we found that soil salt content gradually decreased with the increase of irrigation amount and drip irrigation frequency at the seedling stage. Optimizing drip irrigation frequency has been proven to effectively reduce the excessive accumulation of salt in the soil and promote the migration of salt outside the root zone. Controlling the amount and frequency of drip irrigation can continuously maintain the surface soil moisture, reduce the evaporation effect (evaporation is the main driving factor of salt backflow), and thus inhibit the accumulation of salt in the surface soil. At the same time, frequent irrigation can continuously and slowly leach salt from the seeding layer, thus maintaining a low salt environment. This conclusion is also confirmed by our research results on the desalination rate. For spring irrigation treatment, due to the larger irrigation amount, the salt leaching effect is better at the early stage, resulting in lower salt content at the early seeding stage. In the dry seeding and wet emergence treatment, W2F2 and W3F2 treatments achieved better salt leaching effect in the surface soil due to more frequent and larger irrigation amount, thus obtaining higher desalination rate.

[0084] The dry seeding and wet emergence technique achieves the goal of "adjusting salt with water and promoting seedlings with water" by controlling irrigation amount and frequency. Appropriate irrigation amount and frequency can maintain sufficient and stable soil moisture in the seeding layer. At the same time, through moderate salt leaching and evaporation inhibition, the salt concentration in the surface layer is reduced, thus creating a "sufficient water, low salt, and suitable ventilation" growth environment for seed germination.

[0085] 13. Effect of dry seeding and wet emergence water regulation on cotton root growth:

[0086] Soil water and salt conditions are closely related to the growth and development of plant roots. In our study, root length density and root activity increased with the increase of irrigation amount and drip irrigation frequency at the seedling stage. Appropriate amount of water and appropriate irrigation frequency at the seedling stage can keep the root system in a "wet but not waterlogged" environment, ensuring normal respiration, sufficient energy supply, and high root activity, which is beneficial to nutrient uptake and seedling growth. When the depth of the wet soil layer is appropriate, the roots can obtain water without excessive elongation. At the same time, a low salt environment can reduce osmotic inhibition and promote the coordinated growth of taproot and lateral roots, resulting in relatively high root density. Insufficient irrigation amount or frequency can lead to water shortage in the surface soil, making salt easily accumulate in the root zone, thus causing osmotic stress and ion toxicity, and leading to decreased root activity.

[0087] Root antioxidant enzymes, including superoxide dismutase, peroxidase, and catalase, act as key protective mechanisms against abiotic stresses such as salt and drought stress. Changes in root activity reflect the intensity of the root stress response. When soil salt is effectively leached and soil moisture remains stable, the root is in a low-level stress state, and the activity of antioxidant enzymes is maintained at a basic level (to maintain oxidation balance and ensure normal metabolism), without excessive activation, thus avoiding energy waste. However, the combination of drought and high salinity triggers oxidative stress, prompting root cells to produce a large amount of active oxygen. In response, the antioxidant enzyme system is significantly activated, and the activities of superoxide dismutase, catalase, and peroxidase are enhanced to scavenge active oxygen and protect cell membrane structures. In this study, increasing the amount and frequency of water release from seedlings effectively reduced the activities of superoxide dismutase, peroxidase, and catalase in cotton roots and the content of malondialdehyde. The possible reason is that the increase in water and frequency of emergence can effectively control the salt in the root zone, reduce the salt stress, and avoid hypoxia. Therefore, the activity of antioxidant enzymes remains at a relatively low level, indicating that the root is in a superior physiological state, in which more energy is allocated for growth rather than stress response. This conclusion is also confirmed by our research results on the root-shoot ratio. Appropriate water management measures result in a decrease in the root-shoot ratio of cotton. Overall, in the dry-sowing and wet-emergence water regulation technique, an appropriate amount of irrigation (to meet the water needs of seedlings without causing waterlogging) combined with a reasonable irrigation frequency (multiple applications to maintain surface soil moisture and low salt) constitutes an optimal irrigation scheme. This combination not only ensures that root activity and root length density remain at a relatively high level, promoting nutrient uptake and root expansion, but also reduces salt or drought stress, keeping antioxidant enzyme activity within a moderate range and avoiding excessive energy consumption. Ultimately, it promotes the healthy development of cotton seedling roots, laying a solid foundation for subsequent growth.

