A METHOD FOR SELECTING LAWN GRASS AND ITS APPLICATION FOR PREPARING LAWN SEEDS WITH OPTIMIZED CO2 CAPTURE AND SEQUESTRATION PROPERTIES

Abstract

The field of the invention is that of plant development, and in particular grass seed development, contributing to the reduction of greenhouse gases, especially CO2. The aim of the invention is to provide a method for selecting grass species and varieties, so that they can be classified according to their carbon footprint.This goal is achieved by the process according to the invention, which is characterized in that it essentially consists of: a Cultivating the turfgrasses considered, at least one sample (preferably three) per species or variety; b Taking for each turfgrass considered at least one core comprising each of the soil and the plant cover; c Analyzing in each core, the total carbon C and optionally at least one of the following parameters: total nitrogen N, moisture H and Van Soest fractionation; d Calculating the capacity Cp to capture and sequester CO₂ in number of tonnes of CO₂ captured and sequestered for each species or variety, per unit of cultivation time and per unit of cultivated area, using the total carbon C, and optionally the other parameter(s) obtained by the analysis (c); e Selecting the species and / or varieties according to their capacity Cp to capture and sequester CO₂.

Description

Technical field The field of the invention is that of the development of plants, and in particular of grass seeds contributing to the reduction of greenhouse gases, in particular CO2. More specifically, the invention relates to the development of new grass seed compositions with the lowest possible carbon footprint, both in terms of CO2 emissions during seed production and in terms of CO2 capture and sequestration during use in cultivation. More specifically, the invention aims to develop a useful tool for the development of new grass seed compositions contributing to the reduction of greenhouse gases such as CO2. General - technological background - technical problem Lawns are mixtures of selected fine grasses, usually grasses. The main grass species used for sowing lawns or turf are chosen based on their ornamental qualities, their resistance to trampling, leaf diseases, drought, their lifespan, and the maintenance they require. Lawns are used in cities and gardens, for sports, landscaping, road and river uses. Urban soils are mostly sterile and dry, deprived of air and water by the impermeable asphalt of roads, sidewalks, parking lots, and buildings. Grass plays a vital role in optimizing soil permeability. Rainwater seeps into the subsoil and the water table. This water becomes an available reserve for plant roots, particularly those of nearby trees. Grass also plays another environmental role in the urban ecosystem, creating cold spots that help offset the warming of the city. The positive impact of lawns on sustainable development can also be achieved by reducing the water, fertilizers, phytosanitary products, and energy (mowing) used for their maintenance. The inventors were not satisfied with the known environmental qualities of lawns and so they pushed their thinking further to develop lawns with even more beneficial properties for the environment. To do this, the inventors had the idea of ​​working on the observation that lawns contribute to carbon sequestration through the development and decomposition of Root system. The aerial parts of grasses, composed primarily of green leaves, are capable of capturing carbon dioxide throughout the year. Carbon is captured within the plant and sequestered in the soil through the development and subsequent decomposition of the root system. When plant organic matter degrades, it returns organic matter to the soil. The most stable compounds are semicellulose and lignin (humus). These substances accumulate in the soil over hundreds, even thousands of years. The soil is therefore a larger reservoir of carbon than all the vegetation on Earth and the atmosphere combined. A well-maintained lawn can capture 10 to 12 tons of CO2 per year, in its leaves and roots. Thus, for the same soil surface area, lawns allow twice