Soil moisture at their summer cottage, determine, calculate soil moisture. Water properties of the soil. Methods for determining soil moisture What are the results of determining soil moisture used for?
The humidity of the earth is the most important agrotechnical parameter in soil science, geology, ecology, horticulture, which has a serious impact on the qualitative functioning of the ecological system - biogeocenosis. Today, there are many ways to measure it. In the article we will talk about the determination of soil moisture, compare the effectiveness of various devices for measuring it.
During the growing season, the water level in the tissues and cells of plant organisms is 70-90%.
Reasons for the need for soil moisture
Humidity is one of the main factors affecting soil fertility. It performs the following tasks:
- enrichment of vegetables and fruit crops water;
- soil moisture affects the amount of air, salt levels, as well as the presence of harmful components;
- provides a plastic and dense structure of the earth;
- affects temperature and heat capacity;
- does not allow soil weathering;
- shows the ability of the soil to agrotechnical and agricultural processes.
For the full life of a plant organism, its cells, as well as tissues, should receive sufficient water, in particular during the activation of vital processes.
Optimal soil moisture levels
Optimum soil moisture is such moisture when the roots of the crop do not have a shortage of fluid necessary for development and growth. The level of moisture should not be higher than 60-70% of the total moisture capacity during cultivation vegetable crops, 70-80% - cereals and 80-85% - herbs. ".
Tip #1 It should be noted that the level of optimal humidity during germination should be higher than during the ripening of crops.
At the moment, two types of irrigation are in experimental development - jet and pulse.
How to determine the moisture content of the earth
To date, there are such methods for calculating soil moisture:
- thermostatic weight;
- radioactive - is a measurement of the radiation of radioactive substances in the ground;
- electric - in this case, soil resistance, conductivity, inductance, and capacitance are determined;
- tensometric - the method is based on the difference in water voltage between the phase boundaries;
- optical - this method is characterized by the reflectivity of light fluxes;
- express methods, in particular organoleptic.
The easiest and most common are thermostatic-weight and organoleptic methods. The first is the most accurate, and the second, in turn, requires little time and does not need special equipment. Devices for determining electrical resistance are indicated in the table.
Determination of electrical resistance
In this case, sensors are used that are made of gypsum. These sensors have 2 electrodes connected directly to the meter. The electrical resistance of a material is dependent on the presence of liquid in it, which, accordingly, measures the level of moisture in the earth. Holes are made in the ground to the desired depth, followed by the placement of sensors in them. Close contact between the sensing element and the ground is important (this is a necessary factor for all moisture meters).
Modern types of sensors use a granular material surrounding a special membrane and perforated covers, which are made of steel or PVC. In this way, a longer life of the sensors, the fastest response, as well as the most accurate measurements are achieved. These sensors can be used in irrigation systems that are controlled automatically. Moisture instruments equipped with dielectric probes are listed in the table.
Measurements using TDR and EDR dielectric probes
Determination of indicators of soil moisture using this method is carried out by calculating the dielectric medium, depending on the moisture content of the soil. Checking the presence of moisture in the ground provokes a change in its dielectric constant, and this makes it possible to measure the relationship between these parameters. The advantage of this type of sensor is the ability to transmit measurements without wires.
To date, devices are also presented, the probes of which are constantly in the pipe at the required depth. In this case, readings are taken automatically, and then transferred to the observer. Accordingly, the price of these devices is much higher. Instruments for measuring with soil tensiometers are listed in the table.
| Name | Description |
| Thetaprobe Tensiometer Kit | Multifunctional device used for a variety of studies with tensiometers different types at a depth of up to 90 centimeters |
| Tensiometer DCAT 11 from DataPhysics Instruments GmbH | Measures surface as well as interfacial tension of liquids |
| Tensiometers BPA – 2S | Enables determination of dynamic surface tension |
Tensiometer Method for Measuring Humidity
The tensiometer consists of a ceramic filter, plastic pipe and a vacuum manometer, immediately after filling with water, which is lowered into the ground to calculate the pressure. The liquid moves along the ceramic element, which causes a change in pressure in the pipe, as well as changes in the meter readings. After the procedure of hydration or precipitation in the ground, water does not enter the tube until the potential shift between the ground and the tensiometer. Devices are tubes available for purchase, of different lengths for calculating the indicators of moisture in the earth at various depths.
Devices are used, as a rule, to determine the beginning, as well as the end of irrigation. It is preferable to place them at different depths, for example, 20 or 40 centimeters. Based on the results of the study of the device, it is possible to measure the period of start of irrigation (based on the data of the device placed close to the surface), as well as the time of the end of irrigation (according to the readings of the device located deeper).
How to increase soil moisture
To increase humidity, for example in a greenhouse, you should spray crops, paths, heating appliances, as well as a glass ceiling and increase the amount of irrigation. In addition to hose irrigation, today farms use: sprinkling, subsoil irrigation and drip irrigation. The most popular type is sprinkling, in this case, plants are watered at the same time, the temperature of foliage and evaporation decreases, and overheating of crops is eliminated.
Tip #2 To reduce the level of soil moisture in the greenhouse structure, ventilation should be carried out, air temperature should be raised, and the amount and volume of irrigation should be reduced..
Irrigation rates are calculated in liters per square meter or in cubic meters per hectare.