[0088] 14. Effects of dry-sowing and wet-emergence water regulation on cotton emergence rate, yield, and irrigation water production efficiency:

[0089] The complex interactions between soil-root environment factors and root growth play a key role in optimizing crop establishment and enhancing agricultural productivity in drought farmland ecosystems, especially in the desert-oasis ecotone of Xinjiang. Dry-sowing and wet-emergence water management practices have significant and interrelated effects on cotton emergence rate, yield, and irrigation water productivity. These effects can be attributed to optimizing early soil conditions, balancing water use, and promoting root growth. In this study, the cotton emergence rate of the W2F2 treatment was higher than that of the other treatments. This may be because the 'less-frequent' irrigation method used in the irrigation management practice, i.e., targeted irrigation (focusing on the seed area) after sowing in dry soil, enabled dry-sowing and wet-emergence to ensure that the seeds obtained sufficient water to promote germination while avoiding excessive irrigation that could cause soil compaction or seed rot. In this way, uneven emergence caused by drought stress or waterlogging can be prevented. This was also confirmed by our results on root antioxidant enzyme activity, which showed that appropriate water management measures can provide a favorable environment for cotton growth in the soil root zone. The positive effects on emergence translated into yield advantages and were further strengthened through advantages in subsequent growth stages. Higher emergence rate and more uniform emergence distribution can ensure consistent crop density, reduce field gaps, and thus maximize light use efficiency, nutrient uptake efficiency, and resource use efficiency during the growing season. This can avoid yield losses caused by sparse or unevenly distributed plants. Dry-sowing and wet-emergence promote healthy root development and vigorous growth by reducing stress. Stronger seedlings can better withstand later abiotic stresses (such as drought, salinity, and pests) and maintain higher photosynthesis during the flowering and bolling stages. Our data showed that, with increasing irrigation volume at the emergence stage, both cotton boll number and seed cotton yield showed a gradual upward trend. Notably, the high-frequency irrigation treatment resulted in significantly higher values for both parameters. By adjusting soil moisture and reducing root zone salt accumulation, the use of less but more frequent irrigation practices, especially when combined with appropriate post-emergence irrigation, promotes sustained nutrient uptake and increases boll number. In saline environments, this mechanism can effectively prevent premature leaf senescence and cotton boll shedding caused by salt stress. Over the past two years of experimental periods, the comparison of irrigation water productivity for different irrigation treatments showed that the W2F2 treatment, which had less but more frequent irrigation, had the highest irrigation water productivity among all treatments. Unlike flood irrigation or pre-sowing irrigation, dry-sowing and wet-emergence use less but more frequent irrigation, which is only applied to the seed area, thereby minimizing water loss due to deep percolation or evaporation from non-critical soil layers. This reduces the total water use for irrigation during the dry season, while controlled early water supply stimulates deep root growth, allowing the roots to absorb water from the lower layers of soil, thereby reducing the need for frequent irrigation and improving overall water use efficiency. Therefore, the W2F2 treatment, which has less but more frequent irrigation, is recommended as a sustainable production strategy for cotton fields in the arid and semi-arid regions of southern Xinjiang.It not only ensures the emergence rate, promotes the root growth, and increases the yield by increasing the number of cotton bolls, but also improves the water use efficiency and reduces the agricultural irrigation water consumption.

[0090] In order to verify the experimental effect of the present application, the following examples are adopted:

[0091] Example 1

[0092] Experimental conditions

[0093] Test site: A saline-alkali land in a certain arid region of Xinjiang is selected, the soil texture of the land is sandy loam, the pH value of 0-20 cm soil layer is 8.0, the conductivity is 4.0 dS / m, and the initial content of soil salt is 1.2 g / kg.

