Method for improving grassland productivity by mixed sowing of west jujumulun grass and alfalfa

Abstract

The application discloses a method for improving the productivity of grassland by mixed sowing of Xizhuhmujing sheep grass and alfalfa, and comprises the following steps: 1, site selection and land preparation; 2, seed preparation: before sowing, the Xizhuhmujing sheep grass seeds are selected and soaked in clean water at room temperature for 24 hours to promote germination, and then dried for sowing; the alfalfa seeds are treated by breaking hard seeds; 3, sowing: autumn sowing, the sowing time is not later than two months before the arrival of the first frost; the seeds of the alfalfa and the Xizhuhmujing sheep grass are mixed in a weight ratio of 2:1 and sown in the same row; 4, field management; 5, harvesting: no harvesting in the first year of construction and planting; the alfalfa is cut twice in the second year of construction and planting, and thrice in the third year of construction and planting, and each cutting is performed in the initial flowering period of the alfalfa, and the stubble height is 5-8 cm. The method has significant advantages in the aspects of forage yield, forage quality, economic benefits and ecological benefits.

Description

Technical Field

[0001] This invention belongs to the field of forage cultivation technology, specifically relating to a method for improving grassland productivity through mixed sowing of Leymus chinensis and alfalfa. Background Technology

[0002] Legume-grass intercropping is a classic cultivation technique in the field of forage cultivation to improve grassland productivity, forage quality, and soil fertility. Compared with monoculture, it can effectively utilize the complementary advantages between legumes and grasses, achieving efficient use of light energy and water and fertilizer resources. It is the mainstream technology for improving degraded grasslands and establishing artificial forage bases in northern my country.

[0003] West Ujimqin sheepgrass is a superior native gramineous forage variety independently bred in Inner Mongolia, my country. It boasts advantages such as drought resistance, high yield, and strong adaptability, while effectively overcoming the "three lows" technical challenges of common sheepgrass: low heading rate, low seed setting rate, and low germination rate. Alfalfa, yellow alfalfa, and variegated alfalfa are important leguminous forage resources and are preferred leguminous forages for mixed sowing with gramineous forages.

[0004] Currently, the industry has conducted research and application on related technologies for mixed sowing of Leymus chinensis and alfalfa, and has formed a basic technical solution for mixed sowing of soybeans and cereals. However, the existing technology has the following technical problems, which prevent the formation of a mixed sowing method specifically adapted to Leymus chinensis in Xiwuzhumuqin: 1. Existing mixed grass species combinations and ratios are limited. Current technologies mostly focus on single ratios (such as 1:1 or 3:7) of sheepgrass and alfalfa, without fully considering the differences in interspecific competition between different alfalfa species (such as alfalfa, yellow alfalfa, and variegated alfalfa) and sheepgrass when mixed in different ratios, resulting in poor adaptability and versatility of the technology.

[0005] 2. Existing mixed sowing techniques for legumes and cereals lack optimization for specific varieties. Current research focuses on mixed sowing techniques for common sheepgrass or natural sheepgrass meadows with leguminous forage grasses. For the newly developed superior variety "Xiwuzhumuqin Sheepgrass", there is a lack of an optimized mixed sowing cultivation technology system that matches its biological characteristics.

[0006] 3. Current technologies for soybean-grass intercropping are limited. Current methods for intercropping sheepgrass and alfalfa are relatively limited, often employing either inter-row sowing or broadcasting. This approach fails to adequately consider the systematic impacts of different sowing methods (broadcasting, row sowing, inter-row sowing, etc.) on interspecific competition dynamics, light energy utilization efficiency, and ultimately, yield and quality.

[0007] 4. Existing research on soybean-grass mixed sowing technology relies heavily on empirical summaries and lacks sufficient theoretical support. Most existing soybean-grass mixed sowing technologies are based on field planting experience and fail to clarify the impact of different mixed grass species, ratios, and sowing methods on forage yield and quality. The technical mechanisms are unclear and the parameters are not precise, resulting in low standardization and poor stability of existing soybean-grass mixed sowing technologies, making it difficult to promote and apply them on a large scale and in a standardized manner.