as much CO2 to be sequestered in the soil as a 120-year-old deciduous forest, and as much as a 25-year-old conifer plantation. Lawns therefore contribute to good air quality because they capture and sequester carbon dioxide. Soil carbon sequestration by turfgrass can be improved through plant selection, particularly suitable grasses which, due to the density of their root systems, have the capacity to provide organic matter for humus production. Thus, one of the essential objectives of the invention is to provide a method for selecting species and varieties of lawns, so as to be able to classify them according to their capacity to sequester carbon. The other essential objective of the invention is to propose a new process for obtaining lawn seed compositions with specific properties in terms of sequestration and storage of CO2, i.e. carbon. Description of the invention In this context, the inventors had the merit of developing a process for selecting species, and within the same species, different varieties of lawns in order to be able to prioritize them according to their power to sequester and store carbon from atmospheric CO2. The invention therefore relates, first of all, to a method for selecting species, and within the same species, different varieties of lawns, characterized in that it essentially consists of: a Cultivate the lawns considered, at least one sample (preferably 3) per species or variety; b Take at least one core sample for each lawn considered, each comprising soil and plant cover; c Analyze in each core, the total carbon C and possibly at least one of the following parameters: total nitrogen N, humidity H and Van Soest fractionation; d Calculate the capacity Cp to capture and sequester CO2 in number of tonnes of CO2 captured and sequestered for each species or variety, per unit of cultivation duration and per unit of cultivated area, using the total carbon C, and possibly the other parameter(s) obtained by analysis (c); e Select species and / or varieties according to their Cp capacity to capture and sequester CO2. Such a selection process opens access to the development of lawns that are more or less efficient in terms of carbon capture and sequestration, these lawns constituting effective means of combating global warming. These lawns reduce the carbon footprint measured in CO2 units and thus the quantity of this greenhouse gas directly involved in global warming. The selection process according to the invention also makes it possible to increase the CO2 sequestration and storage capacity of grassed areas by developing more ecological lawn mixtures (species and varieties). The present invention also relates to: o a process for obtaining lawn seed compositions, characterized in that it essentially consists of mixing seeds of species and / or varieties of lawns selected by the process according to the invention; o and a lawn seed composition characterized in that it comprises seeds of at least one species and / or at least one variety of lawn(s) selected by the method according to the invention. The invention makes it possible to propose a strategy for the rational management of lawns in urban environments, in particular by offering maintenance systems adapted to plant requirements (differentiated management of lawns) to reduce the carbon footprint, not only by acting on the consumption of water, fertilizers, phytosanitary products and energy (reduction of mowing), but also by optimizing the sequestration and storage of carbon (CO2) in order to effectively combat global warming, by proposing compositions which make it possible to optimize the ecological footprint. Detailed description of the invention According to a preferred characteristic of the invention, the lawns considered are grasses. Grasses can be, for example: Tall Fescue, Kentucky Bluegrass, Bentgrass, Red Fescue, Perennial Ryegrass. Culture step_(a) Preferably, when growing (a), it is planned: o to mow the lawn so that its height remains less than 10 cm, preferably between 2 and 5 cm, and even more preferably around 3 cm; o to fertilize at a rate of 100 to 200, preferably 150, units of nitrogen / ha / year; and o to water in