Does the region affect soil moisture
The Moscow region is characterized by podzolic, sod-podzolic soils, gray forest, chernozems. For the territory of the Urals - clayey, sandy and podzolic. Podzolic soils are common in Siberia. In the Volga region - chernozems and podzolic, and in the Leningrad region podzolic soils are often found.
In chernozems, the range of active moisture is 46.7% of the weight of dry soil, in gray forest soil - 27.2, in sod-podzolic soil - 26.0. The maximum figures are given. As you can see, the region affects soil moisture through the type of soil, as well as the climatic features of the area, in particular the amount of precipitation. ".
How to calculate the optimal period and amount of watering
Many studies indicate that the most optimal indicators of the need of a plant organism for water can be called the physiological state of a given plant, the sucking power of foliage, the concentration and osmotic pressure of cell sap, etc.:
- often practiced to determine irrigation terms visually, that is, by external signs;
- the next approximate method is the measurement of soil moisture to the touch;
- approximate irrigation rates can be determined using total radiation. The latter in this case is measured in periods between irrigation procedures.
Irrigation scheme for different soil moisture
Soil moisture is one of the main factors of fertility. Consider the main requirements for soil irrigation at various stages of cultivation of vegetable and fruit crops:
- moderate watering - waterlogging should not be allowed, as well as complete drying of the soil;
- spraying the leaves during flowering - abundant watering is carried out in the summer, after the end of flowering during the dormant period of the plant, it is rarely carried out;
- spraying in warm seasons - the earth needs abundant watering in summer, reduced in cold weather.
Humidity control is used to different types land for the highest yields. In turn, it is the basis for the development of rational agricultural technology, which is why the measurement of soil moisture is the most popular soil analysis. It should not be forgotten that the size of the future crop depends on competent watering. Therefore, it is necessary to approach the development of a soil irrigation regime with full responsibility. ".
Answers to common questions
Question number 1. How to determine if there is enough moisture in the ground?
You need to take a little earth in your hand and squeeze it, if moisture does not come out between your fingers, open your palm. The lump of soil has not broken up - this means that the moisture level is satisfactory.
The rate of applied irrigation depends on the season, the plant, the age of the crop, the degree of illumination, as well as the water-physical characteristics of the soil.
Question number 2. How can soil moisture be increased in a greenhouse structure?
In this case, it is necessary to increase watering, lower the temperature slightly, and also spray plants, soil and paths with water.
Question number 3. During what period of plant growth do they need the most moisture?
During the growing season, plant organisms most of all need intensive watering.
Question number 4. What is the best method for measuring soil moisture?
The simplest and most popular are thermostatic-weight and organoleptic methods.
Gardening mistakes that lead to waterlogging of the soil
- The main oversight is the unregulated irrigation of the land.
- It should also be noted the lack of liming and proper fertilizing of soils prone to waterlogging.
- Also, gardeners often forget about the organization drainage system. All this in general negatively affects the quality of the soil.
As such, the concepts of lack of moisture or waterlogging are rather relative. Increased soil moisture, combined with large-scale mineral fertilization, as well as favorable temperature indicators, activates intensive photosynthesis, rapid crop growth and an increase in total biomass. Accordingly, with a decrease in temperature, a similar increased moisture affects already negatively. As you can see, such a parameter as soil moisture is very important in the process of growing any crop on various types soils and in different climatic latitudes.
The invention relates to soil science, melioration and agriculture. In the field where observations of soil moisture are planned, previously, once, at the beginning of the growing season of plants, the density of the soil with undisturbed addition is determined by a well-known method using a cutting ring or cylinder, after which, during the entire growing season, as necessary, with a drill that allows soil to be selected with undisturbed composition, samples of a certain volume are taken along the horizons and weighed on technical scales, directly in the field and without drying the sample in a thermostat (drying cabinet), soil moisture is determined as the difference in density of soils with undisturbed composition in the wet and dry state, referred to the density of the soil with undisturbed constitution and expressed as a percentage of the mass of dry soil. EFFECT: simplification, acceleration and increase in efficiency of determination. 1 z.p. f-ly, 1 tab.
The invention relates to soil science, land reclamation and agriculture and can be used for the rapid determination of soil moisture, setting the timing of the next vegetation irrigation of all crops, as in open field, as well as in greenhouses.
There are several methods (methods) for determining soil moisture and scheduling the next vegetation irrigation of agricultural crops, which can be grouped into the following groups:
Weight (thermostat-weight), based on drying and weighing soil samples;
Tensometric, based on measuring the stress of soil moisture by surface forces arising at the phase boundary;
Radioactive, which is based on a change in intensity radioactive radiation sources of radiation placed in the soil when interacting with water molecules or hydrogen atoms;
Electric, which measures the electrical resistance, conductivity, capacitance and inductance of the soil, depending on its moisture content;
Optical, which measures the degree of absorption or reflection of ray energy, depending on the humidity of the object;
Express methods: according to the state of plants, morphological characteristics, physiological indicators, organoleptic characteristics of the soil, which determine the provision of plants with soil moisture and the degree of its moisture content (Plyusnin I.I., Golovanov A.I. Ameliorative soil science / Edited by A.I. .Golovanova. - M.: Kolos, 1983. - S.61-62; Dospekhov B.A., Vasiliev I.P., Tulikov A.M. Workshop on agriculture / Textbook for universities / / 2nd ed. revised and additional - M.: Agropromizdat, 1987. - P.58-60; Workshop on soil science / Under the editorship of I.S. Kaurichev. - 4th edition revised and additional - M.: Agropromizdat, 1986. - C .97-98; Piunovsky B.A. Workshop on ameliorative agriculture. - 3rd ed. revised and additional - M.: Agropromizdat, 1986. - P.46-54; Dolgov S.I. Agrophysical methods of soil research - M.: Nauka, 1966. - P. 9-227; Verigo S. A., Razumova. L. A. Soil moisture. - L.: Gidrometeoizdat, 1973. - 328 p.; Rode A. A. Fundamentals Soil moisture studies - T.1 Water properties of soils and movement of soil moisture T.2 Methods for determining the water regime of soils. - L.: Gidrometeoizdat, 1965, 1969. - 663 p. and 287 pp.; Discoveries, inventions, industrial designs and trademarks. G01N 5/02 a.s. No. 1196737, G01N 75/56 a.s. No. 898308, G01N 5/00 a.s. No. 1101718, G01N 22/04 a.s. No. 1101722, G01N 25/56 a.s. No. 1173283, G01N 23/24 a.s. No. 693184, G01N 23/00 a.s. No. 53/466, G01N 21/80 a.s. 1109610, G01J 1/04 a.s. 811084, G01N 21/86 a.s. No. 813209.
