Soil moisture in a summer cottage, determine, calculate soil moisture. Determination of soil moisture (thermostatic-weight method) In what units is soil moisture measured?

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Soil moisture is the most important agrotechnical parameter in soil science, geology, ecology, horticulture, which has a serious impact on the quality functioning of ecological system– biogeocenosis. Today there are many ways to measure it. In this article we will talk about determining soil moisture and compare the effectiveness of various devices for measuring it.

Reasons for the need for soil moisture

During the growing season, the water level in the tissues and cells of plant organisms is 70-90%.

Humidity is one of the main factors affecting soil fertility. It implements the following tasks:

enrichment of vegetable and fruit crops water;
soil moisture affects the amount of air, salt level, and the presence of harmful components;
provides a plastic and dense structure of the earth;
affects temperature as well as heat capacity;
does not allow soil weathering;
shows the ability of the soil to agrotechnical and agricultural processes.

For the full functioning of a plant organism, its cells, as well as tissues, should receive sufficient water, in particular during the activation of life processes.

Optimal soil moisture levels

Currently in experimental development There are two types of irrigation - jet and pulse.

Tip #1. Please note that the level optimal humidity during germination should be higher than during the ripening process of crops.

How to determine soil moisture

Today, there are the following methods for calculating soil moisture:

thermostat-weight;
radioactive – represents a measurement of radiation radioactive substances located in the ground;
electric – in in this case soil resistance, conductivity, inductance, and capacitance are determined;
strain gauge - the method is based on the difference in water tension between phase boundaries;
optical - this method is characterized by the reflectivity of light fluxes;
express methods, in particular organoleptic.

The easiest and most common are thermostat-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 listed in the table.

Determination of electrical resistance

In this case, sensors are used that are made of gypsum. These sensors contain 2 electrodes connected directly to the meter. The electrical resistance of a material depends on the presence of liquid in it, which, accordingly, measures the level of moisture in the earth. Holes are made in the ground until required depth with subsequent placement of sensors in them. Close contact between sensitive element, as well as earth (this is a necessary factor for all moisture meters).

Modern types of sensors use granular material surrounding a special membrane and perforated covers, which are made of steel or PVC. This ensures longer service life for the sensors, faster response times, and more accurate measurements. These sensors can be used in irrigation systems that are automatically controlled. Moisture determination instruments equipped with dielectric probes are listed in the table.

Measurements using TDR and EDR dielectric probes

Determination of soil moisture indicators using this method is carried out by calculating the dielectric medium, which depends on soil moisture. 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.

Today there are also devices whose probes are constantly located in the pipe at the required depth. In this case, readings are taken automatically and then transmitted to the observer. Accordingly, the price of these devices is much higher. Instruments for measuring using soil tensiometers are listed in the table.

Name	Description
Thetaprobe tensiometer kit	Multifunctional device used for a variety of tensiometer tests 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	Allows you to determine dynamic surface tension

Tensiometer method for measuring humidity

The tensiometer consists of a ceramic filter, plastic pipe and a vacuum pressure gauge, immediately after filling with water, which is lowered into the ground to calculate the pressure. Liquid moves along ceramic element, which causes a change in pressure in the pipe, as well as changes in the meter readings. After the hydration procedure or precipitation in the ground, water does not enter the tube until the potential shifts between the soil and the tensiometer. The devices are tubes, available for purchase, of different lengths for calculating moisture levels in the ground at various depths.

Devices are used, as a rule, to determine the beginning and end of watering. 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 start period of irrigation (based on the data of a device located close to the surface), as well as the end time of irrigation (according to the readings of a device located deeper).

How to increase soil moisture

To increase humidity, for example in a greenhouse, you should spray crops, paths, heating devices, as well as the glass ceiling and increase the amount of irrigation. In addition to hose irrigation, today farms use: sprinkling, subsurface irrigation and drip irrigation. The most popular type is sprinkling, in this case the plants are simultaneously watered, the temperature of the foliage and evaporation are reduced, and overheating of the crops is eliminated.

Tip #2. To reduce the level of soil moisture in a greenhouse structure, ventilation should be carried out, air temperatures should be raised, and the number and volume of watering should be reduced..

Does region affect soil moisture?

Irrigation rates are calculated in liters per square meter or in cubic meters per hectare.

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 there are chernozems and podzolic soils, and in Leningrad region Podzolic soils are often found.

How to calculate the optimal period and size of watering

Many conducted studies indicate that the most optimal indicators of a plant organism’s need for water include the physiological state of a given plant, the sucking power of foliage, the concentration and osmotic pressure of cell sap, etc.:

It is often practiced to determine irrigation dates using a visual method, that is, by external signs;
the next indicative method is to measure soil moisture by touch;
Approximate irrigation rates can be determined using total radiation. The latter in this case is measured in the periods between watering procedures.

