CN-122022196-A - Determination method for key growth stage of farmland crop drainage in plain area

CN122022196ACN 122022196 ACN122022196 ACN 122022196ACN-122022196-A

Abstract

The invention particularly relates to a method for determining a key growth stage of farmland crop drainage in a plain area, which relates to the technical field of farmland moisture management and comprises the step of superposing canopy transpiration resistance and soil-root system interface resistance calculated by soil water potential time sequence data in series at each sampling time. According to the invention, microclimate and root zone soil water potential time sequence data are integrated, canopy transpiration resistance is calculated based on an energy balance principle, soil-root interface resistance is overlapped in series to obtain the total transmission resistance of the SPAC system, resistance abnormal events are identified through continuous wavelet transform multi-time scale analysis, and quantitative scoring is realized by combining fertility stage division. Through standardized processing, scientific setting of threshold values and comprehensive scoring mechanisms, the method can accurately capture the difference of the risk of the logging in each fertility stage, define the key drainage period and the risk level, provide accurate data support for farmland drainage regulation and control, and avoid water resource waste caused by blind drainage and crop yield reduction caused by untimely drainage.

Inventors

ZENG YIQIANG
JI QIUXIANG
JIANG ZHONGLIN
HUANG XIAOWEI

Assignees

福建省兴禹源水利工程设计有限公司

Dates

Publication Date: 20260512
Application Date: 20260413

Claims (9)