[0008] Therefore, there is an urgent need to develop a method to improve grassland productivity by intercropping West Ujimqin sheepgrass and alfalfa. By precisely optimizing the intercropping grass species, intercropping ratio and sowing method, a dynamic balance of competition among legume and forage grass species can be achieved, which can significantly improve the hay yield, forage nutritional quality and soil fertility of the intercropped grassland. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method to improve grassland productivity by intercropping West Ujimqin sheepgrass and alfalfa, so as to significantly improve the hay yield, forage nutritional quality and soil fertility of the intercropped grassland.

[0010] The objective of this invention is achieved through the following technical solution: a method for improving grassland productivity by intercropping West Ujimqin sheepgrass and alfalfa, comprising the following steps: Step 1: Site selection and preparation; Step 2, Seed Preparation: Before sowing, select whole and plump Sheepgrass seeds from West Ujimqin and soak them in clean water at room temperature for 24-48 hours to promote germination. After drying in the shade, they are used for sowing. Alfalfa seeds are treated to break the hard shell. Soaking improves the germination vigor and germination rate of Sheepgrass seeds from West Ujimqin. The shell-breaking treatment of alfalfa seeds breaks their physical dormancy, which ensures the improvement of the emergence rate and survival rate of the two forage grasses. Step 3: Sowing: The seeds of alfalfa and Leymus chinensis were mixed at a weight ratio of 2:1 and sown in rows. This sowing method takes into account both the nitrogen fixation and supply of alfalfa and the complementary advantages of alfalfa and Leymus chinensis competing for light and heat resources. Step 4: Field Management; Step 5, Results: No harvesting is done in the first year after establishment; two mowings are done in the second year and three mowings are done in the third year, all at the initial flowering stage of alfalfa, with a stubble height of 5-8 cm each time. Not mowing in the first year is conducive to the full development of the forage root system, laying the foundation for sustained high yields in subsequent years; mowing at the initial flowering stage in the second and third years takes into account both grass yield and nutritional quality; leaving a stubble height of 5-8 cm can retain enough regenerating buds to promote rapid regeneration after mowing and avoid grassland decline due to over-mowing.

[0011] Furthermore, in step one, select a flat, well-drained loam or sandy loam plot with a deep soil layer and a soil pH of 6.0–8.5. Six months before sowing, conduct deep plowing to a depth of 25–35 cm to remove weeds and stones. During land preparation, apply 15,000–30,000 kg / hm² of well-rotted organic fertilizer as base fertilizer. Deep plowing breaks up the plow pan, increases soil permeability, and, combined with the application of organic fertilizer as base fertilizer, creates a favorable soil environment for deep root development and nutrient supply throughout the entire growth period of the mixed-sown forage grasses, which is the foundation for high and stable grassland yields.

[0012] Furthermore, spring or autumn sowing can be adopted, with autumn sowing no later than two months before the first frost. If spring sowing is adopted, deep plowing, land preparation, and basal fertilizer application should be carried out in the autumn of the previous year; if autumn sowing is adopted, deep plowing, land preparation, and basal fertilizer application should be carried out in the spring of the same year.

[0013] Furthermore, in step three, the sowing depth is 1-2 cm, the row spacing is 15-30 cm, and 150-200 kg / hm² of diammonium phosphate is applied as seed fertilizer at sowing, with the fertilizer applied 5 cm below the seed. After sowing, the soil is compacted in time.

[0014] Furthermore, in step three, the seeding rate of sheepgrass is 5.0 kg / hm², and the seeding rate of alfalfa is 10.0 kg / hm².

[0015] Furthermore, autumn sowing is carried out. In step four, during the first year of planting, weeding is performed twice during the seedling stage; during the second year, no weeding is performed; during the third year, weeding is performed promptly during the greening-up period and before and after each harvest; during the initial planting period, irrigation is performed once each during the seedling emergence period and before the soil freezes; during the second year, irrigation is performed once during the greening-up period; during the third year, nitrogen, phosphorus, and potassium compound fertilizer is applied in conjunction with irrigation during the greening-up period and after each harvest. Through differentiated management in different years and irrigation during key periods, a balance between water conservation and seedling protection and sustained high yields is achieved.