such a way as to compensate for losses due to transpiration of the turf samples and evaporation due to the climate. In practice, we plan for example: o 25 to 30 mowings / year (height 5cm); o fertilization based on 150 + / -20 nitrogen units / ha (nutritional balance 3 / 1 / 3) in 4 47-2 passes (UF slow-release fertilizer); or reasonable watering. Sampling step (b) It is advantageous for sampling (b) that each core is cylindrical with a diameter between 5 and 20 cm, preferably of the order of 10 cm, and a height between 10 and 30 cm, preferably of the order of 20 cm. Even more preferably for this sample (b), each carrot is divided into three parts: the soil, the roots and the aerial parts. Step analysis, (c). Preferably, for analysis (c), the following measurement methods are used: o Ground: carbon C: NF X31-109 (Determination of organic carbon by sulfochromic oxidation), total nitrogen N: NF ISO 13878 (Determination of total nitrogen content by dry combustion, Dumas method), humidity H (dry matter): NF ISO 11465 (Determination of the weight content of dry matter and water - Gravimetric method); o Roots and aerial parts: total carbon C: internal method derived from NF ISO 14235 (Determination of organic carbon by sulfochromic oxidation) adapted to plants, total nitrogen: internal method according to NF ISO 13878, - humidity H (dry matter): internal method according to NF ISO 11465, Van Soest fractionation: internal method derived from XP U44-162 (characterization of organic matter by biochemical fractionation and estimation of its biological stability, Van Soest method) adapted to plants. Dry matter, bulk density, organic matter are other parameters that can be measured and used in the calculation of Cp according to step (d). Calculation step (d) of Cp Preferably, for calculation (d), the parameters C total carbon, N total nitrogen, H humidity and Van Soest fractionation are used. More preferably, calculation (d) is carried out by multiplying by (44 / 12) the total carbon C of the carrots to express the carbon content in CO2 (CO2 eq), which is the standard known internationally as the basis for expressing greenhouse gases. Even more preferably, the three parts of each carrot are considered and the root part and / or the leaf part of the carrots are multiplied by (44 / 12), and even more preferably the soil part, the root part and the leaf part of the carrots. Selection step (e) of Cp Ranking According to an interesting characteristic of the invention, the species and / or varieties of lawns are classified in increasing or decreasing order of their Cp capacity to capture and sequester CO2. Production of grass seed The mixture of seeds of species and / or varieties of lawns selected by the above-defined process makes it possible to achieve the particularly high level of capture and sequestration of CO2 which reinforces the environmental role of lawns. EXAMPLE In this example, five species are implemented: • Tall fescue • Kentucky bluegrass • Bentgrass • Red fescue • English Ray Grass The aim is to compare carbon storage (capture / sequestration) in different grass cover crops grown identically on the same soil. Ultimately, species are selected based on their Cp capacity to capture and sequester CO2. Step (a) Culture 'Approval' type interview • Mowing: 25 to 30 mowings / year (height 5 cm); • Fertilization based on 150 nitrogen units / ha (nutritional balance 3 / 1 / 3) in 4 passes (UF slow-release fertilizer); • Reasonable watering. Step (b) Sample collection Three samples per species (spatial variability) are taken. The samples have the following average characteristics: • Carrot measuring 10.3 cm in diameter and 19 cm deep (i.e. 1582 cm3). • Sowing autumn 2005, cereal cultivation history. • For each species, three cores of soil + plant cover were taken (10 cm in diameter by 20 cm in depth), i.e. fifteen cores in total. To understand the differences between species, the soil and different parts of the plant must be analyzed separately. Each core sample is therefore divided into three parts: soil, roots, and aerial parts. This separation of the plant into two parts makes it easier to identify differences in carbon