[0094] Cotton variety: Xinluzao No. 50 cotton variety is selected.

[0095] Seeding condition: On April 15, dry seeding is adopted, the seeding depth is 3 cm, a wide-narrow row planting mode is adopted, the wide row is 65 cm, the narrow row is 10 cm, the planting density is 200,000 plants per hectare, and the plant row spacing is 12 cm.

[0096] Drip irrigation system: the drip head spacing on the drip irrigation pipe is 40 cm, and the drip irrigation pipe is laid at a depth of 15 cm.

[0097] Monitoring equipment: soil moisture sensors and soil salt sensors are installed, and the monitoring frequency is once every 3 hours.

[0098] Irrigation scheme

[0099] According to claim 8, the initial content of soil salt is between 1.0-2.0 g / kg, and the irrigation amount for emergence is set to 39 mm. High-frequency drip irrigation is adopted, the first drip irrigation is carried out at the emergence stage of cotton (7 days after seeding), the drip irrigation amount is 20 mm; the second drip irrigation is carried out at the vigorous stage of cotton seedlings (22 days after seeding), the drip irrigation amount is 19 mm. During each drip irrigation, the water flow speed is controlled to be 1.0 L / h, and the pressure is 0.2 MPa.

[0100] Field management

[0101] During the irrigation process, the root activity is detected regularly (every 10 days), and the root activity is determined by using the triphenyl tetrazolium chloride method.

[0102] In the late growth stage of cotton, according to the dynamic changes of soil moisture and salt, a supplementary irrigation is carried out at the flowering and bolling stage (60 days after seeding), and the irrigation amount is 60 mm.

[0103] Data monitoring

[0104] Soil monitoring: During the whole growth period, the soil volumetric water content and soil salt content were monitored by sensors. According to the monitoring results, the irrigation amount was adjusted in time when the soil volumetric water content was less than 15%, and appropriate salt reduction measures (such as increasing irrigation amount to flush salt) were taken when the soil salt content was higher than 2.0 g / kg. The final average soil volumetric water content was maintained between 18% and 28%, and the soil salt content was controlled between 0.8 and 1.8 g / kg.

[0105] Cotton growth condition monitoring:

[0106] Emergence rate: 15 days after sowing, the emergence rate reached 90%.

[0107] Plant height: At the squaring stage (40 days after sowing), the average plant height was 25 cm; at the flowering stage (65 days after sowing), the average plant height was 50 cm.

[0108] Dry matter accumulation: At the boll opening stage, the dry matter of each organ of the cotton plant was determined, and the dry matter accumulation of the aboveground part was 1200 g / m 2 , and the dry matter accumulation of the underground part was 300 g / m 2 .

[0109] Yield: At the boll opening stage of cotton, the yield of the selected plot was determined, and the seed cotton yield reached 4000 kg / hm 2 .

[0110] Irrigation water use efficiency: The calculation showed that the irrigation water use efficiency was 1.8 kg / m 3 .

[0111] Example 2:

[0112] Experimental conditions

[0113] Test site: Located in a saline-alkali soil in a semi-arid area of Gansu, the soil texture is loam, the pH value of 0-20 cm soil layer is 7.8, the electrical conductivity is 3.5 dS / m 1 , and the initial soil salt content is 0.8 g / kg 1 .

[0114] Cotton variety: Zhongmiansuo 619.

[0115] Sowing: Dry sowing was carried out on April 10, with a sowing depth of 2.5 cm, wide-narrow row planting, wide row 70 cm, narrow row 8 cm, planting density 180,000 plants per hectare, and plant row spacing 13 cm.

[0116] Drip irrigation system: The drip head spacing is 35 cm, and the drip irrigation pipe laying depth is 12 cm.