disadvantages known ways determination of soil moisture and the timing of vegetation irrigation is a significant laboriousness, energy intensity and duration of the process in time, the need to use a large amount of laboratory equipment, electrical and radiation and other devices that are quite dangerous for the health of staff and people around. A number of methods for determining soil moisture are characterized by low accuracy, insufficient for their practical application.
closest technical solution determination of soil moisture and the timing of vegetation irrigation are the weight method (thermostatic-weight), in which soil samples for determining soil moisture in the field are taken with a special needle drill, from which the soil is transferred to a pre-weighed cup and closed with a lid. In the laboratory, wet soil in cups is weighed on technical scales and dried in an oven at a temperature of 105 ° C, for 12-14 hours to a constant weight, controlling it on a scale with an accuracy of 0.01 g. Weighing cups with dry soil is carried out through 6 hours and then after 8, 10, 12, 14 hours after the start of drying, until constant weight. Drying time depends on soil moisture and temperature conditions in the oven. Differences in the mass of a cup with dry soil at the next weighing should not exceed 0.05 g.
Soil moisture is determined by the formula:
where β in - the desired moisture content,% of the mass of dry soil;
B is the mass of an empty aluminum cup, g;
B1 - mass of a cup with moist soil before drying, g;
B2 - mass of a cup with dry soil after drying, g.
(Arms B.A., Vasiliev I.P., Tulikov A.M. Workshop on agriculture / Textbook for universities / / 2nd ed. Revised and additional - M .: Agropromizdat, 1987. - P. 57-58).
The disadvantage of this method for determining soil moisture is the significant cost of labor, time and electricity, which is associated with repeated weighing of the soil sample and its prolonged drying in an oven for 12-14 hours to a constant weight.
The technical result achieved by the invention is the simplification of the method for determining soil moisture, the reduction of labor costs, time and electricity, and the possibility of its operational use in the field.
The result is achieved by the fact that in the field where observations of soil moisture are planned, first at the beginning of the growing season of plants, the density of dry soil is determined with undisturbed addition by a well-known method, selection of wet samples using a cutting ring or cylinder, weighing and drying in a thermostat, after which in during the entire growing season, as necessary, with a drill, which allows selecting soil with undisturbed addition along the horizons, they take samples of moist soil of a certain volume and weigh them on technical scales, directly in the field and without drying the sample in a thermostat (drying cabinet) determine soil moisture, as the difference between the densities of undisturbed soil in wet and dry conditions, divided by the density of dry soil with undisturbed texture and expressed as a percentage of the mass of dry soil.
The method for determining soil moisture is that in the field where observations of soil moisture are planned previously at the beginning of the growing season, the density of dry soil with undisturbed addition is determined by a well-known method, selection of wet samples using a cutting ring or cylinder, followed by weighing and drying in a thermostat . After that, during the entire growing season, as needed, daily, ten days, before and after precipitation and irrigation along the horizons, samples of moist soil of a certain volume are taken. Sampling for moisture is carried out with a Negovelov drill, a TSHA cylinder drill, or any other drill that allows taking soil samples with undisturbed composition. These devices allow you to take samples of wet soil with undisturbed addition of a certain volume. Selected samples of moist soil are weighed directly in the field on technical scales with an accuracy of 10 mg and, without drying in a thermostat (drying cabinet), soil moisture is determined. It is found as the difference between the densities of soil with undisturbed texture in wet and dry states, divided by the density of dry soil with undisturbed texture, expressed as a percentage of the mass of dry soil according to the formula:
where βv - soil moisture, % of dry soil mass
p is the mass of the wet soil sample, g;
v is the volume of the wet soil sample corresponding to the volume of the drill, cm 3 ;
dv - density of dry soil with undisturbed composition, g/cm 3 .