1. A method for determining a key growth stage of farmland crop drainage in a plain area, comprising the steps of: acquiring a microclimate time sequence data set and root zone soil water potential time sequence data of a target farmland in a monitoring period, wherein the microclimate time sequence data set comprises canopy temperature data, air temperature data, relative humidity data, net radiation data and wind speed data; Based on the microclimate time sequence data set, calculating the canopy transpiration resistance at each sampling moment by utilizing an energy balance principle, and generating a canopy transpiration resistance time sequence curve; For each sampling moment, serially superposing the canopy transpiration resistance and the soil-root system interface resistance calculated by the soil water potential time sequence data, calculating the total transmission resistance of the SPAC system, and generating the time sequence data of the total transmission resistance of the SPAC system; Performing continuous wavelet transformation on the SPAC system total transmission resistance time sequence data, performing multi-time scale analysis, identifying resistance abnormal rise events, and generating a resistance abnormal event record set; And acquiring fertility stage division information of target crops, performing superposition analysis on the resistance abnormal event record set and a fertility stage time interval, counting occurrence frequency, average duration and average excess threshold of resistance abnormal events in each fertility stage, calculating a waterlogging risk comprehensive score of each fertility stage, and determining a drainage key fertility stage and a corresponding risk grade according to the waterlogging risk comprehensive score.
2. The method for determining the critical growth stage of crop drainage in plain areas according to claim 1, wherein the obtaining of the root area soil water potential time series data comprises the step of converting the soil volume water content into corresponding soil water potential values by utilizing a pre-calibrated soil water content characteristic curve when the data directly collected by the sensor is the soil volume water content, wherein the soil water content characteristic curve is a corresponding relation between the water content and the water potential which are obtained in advance through an indoor test according to the soil texture of a target farmland.
3. The method for determining the critical growth stage of farmland crop drainage in plain areas according to claim 1, wherein the calculation of the crown transpiration resistance comprises the following substeps of multiplying the product of air density and air constant pressure specific heat capacity by the product of crown temperature and air temperature and aerodynamic resistance, calculating to obtain sensible heat flux by dividing aerodynamic resistance, subtracting soil heat flux and sensible heat flux from net radiation based on an energy balance equation, calculating to obtain latent heat flux, multiplying the product of air density and air constant heat capacity by the product of saturated water vapor pressure and actual water vapor pressure based on the difference of the saturated water vapor flux and crown temperature and the actual water vapor pressure, dividing by the product of dry and wet table constant and the latent heat flux, and subtracting aerodynamic resistance, calculating to obtain crown transpiration resistance, wherein the saturated water vapor pressure corresponding to the crown temperature is obtained by calculating through a Tetens formula, and the actual water vapor pressure corresponding to the air temperature is obtained by calculating the product of saturated water vapor pressure and relative humidity.
4. The method for determining the critical growth stage of farmland crop drainage in plain areas according to claim 3, wherein the aerodynamic resistance is obtained by estimating a logarithmic wind profile formula according to wind speed and crop canopy height, specifically, dividing a difference between a wind speed measurement height and a zero plane displacement height by a momentum roughness length to obtain a natural logarithm, dividing the square of the natural logarithm value by the product of the square of von-Kamen constant and wind speed to obtain the aerodynamic resistance, and wherein the zero plane displacement height and the momentum roughness length are determined according to the crop canopy height according to an empirical relationship.
5. The method for determining the critical growth stage of farmland crop drainage in plain areas according to claim 1, wherein the calculation method of the soil-root system interfacial resistance is characterized in that the absolute value of the soil water potential is divided by the product of a root system activity correction coefficient and a reference transpiration rate, the value range of the root system activity correction coefficient is larger than zero and smaller than or equal to one, the root system activity correction coefficient is preset according to the root system growth characteristics of different growth stages of target crops, and the reference transpiration rate is the reference crop transpiration obtained by calculating by using FAOPenman-Monteith formula based on contemporaneous meteorological data under the condition of no water stress.
6. The method for determining the critical growth stage of farmland crop drainage in plain areas according to claim 1, wherein before calculating the total transmission resistance of the SPAC system, the time series data of the canopy transpiration resistance and the soil-root interface resistance are respectively standardized by adopting a Z-score standardization method, and the standardized canopy transpiration resistance and the standardized soil-root interface resistance are overlapped in series to obtain the standardized total transmission resistance of the SPAC system.
7. The method for determining the critical growth stage of farmland crop drainage in plain areas according to claim 1 is characterized in that the specific process of continuous wavelet transformation comprises the steps of selecting Morlet wavelets as a mother wavelet function, carrying out continuous wavelet transformation on total transmission resistance time sequence data of the SPAC system, calculating wavelet coefficient matrixes under all time scales, calculating wavelet power spectrums under all time scales based on the wavelet coefficient matrixes, wherein the wavelet power spectrums are the modular squares of wavelet coefficients, setting power spectrum thresholds on all time scales respectively, extracting time-frequency domain areas with wavelet power spectrum values exceeding the corresponding power spectrum thresholds as time-frequency domain feature modes of resistance abnormality elevation, carrying out merging processing on abnormal time intervals extracted on all time scales, obtaining a union set of the abnormal time intervals overlapped on a time axis, generating a resistance abnormality event record set, and recording the starting time, the ending time and the duration of each resistance abnormality elevation event.
8. The method for determining the critical growth stage of farmland crop drainage in plain areas according to claim 1, wherein the power spectrum threshold is determined based on statistical characteristics of time sequence data of total transmission resistance of the SPAC system in a monitoring period, specifically, the arithmetic average value of the time sequence data of the total transmission resistance of the SPAC system is added with the product of a threshold coefficient and a standard deviation, the threshold coefficient is used for controlling the sensitivity of abnormality determination, and the threshold coefficient is determined according to the sensitivity degree of target crops to waterlogging.
9. A method for determining a key growth stage of a farmland crop drainage in a plains area as described in claim 1, wherein said calculating of a comprehensive score of risk of logging comprises: the method comprises the steps of carrying out normalization processing on occurrence frequency, average duration and average over-threshold of each fertility stage in all fertility stage ranges by adopting a mean value normalization method based on the range, multiplying the occurrence frequency after normalization, the average duration after normalization and the average over-threshold after normalization to obtain comprehensive scores of the risk of the waterlogging of each fertility stage, wherein the average over-threshold is a value obtained by dividing a time integral value of the SPAC system total transmission resistance exceeding a resistance abnormal threshold in each resistance abnormal event in the corresponding fertility stage by the event duration and then carrying out arithmetic average on all resistance abnormal events in the fertility stage, sequencing the comprehensive scores of the risk of the waterlogging of all fertility stages according to the sequence from large to small, extracting the fertility stage with the comprehensive score of the risk of the waterlogging exceeding a preset risk threshold as a drainage key fertility stage, and dividing the drainage key fertility stage into a high risk level, a medium risk level and a low risk level according to the value range of the comprehensive scores of the waterlogging risk.