[0117] Monitoring equipment: soil moisture sensor and soil salt sensor, monitoring frequency is every 2h.

[0118] Irrigation scheme

[0119] Since the initial content of soil salt is less than 1.0g / kg, according to claim 8, the emergence irrigation amount is determined as 25mm. Low frequency drip irrigation is adopted, and only once drip irrigation is carried out at the cotton emergence period (6 days after sowing), and the drip irrigation amount is 25mm. The water flow rate is controlled as 0.8L / h, and the pressure is 0.15MPa.

[0120] Field management

[0121] The cotton root activity is detected regularly (every 10 days).

[0122] In the late growth period of cotton, according to the soil water and salt dynamics, supplementary irrigation is carried out at the flowering period (65 days after sowing), and the irrigation amount is 50mm.

[0123] Data monitoring

[0124] Soil monitoring: during the growth period, real-time monitoring is carried out through the sensor, the irrigation strategy is adjusted, the average soil volume water content is maintained at 16%~26%, and the soil salt content is controlled at 0.6~1.5g / kg.

[0125] Cotton growth condition monitoring:

[0126] Emergence rate: 14 days after sowing, the emergence rate is 85%.

[0127] Plant height: the average plant height at the squaring stage is 23cm, and the average plant height at the flowering stage is 48cm.

[0128] Dry matter accumulation: at the boll opening stage, the aboveground dry matter accumulation is 1100g / m 2 , and the underground dry matter accumulation is 280g / m 2 .

[0129] Yield: the seed cotton yield is determined in the selected plot, which reaches 3800kg / hm 2 .

[0130] Irrigation water use efficiency: the calculated irrigation water use efficiency is 1.7kg / m 3 .

[0131] Example 3:

[0132] Experimental conditions

[0133] Test site: located in a saline-alkali land in a drought area in Inner Mongolia, the soil texture is clay, the pH value of 0-20cm soil layer is 8.2, the conductivity is 4.5dS / m, and the initial content of soil salt is 2.2g / kg.

[0134] Cotton variety: Xinluzhong 77.

[0135] Seeding: Dry seeding on April 20, with a seeding depth of 4 cm, wide-narrow row planting, wide row 60 cm, narrow row 12 cm, planting density 220,000 plants per hectare, plant row spacing 10 cm.

[0136] Drip irrigation system: dripper spacing 45 cm, drip irrigation pipe laying depth 18 cm.

[0137] Monitoring equipment: soil moisture and salt sensors, monitoring frequency every 4 hours.

[0138] Irrigation scheme

[0139] Given that the initial soil salt content is higher than 2.0 g / kg, according to claim 8, the emergence irrigation amount is set to 48 mm. High-frequency drip irrigation is used, with the first drip irrigation amount of 23 mm at the emergence stage (8 days after sowing) and the second drip irrigation amount of 25 mm at the vigorous seedling stage (25 days after sowing). The water flow rate is controlled at 1.2 L / h and the pressure is 0.25 MPa during drip irrigation.

[0140] Field management

[0141] Cotton root activity is detected regularly (every 10 days).

[0142] Supplementary irrigation is carried out at the boll stage (70 days after sowing) in the late growth period of cotton, with an irrigation amount of 70 mm.

[0143] Data monitoring

[0144] Soil monitoring: through sensor data feedback, irrigation is adjusted to maintain the soil volume water content at 17% to 27% and the soil salt content at 0.9 to 1.9 g / kg.

[0145] Cotton growth condition monitoring:

[0146] Emergence rate: 16 days after sowing, the emergence rate is 88%.

[0147] Plant height: the average plant height at the squaring stage is 27 cm, and the average plant height at the flowering stage is 52 cm.

[0148] Dry matter accumulation: at the boll opening stage, the aboveground dry matter accumulation is 1300 g / m 2 , and the underground dry matter accumulation is 320 g / m 2 .

[0149] Yield: plot-determined seed cotton yield reaches 4200 kg / hm 2 .

