# Modification and Validation of Ritchie Model for Evaporation of Maize Field in Saline Alkali Soil

Authors: Xin Zheng; Wenbao Xu; Chunyu Zheng; Hengyan Xie; Bo Li
Journal: Wireless Communications and Mobile Computing
 (2022)

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## Abstract

In order to study the evaporation law of the soil between the corn trees of Daqing salt-alkali soil, the evaporation simulation value of different growth stages in the experimental period was compared with the measured value according to the Ritchie model theory, and the model fit was not well matched by using a homemade microsteaming seepage instrument to study the evaporation of the whole fertility period of corn in the green wind garden test area of Daqing High-tech Zone, as well as rainfall and soil moisture content. The accuracy of the two parameters in Ritchie’s model directly determines the accuracy of the model’s prediction of evaporation. The firstU value and the second-stage α values were revised, respectively, and the model verification was based on the different growth-and-long-term values of corn, and the analysis showed that the average monthly rainfall was a function relationship with the average monthly evaporation. The modified Ritchie model has a maximum evaporation fit of 0.96 for maturity and a minimum fit of 0.91 for seedling. It provides an accurate evaporation prediction model for the accurate prediction of evaporation between saline soil corn classes in Daqing area and provides a theoretical basis for water quantity management and soil salinization prevention and control in the corn planting process.


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## Body

## 1. Introduction

Crop growth cannot be separated from water, and soil evaporation factors are divided into saturated soil and unsaturated soil evaporation, in the actual evaporation process involved in more factors [1]. Penman combines energy balance and mass delivery to arrive at a possible evaporation formula, which is the calculation formula for soil evaporation under sufficient humidity [2–4]. Since then, the relevant scholars have made a series of improvements to the model.Qiao et al. [5], Wei et al. [6], Zhang et al. [7], Cao et al. [8–12], Zhang et al. [13], Zhao Liyuan et al. [14], Wang et al. [15], Ritchie [16], Wang et al. [17], Yang et al. [18], Wang et al. [19], and Zheng et al. [20, 21] established a series of evaporation prediction models for soil evaporation, which explain the evaporation principle of bare soil in the case of insufficient moisture to a certain extent, but in the actual use process, due to the calculation involves too many parameters, so in the promotion and use of the greater restrictions.Ritchie came up with a simplified model based on the Penman model after extensive experimentation in 1972, which was widely popularized in the course of practical use because of the few parameters involved and the accuracy of the evaporation prediction [21–23]. The effect of evaporation on saline soil in Daqing area is obvious, and soil salinization will lead to a decrease in soil fertility, which is not suitable for cultivation. In order to improve the development of soil salinization in Daqing area, as well as the application of water resources, corn is mainly grown in Daqing area. In this context, it is necessary to study the evaporation law between corn trees in the saline soil in Daqing area.At present, people in the process of soil evaporation research for the evaporation of bare soil, for the saline area between corn trees; evaporation prediction is less researched; Daqing City, Heilongjiang Province, is one of the more serious soil salinization areas, and soil evaporation law is different from other regions [1, 10, 24–26].In order to make the Ritchie model more in line with the actual situation of agricultural production, this paper considers that the soil surface cover of corn is different during each reproductive period, and the actual evaporation measurement is carried out by using a homemade micropermeation instrument. According to the local meteorological conditions in Daqing City and the results of the evaporation of the full fertility period of corn, the Ritchie model of the full fertility period under the conditions between the salt-alkali soil corn trees was revised, and the correctness of the correction results was verified. This paper summarizes the evaporation law between the salt-alkali soil corn trees and provides a theoretical basis for the treatment of soil salinization and the management of farmland water.


## 2. Introduction to the Ritchie Model and the Current State of Research

The Ritchie model divides evaporation into two phases. Phase 1 evaporation is carried out at the potential evaporation rate of the soil, which depends primarily on the evaporation capacity of the atmosphere. When the evaporation accumulates to the phase 1 evaporation limit valueU, evaporation enters phase 2. If there is rain in stage 1, evaporation also enters phase 2. The soil evaporation rate in phase 2 is lower than the potential soil evaporation rate, and Ritchie et al. have tested that the cumulative evaporation in phase 2 is proportional to the square root of the duration of the phase. Formula for calculating cumulative evaporation between phase 1 and phase 2 is as follows (Wang et al. [19]):
(1)Stage1:Es1=∑i=1t1Es0i<U,t<t1,(2)Stage1:Es2=αt−t1,t>t1,whereEs1, Es2 is the accumulative evaporation in stage 1 and the stage 2, mm; Es0i is the potential evaporation rate of soil in day i, mm·d-1; α is the hydraulic characteristic coefficient of soil, mm·d-0.5; t1 is the accumulative evaporation duration in the first stage, d; t is the total evaporation duration, d.α is usually determined by experience, and it varies greatly with different soil and different cover of ground surface.The evaporation limit of the first stageU is 12 mm, 9 mm, and 6 mm corresponding to clay, loam, and sandy soil, respectively, which was presented by Ritchie through lots of tests. In the first stage, the potential evaporation rate of soil (Es0) was calculated according to Penman-Monteith formula and it was accumulated day by day.For the bared soil, the potential evaporation rate of soilEs0 is calculated as follows (Wang et al. [19]):
(3)ES0=∆∙Rns−Gs+ρ∙cp∙D/rα∆+γ∙λ,whereΔ is the slope of the saturated vapor pressure-temperature curve; Rns is the net radiation of the soil surface, MJ/(m2·d); Gs is the soil heat flux, MJ/(m2·d); ρ is the density of air, 1.209 kg/m3; Cp is the air specific heat capacity, 1.013×10−3 MJ/(kg·°C); D is the saturated vapor pressure difference, kPa; γ is the hygrometer constant, 0.66 KPa·°C-1; λ is the latent heat of vaporization of water, 2.45 MJ/kg; ra is the aerodynamic drag, s/m.
(4)rα=In2z−d/z0k2∙u,wherez is the reference height, 2 m here; d is the displacement of zero plane. For the bare soil, it is 0; z0 is the surface roughness. For bare soil, it is 0.01 m; k is the Von-Karman constant, 0.41; u is the wind speed at the reference height, m/s. For the soil under the canopy, Es0 can be simplified according to Penman-Monteith formula under the assumption that the potential evaporation rate is not affected by aerodynamic force, as shown in formula:
(5)Es0=∆∙Rns−Gs∆+γ∙λ.In China, Ritchie model has been widely used in simulation and research on evaporation of bare soil and farmland soil with crops, and a lot of research fruits have been obtained (Daamen C. C. et al. [27], Wallace J. S., Jackson N. A. and Ong C. K. [28], Salado-Navarro L. R., Sinclair T. R. and Morandini M. [29]). Yang et al. [18] studied the effects of irrigation and precipitation on evaporation of soil with winter wheat in different growth stages. The results show that in the second stage, the Ritchie model is not only related to the hydraulic characteristic coefficient of soil but also related to meteorological conditions and soil water content. Wang et al. [19] simulated evaporation of the farmland soil with wheat and maize intercropping in the area of Northwest China by using Ritchie model and the sunlight energy transformation model. The parameters of Ritchie model were modified, and the average error of the improved model was 20.8% lower than the original model. Ritchie model is accurate and concise, and the evaporation of soil can be figured out with the meteorological condition data and the soil hydraulic characteristic coefficient α in the second stage. However, Ritchie model is empirical on dividing different stages of soil evaporation, which leads to unfixed value of α. Therefore, most scholars did research work on modifying α by using the test data. At present, there are few researches on the evaporation law, numerical simulation, and the value of α on saline-alkali farmland soil with crops. Based on the existing research knowledge, evaporation on saline-alkali soil in maize field in Daqing was tested, and the law of evaporation on saline-alkali farmland soil in maize field was got. By using the test result, Ritchie model was modified and testified for evaporation on saline-alkali farmland soil in maize field.