[0016] The beneficial effects of this invention are: 1. Significantly increased forage yield. This invention uses a 2:1 weight ratio of alfalfa to sheepgrass in the same row for sowing. The average dry hay yield over two years reached 13,567.5 kg / hm², which is significantly higher than that of sheepgrass and alfalfa sowing alone or other mixed sowing methods.

[0017] 2. The quality of forage is significantly improved. The forage harvested by the method of this invention has a crude protein content of 16.5% to 18.6% and a relative feed value (RFV) maintained in the range of 120 to 145, achieving a synergistic improvement in both high yield and quality.

[0018] 3. The mixed-sown grassland exhibits strong community structure stability. This invention selects alfalfa as the mixed-sown grass species for Leymus chinensis in West Ujimqin. By utilizing the strong nitrogen-fixing ability of alfalfa and its resource niche differentiation effect with Leymus chinensis, a benign complementary and mutually beneficial mechanism that balances competition and complementarity is formed, resulting in strong community structure stability of the mixed-sown grassland.

[0019] 4. Soil fertility is improved. Long-term use of the 2:1 weight ratio of alfalfa to sheepgrass in the same row of the present invention can achieve positive accumulation of total nitrogen content in the soil (an increase of 5.2% over two years), reduce fertilizer input, and achieve sustainable grassland utilization. Detailed Implementation

[0020] The present invention will now be described in detail. Example

[0021] 1. Experimental Design: To verify the technical effects of this invention, a field trial was conducted in 2023 at the Agro-pastoral ecotone experimental demonstration base of the Grassland Research Institute of the Chinese Academy of Agricultural Sciences in Sharqin Town, Tumd Left Banner, Inner Mongolia. The test material was *Leymus chinensis* (West Ujimqin sheepgrass). Leymus chinensis cv. Xiwuzhumuqin), alfalfa ( Medicago sativa ), yellow alfalfa ( Medicago falcata ) and alfalfa ( Medicago ruthenica The experimental design is shown in Table 1.

[0022] This experiment employed a three-factor, three-level orthogonal experimental design (see Table 1). The experimental factors were the mixing ratio, mixing method, and mixing grass species. Three different treatments were set for each of these three factors, resulting in a total of nine mixing treatments. Each mixing treatment was replicated three times. The experimental plot size was 20 m². 2 (4 m × 5 m). At the same time, four forage grasses, namely West Ujimqin sheepgrass, purple alfalfa, yellow alfalfa and variegated alfalfa, were set up as controls, and each single-seeding treatment was replicated three times.

[0023] Table 1 Experimental Design Scheme Site selection and land preparation, seed preparation, sowing, field management, and harvesting are carried out according to the following steps: Step 1: Site Selection and Preparation Choose a flat, well-drained loam or sandy loam plot with a deep soil layer and a soil pH of 7-8 (pH 6.0-8.5 is acceptable). In the autumn of the year before sowing or in the spring of the same year, deep plow to 30 cm (25-35 cm is acceptable) and remove weeds and stones. In conjunction with land preparation, apply 30,000 kg / hm² of well-rotted organic fertilizer (15,000-30,000 kg / hm² is acceptable) as base fertilizer.

[0024] Step 2, Seed Preparation: Choose West Ujimqin sheepgrass, Grassland No. 4 alfalfa, Hulunbuir yellow alfalfa and Mengnong No. 2 alfalfa.

[0025] Before sowing, select whole and plump seeds of Leymus chinensis and soak them in clean water at room temperature for 24 hours (24-48 hours is acceptable) to promote germination. After drying in the shade, they can be used for sowing. Alfalfa, alfalfa, and clover seeds should be treated to break up hard seeds.