Studies carried out in the laboratory of the Soil Reclamation Department of the Novosibirsk State Medical Academy showed a sufficient degree of convergence of the results of determining soil moisture, using the reference thermostatic-weight and new methods (table 1). The studies were carried out in four repetitions with two horizons 0-20 and 20-40 cm, which had a density of dry soil with undisturbed structure, respectively, 1.15 and 1.30 g/cm 3 . With a confidence probability of 95%, the accuracy of the experiment turned out to be quite high and amounted to 0.69%, and the smallest significant difference between the variants turned out to be 0.58% m.s.p. In accordance with this, the error of the experiment turned out to be insignificant and amounted to 0.26–0.27% of the m.d.s. between the variants. Consequently, the accuracy of soil moisture determination by the new method reaches 99%, the relative error is no more than 1%. This allows you to use new way determination of soil moisture for practical purposes in the field of land reclamation, irrigated agriculture and crop production to monitor the dynamics of soil moisture, in water balance studies and when setting the timing of vegetation irrigation.
| Table 1 | |||
| The influence of various methods on the accuracy of determining soil moisture | |||
| Experience Options | Humidity, βw % w.m.s. | Error, % m.s.p. | Relative error, % |
| The density of soil with undisturbed composition is 1.15 g/cm 3 . Thermostat-weight method | 27.50 | - | - |
| The density of soil with undisturbed composition is 1.15 g/cm 3 . New way | 27.23 | 0.27 | 1.00 |
| The density of soil with undisturbed composition is 1.30 g/cm 3 . Thermostat-weight method | 27.81 | - | - |
| The density of soil with undisturbed composition is 1.30 g/cm 3 . New way | 27.55 | 0.26 | 0.99 |
| Experience accuracy, m % | 0.69 | - | - |
| The smallest significant difference, NSR 095, % m.s.p. | - | 0.58 | - |
The new accelerated method for determining soil moisture significantly reduces the time, labor and energy costs when using it in comparison with the standard. When determining humidity by this method, there is no drying of a wet sample in a thermostat, which takes at least 12-14 hours and consumes a significant amount of electricity, approximately 15-20 square meters. There is no need to repeatedly weigh a dried soil sample. The main advantage of the new method for determining soil moisture is the ability to quickly determine soil moisture directly on the field, without the use of bulky laboratory equipment.
1. A method for determining soil moisture, including sampling for analysis, their weighing, characterized in that in the field where observations of soil moisture are planned, the density of dry soil with undisturbed addition is previously determined once at the beginning of the growing season of plants by a well-known method, the selection of wet samples with using a cutting ring or cylinder, followed by weighing and drying in a thermostat, after which, during the entire growing season, as necessary, with a drill, which allows sampling soil with undisturbed composition, samples of moist soil of a certain volume are taken along the horizons and weighed on technical scales, directly into field and without drying the sample in a thermostat (drying cabinet) determine soil moisture as the difference between the densities of soil with undisturbed texture in the wet and dry state, referred to the density of dry soil with undisturbed texture and expressed as a percentage of the mass of dry soil.
2. The method according to claim 1, characterized in that samples of moist soil with undisturbed composition for determining soil moisture can be taken with a Negovelov drill or a TSCA cylinder drill.
STATE UNION STANDARDSSR
SOILS
METHODSDEFINITIONSHUMIDITY,
MAXIMUM
HYGROSCOPIC
HUMIDITYANDHUMIDITY
SUSTAINABLE
WILLINGPLANTS
GOST 28268 - 89
STATE
COMMITTEEUSSRBYMANAGEMENT
QUALITY
PRODUCTSANDSTANDARDS
Moscow
STATE STANDARDUNIONSSR
dateintroduction With 01.06.9 0
before 01.06.95
Non-compliance with the standard is punishable by law
This standard applies to non-stony soils, i.e. soils in which the mass fraction of particles larger than 3 mm does not exceed 0.5%, and establishes methods for determining moisture, maximum hygroscopic moisture and moisture of stable wilting of plants.
1. METHOD FOR DETERMINING SOIL MOISTURE
The essence of the method is to determine the loss of moisture during the drying of the soil.
7 - at soil moisture up to 10%;
5" » »St. 10 %.
1.1. Sampling method
1.3.2. Clean numbered cups BC-1 are dried in a cabinet at a temperature of (105 ± 2)° C for 1 hour, removed from the cabinet, cooled in a desiccator with calcium chloride and weighed with an error of not more than 0.1 g.
1.4 . Conducting an analysis
1.4.1. Analytical soil samples are placed in numbered, dried and weighed cups and closed with lids.
1.4.2. Cups and soil in cups are weighed with an error of not more than 0.1 g.
1.4.3 . The cups are opened and, together with the lids, placed in a heated oven.
The soil is dried to constant weight at a temperature of:
(105±2) ° C - all soils, with the exception of gypsum;
(80±2) ° C - gypsum soils.
Drying time to first weighing:
non-gypsum soils: sandy - 3 hours, others - 5 hours;
gypsum soils - 8 hours.
Post-drying time:
sandy soils - 1 hour;
other soils, including gypsum - 2 hours.
1.4.4. After each drying, the cups with soil are covered with lids, cooled in a desiccator with calcium chloride and weighed with an error of no more than 0.1 g. If weighing is carried out no later than 30 minutes after drying, closed cups can be cooled in the open air without a desiccator. Drying and weighing are stopped if the difference between repeated weighings does not exceed 0.2 g. Soils with a high content organic matter may, upon repeated weighings, have a greater mass than during previous ones,due to the oxidation of organic matter during drying. In such cases, the smallest mass should be taken for calculations.
1.5. Results processing
1.5.1 . The mass ratio of moisture in the soil (W) V percentage is calculated by the formula
Where m 1 - mass of wet soil with a glass and a lid, g;
- mass of dried soil with a glass and a lid, g;
mis the mass of an empty cup with a lid, g.