Irrigation scheme for different soil moisture

In hot and sunny weather, it is recommended to carry out frequent and abundant irrigation; in cool times and in the winter season, watering is reduced.

Soil moisture is one of the main factors of fertility. Let's consider the main requirements for soil irrigation at various stages of cultivation of vegetable and fruit crops:

moderate watering - do not allow the soil to become waterlogged or completely dry out;
spraying leaves during flowering – abundant watering carried out in summer time, after the end of flowering, the plant is rarely carried out during the dormant period;
spraying in warm seasons - the soil requires abundant watering in summer, reduced in cold weather.

Answers to common questions

Question No. 1. How to determine whether there is enough moisture in the soil?

You need to take a little earth in your hand and squeeze it; if moisture does not appear between your fingers, open your palm. The soil lump has not disintegrated - this means that the moisture level is satisfactory.

The rate of irrigation used depends on the season, the plant, the age of the crop, the degree of lighting, as well as the water-physical characteristics of the soil.

Question No. 2. How can you increase soil moisture in a greenhouse structure?

In this case, it is necessary to increase watering, lower the temperature slightly, and also spray the plants, soil and paths with water.

Question No. 3. During what period of plant growth do they need greatest number moisture?

During the growing season, plant organisms most of all need intensive watering.

Question No. 4. What is the best method for measuring soil moisture?

The simplest and most popular are thermostat-weight and organoleptic methods.

Gardener mistakes that lead to waterlogging

The main oversight lies in unregulated irrigation of land.
It should also be noted that there is no liming and proper fertilization of soils prone to waterlogging.
Gardeners also often forget about organization. drainage system. All this generally negatively affects the quality of the soil.

As such, the concepts of lack of moisture or waterlogging are quite relative. High humidity soil in combination with large-scale mineral supplements, as well as favorable temperature indicators, activates intense photosynthesis, rapid growth of crops and an increase in total biomass. Accordingly, when the temperature decreases, a similar increased humidification has a negative effect. As you can see, such a parameter as soil moisture is very important in the process of growing any crop. various types soils and in different climatic latitudes.

Soil moisture is the moisture content in the soil in three states (solid, liquid and gaseous). Soil moisture is expressed as a percentage of dry soil mass or volume. The growth and development of plants largely depends on this ratio of moisture and air in the soil.

How to determine soil moisture

To determine and calculate soil moisture for summer cottage you need to take 20 grams of soil, measured on a technical scale with an accuracy of 0.1 grams, place it in a pre-weighed metal or porcelain cup (or a crucible, which can be bought at a special Medical Equipment store) with a volume of 50 milliliters.

Place in the oven at 100 degrees for 5-6 hours.

The most, of course, optimal- use a drying cabinet, but, as they say, for lack of...

Weigh the dried soil and calculate its water content using the formulas:

The results will help you determine the need for watering.

The following should be especially noted. An urgent need for watering occurs when humidity drops to a level at which plants begin to wither. This level is called wilting moisture and depends on the plant species and soil properties.

The average wilting moisture content is:

IN sandy soils-1 -3 percent,

In sandy loam - 3-6, in loam - 6-15,

In clays - 10-15,

IN peat soils- 50-60 percent.

The optimal humidity for plants on sandy and sandy loam soils is from 10 to 20 percent, on clay and loamy soils - 20-45.

Soil moisture is the most important agrotechnical parameter in soil science, geology, ecology, and horticulture, which has a serious impact on the quality functioning of the ecological system - biogeocenosis. Today there are many ways to measure it. In this article we will talk about determining soil moisture and 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 implements the following tasks:

enrichment of vegetable and fruit crops with water;
soil moisture affects the amount of air, salt level, and the presence of harmful components;
provides a plastic and dense structure of the earth;
affects temperature as well as heat capacity;
does not allow soil weathering;
shows the ability of the soil to agrotechnical and agricultural processes.

For the full functioning of a plant organism, its cells, as well as tissues, should receive sufficient water, in particular during the activation of life processes.

Optimal soil moisture levels

Optimal soil moisture is the moisture level when the roots of the crop do not lack the liquid necessary for development and growth. The moisture level should not be higher than 60-70% of the total moisture capacity during the cultivation process vegetable crops, 70-80% - grain crops 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 soil moisture

Today, there are the following methods for calculating soil moisture:

thermostat-weight;
radioactive - is a measurement of the radiation of radioactive substances found in the earth;
electrical - in this case, soil resistance, conductivity, inductance, and capacitance are determined;
strain gauge - the method is based on the difference in water tension between phase boundaries;
optical - this method is characterized by the reflectivity of light fluxes;
express methods, in particular organoleptic.

