RU2119282C1 - Irrigation norm determining method - Google Patents

Abstract

FIELD: irrigated agriculture. SUBSTANCE: method involves wetting soil layer by supplying water from below; sampling soil and determining soil moisture content; registering wetting process stabilization moment; plotting moisture content diagram and determining irrigation norm; measuring height of moistened zone in predetermined time intervals during wetting of soil; setting dependence H(w)= f (t) and determining average value of equilibrium moisture content

in rated soil layer on the basis of dependence curve and equilibrium moisture content diagram. Irrigation norm is determined by formula:

Description

 The invention relates to the field of irrigated agriculture and can be used for moisture supply of irrigated agricultural fields, namely, to determine the norm of irrigation of crops.

где
m - норма полива, мм;
γ - психрометрический коэффициент, равный 0,000662, 1/град;
P - давление воздуха, гПа;
J - производная давления насыщенного водяного пара по температуре адиабатного насыщения;

- среднесуточный верхний предел активности водяного пара, соответствующий верхнему пределу оптимального увлажнения почвы, доли единиц;

- среднесуточное значение текущей активности водяного пара, доли единицы.A known method of determining the norm of irrigation (1), including measuring the average daily temperature of surface air, a wet thermometer and air pressure, and the calculation of the norm of irrigation is carried out according to the formula

Where
m is the norm of irrigation, mm;
γ - psychrometric coefficient equal to 0,000662, 1 / degree;
P is the air pressure, hPa;
J is the derivative of saturated water vapor pressure with respect to adiabatic saturation temperature;

- the average daily upper limit of water vapor activity, corresponding to the upper limit of optimal soil moisture, fraction of units;

- the average daily value of the current activity of water vapor, a fraction of a unit.

 The disadvantage of this method is that when calculating the irrigation rate, ground parameters are taken into account and the soil properties, their ability to retain moisture, capillary moisture reserves, etc. are not taken into account at all, which as a result leads to an overestimation of the irrigation rate, and therefore, water overruns, soil quality deterioration, rising groundwater levels.

), равной предельной полевой влагоемкости или наименьшей влагоемкости W_FC (2). Способ включает замачивание слоя почвы, фиксирование момента стабилизации процесса замачивания, отбор проб почвы с различных по глубине горизонтов и определение ее влажности, построение эпюр влажности и по эпюре ППВ определяют значение W_FC=ППВ, необходимое для расчета нормы полива по формуле
m_nt=10•γ•h_w(w_FC-w_Cr),м³/га,
где
γ- объемная масса расчетного слоя почвы, т/м³;
h_w- мощность увлажненного слоя, м;
W_FC - наименьшая влагоемкость, % от массы;
W_cr - влажность увлажняемого слоя.The closest in technical essence is the method of determining the irrigation norm m _nt , based on the creation in a moistened soil layer with humidity W _cr - medium humidity (

) equal to the ultimate field moisture capacity or the lowest moisture capacity W _FC (2). The method includes soaking a soil layer, fixing the moment of stabilization of the soaking process, taking soil samples from horizons of different depths and determining its moisture content, plotting moisture plots and using the PPV plot, determine the value of W _FC = PPV necessary to calculate the irrigation rate using the formula
m _n t = 10 • γ • h _w (w _FC -w _Cr ), m ³ / ha,
Where
γ is the bulk mass of the calculated soil layer, t / m ³ ;
h _w is the thickness of the wetted layer, m;
W _FC - the lowest moisture capacity,% by weight;
W _cr is the moisture of the wetted layer.

In the known method, the soil is soaked from above, until complete moisture saturation (boreholeness), then excess water flows down (gravity water), and only after the flow stops, which is detected by electrical conductivity, moisture samples are taken in layers, plots are drawn, PPV = W _{FC is} determined .

A disadvantage of the closest method, in addition to its complexity and the complexity of the implementation, is that when constructing a moisture plot (after irrigation), humidity within the entire calculation layer is taken as a constant equal to W _FC , in FIG. 3 is the area of the AGCD rectangle, and the irrigation rate determined in this way significantly exceeds the equilibrium supply of capillary water in the calculation layer, therefore, part of the supplied irrigation water in the form of a capillary stream goes down beyond the calculation layer, which, in addition to water losses, contributes to the deterioration of soil quality and raising the level groundwater.

, а норму полива определяют по формуле
m $\genfrac{}{}{0ex}{}{\text{P}}{\text{nt}}$ = 100•γ•h_w(w_FC-w_Cr),м³/га,
где
γ- объемная масса расчетного слоя почвы, т/м³;
h_w - мощность увлажненного слоя почвы, м;

- среднее значение равновесной влажности, % от массы;
W_ср- влажность увлажняющего слоя.Significantly simplify the process and determine the optimal irrigation rate corresponding to the minimum loss of irrigation water (only due to vapor diffusion), allows the proposed method of determining the irrigation rate, including soaking the soil layer, fixing the moment of stabilization of the soaking process, sampling the soil and determining its moisture content, plotting humidity and determining the norm of irrigation, which differs in that in the process of soaking (from the bottom), at certain intervals, the height of the moistened zone is measured, the dependence H _у = f (t) between them, based on this dependence and the moisture indicators of the selected soil samples, an equilibrium humidity plot is constructed that takes into account the decrease in humidity with depth from W _FC to W ₀ and, using this plot, determine the average (in the calculation layer ) value of equilibrium humidity

, and the irrigation rate is determined by the formula
m $\genfrac{}{}{0ex}{}{\text{P}}{\text{nt}}$ = 100 • γ • h _w (w _FC -w _Cr ), m ³ / ha,
Where
γ is the bulk mass of the calculated soil layer, t / m ³ ;
h _w is the thickness of the moistened soil layer, m;

- the average value of the equilibrium humidity,% by weight;
W _cf - humidity of the moisturizing layer.