storage and location between different species. The forty-five samples covered by these examples are as follows: • 15 soils: five species * three repetitions • 30 plants: five species * three repetitions * two parts (roots / aerial parts) Step.fc). Analyses For soil samples, the following measurements will be carried out: • Total carbon C: NF X31-109 (Determination of organic carbon by sulfochromic oxidation), • Total nitrogen N: NF ISO 13878 (Determination of total nitrogen content by dry combustion, Dumas method), • Humidity H (dry matter): NF ISO 11465 (Determination of the weight content of dry matter and water - Gravimetric method). Measuring total nitrogen allows the calculation of the soil C / N ratio, which is a first indicator of soil functioning. For plant samples, the following measurements will be carried out: • Total carbon C: internal method derived from NF ISO 14235 (Determination of organic carbon by sulfochromic oxidation) adapted to plants, • Total nitrogen N: internal method according to NF ISO 13878, • Humidity H (dry matter): internal method according to NF ISO 11465, • Van Soest fractionation: internal method derived from XP U44-162 (characterization of organic matter by biochemical fractionation and estimation of its biological stability, Van Soest method) adapted to plants. As with soil, nitrogen measurement will allow the calculation of the C / N ratio of roots and aerial parts in order to put total carbon contents into perspective. Van Soest fractionation aims to determine the different biochemical fractions of plants: lignin, hemicellulose and cellulose (fractions classified from the most resistant to degradation to the most soluble). This allows the carbon content of the plant to be characterized more precisely. For example, if the carbon content is high but is mainly found in cellulose, carbon storage is short-lived because cellulose degrades very quickly and the end product of this degradation is CO2. Conversely, carbon storage mainly in the form of lignin is more sustainable. Analyzing the three repetitions separately triples the number of analyses but allows for the calculation of mean and standard deviation, which allows for more in-depth statistical processing of the results and gives more credibility to the results. On the other hand, Van Soest fractionation is carried out only once per species, on a sample grouping the three repetitions and the two parts, i.e. six samples in total. Indeed, the aim here is to compare the species with each other as a whole. (cl) Analyses carried out on the soil: The results are presented in Table 1 below. TABLE 1 - Analyses carried out on the soil Organic matter Density Dried matter Carbon Nitrogen Carbon CO2 soil Average C / N J______g g / cm3 % % % g / m2 t / ha. 1 4 2419 1.48 1.78 1.03 0.122 8.48 3066.8 Fescue •------- ■■ —+- —.... ........... . high 2 : 2536 3 2592 | 1.47 1.89 1.10 0.143 7.68 3222.6 112.86 3 150 1.69 0.98 0.11 8.93 2944.9 1 1 : 2661.1 1.67 1.17___ 0.68 0.083 8.20 2274.8 Meadow grass -1------1--—............................f' meadows 2 2521 ___1.72 1.34 0.78 0.107 7.28 2679.1 91.84 3 2472.5 1.60 1.38 0.80 0.104 7.71 2560 pl 2516.7 1.76 1.76 1.02 0.136 7.52 3595.2 Aqrostide 2 2369.9 1.70 1.70 0.99 0.124 7.79 3357.1 129.08 3 2439.6 1.64 1.89 1.10 0.136 8.08 3608.8 S 2244.6 1.37 1.28 0.74 0.085 8.76 2037.7 Red fescue 2 2248.6 1.56 1.28 0.74 0.092 8.09 2327.1 89.44 3 2316.9 1.58 1.61 0.94 0.104 9 00 2953.3 English ryegrass 1 2502.8 1.50 2.00 1.16 0.127 9.16 3485.4 2 2543.6 1.56 1.81 L05 0.128 8.22 3275.7 126.06 _ _ 3 2560.7 1.56 1.96 ___1.14 0.124 9.19 3553.3 5 Soil carbon levels are in the same order of magnitude as those found in large-scale cultivation: between 1.2 and 2%. The C / N of 7.3 to 9.4 reflects good biological activity in the soil and therefore good degradation of plant residues. The results give variable carbon rates depending on the type of cover. 10 Descending order, RGA / FE / Eco Trifolium / Meadowgrass / Red Fescue. Bentgrass, Perennial Ryegrass, Tall Fescue, Meadow Grass / Red Fescue. (c.2) Analyses carried out on aerial parts: 15 The results are presented in Table 2 below. TABLE 2 - Measurements taken on the aerial parts of the plant ! leaves Dry matter Carbon Nitrogen C / N Carbon CO2 avg. gg / kg % g / m2 t / ha. ! 