The easiest and most common are thermostat-weight and organoleptic methods. The first is the most accurate, and the second, in turn, requires little time and does not require special equipment. Devices for determining electrical resistance are listed in the table.

Determination of electrical resistance

In this case, sensors are used that are made of gypsum. These sensors contain 2 electrodes connected directly to the meter. The electrical resistance of a material depends 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 required depth and sensors are then placed in them. Close contact between the sensing element and the ground is important (this is a necessary factor for all moisture meters).

Measurements using TDR and EDR dielectric probes

Name	Description
Thetaprobe tensiometer kit	Multifunctional device used for a variety of studies with different types of tensiometers 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	Allows you to determine dynamic surface tension

Tensiometer method for measuring humidity

The tensiometer consists of a ceramic filter, a plastic pipe and a vacuum pressure gauge, which, immediately after filling with water, 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 hydration procedure or precipitation in the ground, water does not enter the tube until the potential shifts between the soil and the tensiometer. The devices are tubes, available for purchase, of different lengths for calculating moisture levels in the ground at various depths.

How to increase soil moisture

To increase humidity, for example in a greenhouse, you should spray crops, paths, heating devices, as well as the 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 the plants are simultaneously watered, the temperature of the foliage and evaporation are reduced, and overheating of the crops is eliminated.

Tip #2. To reduce the level of soil moisture in a greenhouse structure, ventilation should be carried out, air temperatures should be raised, and the number and volume of watering should be reduced..

Irrigation rates are calculated in liters per square meter or in cubic meters per hectare.

Does region affect soil moisture?

The Moscow region is characterized by podzolic, sod-podzolic soils, gray forest soils, and chernozems. For the territory of the Urals - clayey, sandy and podzolic. Podzolic soils are common in Siberia. In the Volga region there are chernozems and podzolic soils, and in the Leningrad region podzolic soils are often found.

For chernozems, the range of active moisture is 46.7% of the weight of dry soil, for gray forest soil - 27.2, for soddy-podzolic soil - 26.0.

How to calculate the optimal period and size of watering

It is often practiced to determine irrigation dates using a visual method, that is, by external signs;
the next indicative method is to measure soil moisture by touch;
Approximate irrigation rates can be determined using total radiation. The latter in this case is measured in the periods between watering procedures.

Irrigation scheme for different soil moisture

Soil moisture is one of the main factors of fertility. Let's consider the main requirements for soil irrigation at various stages of cultivation of vegetable and fruit crops:

moderate watering - do not allow the soil to become waterlogged or completely dry out;
Maximum values are given. As we can see, the region influences soil moisture through the type of soil, as well as the climatic features of the area, in particular the amount of precipitation. "
spraying in warm seasons - the soil requires abundant watering in summer, reduced in cold weather.

spraying 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 carried out rarely; Humidity control is used to different types land for harvesting the highest yields. In turn, it is the basis for the development of rational agricultural technology, which is why measuring soil moisture is the most popular soil analysis. It should not be forgotten that the size of the future harvest depends on proper watering. Therefore it is necessary with full responsibility

Answers to common questions

Question No. 1. How to determine whether there is enough moisture in the soil?

approach the development of a soil irrigation regime. "

Question No. 2. How can you increase soil moisture in a greenhouse structure?

In this case, it is necessary to increase watering, lower the temperature slightly, and also spray the plants, soil and paths with water.

Question No. 3. The rate of irrigation used depends on the season, the plant, the age of the crop, the degree of lighting, as well as the water-physical characteristics of the soil.

During the growing season, plant organisms most of all need intensive watering.

Question No. 4. What is the best method for measuring soil moisture?

The simplest and most popular are thermostat-weight and organoleptic methods.

Gardener mistakes that lead to waterlogging

The main oversight lies in unregulated irrigation of land.
It should also be noted that there is no liming and proper fertilization of soils prone to waterlogging.
During what period of plant growth do they need the most moisture?

As such, the concepts of lack of moisture or waterlogging are quite relative. Increased soil moisture in combination with large-scale mineral fertilizing, as well as favorable temperatures, activates intense photosynthesis, rapid crop growth and an increase in total biomass. Accordingly, when the temperature decreases, a similar increased humidification has a negative effect. As you can see, such a parameter as soil moisture is very important in the process of growing any crop on different types of soil and in different climatic latitudes.

Crop productivity directly depends on timely and optimal soil moisture. Soil moisture control – important point in determining the need for watering.