## 3. Materials and Methods

### 3.1. Experimental Materials

The corn variety is “Qing Dan 3”. Corn in the test area is not treated in a special way and maintains the same agronomic measures as other corns in the field.Evaporation test instrument selected homemade microsteaming meter and microsteaming seepage instrument for the inner diameter of 100 mm, height of 150 mm, and wall thickness of 2 mm cylindrical and material for PVC. Both sides set soft rope production handle. Microsteaming meter is placed in the outer diameter of 114 mm, height of 150 mm, thickness of 2 mm iron pipe, iron tube outer tube to the miniature steaming meter to protect the role. The miniature steamer and its coat iron tubes are shown in Figures1 and 2. The back cover of the microsteaming instrument is used with plastic film to ensure that the surrounding soil is not damaged when the soil is taken, and the accuracy of the test is ensured.Figure 1
Microlysimeters (ML).Figure 2
ML and the iron tube.The Ministrant High-Precision Soil Moisture Monitoring System (TDR Time Domain Reflector) was used for on-site soil moisture detection.On-site weather data is recorded using an HBO-type weather inspector.


### 3.2. Test Method

#### 3.2.1. The Condition of the Test Site

The test was carried out in the green wind garden corn planting test area of Daqing City, Heilongjiang Province (125.2 degrees east longitude and 46.6 degrees north latitude). Daqing City belongs to the northern temperate continental monsoon climate zone, with annual precipitation of 427.5mm and annual evaporation of 1635 mm. The main sources of groundwater recharge in this area are atmospheric precipitation, which is excreted by evaporation and underground runoff, and the water level is affected by certain atmospheric precipitation and evaporation. The dynamic change law of groundwater is July-September, the water level is high, the dry period is in March-May, the water level is low, the annual variation range is 1.0-1.5 m, and the stable water level of groundwater is buried at a depth of 1.70-2.20 m. The average annual temperature is 4.2 degrees C, the annual sunshine hours are 2726 hours, the average frost-free period is 166 days, the average summer temperature is 23.2 degrees C, and the daily temperature difference during crop growth and development is 10 degrees C above. The test field is sandy soil, with a natural moisture content ofw, a density of 24.6%, a dense water holding rate of 1.55 kg/m3, and a water holding rate of 30.6%. Monitoring instruments are selected in the test area for farmland plots with an area of 9m×9m=81m2, and the location of the test site and the distribution of the instruments are shown in Figures 3 and 4.Figure 3
Intertree test site.Figure 4
Monitoring instrument layout.


#### 3.2.2. The Experimental Data Are Divided into Time Periods

The monitoring instruments were laid out on May 20 and tested on May 21. On May 27, corn begins to germinate, fields begin to weed on June 6, and clothes get dressed on July 6. Corn is harvested on October 8, and the trial lasts 142 days. In this field, precipitation is the main source of irrigation. Corn shows that the physical characteristics of different growth stages are different, which has a greater impact on soil evaporation. Therefore, the full reproductive period is divided into seedling period, extraction period, extraction period, grout period, and maturity period as shown in Table1.Table 1
Maize growth period.
Grow periodSeedlingJointingTasselingFillingMatureDate5.27-6.256.26-7.207.21-7.318.1-9.49.5-10.8Duration (day)3025113535


#### 3.2.3. Experimental Design

Corn grown in the test area is in uniform ridge form, with a width of 650 mm, a plant distance of 250 mm(23), and a planting density of 3300 plants/mu (666.7 m2 per acre). The test area is 9m×9m×81m2 and contains 9 3m×3m×9m2 zones. Place a microsteamer (microlysimeters, ML) in the center of each region, using the average of the evaporation measured values of the nine microsteamer meters as the test result. The observation scheme is to weigh 1 micro vaporizer mass (M1) at 8 : 20 daily and 8 : 20 the next day 1 time, and mass M2,M1−M2 is ML. The mass of evaporation of moisture in the internal soil is calculated with the base area of the microsteaming meter to obtain the evaporation amount (mm/d) of the day. The soil exchange cycle set by this test is 3 d, and if there is rain in the test, the soil exchange treatment is carried out immediately after the rainfall to ensure the accuracy of the test.


### 3.3. Experimental Parameters Are Determined

#### 3.3.1. Test Methods for Meteorological Indexes

The meteorological parameters required for the test are temperature, relative humidity, wind speed, and rainfall at 2 m, and the HBO-type weather inspector is used to observe bare soil and instrument meteorological indicators: including the highest minimum temperature at 2 m (with an accuracy of 0.01 degrees C) and wind speed (with accuracy). 0.01 m/s), relative humidity (0.1% accuracy), sunshine hours (0.1 h accuracy), rainfall (0.1 mm accuracy), etc., are for calculating the parameters of the model. Meteorological indicator observations are monitored continuously 24 hours a day, and data is recorded every 15 minutes. Parameters for model calculations are averaged throughout the day without special instructions. The small weather station is located in an open area near the test area. The observatory is 450 m from the test site.


#### 3.3.2. Test Methods for Evaporation

Prior to the test, the microsteamer is first carried out to collect soil, and the miniature steamer is gently smashed into the soil with a hammer, and to the top and the ground is flush. Dig out the surrounding soil and remove the miniature steamer filled with the original soil column. Remove excess soil from the bottom and seal the bottom with plastic film. After weighing, the miniature steamer is embedded in the outer barrel and the entire device is buried in a preset location, with the top leveling the ground.


#### 3.3.3. Test Methods for Soil Water Content

The MiniTRASE high-precision soil moisture monitoring system was used to test the water content at the height of 75 mm below ground, which is the center of ML. In order to avoid disturbing farm machine’s work, the soil moisture monitoring system was placed 10 m away from the farmland. The data of soil water content were recorded at 8 : 20 in the morning every day.The observed range is 20 mm, 75 mm, and 150 mm soil in the test area as shown in Figure5. The micro vaporometer used for the test observation is 150 mm high and has a back cover, setting the range to when observing soil moisture content between trees 20 mm, 75 mm, and 150 mm. Each layer of soil is arranged with a probe. Observation method: after observing the evaporation between trees every day, the soil moisture content was observed, and the water content of the soil layer was taken from 20 mm, 75 mm, and 150 mm. The average is the amount of water in the soil for the day.Figure 5
0 mm-150 mm probe layout diagram.


## 3.1. Experimental Materials

The corn variety is “Qing Dan 3”. Corn in the test area is not treated in a special way and maintains the same agronomic measures as other corns in the field.Evaporation test instrument selected homemade microsteaming meter and microsteaming seepage instrument for the inner diameter of 100 mm, height of 150 mm, and wall thickness of 2 mm cylindrical and material for PVC. Both sides set soft rope production handle. Microsteaming meter is placed in the outer diameter of 114 mm, height of 150 mm, thickness of 2 mm iron pipe, iron tube outer tube to the miniature steaming meter to protect the role. The miniature steamer and its coat iron tubes are shown in Figures1 and 2. The back cover of the microsteaming instrument is used with plastic film to ensure that the surrounding soil is not damaged when the soil is taken, and the accuracy of the test is ensured.Figure 1
Microlysimeters (ML).Figure 2
ML and the iron tube.The Ministrant High-Precision Soil Moisture Monitoring System (TDR Time Domain Reflector) was used for on-site soil moisture detection.On-site weather data is recorded using an HBO-type weather inspector.


