SU1639498A1 - Method for determining irrigation time - Google Patents

Abstract

The invention relates to methods for determining the timing of irrigation of plants in agriculture, mainly in the vegetable production of a protected ground. The aim of the invention is to increase the reliability of determining the dates of pouring plants. Continuously register a change in the capacitance of a capacitor sensor mounted on a plant when a high-frequency current flows. At the same time, irrigation is prescribed when the capacitance of the sensor reaches a given value. 2 Il.

Description

The invention relates to methods for determining the timing of irrigation of plants in agriculture, mainly in the vegetable production of a protected ground.

The aim of the invention is to increase the reliability of determining the timing of irrigation of plants.

Figure 1 shows a diagram of the device for implementing the method; Fig. 2 is a graph showing the change in capacitance of a sensor mounted on a cucumber plant, with an increase in the substrate upon reaching a certain level of decreasing the value of capacitance (watering is indicated by arrows).

The diagram shows a generator of 1 sinusoidal oscillations, an AC bridge 2, and a recording potentiometer sensor 3.

The method is carried out as follows.

The sensor in the form of two parallel stainless steel plates installs a cucumber plant on the stem. The sensor covers are flush with plant tissue, not

breaking them. By means of a two-wire communication line, the sensor is connected to one of the arms of the AC bridge powered by a high-frequency generator. The change in the sensor capacity indicates the change in the water content of the plant.

The AC bridge is powered by a generator, the voltage amplitude at the output of which is kept at a fixed level. When the sensor capacitance changes due to a decrease or increase in the water content in the plant tissues, a voltage change occurs in the diagonal of the bridge, which is rectified and fed through the voltage divider P5P6 to the self-recording potentiometer KSP-04.

The sensor is included in one of the arms of the AC bridge, which is powered by a sinusoidal oscillator with an amplitude of 1 V. The frequency of the voltage supply is not 100 kHz. At this alternating current frequency, the plant tissues are dielectric, since they are based on a parallel sensor replacement circuit (capacitance.

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resistance-bounded) the dielectric loss angle tangent is much less than one, and therefore, the impedance of the sensor is determined by its capacitance.

Before starting the measurement, the bridge is balanced in amplitude with resistances R4R3 and phase Ci, and then capacitor Ci is out of balance so that when connected in parallel with a constant capacitance sensor equal to 100 pF, the voltage across the resistance Re increases by 10.

Before any method fix the value of the capacitance of the sensor (dotted line). After irrigation, the capacity is increased by increasing the amount of free water in the plant and when the capacity is again reduced to a fixed level, irrigation, etc., is prescribed. (watering moments are shown by arrows on the chart). In the dark period, the time between successive irrigations according to this method increases due to a decrease in transpiration.

Improving the reliability of determining the timing of irrigation using this method is achieved by: eliminating the integrity of plant tissues, while measuring the electrical resistance at a constant current, the sensor electrodes destroy them, which has an adverse effect on the normal functioning of the plant, resulting in increased measurement error; the resistance of plant tissue to direct current depends both on the content of free water in the plant and on the chemically bound; fluctuations in the chemical composition of cell sap in a plant reduces the reliability of measurement results; the occurrence of electrochemical processes

in plant tissues, the conductivity of the system will change.

In this method, the capacitance of the sensor C is directly proportional to the dielectric constant g, which uniquely depends on the amount of free water in the plant, since water 80, K chemical high water 4,, 0, i.e. Ј Ev water (chemical bond z.vody. In

As a result, the capacity is determined by the amount of free water in the plant and by slight variations in chemical composition. The effect of polarization of electrodes at a frequency of 100 kHz is negligible.

The sensitivity of moisture measurement by determining the DC resistance in a region of high moisture content (cucumber and tomato plants contain 95% water each) is significantly less than when measuring the impedance at high frequency.

The continuity of registration provides an intimate picture of the course of a change in a plant's need for moisture, as a result of which the probability of occurrence is reduced.

water imbalance.

Claims (1)

Discreteness of information can lead to water starvation of a plant in the period between measurements. Invention Formula The method of determining the timing of irrigation plants, including the recording of the electrical characteristics of the plant, characterized in that, in order to increase the reliability of the determination, the capacitance of a capacitor sensor mounted on a plant, when high-frequency alternating current flows, is compared with a predetermined value, and the irrigation time is established when the capacitance of the sensor reaches a predetermined value. Phi. one ABOUT J