[0026] Step 3: Sowing: Sowing time: Autumn sowing is preferred when there is no irrigation. Sowing time should not be later than two months before the first frost.

[0027] Table 1 shows the mixed-sowing grass species, mixing ratios, and mixing methods. All mixing ratios are based on seed weight. For mixed sowing, the seeding rate of *Leymus chinensis* (West Ujimqin grass) was 5.0 kg / hm². The seeding rates of alfalfa, yellow alfalfa, and variegated alfalfa were calculated based on the mixing ratios for different treatments. For monoculture, the seeding rate of *Leymus chinensis*, alfalfa, yellow alfalfa, and variegated alfalfa was 5.0 kg / hm². The sowing depth was 2 cm (1–2 cm is acceptable), and the row spacing was 30 cm (15–30 cm is acceptable). The soil was compacted promptly after sowing. 150 kg / hm² (150–200 kg / hm² is acceptable) of diammonium phosphate was applied as seed fertilizer at sowing, 5 cm below the seed.

[0028] Step 4: Field Management 1. Weed control: Weeds should be removed promptly. In the first year of planting, weeding should be done twice during the seedling stage; in the second year of planting, weeding should not be done; in the third year of planting, weeds should be removed promptly during the greening period and before and after each harvest.

[0029] 2. Water and fertilizer management: In the early stage of planting, irrigate once during the seedling stage and once before the soil freezes; in the second year of planting, irrigate once during the greening stage; in the third year of planting, irrigate and top-dress during the greening stage and after each harvest, and apply nitrogen, phosphorus and potassium compound fertilizer in conjunction with irrigation, with an application rate of 150 kg / hm² (150-200 kg / hm² is acceptable).

[0030] Step 5, Results: Harvest alfalfa at the initial flowering stage. Do not harvest in the first year after planting; harvest twice in the second year after planting; harvest three times in the third year after planting. Leave a stubble height of 5 cm (5-8 cm is acceptable) after each harvest.

[0031] The membership function method was used to normalize the four positive indicators of total hay yield, crude protein content (CP), relative feed value (RFV), and land equivalent ratio (LER) for each treatment. The comprehensive evaluation value of each treatment for each year was calculated, and the average of the two years was taken to obtain the final comprehensive ranking.

[0032] 2. Experimental Results and Analysis: 1) Analysis of yield, nutritional quality, and land equivalent ratio: Tables 2 and 3 show the results of hay yield, crude protein (CP), relative feed value (RFV), and land equivalent ratio (LER) for each treatment in 2024 and 2025. Hay yield was obtained by weighing after mowing, and crude protein content was determined using the Kjeldahl method.

[0033] Relative Feed Value (RFV) is calculated using the following formula: Dry matter intake (DMI, % BW) = 120 / NDF (% DM); Digestible dry matter (DDM, % DM) = 88.9 - 0.779 × ADF (% DM); RFV = (DMI × DDM) / 1.29.

[0034] In the formula, NDF is neutral detergent fiber and ADF is acid detergent fiber, and the content of both is expressed as a percentage of dry matter (%DM).

[0035] The formula for calculating the Land Equivalent Ratio (LER) is: LER = Yig / Ymg + Yil / Yml; Wherein, Yig is the hay yield of Leymus chinensis in the mixed-sowing treatment; Ymg is the hay yield of Leymus chinensis monoculture control; Yil is the hay yield of alfalfa in the mixed-sowing treatment; and Yml is the hay yield of alfalfa monoculture control.