## 3.2. Test Method

### 3.2.1. The Condition of the Test Site

The test was carried out in the green wind garden corn planting test area of Daqing City, Heilongjiang Province (125.2 degrees east longitude and 46.6 degrees north latitude). Daqing City belongs to the northern temperate continental monsoon climate zone, with annual precipitation of 427.5mm and annual evaporation of 1635 mm. The main sources of groundwater recharge in this area are atmospheric precipitation, which is excreted by evaporation and underground runoff, and the water level is affected by certain atmospheric precipitation and evaporation. The dynamic change law of groundwater is July-September, the water level is high, the dry period is in March-May, the water level is low, the annual variation range is 1.0-1.5 m, and the stable water level of groundwater is buried at a depth of 1.70-2.20 m. The average annual temperature is 4.2 degrees C, the annual sunshine hours are 2726 hours, the average frost-free period is 166 days, the average summer temperature is 23.2 degrees C, and the daily temperature difference during crop growth and development is 10 degrees C above. The test field is sandy soil, with a natural moisture content ofw, a density of 24.6%, a dense water holding rate of 1.55 kg/m3, and a water holding rate of 30.6%. Monitoring instruments are selected in the test area for farmland plots with an area of 9m×9m=81m2, and the location of the test site and the distribution of the instruments are shown in Figures 3 and 4.Figure 3
Intertree test site.Figure 4
Monitoring instrument layout.


### 3.2.2. The Experimental Data Are Divided into Time Periods

The monitoring instruments were laid out on May 20 and tested on May 21. On May 27, corn begins to germinate, fields begin to weed on June 6, and clothes get dressed on July 6. Corn is harvested on October 8, and the trial lasts 142 days. In this field, precipitation is the main source of irrigation. Corn shows that the physical characteristics of different growth stages are different, which has a greater impact on soil evaporation. Therefore, the full reproductive period is divided into seedling period, extraction period, extraction period, grout period, and maturity period as shown in Table1.Table 1
Maize growth period.
Grow periodSeedlingJointingTasselingFillingMatureDate5.27-6.256.26-7.207.21-7.318.1-9.49.5-10.8Duration (day)3025113535


### 3.2.3. Experimental Design

Corn grown in the test area is in uniform ridge form, with a width of 650 mm, a plant distance of 250 mm(23), and a planting density of 3300 plants/mu (666.7 m2 per acre). The test area is 9m×9m×81m2 and contains 9 3m×3m×9m2 zones. Place a microsteamer (microlysimeters, ML) in the center of each region, using the average of the evaporation measured values of the nine microsteamer meters as the test result. The observation scheme is to weigh 1 micro vaporizer mass (M1) at 8 : 20 daily and 8 : 20 the next day 1 time, and mass M2,M1−M2 is ML. The mass of evaporation of moisture in the internal soil is calculated with the base area of the microsteaming meter to obtain the evaporation amount (mm/d) of the day. The soil exchange cycle set by this test is 3 d, and if there is rain in the test, the soil exchange treatment is carried out immediately after the rainfall to ensure the accuracy of the test.


## 3.2.1. The Condition of the Test Site

The test was carried out in the green wind garden corn planting test area of Daqing City, Heilongjiang Province (125.2 degrees east longitude and 46.6 degrees north latitude). Daqing City belongs to the northern temperate continental monsoon climate zone, with annual precipitation of 427.5mm and annual evaporation of 1635 mm. The main sources of groundwater recharge in this area are atmospheric precipitation, which is excreted by evaporation and underground runoff, and the water level is affected by certain atmospheric precipitation and evaporation. The dynamic change law of groundwater is July-September, the water level is high, the dry period is in March-May, the water level is low, the annual variation range is 1.0-1.5 m, and the stable water level of groundwater is buried at a depth of 1.70-2.20 m. The average annual temperature is 4.2 degrees C, the annual sunshine hours are 2726 hours, the average frost-free period is 166 days, the average summer temperature is 23.2 degrees C, and the daily temperature difference during crop growth and development is 10 degrees C above. The test field is sandy soil, with a natural moisture content ofw, a density of 24.6%, a dense water holding rate of 1.55 kg/m3, and a water holding rate of 30.6%. Monitoring instruments are selected in the test area for farmland plots with an area of 9m×9m=81m2, and the location of the test site and the distribution of the instruments are shown in Figures 3 and 4.Figure 3
Intertree test site.Figure 4
Monitoring instrument layout.


## 3.2.2. The Experimental Data Are Divided into Time Periods

The monitoring instruments were laid out on May 20 and tested on May 21. On May 27, corn begins to germinate, fields begin to weed on June 6, and clothes get dressed on July 6. Corn is harvested on October 8, and the trial lasts 142 days. In this field, precipitation is the main source of irrigation. Corn shows that the physical characteristics of different growth stages are different, which has a greater impact on soil evaporation. Therefore, the full reproductive period is divided into seedling period, extraction period, extraction period, grout period, and maturity period as shown in Table1.Table 1
Maize growth period.
Grow periodSeedlingJointingTasselingFillingMatureDate5.27-6.256.26-7.207.21-7.318.1-9.49.5-10.8Duration (day)3025113535


## 3.2.3. Experimental Design

Corn grown in the test area is in uniform ridge form, with a width of 650 mm, a plant distance of 250 mm(23), and a planting density of 3300 plants/mu (666.7 m2 per acre). The test area is 9m×9m×81m2 and contains 9 3m×3m×9m2 zones. Place a microsteamer (microlysimeters, ML) in the center of each region, using the average of the evaporation measured values of the nine microsteamer meters as the test result. The observation scheme is to weigh 1 micro vaporizer mass (M1) at 8 : 20 daily and 8 : 20 the next day 1 time, and mass M2,M1−M2 is ML. The mass of evaporation of moisture in the internal soil is calculated with the base area of the microsteaming meter to obtain the evaporation amount (mm/d) of the day. The soil exchange cycle set by this test is 3 d, and if there is rain in the test, the soil exchange treatment is carried out immediately after the rainfall to ensure the accuracy of the test.


## 3.3. Experimental Parameters Are Determined

### 3.3.1. Test Methods for Meteorological Indexes

The meteorological parameters required for the test are temperature, relative humidity, wind speed, and rainfall at 2 m, and the HBO-type weather inspector is used to observe bare soil and instrument meteorological indicators: including the highest minimum temperature at 2 m (with an accuracy of 0.01 degrees C) and wind speed (with accuracy). 0.01 m/s), relative humidity (0.1% accuracy), sunshine hours (0.1 h accuracy), rainfall (0.1 mm accuracy), etc., are for calculating the parameters of the model. Meteorological indicator observations are monitored continuously 24 hours a day, and data is recorded every 15 minutes. Parameters for model calculations are averaged throughout the day without special instructions. The small weather station is located in an open area near the test area. The observatory is 450 m from the test site.


### 3.3.2. Test Methods for Evaporation

Prior to the test, the microsteamer is first carried out to collect soil, and the miniature steamer is gently smashed into the soil with a hammer, and to the top and the ground is flush. Dig out the surrounding soil and remove the miniature steamer filled with the original soil column. Remove excess soil from the bottom and seal the bottom with plastic film. After weighing, the miniature steamer is embedded in the outer barrel and the entire device is buried in a preset location, with the top leveling the ground.


