A method for rapidly measuring roots in the field

Abstract

The present invention belongs to the technical field of root system measurement, and particularly relates to a method for quickly measuring the root system distribution of field crops. A plurality of groups of positive and negative paired electrodes are vertically pre-buried in the soil profile. Under the conditions of predetermined soil moisture and plant growth period, the measurement is carried out by the following steps: Step a: Measuring the soil capacitance with the help of the electrodes; Step b: Converting the measured soil capacitance into plant root system characteristic parameters according to the existing prediction model; Step c: Combining the depth information of different soil layers with the plant root system characteristic parameters to obtain the distribution of root system characteristics in the soil. The present invention directly measures the capacitance of the soil where the plant is located by the way of pre-burying electrodes, and then obtains the plant root system characteristic parameters by comparing with the existing prediction model, so that the root system distribution can be quickly determined by measuring the soil capacitance, and the measurement efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of root system determination, and in particular relates to a method for rapidly determining root system distribution in a field. Background Art

[0002] In order to measure the root system of plants, the current common practice is to use excavation and soil drilling. For example, 10 layers or more of soil samples need to be taken within a depth of 1 meter, and the obtained soil samples need to be further cleaned and processed. Therefore, these traditional methods are inefficient, destructive and have poor repeatability. Another in-situ measurement method is to set up root tubes and let the roots grow around the tubes. However, this method will cause the root growth environment to be destroyed. It is not the natural state of root growth, and the data analysis efficiency is low.

[0003] The root capacitance method is currently the most widely used in-situ non-destructive measurement method for field crop root measurement. Generally, the root capacitance is measured by inserting a positive electrode into the plant stem and a negative electrode into the soil, and the root size is measured based on the relationship between the root capacitance and the root characteristics. However, the relationship between the root capacitance and the root system measured by inserting electrodes into the plant stem is unstable, and can only reflect the size of the entire root system, but cannot reflect the distribution of the root system in different soil layers, and cannot effectively obtain key root information. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a method for quickly determining the root distribution in the field, which can realize in-situ non-destructive measurement of the root distribution and can quickly determine the root distribution by measuring the capacitance of the soil.

[0005] The specific technical solution adopted by the present invention is:

[0006] A method for rapidly measuring the root distribution of field crops is to bury multiple sets of positive and negative paired electrodes in the soil profile in the vertical direction, and to perform the measurement under the conditions of predetermined soil moisture and plant growth period using the following steps:

[0007] Step a: obtaining the change of soil capacitance at low frequency or obtaining soil capacitance at high frequency at a certain time point by means of electrodes at a certain time interval t;

[0008] Step b: converting the measured soil capacitance into plant root characteristic parameters according to the existing prediction model;

[0009] Step c: Combine the depth information of different soil layers with the characteristic parameters of plant roots to obtain the distribution of root characteristics in the soil.

[0010] Also included are existing prediction model building methods:

[0011] Step 1: Select multiple plants for measurement. Set up measurement profiles beside each selected plant, set electrodes in different soil layers of the measurement profiles, and obtain the change in soil capacitance at low frequencies or the soil capacitance at high frequencies at a certain time point through the electrodes at a time interval t.

[0012] Step 2: Sample the soil layers where the plants are located layer by layer, take out the plant root samples in the soil layers and measure the root characteristics to complete the acquisition of root characteristics in each soil layer.

[0013] Step 3: Combine the measured soil capacitance and the root characteristics in the corresponding soil layers to establish a relationship model for predicting root characteristics from soil capacitance.

[0014] In Step 1, the selection criteria for plants in low-frequency measurement are the same species of crops growing on the same soil, creating different root characteristics by using different varieties and / or irrigation measures, and selecting multiple plants at the same growth stage.

[0015] In Step 1, the selection criteria for plants in high-frequency measurement are the same species of crops growing on the same soil, creating different root characteristics by using different varieties, the crops have not experienced severe drought stress, that is, the soil water content is not lower than 65% of the field capacity, the soil water content reaches more than 75% of the field capacity during high-frequency measurement, and multiple plants are selected at the same growth stage.

[0016] In Step a, the measurement time interval of soil capacitance at low frequencies is t, and the value range of t is 5 - 7 days; obtain EC1 for the first measurement of soil capacitance at low frequencies, measure and obtain EC2 after a time interval t, and the difference △EC = EC1 - EC2. Determine the relationship between △EC and root characteristics through an existing prediction model, and calculate the root characteristics inversely.

[0017] The plant root characteristic parameters include root length, biomass, surface area or volume characteristics.