The result of the analysis is taken as the arithmetic mean of the results of two parallel determinations. Calculations are carried out to the second decimal place, followed by rounding the result to the first decimal place.
1.5.2. Permissible relative deviations of the results of parallel determinations from their arithmetic mean at a confidence level Р=0.95 are, % of the measured value:
5 - at soil moisture up to 10%;
3" »» St. 10 %.
2. METHOD FOR DETERMINING THE MAXIMUM HYGROSCOPIC SOIL MOISTURE
The essence of the method is to saturate the soil with vaporous moisture, followed by the determination of soil moisture.
The limiting value of the total relative error of the method at a confidence level Р=0.95 is, % of the measured value:
10 - at maximum hygroscopic humidity up to 5%;
7»»»St. 5 %.
2.1. Sampling method
2.1.1 . Sampling - by .
2.1.2. From the sample received for analysis, large plant residues (stems, sod, large roots, etc.) are removed with tweezers. The soil is dried in the open air to an air-dry state, ground by hand in a mortar and pestle with a rubber tip. mineral soil allowed to grind in special mills.
2.1.3 . The crushed soil is sifted through a sieve according to GOST 214: mineral soil through a sieve with holes with a diameter of 1 mm, peat - 2 mm.
2.1.4 . Two analytical samples weighing 5–15 g each are taken from the crushed and sifted soil by quartering.
2.2 . Equipment, materials and reagents
Drying cabinet with temperature controller from 80 to 105 °C with control error up to 2 °C.
Glass cups for weighing with SN-type lids according to GOST 25336.
Tracing paper or parchment paper, plastic wrap.
Vaseline technical.
Potassium sulphate according to GOST 4145, analytical grade.
Water distilled according to .
Calcium chloride technical.
2.3. Preparation for analysis
2.3.1. Preparation of a desiccator with a saturated solution of potassium sulfate
Distilled water, heated to (40 ± 5) ° C, is poured into the desiccator in a layer equal to 1/2 of the height from the bottom of the desiccator to the porcelain insert. Potassium sulphate is poured and dissolved with stirring until insoluble crystals of potassium sulphate appear at the bottom of the desiccator.
2.3.2. Preparation of glass cups with lids
Clean numbered cups are dried in a cabinet, cooled in a desiccator with calcium chloride and weighed to the nearest 0.001 g.
2.4. Conducting an analysis
2.4.1. Analytical samples taken according to paragraphs. - , are placed in pre-numbered, dried and weighed cups, selecting the diameter of the cups so that the soil layer in them does not exceed 4 mm.
2.4.2 . Cups with soil without lids are placed in a desiccator with a saturated solution of potassium sulfate to saturate the soil with water vapor. The lid of the desiccator is closed hermetically, achieving a mirror finish on the surface of the sections, as indicated in. To prevent condensation of water vapor during sudden temperature fluctuations in the room, the desiccator is placed in a thermal inertial protection (a blanket, a foam shell, etc.). It is allowed to saturate the soil in vacuum desiccators or in vacuum cabinets.
2.4.3. The first weighing of cups with soil is carried out 15 days after the start of saturation. To do this, open the desiccator, close the cups with soil with lids and weigh them with an error of not more than 0.001 g.
2.4.4. Re-weighing is done every 5 days. The saturation of the soil with moisture is considered complete if the mass difference during repeated weighings is no more than 0.005 g.
2.4.5. After saturation, soil moisture is determined by , but the weighing is carried out with an error of not more than 0.001 g.
2.5. Results processing
2.5.1. The maximum hygroscopic humidity in percent is calculated from
The result of the analysis is taken as the arithmetic mean of the results of two parallel determinations. The calculation is carried out to the third decimal place, followed by rounding to the result to the second decimal place,
2.5.2. Permissible relative deviations of the results of parallel determinations from their arithmetic mean at a confidence level Р=0.95 are, % of the measured value:
7 - at maximum hygroscopic soil moisture up to 5%
5"" »» St. 5 %.
3. METHOD FOR DETERMINING THE HUMIDITY OF THE STABLE WILTING OF THE PLANT
The essence of the method lies in growing plants by the method of vegetative miniatures, reducing the moisture reserves in the soil to a steady loss of turgor by plant leaves and determining soil moisture.
The limiting value of the total relative error of the method at a confidence level Р=0.95 is, % of the measured value:
10 - at a moisture content of stable wilting up to 10%;
7»»»St. 10 %.
3.1. Sampling method
3.1.1. Sampling - by . Sample preparation - by
3.1.2 . The soil is crushed by hand in a mortar and pestle with a rubber tip and sifted through a sieve according to GOST 214 with holes with a diameter of 3 mm.
3.1.3 . In the sifted soil, the moisture content is determined as a percentage according to paragraphs. -
3.1.4 . Two soil samples are taken by the quartering method. Weight of wet soil sample (mvp) in grams is calculated by the formula
mvp = 1,65 W- 165,
Where W - soil moisture, %.
3.2 . Equipment, materials and reagents
Glass glasses with a capacity of 200 cm 3, type B, execution 1 or 2 according to GOST 25336.
Daylight installation providing 5000 lux area illumination.
Aspiration psychrometer.
Cuvette with coarse sand.
Measuring cylinders with a capacity of 100 and 250 cm 3 but.
Desiccator version 2 according to GOST 25336 with insert version 1 according to .