### 3.3.3. Test Methods for Soil Water Content

The MiniTRASE high-precision soil moisture monitoring system was used to test the water content at the height of 75 mm below ground, which is the center of ML. In order to avoid disturbing farm machine’s work, the soil moisture monitoring system was placed 10 m away from the farmland. The data of soil water content were recorded at 8 : 20 in the morning every day.The observed range is 20 mm, 75 mm, and 150 mm soil in the test area as shown in Figure5. The micro vaporometer used for the test observation is 150 mm high and has a back cover, setting the range to when observing soil moisture content between trees 20 mm, 75 mm, and 150 mm. Each layer of soil is arranged with a probe. Observation method: after observing the evaporation between trees every day, the soil moisture content was observed, and the water content of the soil layer was taken from 20 mm, 75 mm, and 150 mm. The average is the amount of water in the soil for the day.Figure 5
0 mm-150 mm probe layout diagram.


## 3.3.1. Test Methods for Meteorological Indexes

The meteorological parameters required for the test are temperature, relative humidity, wind speed, and rainfall at 2 m, and the HBO-type weather inspector is used to observe bare soil and instrument meteorological indicators: including the highest minimum temperature at 2 m (with an accuracy of 0.01 degrees C) and wind speed (with accuracy). 0.01 m/s), relative humidity (0.1% accuracy), sunshine hours (0.1 h accuracy), rainfall (0.1 mm accuracy), etc., are for calculating the parameters of the model. Meteorological indicator observations are monitored continuously 24 hours a day, and data is recorded every 15 minutes. Parameters for model calculations are averaged throughout the day without special instructions. The small weather station is located in an open area near the test area. The observatory is 450 m from the test site.


## 3.3.2. Test Methods for Evaporation

Prior to the test, the microsteamer is first carried out to collect soil, and the miniature steamer is gently smashed into the soil with a hammer, and to the top and the ground is flush. Dig out the surrounding soil and remove the miniature steamer filled with the original soil column. Remove excess soil from the bottom and seal the bottom with plastic film. After weighing, the miniature steamer is embedded in the outer barrel and the entire device is buried in a preset location, with the top leveling the ground.


## 3.3.3. Test Methods for Soil Water Content

The MiniTRASE high-precision soil moisture monitoring system was used to test the water content at the height of 75 mm below ground, which is the center of ML. In order to avoid disturbing farm machine’s work, the soil moisture monitoring system was placed 10 m away from the farmland. The data of soil water content were recorded at 8 : 20 in the morning every day.The observed range is 20 mm, 75 mm, and 150 mm soil in the test area as shown in Figure5. The micro vaporometer used for the test observation is 150 mm high and has a back cover, setting the range to when observing soil moisture content between trees 20 mm, 75 mm, and 150 mm. Each layer of soil is arranged with a probe. Observation method: after observing the evaporation between trees every day, the soil moisture content was observed, and the water content of the soil layer was taken from 20 mm, 75 mm, and 150 mm. The average is the amount of water in the soil for the day.Figure 5
0 mm-150 mm probe layout diagram.


## 4. Test Result Analysis

### 4.1. The Results of Particle-Level Matching of the Physical Properties of the Field Soil Sample

In accordance with the Geotechnical Testing Procedure (SL237-1999), geotechnical testing was carried out, and the physical properties and grades of farmland soil on site are shown in Tables2 and 3.Table 2
Test soil physical properties and physical index.
Physical properties indexPhysical state metricsNatural density/(g/cm3)Water content/(%)Field water holding rate/(%)Wilting point/(%)Plasticity indexLiquidity index1.5524.6%30.6%12.2%7.851.26Table 3
Physical and mechanical properties test soil samples.
2~100.05~20.005~0.05<0.005d10d30d60CuCc060.320.519.20.0030.0170.078261.23Table3 shows that the local soil sample is sandy.


### 4.2. Analysis of the Law of the Measured Values of Soil Moisture Content and Evaporation between Trees

The evaporation between trees is influenced by many factors, and the soil moisture content (0-150 mm soil layer) is an important test parameter, and it is also the main factor affecting the evaporation process. The microsteaming meter used in the intertree evaporation test was 150 mm high, and the soil moisture content was observed by 20 mm, 75 mm, and 150 mm soil layers. Volume object: take 20 mm, 75 mm, and 150 mm three-soil layer water content average for the soil moisture content of the day volume. In order to better explain the relationship between soil moisture content and the evaporation of trees, the relationship between the water content of soil week by week and the evaporation between trees is established, as shown in Figure6.Figure 6
A week-by-week change in soil moisture content.As shown in Figure6, the soil moisture content (20-150 mm soil layer) during the test period is synchronized with the general change trend of the measured values, i.e., the measured values increase with the increase of soil moisture content and decrease with the decrease of soil moisture content. The maximum soil moisture content during the test period was 24.99%, and the measured value between trees was 3.06 mm·d-1 (07-14), the minimum soil moisture content is 14.84%, and the measured value between trees is 1.21 mm·d-1 (08-25). The weekly moisture content fits with the weekly measured values as shown in Figure 7.Figure 7
The weekly moisture content and the weekly measured values are fitted in figure.As can be seen from Figure7, the regression coefficient R2≈0.79 is a secondary function relationship, which is y=0.0516x2−1.8728x+17.679. At the soil moisture content rate of 14.84% to 18.34%, the soil moisture content increased and the measured value decreased, and the soil moisture content decreased at 18. At 34%-24.99%, the soil moisture content increased.


### 4.3. Analysis of Rainfall and Evaporation Test Results

The evaporation test experiment between corn trees totaled 142 d, with 44 days of rainfall and a total rainfall of 333.99 mm. The measured values of daily rainfall and daily evaporation between trees are distributed as shown in Figure8.Figure 8
Distribution of measured daily rainfall value and measured daily evaporation value.As shown in Figure8, the rainfall during the maize fertility period is unevenly distributed, with low frequency and dispersion of rainfall in the early period (May-June) and an average evaporation of 1.91 mm·d-1. Rainfall is frequent in the medium term (July-August) with an average evaporation of 2.82 mm·d-1. Late (September-October) rainfall is concentrated in September, with an average evaporation of 0.91 mm·d-1.To eliminate the effect of the irregularity of rainfall on experimental analysis, it is proposed to analyze the relationship between the two on a monthly basis, as shown in Figure9(a).Figure 9
Relationship between monthly measured value and rainfall.
(a)
Change relationship(b)
The fit relationshipAs shown in Figure9(a), the relationship between the average monthly rainfall and the change in the average monthly evaporation was obvious after monthly analysis. The law of monthly rainfall and monthly evaporation change: evaporation increases with rainfall and decreases with rainfall. The average rainfall and evaporation in June is higher than in May, and the monthly average rainfall and evaporation reaches the maximum in July, followed by the average in August-October rainfall and evaporation decreased in turn.As shown by Figure9(b), the linear fit between the average monthly rainfall and the average monthly evaporation is good, and the relationship is as follows: y=4.2051x−1.3814, R2=0.92. By analyzing the fit month by month, the two have a good quantitative relationship, which can provide a data base for the prediction and forecast of evaporation if the annual rainfall difference is not large.