1 3.66 215 1.47 14.60 89.2 Felucca ' high - z 2.96 274 1.46 18.80 91.9 3.46 2.93 307 1.48 20.70 101.9 262 1.38 19.00 98.7 Kentucky bluegrass 2 3.44 321 1.69 19.00 137.8 4.41 3.09 335 1.78 18.80 124.2 L____i_____ 2.36 304 1.29 23.60 95.1 Bentgrass 2 4.25 390 0.82 47.60 219.7 5.47 111¾ 6.34 161 0.87 18.50 132.6 3.82 318 1.18 26.90 143 Fescue 9 red . * 4.25 1.17 31.70 193 6.17 3.65 363 1.15 31.60 168.7 i 1 2.76 155 1.01 15.30 50.4 Ryegrass ........... English ... _?------ 377 1.17 32.20 144 9 4.56___ I 3 3.92 370 1.14 32.50 177.5 I 5 The carbon content in the aerial tissues will vary depending on the height of the mowing. It is important to note that the aerial part of lawns represents on average only 10% of the plant (90% of the dry matter is composed of roots). 0 (c.3) Analyses carried out on the root parts: The results are presented in Table 3 below. TABLE 3 - Measurements taken on the root parts of the plant roots Dry matter Carbon Nitrogen C / N Carbon CO2 avg. gg / kg % g / m2 t / ha. 1 1 18.72 217.00 0.49 44.30 460.30 Tall fescue _ 22.71 144.00 0.46 31.30 370.60 14.16 3 24.91 116.00 0.43 27.00 327.40 . “T — y 51.29 81.00 0.38 21.30 498.60 Kentucky Bluegrass 40.36 110.00 0.58 19.00 554.30 20.58 62.57 84.00 0.46 18.30 630.80 ii 15.82 111.00 0.49 22.70 232.80 Bentgrass . 2 23.37 87.00 0.44 19.80 269.50 15.95 43.21 143.00 0.49 29.20 802.70 90.72 124.00 0.30 41.30 1324.20 r6lUC|U6 red 60.88 156.00 0.45 34.70 1162.30 47.22 [MM 90.87 119.00 0.37 32.20 1376.80 1__________1 _____ 20 08 117.00 0.31 376.70 276.60 Ray grass ■ ' . .. - —..... — -- _ , 2 Angiais - - - — 21.24 141.00 0.36 _ _39.20 366.50 11.60 17.97 139.00 0.52 26.70 305.70 Carbon concentration levels in roots are highly variable. 5 47.22 t / ha of carbon for turf red fescue, which is three to four times higher concentration than the average for other species. The quantity of this species in root dry matter is approximately 10 kg / m2 and represents 95% of the total weight of the plant. (c.4) Conclusion on carbon concentration in turf grasses: 0 The results are presented in Table 4 below. TABLE 4 - Means and standard deviations of measurements taken on soil / leaves / roots total C (soil) C (leaves) C (roots) C (plant) C (total) g / m2 ]__g / m2__ q / m3 ___g / m4 __ ___g / m2___ Fescue | medium and 3078.10 94.30 386.10 480.40 3558.50 tall i difference 139.20 6.70 67.80 62.00 163.30 Bluegrass medium and 2504.70 120.30 561.20 681.50 3186.20 meadow difference 207.80 19.80 66.40 79.40 273.40 . , I medium and I Agrostide i / _ , 3520.04 149.20 435.00 584.20 4104.24 ocûrt 141.50 63.90 319.00 314.60 382.60 Fescue medium and 2439.40 168.20 1287.80 1456.00 3895.40 red gap 468.00 25.00 111.80 95.60 530.10 : Ryegrass medium and 3438.10 I 124.20 316.30 -40.50 3878.50 English gap 144.70 | 66.00 45.90 99.40 137.30 The root system is the carbon storage organ of the plant. Its high proportion at the plant level is 90% on average. Differences in dry matter content between species give us significant variability. Red fescue grass is the species that contains the most carbon, about three times more than the average of the other species. Figures 1 to 3 attached are histograms which show the carbon content in g / m2 respectively of the soil, leaves and roots and soil + plant for the five species concerned. It is in a permanent cover of red fescue where the concentration remains the highest. Descending classification: AGR / FRC / RGA / FE / PP. (c.5) Fractionation of organic matter produced by grasses: In order to understand the transfers of organic matter in the soil, these were fractionated at the plant level in order to access the potential for stable humus production for each species. TABLE 5 - Biochemical fractionation of organic matter OM soluble cellulose hemicellulose lignin % MO % MO % MO % MO Tall fescue 2670 27.30 38.50 7 90 Kentucky bluegrass 32.90 21.80 34.80 10.90 Bentgrass 33.70 17.50 34.70 ■4.50 Red fescue 31.40 23:30 34.00 11.70 Perennial ryegrass 24.00 26.80 38 40 10.12 Figure 4 illustrates in histogram form the soluble- cellulose / hemicellulose / lignin in % for each species. Figure 5 illustrates in histogram form the soluble- cellulose / hemicellulose / lignin in organic matter fractions OM (g / m2) as well as dry matter in kg / m2 for each species. The hemicellulose and soluble fractions are the most important. The lignin fraction represents approximately 10%. These results indicate good potential degradation of plant residues, which is confirmed by the relatively low C / N of the soil. Red fescue is the species that produces the most dry matter and stores the most carbon per m2 in these tissues. However, this carbon is not found in the soil, since the carbon stock in the soil under red fescue is the lowest of the six modalities. (c.7) General conclusion: It is in a permanent cover (plant + soil) of red fescue that the carbon concentration remains the highest. Descending classification: AGR / FRC / RGA / FE / PP If only carbon sequestration in the soil (carbon sink) is taken into account. Descending classification: RGA / FE / AGR / PP / FRC Step (d) Calculation of annual sequestration Cp of CO2 eq (dl) Balance of CO? sequestered in the soil per ha after 30 months: Cp is calculated by converting C to CO2 eq = C * 44 / 12 CO2 eq refers to CO2 equivalent. Annual sequestration = CO2 eq (30 months) / 2.5 TABLE 6 soil C (soil) C (soil) t / ha after30 CO2 eq (soil) t / ha (* 44 / 12) CO2 eq in the soil before turfing t. / ha CO2 eq sequestered in the soil t. / ha CO2 eq sequestered in the soil. t. / ha / year g / m2 month ab „ . ... (ab) (a - b) / 2.5 Tall fescue 3078.10 30.78 C2.86 77.60 35.26 14.11 Meadow grass 2504.70 25.05 91.84 77.60 14.24 5.70 Bent grass 3520.04 35.20 129.07 77.60 51.47 20.59 Red fescue English ryegrass 2439.40 24.39 89.44 77.60 11.84 4.74 3438.10 34.38 126.06 77.60 48.46 19.39 Figure 6 shows the last right column of Table 6 as a histogram. (d.2) Balance of CO? eq capture in the leaves / roots of lawn grasses: TABLE 7 leaves Avg. dry matter 9. . Carbon g / m2 Avg. carbon t / ha. Avg. CO2 eq t / ha. Tall fescue 3.18 44.33 0 94 3 46 Kentucky bluegrass 3.22 78.83 0 79 2.89 Bentgrass -1.32 _____149.13 1.49 5.47 Red fescue Perennial ryegrass i 3.91 3.27 168.23 124.27 1.68 L24 6.17 4.56 TABLE 8 roots Avg. dry matter g Carbon g / m2 Avg. carbon t / ha. Avg. CO2 eq t / ha. Tall fescue 22.11 386.10 3.86 14.16 Kentucky bluegrass 51.41 561.23 5.61 20.58 Bentgrass 27.47 435.00 4.35 15.95 Red fescue 80.82 1287.77 12.88 47.22 Perennial ryegrass 19.76 316.27 3.16 11.60 For the leaves and roots, this is the capture and storage of CO2 eq after 30 months and not an annual sequestration rate. The attached figure 7 illustrates the CO2 eq avg columns of tables 7 and 8 by a histogram expressing the tonnes of CO2 captured by the plants per hectare after 30 months. TABLE 9 CO2 captured and sequestered in 30 months, less CO2 in the soil, sequestered before the tests were set up. total 30 months CO2 eq (soil) t / ha CO2 eq in soil before sodding t. / ha CO2 eq sequestered in soil t. / ha CO2 eq captured t. / ha CO2 eq captured t. / ha CO2 eq captured and sequestered t. / ha after 30 months soil roots leaves Total Cp Tall fescue H 2.86 77.60 35.26 14.16 3.46 52.88 Kentucky bluegrass 91.84 77.60 14.24 20.58 2.89 37.71 Bentgrass 129.07 77.60 51.47 15.95 5.47 72.89 Red fescue 89.44 77.60 11.84 47.22 6.17 65.23 Perennial ryegrass 126 06 ...77 60 48 16 ____11.60 _ 4 64 62 ! Total Cp = CO2 eq soil + CO2 eq leaves + CO2 eq roots Figure 8 attached illustrates Table 9 by a histogram expressing the tonnes of CO2 captured and sequestered by plants and by the soil per hectare after 30 months. The 77.60t CO2 / ha. of the control (agricultural soil without grass cover) were removed. Different lawn seed compositions can be prepared by mixing species with different Cp determined in the present example. 1) Composition for very well-kept lawns like golf greens: pure bentgrass. 2) Composition for ornamental lawns: o 25% perennial ryegrass o 75% red fescue 3) Composition for large spaces: o 45% perennial ryegrass o 55% red fescue 4) Composition for drying lands: o 35% perennial ryegrass o 45% tall fescue o 20% red fescue The Cp of these compositions 1, 2, 3, 4 is increasing.