Soil moisture control methods

1. Weight method with drying the soil sample in a thermostat at 105 degrees to a constant mass value for 8 hours. The difference in weight of the soil sample before and after drying determines the moisture content.

2. Accelerated weight drying method using alcohol roasting of the soil. The soil sample is moistened with alcohol and burned in special bottles when there is a lack of oxygen. Soil organic matter practically does not burn out when alcohol burns (differences up to 1.5%). The moisture content is judged by the difference in sample masses before and after firing.

3. The tensiometric method for determining soil moisture is based on the ability of the soil to absorb from environment moisture until completely saturated.

The tensiometer device is a closed vessel with a certain volume of water connected to a container where the soil sample is located. One of the walls of the device is made in the form of a membrane, capable of deflecting under the influence of a vacuum from the suction force of the soil. The degree to which the membrane deviates from zero is an indicator of the moisture content of the soil sample. Laboratory method for accurately assessing the moisture content of samples.

4. Method for determining humidity depending on the degree of reflection of an electromagnetic wave wet surface. Water molecules are able to absorb part of the high-frequency energy of an electromagnetic wave. The degree of its reflection varies depending on the degree of moisture of the material and is measured by the sensor, and the processor calculates the indicator depending on the type of material being measured.

Soil moisture meter MG-44 works according to this method and is intended for professional work in hydrology. In addition to soil, it can measure the moisture content of various bulk products (grain, crushed stone, sand), as well as pasty products (butter, margarine) and other materials. The device is easy to use, reliable, and has a liquid crystal display. Measurement accuracy up to 1% in the humidity range 0 – 100%.

5. The electromoisture measuring method is based on measuring changes in electromotive force direct current when passing a section of soil between two metal electrodes.

At different soil moisture levels, the electromotive force of the current will be different. The method is indirect, the measurement tolerance error is up to 5%. The degree of accuracy of moisture measurement is affected by the presence of salts in the soil.

Instruments based on this method are designed for measuring humidity in field conditions to more accurately determine the timing of watering irrigated areas at soil temperatures of 1 - 50 degrees. Measurement time – 1 minute.

Household soil moisture meters

Based on the electromoisture meter method of measuring soil moisture, household meters are currently being produced for gardeners and amateur gardeners.

The simplest soil moisture indicator has a probe for deepening and a measuring unit with a battery. On a graduated scale, a mechanical indicator (arrow) will show what soil moisture is at a certain depth in the selected location.

A more complex device can be structurally designed as a multifunctional device (4 in one). Modules for determining soil moisture, temperature, acidity and degree of illumination are installed on the basis of one design.

Models with a liquid crystal display and a microprocessor capable of measuring and calculating indicators depending on the entered parameters are convenient. An example of such devices is the PH300 or KC-300 soil analyzers.

The KC-300 device weighs only 75 g, has a backlit liquid crystal display and a 20 cm long probe. Powered by one 9V battery, 5 levels of soil moisture measurement, 9 levels of illumination, 12 levels of acidity.

Traditional methods for determining soil moisture

To determine soil moisture without instruments in a greenhouse or area with a high organic content, you can take a handful of soil from a depth of 10–20 cm and squeeze it in your hand.

If, after opening the palm, the outlines of fingers remain on the lump, then we can assume that the humidity of such soil is about 70%. When an earthen clod is scattered, the soil will have a moisture content of less than 60%, and the protruding moisture on the coma will indicate a soil moisture content above 80%.

At the sites open ground lump will not form at a humidity of less than 60% and only on heavy loams can it retain its outline.

If a ball can be formed, but when lightly pressed it falls apart, then the moisture content of such soil is in the range of 70 - 75%.

A denser ball, wetting or in places moistening the filter paper when touched, indicates the presence of moisture in such soil at a level of 80 - 85%.

Rolling a handful of soil into a dense viscous lump on loamy soil indicates a humidity above 90%, and on sandy loam soils a lump of such humidity will also ooze moisture.

A few more simple techniques to determine the overall readiness of the soil for spring cultivation.

The soil, ready for cultivation, after plowing in sunny weather dries out (lightens) on two-thirds of the ridge after cultivating the area with a plow without harrowing.

A pointed stick, after being pulled across a plowed area, practically does not get dirty on the ground, and the soil crumbles from its impact.

A handful of earth taken from a depth of 5–10 cm is squeezed in the palms to form a lump and thrown from a height of 1 m to the ground.
If the lump partially crumbles, then planting can begin.
If it crumbles almost completely, then the soil is already beginning to dry out.
If the lump remains intact with traces of deformation, you should wait to sow.