## 4.1. The Results of Particle-Level Matching of the Physical Properties of the Field Soil Sample

In accordance with the Geotechnical Testing Procedure (SL237-1999), geotechnical testing was carried out, and the physical properties and grades of farmland soil on site are shown in Tables2 and 3.Table 2
Test soil physical properties and physical index.
Physical properties indexPhysical state metricsNatural density/(g/cm3)Water content/(%)Field water holding rate/(%)Wilting point/(%)Plasticity indexLiquidity index1.5524.6%30.6%12.2%7.851.26Table 3
Physical and mechanical properties test soil samples.
2~100.05~20.005~0.05<0.005d10d30d60CuCc060.320.519.20.0030.0170.078261.23Table3 shows that the local soil sample is sandy.


## 4.2. Analysis of the Law of the Measured Values of Soil Moisture Content and Evaporation between Trees

The evaporation between trees is influenced by many factors, and the soil moisture content (0-150 mm soil layer) is an important test parameter, and it is also the main factor affecting the evaporation process. The microsteaming meter used in the intertree evaporation test was 150 mm high, and the soil moisture content was observed by 20 mm, 75 mm, and 150 mm soil layers. Volume object: take 20 mm, 75 mm, and 150 mm three-soil layer water content average for the soil moisture content of the day volume. In order to better explain the relationship between soil moisture content and the evaporation of trees, the relationship between the water content of soil week by week and the evaporation between trees is established, as shown in Figure6.Figure 6
A week-by-week change in soil moisture content.As shown in Figure6, the soil moisture content (20-150 mm soil layer) during the test period is synchronized with the general change trend of the measured values, i.e., the measured values increase with the increase of soil moisture content and decrease with the decrease of soil moisture content. The maximum soil moisture content during the test period was 24.99%, and the measured value between trees was 3.06 mm·d-1 (07-14), the minimum soil moisture content is 14.84%, and the measured value between trees is 1.21 mm·d-1 (08-25). The weekly moisture content fits with the weekly measured values as shown in Figure 7.Figure 7
The weekly moisture content and the weekly measured values are fitted in figure.As can be seen from Figure7, the regression coefficient R2≈0.79 is a secondary function relationship, which is y=0.0516x2−1.8728x+17.679. At the soil moisture content rate of 14.84% to 18.34%, the soil moisture content increased and the measured value decreased, and the soil moisture content decreased at 18. At 34%-24.99%, the soil moisture content increased.


## 4.3. Analysis of Rainfall and Evaporation Test Results

The evaporation test experiment between corn trees totaled 142 d, with 44 days of rainfall and a total rainfall of 333.99 mm. The measured values of daily rainfall and daily evaporation between trees are distributed as shown in Figure8.Figure 8
Distribution of measured daily rainfall value and measured daily evaporation value.As shown in Figure8, the rainfall during the maize fertility period is unevenly distributed, with low frequency and dispersion of rainfall in the early period (May-June) and an average evaporation of 1.91 mm·d-1. Rainfall is frequent in the medium term (July-August) with an average evaporation of 2.82 mm·d-1. Late (September-October) rainfall is concentrated in September, with an average evaporation of 0.91 mm·d-1.To eliminate the effect of the irregularity of rainfall on experimental analysis, it is proposed to analyze the relationship between the two on a monthly basis, as shown in Figure9(a).Figure 9
Relationship between monthly measured value and rainfall.
(a)
Change relationship(b)
The fit relationshipAs shown in Figure9(a), the relationship between the average monthly rainfall and the change in the average monthly evaporation was obvious after monthly analysis. The law of monthly rainfall and monthly evaporation change: evaporation increases with rainfall and decreases with rainfall. The average rainfall and evaporation in June is higher than in May, and the monthly average rainfall and evaporation reaches the maximum in July, followed by the average in August-October rainfall and evaporation decreased in turn.As shown by Figure9(b), the linear fit between the average monthly rainfall and the average monthly evaporation is good, and the relationship is as follows: y=4.2051x−1.3814, R2=0.92. By analyzing the fit month by month, the two have a good quantitative relationship, which can provide a data base for the prediction and forecast of evaporation if the annual rainfall difference is not large.


## 5. Ritchie Model Correction and Validation

In the process of soil evaporation, it is obvious that it is influenced by regional climate and its own soil quality. In order to measure the evaporation between the salt-alkali soil corn trees in Daqing area, we first need to analyze the applicability of the Ritchie model, analyze the fit degree of the field measured value and the theoretical calculation value when the model is verified, and verify the applicability, and if the model is not well fitted, we need to simulate the evaporation test between the corn trees in Daqing salt-alkali soil area according to the measured value, in order to verify the generality of the Ritchie model.


### 5.1. Analysis of the Applicability of Bare Soil of Ritchie Model under Saline Soil Conditions

The applicability of the Ritchie model in Daqing saline soil area is analyzed by fitting the evaporative measured value (Et) with the Ritchie model calculation value (Ec). According to Ritchie model theory, the value of the evaporation limit value of U in the first stage is 12 mm, 9 mm, and 6 mm according to clay, soil, and sand. According to the soil particle grade distribution of Table 3 of the soil sample test value and Table 3 of this test site, the soil in this region can be withdrawn from the soil as partial sandy soil, and according to the relevant theory obtained by the Ritchie model, the evaporation limit value of the first stage in this region can be obtained with a value of 8 mm. The second stage hydraulic characteristic coefficient α is valued at 4.62 mm/d0.5 [9].The intercorn evaporation experiment was conducted from May 20th to October 08th in the corn-growing area of Daqing High-tech District. The corn in the test area was sown on 19 May and matured to harvest on 08 October, with a total of 142 d. Fit and regression ofEt and Ec were analyzed over different lives and ages. Analysis of the fit of different lifetimes based on empirical factors is shown in Figure 10:Figure 10
Curve fitting of calculated and test evaporation for maize growth period.As shown in Figure10, the fitting equation between the calculated and measured values of different corn life and long-term is as follows:
(6)y=0.5975x+0.708,R2=0.12seedling,y=0.3836x+1.6182,R2=0.47jointing,y=1.4569x−0.979,R2=0.37tasseling,y=0.475x+0.0.4907,R2=0.35filling,y=0.3429x+0.5286,R2=0.76mature.From this equation, it can be seen that the uncorrected Ritchie model is not suitable for predicting evaporation between saline soil trees in Daqing area, so in order to obtain the Ritchie model suitable for evaporation between saline soil corn trees in Daqing area, we need to revise the parameters.


### 5.2. Correction Analysis ofU Values in the Ritchie Model under section Conditions

#### 5.2.1.U Value Correction Analysis

The soil at this test site is sandy soil, and the first stage evaporation limit value set at the time of calculation isU to 8 mm. As can be seen from the Ritchie model calculation formula (1), the different values of U affect the division of the evaporation phase of the model, thus affecting the calculation results. The Ritchie model is therefore calculated with different U values. You are drawn to 9 mm, keep the α value unchanged, and get the Ritchie model calculated value (Ec′). The values of the Et test points are fitted to the following figure:
(7)y=0.93619x−0.04383,R2=0.85seedling,y=1.0812x−0.58297,R2=0.84jointing,y=1.21633x−1.22916,R2=0.89tasseling,y=0.81047x+0.43869,R2=0.91filling,y=1.05296+0.01451,R2=0.96mature.As can be seen from Figure11, the correction accuracy of U has improved, but the forecast values are not accurate enough in the seedling period, so the α values need to be corrected. The calculated value of the evaporation of the Ritchie model obtained by U is 9 mm, and the fitted regression coefficient of the measured value is different according to the different term and long-term fit values, and the overall fit effect is not ideal, so other methods need to be considered to correct the α value of the model.Figure 11
Curve fitting of the calculated evaporation and the tested evaporation during maize growth period whenU value was modified.