Laboratory scales of the 2nd class of accuracy with the highest weighing limit of 200 g according to .
Tracing paper or polyethylene film.
Ammonium phosphate one-substituted according to GOST 3771, analytical grade.
Ammonium nitrate according to GOST 22867, analytical grade.
Potassium nitrate according to GOST 4217, analytical grade.
Water distilled according to .
3.3. Preparation for analysis
3.3.1. Prepare a solution of the nutrient mixture at the rate of 50 cm 3 per glass. The preparation of the nutrient mixture is carried out by dissolving the following salts in 5 dm 3 of water:
monosubstituted ammonium phosphate - 2.03 g;
ammonium nitrate - 3.88 g;
potassium nitrate - 2.68 g.
3.3.2. Circles are cut out of tracing paper according to the size of a glass to protect against evaporation from the soil surface.
3.3.3 . Seeds of barley, oats or cotton are selected for sowing with a germination capacity of at least 95% (seeds of the 1st class according to GOST 10469, GOST 10470, GOST 5895). In cotton-growing areas, cotton seeds are used for cultivation, in all the rest - barley or oats.
3.3.4 . To germinate seeds, take a cuvette filled with richly moistened sand. The sand is moistened to such an extent that when the cuvette is tilted, water appears on the surface. Seeds are laid evenly, covered with a sheet of paper, and placed in a room with a temperature of (20 ± 2)° C. Methods of seed germination are allowed, established by GOST 12038. The course of seed germination is monitored daily.
3.4. Conducting an analysis
3.4.1. The soil selected for analysis is poured into glass beakers with a capacity of 200 cm 3 . By lightly tapping the bottom of the glass on the surface of the table or a spatula on the walls of the glass, the soil is compacted to a volume of 150 cm 3. If, when pouring it into a glass, it is below the line, the analysis is carried out without compaction.
3.4.2. Plants are grown with moisture close to optimal, which corresponds to the following soil moisture values and:
sand, sandy loam - 10-15%;
light, medium loam - 15-25%;
heavy loam, clay - 25-35%.
The mechanical composition of the soil is determined according to laboratory analysis; visual determination is allowed according to the method given in.
mass of water ( m B) in grams needed to achieve this level of moisture is calculated by the formula
Where W wholesale - optimal soil moisture corresponding to the specified intervals and mechanical composition of the soil, %;
W- soil moisture determined by ,%. Watering the soil to a predetermined level is carried out first with a nutrient mixture of 50 cm 3 per glass, and then with clean water and controlled by the weight of the glass with soil. Weighing is carried out with an error of up to 0.1 g.
3.4.3. Nipped seeds with a sprouted root no more than half the length of the grain are selected with tweezers and planted in moist soil, 5 pcs. for one glass. Seeds are planted in holes previously made with tweezers to a depth of about 0.5 cm, covered with soil. After planting the seeds, the glasses are covered with a sheet of thick paper to prevent the soil surface from drying out quickly.
3.4.4. When seedlings appear, the paper is removed and the plants are placed in glasses under an artificial lighting installation with an illumination intensity of (5000 ± 500) lux. An aspiration psychrometer is placed in the center of the installation at the grass stand level. Plants are grown at room temperature and lighting duration 16 h per day.
3.4.5. Every day, control weighing of glasses is carried out with an error of up to 0.1 g. When the moisture reserves in the soil decrease to the lower limit of optimal moisture, corresponding to(75 ± 5)% of the optimum humidity, watering is carried out to the optimum humidity, controlling it by weighing with an error of up to 0.1 g.
3.4.6. After the appearance of the first (in cotton, the first real) leaf, two out of five plants are removed, leaving the three most developed.
3.4.7. Every day in the morning and at noon, observations are made of the condition of the plants. When the third leaf of barley or oats develops to the level of the second, and the phase of deployment of the third real leaf begins in cotton, holes are cut in tracing-paper mugs prepared according to the size of a glass, into which plants are inserted, and tracing-paper mugs are laid on the soil surface so that the edges of the tracing paper did not touch the sprouts. After that, sand is poured onto the mugs in an even layer with a thickness of at least 2 cm.
3.4.8. After filling the mugs with sand, control weighing and watering are stopped. As soon as plants are noticed during the observation, in which turgor is reduced on all leaves, they are rearranged into a desiccator, where the air humidity is close to saturation. The desiccator is placed overnight in thermal inertia protection from auxiliary means (a blanket, a foam shell, etc.) to prevent sharp temperature fluctuations and condensation of water vapor inside the desiccator. If by morning the plant has restored turgor on at least one leaf, the glass is returned to the installation of artificial lighting. If by morning the turgor has not recovered on any leaf, then the soil in this glass has reached the moisture content of stable wilting and the glass is taken apart on the same day.
3.4.9. Plants are cut. Remove sand, tracing paper and the top 2 cm of soil. The remaining soil is freed from the roots and the soil moisture is determined by , which is the moisture content of stable wilting of plants.
3.5. Results processing
3.5.1. Humidity of stable wilting of plants (W B3) as a percentage is calculated by the formula.
The arithmetic mean of the results of four parallel determinations is taken as the result of the analysis. The result is calculated as a percentage to the second decimal place, followed by rounding to the first decimal place.
3.5.2. Permissible relative deviations of the results of parallel determinations from their arithmetic mean at a confidence level Р=0.95 are, % of the measured value:
7 - at a moisture content of stable wilting up to 10%;
5 »» » » St. 10 %.