[0150] Irrigation water use efficiency: the calculated irrigation water use efficiency is 1.9 kg / m 3 .

[0151] Comparative example: traditional irrigation method

[0152] Experimental conditions

[0153] Test site: a plot adjacent to Example 1, with similar conditions of soil texture, pH value, conductivity, etc., and an initial soil salt content of 1.2 g / kg.

[0154] Cotton variety: Xinluzao No. 50.

[0155] Sowing conditions: sowing on April 15, sowing depth 3 cm, planting pattern and density same as Example 1.

[0156] Irrigation system: traditional flood irrigation method was used, two times of flood irrigation in winter and spring, each time with an irrigation amount of 600 m 3 / hm 2 .

[0157] Field management

[0158] According to the traditional cotton field management method, no regular intertillage and weeding operations were performed.

[0159] Data monitoring

[0160] Soil monitoring: during the cotton growth period, the soil volume moisture content fluctuated greatly, being too high in the early stage due to flood irrigation, reaching more than 40%, and rapidly decreasing in the later stage, being difficult to maintain in the appropriate interval; the soil salt content decreased in the early stage, but increased again in the later stage due to water evaporation, the average soil salt content being between 1.5-3.0 g / kg, higher than that of Example 1.

[0161] Cotton growth condition monitoring:

[0162] Emergence rate: 15 days after sowing, the emergence rate was only 60%.

[0163] Plant height: the average plant height at the squaring stage was 20 cm, and the average plant height at the flowering stage was 40 cm, significantly lower than that of Example 1.

[0164] Dry matter accumulation: at the boll opening stage, the aboveground dry matter accumulation was 800 g / m 2 , and the underground dry matter accumulation was 200 g / m 2 .

[0165] Yield: plot-determined seed cotton yield was only 3000 kg / hm 2 .

[0166] Irrigation water use efficiency: the irrigation water use efficiency was calculated to be 1.0 kg / m 3 , which is much lower than that of Example 1.

[0167] Table 4 (Comparison table of soil conditions, growth indexes and yield efficiency of cotton in saline-alkali land under different irrigation methods)

[0168]

[0169] Conclusion: The soil volumetric water content of Examples 1-3 is maintained in the appropriate interval of 16% to 28% (core requirement interval of cotton growth), and the fluctuation range is small, which can continuously provide a stable water environment for the root system; while the comparative example is prone to root anoxia due to the high water content of more than 40% in the early stage, and drought is caused by rapid decline in the later stage, which cannot meet the water requirement of continuous growth of cotton. The soil salt content of Examples 1-3 is always controlled in the safe range of 0.6 to 1.9 g / kg, which effectively avoids the damage of saline-alkali stress to the cotton root system; the salt content of the comparative example is as high as 1.5 to 3.0 g / kg, and the salt content rises in the later stage due to water evaporation, which significantly inhibits the ability of cotton to absorb nutrients and water. The emergence rate of Examples 1-3 is all more than 85% (the highest is 90%), which is much higher than that of the comparative example of 60%. This is because the present application creates a "low salt + suitable moisture" germination environment for seeds in the emergence stage through precise drip irrigation, while the high salt residue and uneven water of traditional irrigation lead to a large number of seeds that cannot break through the soil normally. At the present budding stage, the average plant height of Examples 1-3 (23-27 cm) is 15% to 35% higher than that of the comparative example (20 cm); at the flowering stage, the height of Examples (48-52 cm) is 20% to 30% higher than that of the comparative example (40 cm). It shows that the water and salt regulation of the present application can promote the vegetative growth of cotton and form a more robust plant structure.

[0170] In summary, the salt-alkali land cotton yield-increasing and water-saving type dry sowing and wet emergence irrigation method of the present application solves the four core problems of "difficult emergence, weak growth, low yield, and high water consumption" of cotton in saline-alkali land through the combined strategy of "precise drip irrigation + dynamic monitoring + salt regulation", which has overall advantages compared with traditional irrigation and is suitable for large-scale application in arid / semi-arid saline-alkali cotton areas.