[0036] Table 2. Hay yield and nutritional quality of each treatment in 2024 Lc-CK 5353.50 13.47 99.5 — Ms-CK 6651.56 18.28 136.8 — Mr-CK 5632.45 16.68 122.3 — Mf-CK 9095.84 18.85 155.3 — LcMs-SB1 10009.90 18.6 128.5 1.48 LcMr-JH1 5429.17 15.84 104.5 0.91 LcMf-TH1 5628.38 17.53 118.7 0.94 LcMs-TH2 10620.69 16.98 120.3 1.75 LcMr-SB2 6300.55 15.33 113.7 1.14 LcMf-JH2 5642.17 18.11 125 0.94 LcMs-JH3 9122.30 17.74 119 1.62 LcMr-TH3 4450.94 15.43 104.7 0.75 LcMf-SB3 6012.53 19 146.6 1 Table 3. Hay yield and nutritional quality of each treatment in 2025 Lc-CK 10438.93 15.47 107.2 — Ms-CK 15475.73 18.1 157 — Mr-CK 6623.34 15.52 154.7 — Mf-CK 13538.47 18.15 168.4 — LcMs-SB1 15974.22 17.54 143.7 1.43 LcMr-JH1 10044.80 14.5 112.8 0.97 LcMf-TH1 15037.45 16.31 145 1.08 LcMs-TH2 16514.32 16.62 144.7 1.52 LcMr-SB2 9248.53 15.44 121.3 0.95 LcMf-JH2 14399.57 17.25 134.9 1.27 LcMs-JH3 13411.08 17.96 142.1 1.24 LcMr-TH3 9150.85 15.65 116.7 0.89 LcMf-SB3 11666.62 16.29 135.5 1.08 As shown in Tables 2 and 3, the LcMs-TH2 treatment (alfalfa and Leymus chinensis seed weight ratio of 2:1, row sowing) had the highest total hay yield in 2024 and 2025, reaching 10620.69 kg / hm² and 16514.32 kg / hm², respectively. Its land equivalent ratio (LER) was 1.75 and 1.52 in 2024 and 2025, respectively, both significantly greater than 1, indicating a clear land use advantage for this mixed sowing treatment. In contrast, the LcMr series treatments generally had lower total hay yield and LER, with some treatments having a LER of less than 1, indicating severe interspecific competition inhibition during alfalfa and Leymus chinensis mixed sowing.

[0037] 2) Economic Benefit Analysis: Tables 4 and 5 detail the economic benefits of each treatment in 2024 and 2025.

[0038] In the calculation of economic benefits, the total input includes the costs of seeds, fertilizers, irrigation, machinery operations, and labor. Grass yield and total output are calculated based on the market price of forage in that year (1.3 yuan / kg for hay); Net profit = Total output - Total input; Rate of return = (Net profit / Total investment) × 100%; Input-output ratio = total output / total input.

[0039] Table 4. Detailed breakdown of economic benefits for each treatment method in 2024 Lc-CK 4593 6959.6 6959.6 2366.6 51.5 1.52 Ms-CK 4473 9977.4 9977.4 5504.4 123.1 2.23 Mr-CK 4443 7322.3 7322.3 2879.3 64.8 1.65 Mf-CK 4608 11824.5 11824.5 7216.5 156.7 2.57 LcMs-SB1 4533 14013.9 14013.9 9480.9 209.2 3.09 LcMr-JH1 4743 7329.4 7329.4 2586.4 54.5 1.55 LcMf-TH1 4602 7598.3 7598.3 2996.3 65.1 1.65 LcMs-TH2 4513 14869 14869 10356 229.5 3.3 LcMr-SB2 4493 8505.8 8505.8 4012.8 89.3 1.89 LcMf-JH2 4908 7617 7617 2709 55.2 1.55 LcMs-JH3 4773 12771.2 12771.2 7998.2 167.6 2.68 LcMr-TH3 4481 6008.7 6008.7 1527.7 34.1 1.34 LcMf-SB3 4604 8116.9 8116.9 3512.9 76.3 1.76 Table 5. Detailed breakdown of economic benefits for each treatment method in 2025 Lc-CK 6542 13570.6 13570.6 7028.6 107.4 2.07 Ms-CK 6542 23213.6 23213.6 16671.6 254.8 3.55 Mr-CK 6542 8610.3 8610.3 2068.3 31.6 1.32 Mf-CK 6542 17600.1 17600.1 11058.1 169.1 2.69 LcMs-SB1 6542 22363.9 22363.9 15821.9 241.9 3.42 LcMr-JH1 6542 13560.5 13560.5 7018.5 107.3 2.07 LcMf-TH1 6542 20300.5 20300.5 13758.5 210.3 3.1 LcMs-TH2 6542 23120 23120 16578 253.4 3.53 LcMr-SB2 6542 12485.5 12485.5 5943.5 90.9 1.91 LcMf-JH2 6542 19439.5 19439.5 12897.5 197.2 2.97 LcMs-JH3 6542 18775.5 18775.5 12233.5 187 2.87 LcMr-TH3 6542 12353.7 12353.7 5811.7 88.9 1.89 LcMf-SB3 6542 15749.9 15749.9 9207.9 140.8 2.41 Table 6 summarizes the cumulative economic benefits for 2024 and 2025. The calculation method for the relevant values ​​of cumulative economic benefits is as follows: Cumulative net profit = 2024 net profit + 2025 net profit; Increased income compared to monoculture of Leymus chinensis = Cumulative net income from treatment - Lc - CK cumulative net income; Average return = (2024 return + 2025 return) / 2; Average input-output ratio = (2024 input-output ratio + 2025 input-output ratio) / 2.