#### 5.2.2. Correction Analysis ofα Values in the Ritchie Model

The accuracy of Ritchie model calculation is mainly related to theU value of the evaporation limit value of the first stage and the α value of the second stage. The previous section corrected the U value to evaluate the calculation accuracy of the Ritchie model, and the effect was not satisfactory. This chapter is intended to correct the values of the second phase α, and the model is modified to compare with the precorrection simulation. The correction data are taken from a complete rainfall evaporation process in August, 18-19, and a complete rainfall evaporation process in September, i.e., 1-7. The rest of the data is left to validation of the remediation results.Here is how to fix it.The previous calculation of the value of bare soil evaporation based on the Ritchie model was based on theα value used, taken from the literature, which provides a value of 4.62 mm/d for the α value. However, its test area is the Inner Mongolia Hetao area (belonging to the Loess Plateau), the soil is loess, and in this paper, Daqing salt-alkali soil area, sandy soil quality is different. The size of the Ritchie model’s second-stage α value is related to the soil’s own water holding capacity, and different soil conditions in the region affect the α value. Therefore, this chapter intends to use the naked soil test data of Daqing salt-alkali soil area to correct the α value and get the α value suitable for Daqing area.The Ritchie model is modified by the data of this experiment to obtain the parameters suitable for the region. Because of differences between tree evaporation and bare soil evaporation, such as crop stems, leaves will reduce sunlight on the surface, rainfall will not directly into the soil, etc., these factors will affect the model calculation evaporation results (Et′). In order to further verify the rationality of the correction method, it is proposed to simulate the evaporation between the seedlings and the calculated value of the modified Ritchie model.The soil type of the test site is sandy soil, and the evaporation limit value of the first stage is set at 8 mmU. In the seedling phase, the second stage of evaporation occurs on May 27th-May 31st, June 05th-June 08, and June 14-June 18; take advantage of 05 first evaporation on the day of June 27, June 5, and June 14 α model; the value is corrected, and the α value is validated using subsequent experimental data. α value correction values and related coefficients are shown in Table 4.Table 4
Value ofα value and correlation coefficient in seeding stage.
NumberHydraulic property coefficient/αCorrelation coefficient (linear)12.140.83222.880.83533.160.84943.570.86553.720.91863.890.84374.100.837As shown in Table4, the α values are regression analyzed, and the fitting of the calculated values to the measured values is optimal when α is 3.72 mm/d0.5. The accuracy of the model is verified by the measured data, and the fit of the two is analyzed. Et′ and Et for the seedling period, error rate, and rainfall are shown in Table 5.Table 5
Et′ and Et, error rate, and rainfall in seedling stage.
NameTotal evaporation of seedling period/(mm)Daily average evaporation of seedling period/(mm/d)Model error rate/(%)Root-mean-square errorTotal seedling rainfall/(mm)Et55.041.533.92%1.0043.59The other issues have also been amended.


### 5.3. Ritchie Model Correction Result Analysis

#### 5.3.1. Corn Full Fertility Cycleα Value

The parameters of the Ritchie model calculated from the above methodα conform to the above method, as shown in Table 6.Table 6
The full fertility cycle of cornα value.
SeedlingJointingTasselingFillingMatureα (mm·d-0.5)3.724.552.681.50.6


#### 5.3.2. The Calculation of Evaporation in Corn Fields during Corn Growth

Corn germinates on May 27, and on June 25, 50% of the plant’s first root is 2 cm above the ground. Nitrogen fertilizer is applied to the fields where corn grows fastest on July 6. Stem nodes increase during this period, which promotes the enlargement of the upper lobe and acetylation photosynthesis. At the same time, the increase of precipitation has an impact on corn growth, soil evaporation, model modification, and simulation.The precipitation during the grouting period was 68.8 mm, which was less than the extraction period and higher than that of the seedling period. During dry periods, Daqing’s weather is warmer in summer, but the average daily evaporation during that period is lower than in the following period. Corn leaves get bigger and wider, blocking sunlight from the surface of the soil. At the same time, precipitation has become frequent. In this case, the evaporation becomes weak. The field during the distribution test of calculated corn evaporation and experimental evaporation.The precipitation during the grouting period is 38.8 mm, which is lower than the grouting, extraction, and seeding periods. During this period, the soil was full of water. Higher temperatures ofα are the first three periods. The roots of the corn are yellowed, the leaves at the bottom begin to wither, and the flowers become thinner.In the mature period, it is in early autumn, so the temperature, sunshine conditions, and other conditions are worse than the festival period, pulping period, and filling period. The fruit of corn has matured. Leaves, stems, and roots wither yellow. The daily evaporation decreases gradually, as does the soil moisture content and precipitation.The calculated distribution of corn growth evaporation and experimental evaporation is shown in Figure12.Figure 12
Distribution of the calculated evaporation and the tested evaporation in maize growth period.As can be seen from Figure12, the calculated evaporation of corn fields is basically the same as the experimental evaporation of seedlings, and in most cases, the calculated value is higher than the measured value. At the beginning of the experiment, the surface of the test site can be regarded as a bare soil site, and the measured data evaporation law is the same as the evaporation law of bare soil. The calculated evaporation of the extraction period is slightly less than the test value of the extraction period. It can be seen that the matching degree of the curve is better than that of the seedling period and the extraction period. It can be seen that the calculated evaporation is slightly larger than the effective value tested. Grout from August 1 to September 4, with large temperature changes in the morning and night, and the calculated evaporation is much greater than the test value. The fitted curve is the same as the engagement curve, which is worse than the pumping period curve. During the maturity period, it can be seen that the calculated evaporation is slightly lower than the test value in early September and slightly higher than the test value in mid-September.The evaporation calculation and evaporation test values for each of the corns mentioned above are linearly fitted, as shown in Figure13.Figure 13
Curve fitting of the calculated evaporation and the tested evaporation during maize growth period whenα value was modified.As can be seen from Figure13, the relationship between calculated evaporation and experimental evaporation is linear:
(8)y=0.7758x+0.5057,R2=0.91seedling,y=0.893x+0.2121,R2=0.93jointing,y=1.0549x−0.0051,R2=0.94tasseling,y=0.983x−0.2492,R2=0.93filling,y=1.0142x−0.0168,R2=0.96mature.TheP<0.01can be calculated from the variance analysis, indicating a significant difference in variance. Compared with other corn growths, the ripening curve matches best.The soil moisture content, soil precipitation, and evaporation of the whole corn in Daqing saline soil test area were observed. The relationship between corn precipitation and soil evaporation is established, and the relationship between soil moisture content and corn soil evaporation is established. Suitable parameter values: the seeding period of the Ritchie model of saline soilα is 3.72 mm·d-0.5, the extraction period is 4.55 mm·d-0.5, and the extraction period is 2.68 mm·d-0.5. The grouting period is 1.50 mm·d-0.5. Maturity is 0.60 mm·d-0.5.