[0171] Although embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A kind of saline-alkali soil cotton yield-increasing water-saving type dry sowing wetting irrigation method, it is characterized by, The method comprises the following steps: Selecting a saline-alkali soil in an arid or semi-arid region as a cotton planting area, wherein the soil pH value of the saline-alkali soil is 7.5-8.5, and the conductivity is 3.0-5.0 dS / m; In winter and spring, instead of traditional flooding irrigation, dry seeding is adopted, and the seeding depth is 2-5 cm; After seeding, in the cotton seedling stage and the vigorous growth stage of the cotton seedlings, according to the soil texture, cotton variety and local climate conditions, the appropriate seedling irrigation amount and drip irrigation frequency are determined, the precise irrigation is performed through the drip irrigation system laid in the cotton field, the soil is kept in a suitable water and salt state, the cotton seedlings are promoted to emerge and grow, and the irrigation water use efficiency is improved; During the whole cotton growth period, the soil water and salt are monitored in real time through soil water and salt sensors, and the seedling irrigation amount and the drip irrigation frequency are adjusted in time according to the monitoring results, so that the soil volume water content is maintained at 15%-30%, and the soil salt content is controlled between 0.5 and 2.0 g / kg.

2. The method according to claim 1, wherein the method is characterized in that, The drip irrigation frequency is divided into two types: Low-frequency drip irrigation: drip irrigation is performed once in the cotton seedling stage; High-frequency drip irrigation: drip irrigation is performed once in the cotton seedling stage and once again in the vigorous growth stage of the cotton seedlings; Compared with the low-frequency drip irrigation, the high-frequency drip irrigation can significantly improve the cotton plant height, dry matter accumulation amount and yield, and improve the irrigation water use efficiency.

3. The saline-alkali soil cotton yield-increasing water-saving type dry sowing and wet emergence irrigation method according to claim 1, characterized in that, The drip irrigation system comprises a drip irrigation pipe laid in the cotton field, a plurality of drippers are arranged on the drip irrigation pipe, the distance between the drippers is 30-50 cm, which is adjusted according to the cotton planting density, and the laying depth of the drip irrigation pipe is 10-20 cm, so that the irrigation water can uniformly penetrate into the soil and avoid local waterlogging or drought.

4. The method according to claim 1, wherein the method is characterized in that, When the drip irrigation is performed, the water flow speed is controlled to be 0.5-1.5 L / h, and the pressure is controlled to be 0.1-0.3 MPa, so that the water can uniformly penetrate into the soil and the water evaporation loss is reduced.

5. The method according to claim 1, wherein the method is characterized in that, Further, the root activity is detected regularly during the irrigation process, the root activity is determined by the triphenyltetrazolium chloride method, the root activity is maintained at a high level, and the healthy growth of the cotton seedlings is promoted.

6. The method according to claim 1, wherein the method is characterized in that, The monitoring frequency of the soil water sensor and the soil salt sensor is once every 2-4 hours, the monitoring data is transmitted to the control center in real time through a wireless transmission module, and the control center automatically adjusts the operation parameters of the drip irrigation system according to the preset soil water and salt threshold values.

7. The method according to claim 1, wherein the method is characterized in that, Further, in the late growth period of the cotton, supplementary irrigation is performed in time according to the dynamic changes of the soil water and salt.

8. The method according to claim 1, wherein the method is characterized by, The seedling irrigation amount is adjusted according to the cotton variety and the initial soil salt content: When the initial soil salt content is lower than 1.0 g / kg, the seedling irrigation amount is 22.5-28.5 mm; When the initial soil salt content is between 1.0 and 2.0 g / kg, the seedling irrigation amount is 37.5-40.5 mm; When the initial soil salt content is higher than 2.0 g / kg, the seedling irrigation amount is 45.0-50.5 mm.

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