[0040] Table 6. Cumulative Economic Effects Over Two Years Lc-CK 6542 — 84.4 1.84 Ms-CK 6542 — 201.4 3.01 Mr-CK 6542 — 45 1.45 Mf-CK 6542 — 164 2.64 LcMs-SB1 6542 15907.6 228.5 3.28 LcMr-JH1 6542 209.7 85.1 1.85 LcMf-TH1 6542 7359.6 150.4 2.5 LcMs-TH2 6542 17538.8 243.6 3.44 LcMr-SB2 6542 561.1 90.2 1.9 LcMf-JH2 6542 6211.3 136.3 2.36 LcMs-JH3 6542 10836.5 178.8 2.79 LcMr-TH3 6542 -2055.8 66.6 1.67 LcMf-SB3 6542 3325.6 114.1 2.14 As shown in Tables 4-6, the LcMs-TH2 treatment (alfalfa and Leymus chinensis seed weight ratio of 2:1, row sowing) had significantly higher net income, rate of return, and input-output ratio in 2024 and 2025 than other treatments, with a cumulative net income of 26,934 yuan / hm², an increase of 17,538.8 yuan / hm² compared to Leymus chinensis monoculture, and an average rate of return of 241.45%. In contrast, the cumulative net income of some alfalfa mixed sowing treatments (such as LcMr-TH3) was even lower than that of Leymus chinensis monoculture, indicating poor economic benefits of alfalfa and Leymus chinensis mixed sowing.

[0041] 3) Ecological effect analysis: Table 7 shows the changes in total nitrogen, available phosphorus, and available potassium content in soils under each treatment in 2024 and 2025. Soil samples were collected from the 5-20 cm soil layer after each harvest. Total nitrogen content was determined using the Kjeldahl method, available phosphorus content was determined using the sodium bicarbonate extraction-molybdenum antimony colorimetric method, and available potassium content was determined using the flame photometry method.