#### 5.3.3. A Comparative Analysis before and after Model Correction

As can be seen from Table7, the degree of fit between the evaporation calculated by the modified Ritchie model and the evaporation of corn is 0.91-0.96, and the model error is significantly reduced, indicating that the modified Ritchie model can accurately simulate the evaporation of saline soil.Table 7
Contrast before and after correction of Ritchie model.
Nameα value/(mm·d-0.5)U valueModel error rate/(%)Regression coefficient/R2Seedling stage3.7283.920.91Shooting period4.554.000.93Tasseling stage2.680.600.94Postulation period1.500.600.93Maturation period0.600.690.96


## 5.1. Analysis of the Applicability of Bare Soil of Ritchie Model under Saline Soil Conditions

The applicability of the Ritchie model in Daqing saline soil area is analyzed by fitting the evaporative measured value (Et) with the Ritchie model calculation value (Ec). According to Ritchie model theory, the value of the evaporation limit value of U in the first stage is 12 mm, 9 mm, and 6 mm according to clay, soil, and sand. According to the soil particle grade distribution of Table 3 of the soil sample test value and Table 3 of this test site, the soil in this region can be withdrawn from the soil as partial sandy soil, and according to the relevant theory obtained by the Ritchie model, the evaporation limit value of the first stage in this region can be obtained with a value of 8 mm. The second stage hydraulic characteristic coefficient α is valued at 4.62 mm/d0.5 [9].The intercorn evaporation experiment was conducted from May 20th to October 08th in the corn-growing area of Daqing High-tech District. The corn in the test area was sown on 19 May and matured to harvest on 08 October, with a total of 142 d. Fit and regression ofEt and Ec were analyzed over different lives and ages. Analysis of the fit of different lifetimes based on empirical factors is shown in Figure 10:Figure 10
Curve fitting of calculated and test evaporation for maize growth period.As shown in Figure10, the fitting equation between the calculated and measured values of different corn life and long-term is as follows:
(6)y=0.5975x+0.708,R2=0.12seedling,y=0.3836x+1.6182,R2=0.47jointing,y=1.4569x−0.979,R2=0.37tasseling,y=0.475x+0.0.4907,R2=0.35filling,y=0.3429x+0.5286,R2=0.76mature.From this equation, it can be seen that the uncorrected Ritchie model is not suitable for predicting evaporation between saline soil trees in Daqing area, so in order to obtain the Ritchie model suitable for evaporation between saline soil corn trees in Daqing area, we need to revise the parameters.


## 5.2. Correction Analysis ofU Values in the Ritchie Model under section Conditions

### 5.2.1.U Value Correction Analysis

The soil at this test site is sandy soil, and the first stage evaporation limit value set at the time of calculation isU to 8 mm. As can be seen from the Ritchie model calculation formula (1), the different values of U affect the division of the evaporation phase of the model, thus affecting the calculation results. The Ritchie model is therefore calculated with different U values. You are drawn to 9 mm, keep the α value unchanged, and get the Ritchie model calculated value (Ec′). The values of the Et test points are fitted to the following figure:
(7)y=0.93619x−0.04383,R2=0.85seedling,y=1.0812x−0.58297,R2=0.84jointing,y=1.21633x−1.22916,R2=0.89tasseling,y=0.81047x+0.43869,R2=0.91filling,y=1.05296+0.01451,R2=0.96mature.As can be seen from Figure11, the correction accuracy of U has improved, but the forecast values are not accurate enough in the seedling period, so the α values need to be corrected. The calculated value of the evaporation of the Ritchie model obtained by U is 9 mm, and the fitted regression coefficient of the measured value is different according to the different term and long-term fit values, and the overall fit effect is not ideal, so other methods need to be considered to correct the α value of the model.Figure 11
Curve fitting of the calculated evaporation and the tested evaporation during maize growth period whenU value was modified.


### 5.2.2. Correction Analysis ofα Values in the Ritchie Model

The accuracy of Ritchie model calculation is mainly related to theU value of the evaporation limit value of the first stage and the α value of the second stage. The previous section corrected the U value to evaluate the calculation accuracy of the Ritchie model, and the effect was not satisfactory. This chapter is intended to correct the values of the second phase α, and the model is modified to compare with the precorrection simulation. The correction data are taken from a complete rainfall evaporation process in August, 18-19, and a complete rainfall evaporation process in September, i.e., 1-7. The rest of the data is left to validation of the remediation results.Here is how to fix it.The previous calculation of the value of bare soil evaporation based on the Ritchie model was based on theα value used, taken from the literature, which provides a value of 4.62 mm/d for the α value. However, its test area is the Inner Mongolia Hetao area (belonging to the Loess Plateau), the soil is loess, and in this paper, Daqing salt-alkali soil area, sandy soil quality is different. The size of the Ritchie model’s second-stage α value is related to the soil’s own water holding capacity, and different soil conditions in the region affect the α value. Therefore, this chapter intends to use the naked soil test data of Daqing salt-alkali soil area to correct the α value and get the α value suitable for Daqing area.The Ritchie model is modified by the data of this experiment to obtain the parameters suitable for the region. Because of differences between tree evaporation and bare soil evaporation, such as crop stems, leaves will reduce sunlight on the surface, rainfall will not directly into the soil, etc., these factors will affect the model calculation evaporation results (Et′). In order to further verify the rationality of the correction method, it is proposed to simulate the evaporation between the seedlings and the calculated value of the modified Ritchie model.The soil type of the test site is sandy soil, and the evaporation limit value of the first stage is set at 8 mmU. In the seedling phase, the second stage of evaporation occurs on May 27th-May 31st, June 05th-June 08, and June 14-June 18; take advantage of 05 first evaporation on the day of June 27, June 5, and June 14 α model; the value is corrected, and the α value is validated using subsequent experimental data. α value correction values and related coefficients are shown in Table 4.Table 4
Value ofα value and correlation coefficient in seeding stage.
NumberHydraulic property coefficient/αCorrelation coefficient (linear)12.140.83222.880.83533.160.84943.570.86553.720.91863.890.84374.100.837As shown in Table4, the α values are regression analyzed, and the fitting of the calculated values to the measured values is optimal when α is 3.72 mm/d0.5. The accuracy of the model is verified by the measured data, and the fit of the two is analyzed. Et′ and Et for the seedling period, error rate, and rainfall are shown in Table 5.Table 5
Et′ and Et, error rate, and rainfall in seedling stage.
NameTotal evaporation of seedling period/(mm)Daily average evaporation of seedling period/(mm/d)Model error rate/(%)Root-mean-square errorTotal seedling rainfall/(mm)Et55.041.533.92%1.0043.59The other issues have also been amended.


## 5.2.1.U Value Correction Analysis

The soil at this test site is sandy soil, and the first stage evaporation limit value set at the time of calculation isU to 8 mm. As can be seen from the Ritchie model calculation formula (1), the different values of U affect the division of the evaporation phase of the model, thus affecting the calculation results. The Ritchie model is therefore calculated with different U values. You are drawn to 9 mm, keep the α value unchanged, and get the Ritchie model calculated value (Ec′). The values of the Et test points are fitted to the following figure:
(7)y=0.93619x−0.04383,R2=0.85seedling,y=1.0812x−0.58297,R2=0.84jointing,y=1.21633x−1.22916,R2=0.89tasseling,y=0.81047x+0.43869,R2=0.91filling,y=1.05296+0.01451,R2=0.96mature.As can be seen from Figure11, the correction accuracy of U has improved, but the forecast values are not accurate enough in the seedling period, so the α values need to be corrected. The calculated value of the evaporation of the Ritchie model obtained by U is 9 mm, and the fitted regression coefficient of the measured value is different according to the different term and long-term fit values, and the overall fit effect is not ideal, so other methods need to be considered to correct the α value of the model.Figure 11
Curve fitting of the calculated evaporation and the tested evaporation during maize growth period whenU value was modified.