[0018] The thickness h of the soil layer is 10 cm, the total depth of soil layering is H, where 10h ≤ H ≤ 20h, and the starting layer for sampling is the soil layer with a depth of 1h from the ground surface.

[0019] The low frequency is a low-frequency frequency below 100 Hz, and the high frequency is a high-frequency frequency above 50 kHz.

[0020] The predetermined soil moisture condition at low frequencies is that the soil water content is lower than the field capacity, and the predetermined plant growth stage condition is the flowering and filling stages of the plants.

[0021] The predetermined soil moisture condition at high frequencies is that the soil water content is above 75% of the field capacity, and the predetermined plant growth stage condition is the entire growth period of the plants.

[0022] The beneficial effects of the present invention are as follows:

[0023] The present invention directly measures the capacitance of the soil where the plants are located by means of embedded electrodes, and then obtains the root system characteristic parameters of the plants by comparing with the existing prediction models. Therefore, the root system distribution can be quickly determined by measuring the capacitance of the soil, the measurement efficiency is improved, and the in-situ measurement of the root system distribution can be realized. Description of the Drawings

[0024] Figure 1 For the relationship between soil capacitance and root biology under sufficient and drought stress conditions

[0025] Figure 2 The relationship between soil capacitance and root length under sufficient water supply conditions Detailed Embodiment

[0026] The present invention will be further described below: The present invention obtains the effects of high measurement efficiency, small destructiveness and high repeatability through in-situ measurement. Specifically, the present invention is a method for quickly measuring the root system distribution of field crops. Along the vertical direction in the soil profile, multiple groups of positive and negative paired electrodes are embedded. Under the conditions of predetermined soil moisture and plant growth period, the following steps are used for measurement:

[0027] Step a: With the help of the electrodes, the change amount of the soil capacitance at low frequency is obtained through the electrodes at a certain time interval t, or the soil capacitance at high frequency at a certain time point is obtained.

[0028] Step b: Convert the measured soil capacitance into plant root system characteristic parameters with the existing prediction model.

[0029] Step c: Combine the depth information of different soil layers with the plant root system characteristic parameters to obtain the distribution of the root system characteristics in the soil.

[0030] The electrodes are arranged in an equidistant array in the vertical direction, and the electrodes are inserted horizontally or vertically. During the growth of the plants, the roots grow between the positive and negative paired electrodes, so that the change of the soil reading measured by the electrodes is reflected, and then the root system characteristics between the electrodes are reflected.

[0031] Previous experiments have shown that the soil capacitance value at low frequency is negatively correlated with the root system characteristics and positively correlated with the soil moisture and ions. In the case of no rainfall and irrigation, continuously measure the change of the low-frequency soil capacitance at different times, and these changes are caused by the growth and absorption of the roots.

[0032] Based on the previous experiments, it can be determined that the change in soil capacitance measured at low frequencies within a certain time interval t is caused by the absorption of soil water and ions by the roots of the plants to be measured. When the measurement period is restricted to after the plant blossoms, that is, during the flowering and filling stages of the plant when the roots of the plant stop growing, then the change in soil capacitance over a period of time is caused by root absorption. Therefore, after obtaining the change in capacitance within a certain time interval t, the root characteristic parameters corresponding to this change in capacitance can be obtained by comparing with the existing prediction model.

[0033] When the soil water content reaches more than 75% of the field capacity and the crop root characteristics without drought stress are positively correlated with the high-frequency soil capacitance under wet conditions, it indicates that the soil capacitance can directly measure the root characteristics under these conditions.

[0034] After obtaining the root characteristics and combining with the pre-buried electrode positions, the root distribution in the electrode layout space can be obtained.

[0035] Table 1: Conditions for the measurement in the present invention

[0036]

[0037] Note: Between the paired positive and negative electrodes is a measurement point.

[0038] Furthermore, the present invention also includes a method for establishing an existing prediction model:

[0039] Step 1, select multiple plants for measurement, respectively set measurement profiles beside each selected plant, set electrodes in different soil layers of the measurement profile, and obtain the change in soil capacitance at low frequencies or the soil capacitance at high frequencies at a certain time point through the electrodes within a certain time interval t;

[0040] Step 2, sample each soil layer where the plant is located, take out the root samples of the plant in this soil layer and measure the root characteristics to complete the acquisition of the root characteristics in each soil layer;

[0041] Step 3, combine the measured soil capacitance with the root characteristics in the corresponding soil layer to establish a relationship model for predicting root characteristics with soil capacitance.

[0042] Table 2: Measurement conditions when establishing the prediction model in the present invention

[0043]

[0044] The plant root characteristic parameters include root length, biomass, surface area or volume characteristics.