среднее в расчетном слое значение равновесной влажности.The essence of the method lies in the fact that when determining the norm of irrigation, the stocks of capillary water are taken into account, for which instead of W _{FC the} lowest moisture capacity is determined

the average value of the equilibrium humidity in the calculation layer.

 The proposed method for determining the norm of irrigation is as follows.

 Of the monoliths selected in a pit and dried to an air-dry state, a column of soil is made using a wooden formwork with one glass wall. The column is installed in a water pan, where a constant water level is maintained using a Marriott vessel. In the proposed method, the saturation of the monolith goes from below (capillary), which greatly speeds up, simplifies the process, allows you to observe it visually, and in addition, instead of a series of diagrams for the prototype, the construction is reduced to one diagram (equilibrium).

Опыт по увлажнению почвы в колонке прекращают после стабилизации расхода. Затем колонку почвы разбирают, отбирая пробы на влажность через каждые 5 см по высоте. Влажность проб определяют термостатно-весовым методом и по значениям влажности строят эпюру равновесной влажности W_pf(H_у) (фиг. 1).During the experiment, at intervals of time Δtt, measurements are made of the height of the humidified zone H _y and the volume of absorbed water ΔW _po W _po , after each measurement, the flow rate of absorbed water q is determined by the formula

The soil wetting experiment in the column is terminated after stabilization of the flow rate. Then the soil column is disassembled, taking samples for moisture every 5 cm in height. The moisture content of the samples is determined by the thermostat-weighting method, and from the values of humidity a plot of the equilibrium humidity W _p f (H _у ) is built (Fig. 1).

According to the results of measurements in the process of soaking, a graph of H _y = f (t) is constructed in the form logH _y = f (logt). The graph has the form of a straight line with two break points (Fig. 2), which reflect the change in the patterns of capillary motion of water in different equilibrium humidity ranges: the first stage is at W _p > W _FC (on the graph, the segment is up to t. F), the second is at W ₀ ≤W _p ≤W _FC (segment FE) and the third for W _p <W ₀ (segment after t. E). The first point F corresponds to the humidification height with equilibrium humidity W _FC . The second point of the graph - T. E, corresponds to the height of the capillary rise of water H _y with the corresponding humidity W ₀ , which is the limit of the capillary movement of water. Point E on the plot of equilibrium humidity gives t. C (H _y ), lowering the vertical to the abscissa axis, get t. D and the corresponding W ₀ . Point F of the graph (Fig. 2) on the plot of equilibrium humidity gives T. B ₁ and T. B (H _y = H _FC ). Lowering from t.B the vertical to the abscissa axis, get tA and its corresponding W _FC . The plot with the area ABSD (Fig. 1) is calculated; for convenience, it is presented in the form shown in Fig. 3.

The calculation of the irrigation norm according to the calculated diagram is performed as follows: on the vertical axis, the set value of the depth of the wetted layer h _{w is} laid (i.e., 1,2,3,4,5,6 correspond to a depth of 0.3-0.4-0.5 -0.6-0.7-0.8 m), through the marked points draw straight lines parallel to the BS to the intersection with the border of the plot (AD or AB), mark points a, b, c, d, d.

возрастающее с увеличением глубины расчетного слоя.Within the obtained plots for each value of h _w determine the average value of the equilibrium humidity

increasing with increasing depth of the computational layer.

рассчитывают запасы капиллярной воды для диапазона влажности

по формуле

.By values

calculate capillary water reserves for humidity range

according to the formula

.

Предлагаемый способ определения нормы полива позволяет значительно упростить процесс и определить оптимальную норму полива (фиг. 4), что в конечном результате позволит значительно сократить расход поливной воды, сохранить качество почв и уменьшить влияние на уровень грунтовых вод.Irrigation rate is determined by the formula
m $\genfrac{}{}{0ex}{}{\text{P}}{\text{nt}}$ = W _k + 100 • γ • h _w (W _o - W _Cr ), m ³ / ha,
or in its simplest form

The proposed method for determining the irrigation rate can significantly simplify the process and determine the optimal irrigation rate (Fig. 4), which in the end result will significantly reduce the irrigation water consumption, maintain soil quality and reduce the effect on the groundwater level.

Claims (1)

The method of determining the irrigation rate, including soaking the soil layer, fixing the moment of stabilization of the soaking process, sampling the soil and determining its moisture content, plotting the moisture plot and determining the irrigation rate, characterized in that during the soaking from below, at certain intervals, the height of the moistened zone is measured, the height is established therebetween dependence H _y = f (t), on the basis of this dependence and humidity indicators selected soil samples build epure equilibrium moisture content takes into account the decrease in humidity g Ubin W _FC from ₀ to W, and using this Diagrams, determine the mean (calculated in bed), the value of the equilibrium moisture content W _p, and irrigation rate is determined by the formula

where γ is the bulk density of the calculated soil layer, t / m ³ ; h _w is the thickness of the moistened soil layer, m; W _p - the average value of the equilibrium humidity,% by weight; W _cr is the moisture of the wetted layer.

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