Description

Determination method for key growth stage of farmland crop drainage in plain area Technical Field The invention relates to the technical field of farmland moisture management, in particular to a method for determining a key growth stage of farmland crop drainage in a plain area. Background In the management of farmland production in plain areas, waterlogging is one of the important water disasters affecting crop yield. The essence of the waterlogging is that a moisture transmission channel in a soil-crop-atmosphere continuum (SPAC system) is blocked, and root system hypoxia is caused when the soil in a root zone is in an excessively wet state for a long time, so that the water absorbing capacity of crops is obviously reduced. In the prior art, the soil moisture state and the atmospheric evaporation requirement are generally monitored independently, the drainage and irrigation time is judged through respective threshold values, and the critical judgment of the growth stage depends on the moisture state evaluation of a single link. However, this approach does not reflect the resistance change of the complete transmission link in the SPAC system. Particularly, under the meteorological conditions of high humidity and low evaporation, the monitoring value of the soil moisture content can be in a normal range, but the crops are subjected to water stress due to the damage of root system functions, at the moment, the abnormal rise of systematic transmission resistance is difficult to identify by a single-link monitoring method, so that the judgment of a drainage critical period is inaccurate, and the drainage opportunity is delayed. Disclosure of Invention The invention aims to solve the problems and provides a method for determining the key growth stage of farmland crop drainage in plain areas. In order to achieve the above purpose, the present invention adopts the following technical scheme: A method for determining a key growth stage of farmland crop drainage in a plain area comprises the following steps: acquiring a microclimate time sequence data set and root zone soil water potential time sequence data of a target farmland in a monitoring period, wherein the microclimate time sequence data set comprises canopy temperature data, air temperature data, relative humidity data, net radiation data and wind speed data; Based on the microclimate time sequence data set, calculating the canopy transpiration resistance at each sampling moment by utilizing an energy balance principle, and generating a canopy transpiration resistance time sequence curve; For each sampling moment, serially superposing the canopy transpiration resistance and the soil-root system interface resistance calculated by the soil water potential time sequence data, calculating the total transmission resistance of the SPAC system, and generating the time sequence data of the total transmission resistance of the SPAC system; Performing continuous wavelet transformation on the SPAC system total transmission resistance time sequence data, performing multi-time scale analysis, identifying resistance abnormal rise events, and generating a resistance abnormal event record set; And acquiring fertility stage division information of target crops, performing superposition analysis on the resistance abnormal event record set and a fertility stage time interval, counting occurrence frequency, average duration and average excess threshold of resistance abnormal events in each fertility stage, calculating a waterlogging risk comprehensive score of each fertility stage, and determining a drainage key fertility stage and a corresponding risk grade according to the waterlogging risk comprehensive score. Preferably, the acquisition of the root zone soil water potential time sequence data comprises the step of converting the soil volume water content into a corresponding soil water potential value by utilizing a pre-calibrated soil water content characteristic curve when the data directly acquired by the sensor is the soil volume water content, wherein the soil water content characteristic curve is a corresponding relation between the water content and the water potential which are pre-acquired through an indoor test according to the soil texture of a target farmland. The calculation of the crown transpiration resistance preferably comprises the substeps of multiplying the product of air density and air constant pressure specific heat capacity by the difference of crown temperature and air temperature based on the difference of crown temperature and air temperature and aerodynamic resistance, dividing the product by aerodynamic resistance, calculating the sensible heat flux, subtracting the soil heat flux and the sensible heat flux from net radiation based on an energy balance equation, calculating the latent heat flux, multiplying the product of air density and air constant pressure specific heat capacity by the difference of saturated water vapor pressure and actual