It must be remembered that timely and correct determination of soil moisture allows you to reduce consumption. water resources and associated indirect costs of irrational use of fertilizers, crop loss and deterioration in product quality. Calculation methods and recommendations for the optimal level of moisture allow you to determine the exact amount of water for plants, which prevents the leaching of fertilizers, stimulants and herbicides into the lower layers of the soil, and also eliminates water shortages for plants, allowing you to obtain a high yield of environmentally friendly products.

The thermostat-weight method is the main and most precise method determination of soil moisture. This method is also simple and, despite a certain time investment, allows you to do without expensive equipment.

To determine humidity, the following tools and accessories are required:
1. A drill for taking samples 60-100 cm long (depending on the depth of the root layer of the soil), on which marks are applied every 10 cm. The photo shows the tip.
2. Heat-resistant cups (bugs), usually aluminum, which are pre-weighed and the empty weight is applied to the lid. It is convenient to choose a box where the cups are tightly placed for transportation to the field.
3. Scales with a division value of 0.1 g (or 0.01 g) and a maximum measurable weight of at least 200 g
4. Thermostat drying cabinet with a drying temperature of 105°C

The sampling process is as follows:

The required number of cups, a plate, a knife and a soil drill are collected.
After arriving at the site for taking soil samples, a place is selected where there is a characteristic density of crops (plantings) of plants. For the accuracy of the experiment, it is necessary to choose a sampling location near the root system of the plant (in a row, if the plants grow on a ridge, on the ridge itself). After choosing a place, lightly trample it (but do not compact it), this is necessary in order to dry upper layer during the process it did not crumble inside the hole.
Then place a plate next to it and a cup for soil on it. You can do without a plate if the soil is dry and nothing sticks to the bottom of the cup.

Next, use a drill to pierce the soil to the first mark, turn the drill slightly and remove it. Using a knife, carefully pour the soil into a cup and immediately close it tightly to prevent moisture evaporation and place it in a box.
A second sample is taken to the next mark. After the drill has been removed, starting from the second mark, it is necessary to cut off the soil above the 10 cm mark, because This is the soil that crumbled or was cut off by the tip during the process of immersing the drill into the soil.
It should look like this:

It should be noted that the tip must be thoroughly cleaned of soil before each dive.
If the soil in the lower layers is moist and does not crumble (or the fence is carried out on heavy and medium soils), then to speed up the process, you can clean out the required layer and then throw away the remains.

Note. For the accuracy of the experiment, it is necessary to take samples at one point in triplicate.

After filling all the cups, they are carefully (so that they do not mix) transported to the laboratory where they are weighed and the data is entered into a log.

To automate and speed up calculations, we use MS Excel. Fill in the columns No. of the bottle, weight of the empty cup, weight of the cup with wet soil. open the glass and place it on the tray.

Next, the samples are placed in a drying cabinet in which the temperature is set to 105 degrees C, and dried for at least 6 hours.
After drying, remove the tray and immediately close the cups so that moisture from the air is not adsorbed into the soil. Then we cool the cups for 10-15 minutes and weigh them, filling in the column in the table with the weight of the cup with dry soil.

The calculation in the table is carried out as follows:
Column “Mass of dry soil (indicated O in the figure)” = “weight of the weighing bottle with dry soil (N)” - “weight of the weighing bottle (L)”
Column “mass of evaporated water (P)” = “weight of a bottle with wet soil (M)” - “mass of a bottle with dry soil (N)”
Column "percentage of moisture (R) = "weight of water (P)" / "weight of dry soil (O)" * 100%

To find out the amount of moisture in the soil as a percentage of the minimum moisture capacity, you need to know the amount of water that the soil layer is able to hold in its pores without being discharged into the lower layers. This is determined empirically using flooded areas on which humidity is measured for 3-5 days (depending on the type of soil), when the relative humidity value is established at a more or less constant level - this should be considered the value of 100% NV (lowest moisture capacity or PPV - maximum field moisture capacity).

Current soil moisture value in %НВ = “rel. humidity (R)" / "rel. value humidity at 100% HB * 100%

To determine the soil moisture of the root layer, it is necessary to take the average value of all layers to the desired depth.
To speed up calculations of irrigation rates, you can create a table of moisture reserves (usually in t/ha or cubic m/ha) in different soil layers and at different meanings%NV. After this you can quickly calculate required amount irrigation water for the actual NV value and the planned NV value, the difference is the irrigation rate. At in different ways The watering rate must be increased slightly, taking into account losses due to evaporation, runoff, etc. You can learn more about the norms, techniques and methods of watering from ours.

Good luck in your work and high yields!

A.M. Menshikh, Ph.D.

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