[0045] The thickness h of the soil layer is 10 cm, and the total depth of the soil layer is H, where 10h ≤ H ≤ 20h. The starting layer for sampling is the soil layer with a depth of 1h from the ground surface.

[0046] The present invention pre - establishes models of roots and soil capacitance for different varieties and different growth periods under different soil moisture conditions, including creating different soil moisture conditions. When establishing the prediction model, more than 30 points of soil capacitance with roots are measured for the selected plants, root samples are collected and measured, and the characteristic parameters of the plant roots are determined, so as to establish the existing prediction model. This prediction model, as Figure 1 highlights the relationship between low - frequency capacitance and root characteristics, where the biomass (dry weight of roots) of plants is linearly related to the soil capacitance reading. Figure 2 shows the root characteristics of different wheat varieties including Jimai 38, Jimai 22, Jinmai 47, and Shixin 633, and highlights the linear relationship between root length and high - frequency soil capacitance reading.

[0047] Specific embodiment: After the prediction model is established, the root characteristics corresponding to the measured soil capacitance reading can be obtained. Taking the comparison between the root characteristics calculated from the measured soil capacitance at high frequency and the measured root characteristics as an example, it is shown in the following table.

[0048] Table 3:

[0049]

Claims

1. A method for rapidly determining the root distribution of field crops. Features: Multiple sets of positive and negative paired electrodes are pre-buried vertically in the soil profile. During the growth of the plant, the roots grow between the positive and negative paired electrodes. Under the conditions of predetermined soil moisture and plant growth period, the measurement is carried out using the following steps: Step a: obtaining the change of soil capacitance at low frequency or obtaining soil capacitance at high frequency at a certain time point by means of electrodes at a certain time interval t; The low frequency is a low frequency lower than 100 Hz, the predetermined soil moisture condition under the low frequency is that the soil moisture content is lower than the field water holding capacity, and the predetermined plant growth period condition is the flowering and filling period of the plant; The high frequency is a high frequency higher than 50kHz, the predetermined soil moisture condition under the high frequency is that the soil moisture content is above 75% of the field water holding capacity, and the predetermined plant growth period condition is the full growth period of the plant; wherein, the soil moisture content of the plant measured by the high frequency during its growth period is higher than 65% of the field water holding capacity; Step b: converting the measured soil capacitance into plant root characteristic parameters according to the existing prediction model; Step c: Combine the depth information of different soil layers with the characteristic parameters of plant roots to obtain the distribution of root characteristics in the soil.

2. The method for rapidly determining the root distribution of field crops according to claim 1, Features: Also included are existing prediction model building methods: Step 1, select multiple plants for measurement, set measurement profiles next to each selected plant, set paired horizontal electrodes in different soil layers of the measurement profiles, and obtain the change of soil capacitance under low frequency or the soil capacitance under high frequency at a certain time point through the electrodes at a certain time interval t; Step 2, sampling the soil layer where the plant is located layer by layer, taking out the plant root samples in the soil layer and measuring the root characteristics, so as to complete the acquisition of the root characteristics in each soil layer; Step 3: Combine the measured soil capacitance with the root characteristics in the corresponding soil layer to establish a relationship model for predicting root characteristics using soil capacitance.

3. The method for rapidly determining the root distribution of field crops according to claim 2, Features: In step 1, the selection criteria for plants in low-frequency measurement are the same crops grown on the same soil, different varieties and / or irrigation measures are used to create different root characteristics, and multiple plants in the same growth period are selected.

4. The method for rapidly determining the root distribution of field crops according to claim 2, Features: In step 1, the selection criteria for plants in high-frequency measurement are the same crops grown on the same soil, using different varieties to create different root characteristics, the soil moisture content reaches more than 75% of the field water holding capacity during high-frequency measurement, and multiple plants are selected in the same growth period.

5. The method for rapidly determining root distribution of field crops according to claim 1, Features: In step a, the measurement time interval of the soil capacitance at low frequency is t, and the value range of t is 5 - 7 days; the first measurement of the soil capacitance at low frequency obtains EC1, and after the time interval t, EC2 is measured. The difference between the two, △EC = EC1 - EC2. The relationship between △EC and the root characteristics is determined through the existing prediction model, and the root characteristics are calculated inversely.

6. The method for rapidly measuring the root distribution of field crops according to claim 1, characterized in that: the plant root characteristic parameters include root length, biomass, surface area or volume characteristics.

7. The method for rapidly measuring the root distribution of field crops according to claim 2, characterized in that: in step 2, the soil layer thickness h is 10 cm, the total depth of soil stratification is H, where 10h ≤ H ≤ 20h, and the starting layer for sampling is the soil layer with a depth of 1h from the ground surface.

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