ANNEX 1
Reference
PREPARATION OF EQUIPMENT FOR SOIL MOISTURE DETERMINATION
1. Installation and adjustment of scales
General-purpose laboratory scales of the 4th accuracy class with the highest weighing limit of 100 g are set according to the level, then the beginning of the scale is set corresponding to 0.0 g. The correct installation of the noses and their adjustment is checked with weights of the 2nd accuracy class. The beginning of the scale, the middle of the scale, corresponding to 50.0 g, and the end of the scale, corresponding to 100.0 g, must coincide with the indicated divisions of the scale with an error of not more than 0.1 g. matches. The balance allows you to work in the intervals 0-100, 100-200, 200-300, 300-400 and 400-500 g. The specified requirements must be met in each of these intervals.
2. Installation and adjustment of the drying cabinet
Soil moisture is a percentage of the amount of water contained in the soil.
The hard life of moles, or why does the soil need water?
One might think that the soil must contain water so that the moles do not die of thirst. No matter how unexpected and strange such an opinion may seem, there is some truth in it: moisture is really important for many underground inhabitants. But this is not the most important task of water, there are others.
What are these main tasks?
- providing water to plants.
- The level of soil moisture affects the air content, its salinity and the content of toxic substances.
- support of soil structure, plasticity and density.
- impact on temperature regime and heat capacity.
- preventing soil erosion.
- determines the readiness of the land for agricultural and agrotechnical activities.
Taste and color...
Water and soil are simply made for each other. Just like air and fire. What else affects soil moisture? The amount of water contained in the soil affects the color. The wetter the soil, the darker it appears. This can be somewhat misleading, because the color of the soil determines the level of its fertility by eye. The more humus in the soil, the darker it is.
From here, by the way, came the term "chernozem" - organically rich soil, "black earth".
So, soil moisture is an important agrotechnical parameter in soil science, geology, ecology, horticulture, which has a serious impact on the full functioning of such an ecological system as biogeocenosis.
... not to measure with a common arshin?
If there is some parameter in nature, there is a desire to measure it without fail - out of curiosity, scientific or practical considerations.
How is soil moisture determined? Of course, there are several ways, and new ones appear from time to time.
Someone sits inventing a perpetual motion machine and developing artificial intelligence, and someone puzzles over the question - how else to contrive and non-standard measure the level of soil moisture?
It is safe to say that today there are the following methods for determining soil moisture:
- Thermostatic weight.
- Radioactive - measures the radiation of radioactive elements placed in the soil.
- Electrical - measurement of soil resistance, conductivity, inductance and capacitance.
- Tensometric - based on the difference in water voltage between the phase boundaries.
- Optical - based on the reflectivity of light fluxes.
- Express methods (primarily organoleptic).
The most simple and popular are the first and last methods - thermostatic-weight and organoleptic. The first of them is more accurate, and the second takes a minimum of time and does not require special equipment.
Golden hands - organoleptic method
To conduct an examination in this way, it is enough just to take a handful of earth in your hand and evaluate its qualities. In terms of gradation levels look like this:
- Dry earth - the hand does not feel cool, the compression of the soil does not lead to the formation of a lump, the soil crumbles.
- Fresh earth - coolness is felt, when compressed, a fairly stable soil lump is formed.
- Wet earth - a clear feeling of coolness in the hand, compression forms a dense lump, but when you try to roll it out, it collapses.
- Raw earth - after contact with the soil, the hand remains wet, the soil is plastic - you can sculpt and roll it out.
- Wet ground - water flows down the hands, the soil is very sticky, shiny.
Soil baking oven - thermostatic weight method
The method is very accurate, and it is not particularly complicated. But here you will need some equipment: scales, a thermostat, a drill and a few bottles. With the help of a drill, several samples of the earth are taken at different depths and from different areas. Then the earth is weighed, distributed into bottles - heat-resistant cups (their weight is known in advance).
After that, the soil samples are dried in a thermostat until they completely lose moisture. It remains only to weigh them and calculate the difference between the initial and final mass - this will be the weight of the water contained in the soil.
Water properties of the soil. Methods for determining soil moisture
The main water properties of the soil include its water permeability, water-retaining and water-lifting capacity.
Soil permeability is commonly referred to as the ability of the soil to absorb and pass water through it from its upper horizons to its lower ones. It can be divided into two stages. The first stage is called imbibing and manifests itself in drier soils, when moisture-free pores begin to fill with water. During the soaking period, the water permeability of the soil under the forest is significantly higher than in the soil in open areas, which is explained by the better structure of forest soils. With the end of soaking, the water permeability of forest soils and adjacent soils in open areas levels off.
The second stage is presented filtration. It usually occurs during heavy rainfall. At this time, in the soil, which is already completely saturated with water, moisture begins to move under the influence of gravity and the pressure gradient.
Water permeability depends on the mechanical composition, humus content and soil structure. The intensity of soil permeability depends on the size and number of pores.
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Light sandy and sandy soils having a large number of large pores, always have high water permeability.
Water holding capacity is the ability to retain water in its pores. To characterize the water-holding capacity of the soil, the concept of its moisture capacity has been introduced. Moisture capacity is called the largest amount of water, ĸᴏᴛᴏᴩᴏᴇ the soil can hold with the help of certain forces. It is usually expressed as a percentage of the mass of dry soil. One of the factors in the water-retaining capacity of soils is the property of soil particles to sorb vaporous moisture on their surface. This ability of the soil is called hygroscopicity, and the vaporous moisture itself, held on the surface of the solid phase, is called hygroscopic.