[0042] Table 7 Soil nutrient content of each treatment (comparison between 2024 and 2025) Lc-CK 0.94 0.89 -5.3 16.75 19.7 17.6 138.5 160.2 15.7 Ms-CK 1.11 0.92 -17.1 25.1 21.5 -14.3 137.2 158.6 15.6 Mr-CK 0.92 0.88 -4.3 23.17 18.9 -18.4 137.9 155.3 12.6 Mf-CK 0.75 0.91 21.3 16.87 20.8 23.3 136.9 156.8 14.5 LcMs-SB1 1.12 0.96 -14.3 24.75 22.3 -9.9 138.5 155.4 12.2 LcMr-JH1 1.01 0.9 -10.9 21.14 19.5 -7.8 137.5 154.2 12.1 LcMf-TH1 1.01 0.92 -8.9 18.11 20.2 11.5 131.9 153.6 16.4 LcMs-TH2 0.97 1.02 5.2 29.53 25.8 -12.6 136.2 152.1 11.7 LcMr-SB2 0.94 0.91 -3.2 13.01 19.8 52.2 135.9 153.8 13.2 LcMf-JH2 1.03 0.94 -8.7 13.01 20.5 57.6 133.2 154.5 16 LcMs-JH3 0.83 0.98 18.1 13.83 23.1 67 134.9 151.2 12.1 LcMr-TH3 0.91 0.87 -4.4 18.38 18.5 0.7 135.8 152.5 12.3 LcMf-SB3 1.04 0.93 -10.6 14.68 20 36.2 141.5 153 8.1 Table 7 shows that the LcMs-TH2 treatment (alfalfa and Leymus chinensis seed weight ratio 2:1, row sowing) was the only treatment to achieve positive accumulation of total nitrogen in the soil (a 5.2% increase over two years), with a total nitrogen content of 1.02 g / kg in 2025, the highest among all treatments. The available phosphorus content of this treatment (25.8 mg / kg) was also significantly higher than other treatments, demonstrating the nitrogen fixation and phosphorus activation capabilities of the mixed sowing of alfalfa and Leymus chinensis. The available potassium content was slightly lower than that of Leymus chinensis monoculture, suggesting appropriate potassium fertilizer application in production. Meanwhile, the total nitrogen decreased by 17.1% in alfalfa monoculture (Ms-CK), indicating that if alfalfa is sown alone for a long period without other management practices, soil nitrogen consumption exceeds accumulation.

[0043] 3. Overall Evaluation: Table 8 shows the comprehensive evaluation values ​​and rankings of membership functions. The results indicate that the LcMs-TH2 treatment (seed weight ratio of alfalfa to Leymus chinensis 2:1, row sowing) had the highest comprehensive evaluation value (0.794), followed by LcMs-SB1 (0.774) and LcMs-JH3 (0.663). The comprehensive values ​​of all treatments involving alfalfa were generally below 0.3, while those related to alfalfa ranged from 0.55 to 0.68.

[0044] Table 8. Comprehensive Evaluation Values ​​and Rankings of Membership Functions LcMs-SB1 0.723 0.825 0.774 2 LcMr-JH1 0.244 0.137 0.191 9 LcMf-TH1 0.398 0.701 0.550 6 LcMs-TH2 0.749 0.838 0.794 1 LcMr-SB2 0.302 0.223 0.263 8 LcMf-JH2 0.398 0.663 0.531 7 LcMs-JH3 0.638 0.687 0.663 3 LcMr-TH3 0.040 0.160 0.100 10 LcMf-SB3 0.626 0.468 0.547 5 Based on the field trial data from 2024 and 2025 and the above analysis, the following conclusions are drawn: 1) Optimal Technical Solution: The method proposed in this invention, which involves sowing alfalfa and Leymus chinensis in the same row at a seed weight ratio of 2:1 (Leymus chinensis seeding rate 5.0 kg / hm², alfalfa seeding rate 10.0 kg / hm²), demonstrates optimal performance in terms of hay yield, nutritional quality, economic benefits, and ecological benefits. The two-year average hay yield reached 13567.5 kg / hm², with a land equivalent ratio of 1.64, a crude protein content of 16.8%, and a relative feed value of 132.5, all significantly superior to other mixed sowing treatments and monoculture controls.

[0045] 2) Improved yield and quality: Compared with monoculture of sheepgrass in Xiwuzhumuqin, the optimal technical solution of this invention increases hay yield by 72% to 98%, crude protein content by 3.3% to 4.5%, and relative feed value from 103 to 128 to 140, achieving a synergistic improvement in high yield and quality.

[0046] 3) Significant economic benefits: The optimal technical solution of this invention achieved a cumulative net income of 26,934 yuan / hm² over two years, which is 17,539 yuan / hm² more than that of monoculture of Leymus chinensis in West Ujimqin, with an average rate of return of 241.45% and an input-output ratio of 3.42, ranking first in economic benefits among all treatments. The overall economic benefits of the mixed sowing treatment of alfalfa and Leymus chinensis in West Ujimqin are significantly better than those of mixed sowing treatments of alfalfa and clover, and the cumulative net income of some of the latter two treatments is even lower than that of monoculture of Leymus chinensis in West Ujimqin.