Claims

CLAIMS -1- Method for selecting species, and within the same species, different varieties of lawns, characterized in that it essentially consists of: a Cultivate the lawns considered, at least one sample (preferably three) per species or variety; b Take at least one core sample for each lawn considered, each comprising soil and plant cover; c Analyze in each core, the total carbon C and possibly at least one of the following parameters: total nitrogen N, humidity H and Van Soest fractionation; d Calculate the capacity Cp to capture and sequester CO2 in number of tonnes of CO2 captured and sequestered for each species or variety, per unit of cultivation duration and per unit of cultivated area, using the total carbon C, and possibly the other parameter(s) obtained by analysis (c); e Select species and / or varieties according to their Cp capacity to capture and sequester CO2. -2- Method according to claim 1, characterized in that the lawns are grasses. -3- Method according to at least one of the preceding claims, characterized in that during cultivation (a), the following are provided: o to mow the lawn so that its height remains less than 10 cm, preferably between 2 and 5 cm, and even more preferably around 3 cm; o to fertilize at a rate of 100 to 200, preferably 150, units of nitrogen / ha / year; and o to water in such a way as to compensate for losses due to transpiration of the turf samples and evaporation due to the climate. -4- Method according to at least one of the preceding claims, characterized in that for sampling (b), each core is cylindrical with a diameter of between 5 and 20 cm, preferably of the order of 10 cm, and a height of between 10 and 30 cm, preferably of the order of 20 cm. -5- Method according to at least one of the preceding claims, characterized in that for sampling (b), each core is divided into three parts: soil, roots and aerial parts. -6- Method according to at least one of the preceding claims, characterized in that for the analysis (c), the following measuring methods are used: o soil: carbon C: NF X31-109 (Determination of organic carbon by sulfochromic oxidation), total nitrogen N: NF ISO 13878 (Determination of total nitrogen content by dry combustion, Dumas method), humidity H (dry matter): NF ISO 11465 (Determination of the weight content of dry matter and water - Gravimetric method); o roots and aerial parts: total carbon C: internal method derived from NF ISO 14235 (Determination of organic carbon by sulfochromic oxidation) adapted to plants, total nitrogen: internal method according to NF ISO 13878, humidity H (dry matter): internal method according to NF ISO 11465, Van Soest fractionation: internal method derived from XP U44-162 (characterization of organic matter by biochemical fractionation and estimation of its biological stability, Van Soest method) adapted to plants. -7- Method according to claim 1, characterized in that for calculation (d), the total carbon C of the carrots is multiplied by (44 / 12). -8- Method according to claim 1, characterized in that for calculation (d), the three parts of each carrot are considered and the roots and / or leaves of the carrots are multiplied by (44 / 12), and even more preferably the soil, roots and leaves of the carrots. -9- Method according to at least one of the preceding claims, characterized in that the species and / or varieties of lawns are classified in increasing or decreasing order of their capacity Cp to capture and sequester CO2. -10- Process for obtaining lawn seed compositions, characterized in that it essentially consists of mixing seeds of species and / or varieties of lawns selected by the process according to any one of claims 1 to 9.

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