The value of hygroscopic moisture depends on the specific surface of the soil, the content of humus in it, the composition of exchangeable bases and the composition of minerals. The higher the air humidity, the greater the hygroscopicity of the soil. Hygroscopicity increases with increasing soil humus content and cation absorption capacity.
Maximum hygroscopic humidity (MHW)- ϶ᴛᴏ the greatest amount of moisture, ĸᴏᴛᴏᴩᴏᴇ absolutely dry soil can absorb from air almost completely saturated with vapors (with a relative humidity of 100%). MHW is a very important indicator, since it can be used to calculate the humidity sustainable wilting of plants and, accordingly, the reserves of hard-to-reach moisture in the soil.
At a relative air humidity of more than 80%, the sorption of water vapor is accompanied by moisture condensation at the junctions between soil particles, which occurs due to the lower elasticity of water vapor above the concave surface. For this reason, the soil, saturated to the maximum hygroscopic moisture, retains the ability to attract new portions of it when in contact with water. Such moisture, condensed on concave surfaces and retained by the soil with less force, is commonly called loosely bound water.
The greatest amount of strongly bound moisture, which can be retained on the surface of soil particles with the help of sorption forces, is characterized by maximum adsorption capacity (MAV). This type of moisture capacity is usually 30-40% less than the maximum hygroscopic humidity.
The largest amount of loosely bound water, ĸᴏᴛᴏᴩᴏᴇ soil can hold with the help of molecular attraction forces, is commonly called maximum molecular moisture capacity (MMV). In sandy soils, MMW does not exceed 5-7%, and the thickness of the film around soil particles is several tens of molecules. In clay soils, the MMW can reach 25-30%, but in them, due to the smaller pore diameter, the film of loosely bound water should be much thinner.
Full moisture capacity (PV) It is customary to call the largest amount of water, ĸᴏᴛᴏᴩᴏᴇ the soil can absorb when all its pores are completely filled.
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The soil can remain in this state for a long time only if the moisture in large non-capillary pores is supported from below by groundwater. If this does not happen, then the gravitational waters flow down under the action of gravity. In this case, the soil goes into a state of moisture, called the least (HB) or maximum field moisture capacity.
It is observed in the groundwater horizon, as well as when it is excessively moistened by irrigation water or torrential rains.
Optimum humidity For most agricultural plants, it is conventionally accepted to consider a moisture content approximately equal to 50% of the total soil moisture capacity.
The smallest (NV) or maximum field moisture capacity (PPV)- ϶ᴛᴏ the greatest amount of moisture, ĸᴏᴛᴏᴩᴏᴇ can be retained by the soil after the runoff of gravity water in the absence of soil stratification and deep groundwater. In well-structured heavy soils, the value of this indicator is 30-35% of the mass of dry soil, in sandy soils - 10-15%.
The largest amount of capillary-backed moisture, ĸᴏᴛᴏᴩᴏᴇ, can keep the soil above the groundwater level is commonly called capillary moisture capacity (KV). This moisture capacity depends on the number of capillary pores and the depth of groundwater. The closer the groundwater is to the soil, the higher its capillary capacity.
All types of moisture capacity depend on the mechanical composition, humus content, soil structure. Soils are clayey, structural, with a higher content of humus, more moisture-intensive than sandy, sandy loamy soils, where there is less humus, a worse structure and a lighter mechanical composition.
Water-lifting capacity is the property of the soil to lift moisture through the capillary pores from the lower layers to the upper ones. Water moves most intensively due to capillary forces in pores, the diameter of which is in the range of 0.1-0.003 mm. With an increase in the pore diameter, the rate of water rise increases, but the height of its rise decreases. The pores, the size of which is less than 0.003 mm, as a rule, are filled with bound film moisture, and the height and rate of water rise in them are noticeably reduced. Water in such pores moves like a film. Capillary forces begin to appear in pores with a diameter of less than 8 mm. Pores with a size of 100 to 3 microns (micron) have the greatest capillary force.
Soil moisture is divided into absolute and relative.
Absolute moisture is the total amount of water in the soil, expressed as a percentage of the mass of the soil.
Relative humidity - the ratio of the absolute moisture content of a given soil to its maximum field capacity.
The availability of soil moisture to cultivated plants is determined by relative and absolute soil moisture.
Plant wilting moisture - soil moisture at which plants show signs of wilting that do not disappear when plants are placed in an atmosphere saturated with water vapor, that is, this is the lower limit of moisture availability for plants. Knowing the absolute humidity and the wilting point of plants, it is possible to calculate the reserve of productive moisture.
Productive (active) moisture - the amount of water in excess of wilting moisture, used by plants to create a crop. So, if the absolute moisture content of a given soil in the arable layer is 43%, and the wilting moisture content is 13%, then the reserve of productive moisture is 30%. For ease of determination, the amount of productive moisture is expressed in millimeters of water column. In this form, productive moisture is easier to compare with the amount of precipitation. Each millimeter of water on an area of 1 ha corresponds to 10 tons of water.
Water properties of the soil. Methods for determining soil moisture - the concept and types. Classification and features of the category "Soil water properties. Methods for determining soil moisture" 2017, 2018.