[0047] 4) Outstanding ecological benefits: The optimal technical solution of this invention is the only treatment that achieves positive accumulation of total nitrogen in the soil (a 5.2% increase over two years), with a total nitrogen content of 1.02 g / kg in 2025, the highest among all treatments; at the same time, the available phosphorus content is 25.8 mg / kg, significantly higher than other treatments, demonstrating the biological nitrogen fixation and phosphorus activation capabilities of the optimal technical solution of this invention. Most other treatments showed a decreasing trend in total soil nitrogen, requiring long-term reliance on chemical nitrogen fertilizers for cultivation.

[0048] In summary, the method of the present invention has significant advantages in terms of forage yield, forage quality, economic benefits, and ecological benefits, and has outstanding technological progress and widespread application value.

[0049] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for improving grassland productivity through mixed sowing of Leymus chinensis and alfalfa in West Ujimqin, characterized in that... Includes the following steps: Step 1: Site selection and preparation; Step 2, Seed Preparation: Before sowing, select whole and plump Sheepgrass seeds from West Ujimqin and soak them in clean water at room temperature for 24-48 hours to promote germination. After drying in the shade, they can be used for sowing. Alfalfa seeds should be treated to break up hard seeds. Step 3: Sowing: Mix alfalfa and sheepgrass seeds in a 2:1 ratio by weight and sow in rows in the same row. Step 4: Field Management; Step 5, Results: No harvest is made in the first year after planting; two harvests are made in the second year after planting and three harvests are made in the third year after planting. All harvests are made at the initial flowering stage of alfalfa, and the stubble height is 5-8 cm each time.

2. The method for improving grassland productivity by intercropping West Ujimqin sheepgrass and alfalfa according to claim 1, characterized in that: In step one, select a flat, well-drained loam or sandy loam plot with a deep soil layer and a soil pH of 6.0–8.

5. Six months before sowing, carry out deep plowing to a depth of 25–35 cm to remove weeds and stones. In conjunction with land preparation, apply 15,000–30,000 kg / hm² of well-rotted organic fertilizer as base fertilizer.

3. The method for improving grassland productivity by intercropping West Ujimqin sheepgrass and alfalfa according to claim 1, characterized in that: In step three, spring or autumn sowing is adopted, with autumn sowing no later than two months before the first frost.

4. The method for improving grassland productivity by intercropping West Ujimqin sheepgrass and alfalfa according to claim 1, characterized in that: In step three, the sowing depth is 1-2 cm, the row spacing is 15-30 cm, and 150-200 kg / hm² of diammonium phosphate is applied as seed fertilizer at the time of sowing, with the fertilizer applied 5 cm below the seed. After sowing, the soil should be compacted in time.

5. The method for improving grassland productivity by intercropping West Ujimqin sheepgrass and alfalfa according to claim 1, characterized in that: In step three, the seeding rate of sheepgrass is 5.0 kg / hm², and the seeding rate of alfalfa is 10.0 kg / hm².

6. The method for improving grassland productivity by intercropping West Ujimqin sheepgrass and alfalfa according to claim 1, characterized in that: In autumn sowing, in step four, weeding is carried out twice during the seedling stage in the first year of planting; no weeding is carried out in the second year of planting; and weeding is carried out in a timely manner during the greening period and before and after each harvest in the third year of planting.

7. The method for improving grassland productivity by intercropping West Ujimqin sheepgrass and alfalfa according to claim 1, characterized in that: In autumn sowing, in step four, water once each during the seedling emergence period and before the soil freezes in the early stage of planting; water once during the greening period in the second year of planting; and apply nitrogen, phosphorus and potassium compound fertilizer during the greening period and after each harvest, in conjunction with watering, in the third year of planting.

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