## 5.2.2. Correction Analysis ofα Values in the Ritchie Model

The accuracy of Ritchie model calculation is mainly related to theU value of the evaporation limit value of the first stage and the α value of the second stage. The previous section corrected the U value to evaluate the calculation accuracy of the Ritchie model, and the effect was not satisfactory. This chapter is intended to correct the values of the second phase α, and the model is modified to compare with the precorrection simulation. The correction data are taken from a complete rainfall evaporation process in August, 18-19, and a complete rainfall evaporation process in September, i.e., 1-7. The rest of the data is left to validation of the remediation results.Here is how to fix it.The previous calculation of the value of bare soil evaporation based on the Ritchie model was based on theα value used, taken from the literature, which provides a value of 4.62 mm/d for the α value. However, its test area is the Inner Mongolia Hetao area (belonging to the Loess Plateau), the soil is loess, and in this paper, Daqing salt-alkali soil area, sandy soil quality is different. The size of the Ritchie model’s second-stage α value is related to the soil’s own water holding capacity, and different soil conditions in the region affect the α value. Therefore, this chapter intends to use the naked soil test data of Daqing salt-alkali soil area to correct the α value and get the α value suitable for Daqing area.The Ritchie model is modified by the data of this experiment to obtain the parameters suitable for the region. Because of differences between tree evaporation and bare soil evaporation, such as crop stems, leaves will reduce sunlight on the surface, rainfall will not directly into the soil, etc., these factors will affect the model calculation evaporation results (Et′). In order to further verify the rationality of the correction method, it is proposed to simulate the evaporation between the seedlings and the calculated value of the modified Ritchie model.The soil type of the test site is sandy soil, and the evaporation limit value of the first stage is set at 8 mmU. In the seedling phase, the second stage of evaporation occurs on May 27th-May 31st, June 05th-June 08, and June 14-June 18; take advantage of 05 first evaporation on the day of June 27, June 5, and June 14 α model; the value is corrected, and the α value is validated using subsequent experimental data. α value correction values and related coefficients are shown in Table 4.Table 4
Value ofα value and correlation coefficient in seeding stage.
NumberHydraulic property coefficient/αCorrelation coefficient (linear)12.140.83222.880.83533.160.84943.570.86553.720.91863.890.84374.100.837As shown in Table4, the α values are regression analyzed, and the fitting of the calculated values to the measured values is optimal when α is 3.72 mm/d0.5. The accuracy of the model is verified by the measured data, and the fit of the two is analyzed. Et′ and Et for the seedling period, error rate, and rainfall are shown in Table 5.Table 5
Et′ and Et, error rate, and rainfall in seedling stage.
NameTotal evaporation of seedling period/(mm)Daily average evaporation of seedling period/(mm/d)Model error rate/(%)Root-mean-square errorTotal seedling rainfall/(mm)Et55.041.533.92%1.0043.59The other issues have also been amended.


## 5.3. Ritchie Model Correction Result Analysis

### 5.3.1. Corn Full Fertility Cycleα Value

The parameters of the Ritchie model calculated from the above methodα conform to the above method, as shown in Table 6.Table 6
The full fertility cycle of cornα value.
SeedlingJointingTasselingFillingMatureα (mm·d-0.5)3.724.552.681.50.6


### 5.3.2. The Calculation of Evaporation in Corn Fields during Corn Growth

Corn germinates on May 27, and on June 25, 50% of the plant’s first root is 2 cm above the ground. Nitrogen fertilizer is applied to the fields where corn grows fastest on July 6. Stem nodes increase during this period, which promotes the enlargement of the upper lobe and acetylation photosynthesis. At the same time, the increase of precipitation has an impact on corn growth, soil evaporation, model modification, and simulation.The precipitation during the grouting period was 68.8 mm, which was less than the extraction period and higher than that of the seedling period. During dry periods, Daqing’s weather is warmer in summer, but the average daily evaporation during that period is lower than in the following period. Corn leaves get bigger and wider, blocking sunlight from the surface of the soil. At the same time, precipitation has become frequent. In this case, the evaporation becomes weak. The field during the distribution test of calculated corn evaporation and experimental evaporation.The precipitation during the grouting period is 38.8 mm, which is lower than the grouting, extraction, and seeding periods. During this period, the soil was full of water. Higher temperatures ofα are the first three periods. The roots of the corn are yellowed, the leaves at the bottom begin to wither, and the flowers become thinner.In the mature period, it is in early autumn, so the temperature, sunshine conditions, and other conditions are worse than the festival period, pulping period, and filling period. The fruit of corn has matured. Leaves, stems, and roots wither yellow. The daily evaporation decreases gradually, as does the soil moisture content and precipitation.The calculated distribution of corn growth evaporation and experimental evaporation is shown in Figure12.Figure 12
Distribution of the calculated evaporation and the tested evaporation in maize growth period.As can be seen from Figure12, the calculated evaporation of corn fields is basically the same as the experimental evaporation of seedlings, and in most cases, the calculated value is higher than the measured value. At the beginning of the experiment, the surface of the test site can be regarded as a bare soil site, and the measured data evaporation law is the same as the evaporation law of bare soil. The calculated evaporation of the extraction period is slightly less than the test value of the extraction period. It can be seen that the matching degree of the curve is better than that of the seedling period and the extraction period. It can be seen that the calculated evaporation is slightly larger than the effective value tested. Grout from August 1 to September 4, with large temperature changes in the morning and night, and the calculated evaporation is much greater than the test value. The fitted curve is the same as the engagement curve, which is worse than the pumping period curve. During the maturity period, it can be seen that the calculated evaporation is slightly lower than the test value in early September and slightly higher than the test value in mid-September.The evaporation calculation and evaporation test values for each of the corns mentioned above are linearly fitted, as shown in Figure13.Figure 13
Curve fitting of the calculated evaporation and the tested evaporation during maize growth period whenα value was modified.As can be seen from Figure13, the relationship between calculated evaporation and experimental evaporation is linear:
(8)y=0.7758x+0.5057,R2=0.91seedling,y=0.893x+0.2121,R2=0.93jointing,y=1.0549x−0.0051,R2=0.94tasseling,y=0.983x−0.2492,R2=0.93filling,y=1.0142x−0.0168,R2=0.96mature.TheP<0.01can be calculated from the variance analysis, indicating a significant difference in variance. Compared with other corn growths, the ripening curve matches best.The soil moisture content, soil precipitation, and evaporation of the whole corn in Daqing saline soil test area were observed. The relationship between corn precipitation and soil evaporation is established, and the relationship between soil moisture content and corn soil evaporation is established. Suitable parameter values: the seeding period of the Ritchie model of saline soilα is 3.72 mm·d-0.5, the extraction period is 4.55 mm·d-0.5, and the extraction period is 2.68 mm·d-0.5. The grouting period is 1.50 mm·d-0.5. Maturity is 0.60 mm·d-0.5.


### 5.3.3. A Comparative Analysis before and after Model Correction

As can be seen from Table7, the degree of fit between the evaporation calculated by the modified Ritchie model and the evaporation of corn is 0.91-0.96, and the model error is significantly reduced, indicating that the modified Ritchie model can accurately simulate the evaporation of saline soil.Table 7
Contrast before and after correction of Ritchie model.
Nameα value/(mm·d-0.5)U valueModel error rate/(%)Regression coefficient/R2Seedling stage3.7283.920.91Shooting period4.554.000.93Tasseling stage2.680.600.94Postulation period1.500.600.93Maturation period0.600.690.96


## 5.3.1. Corn Full Fertility Cycleα Value

The parameters of the Ritchie model calculated from the above methodα conform to the above method, as shown in Table 6.Table 6
The full fertility cycle of cornα value.
SeedlingJointingTasselingFillingMatureα (mm·d-0.5)3.724.552.681.50.6


## 5.3.2. The Calculation of Evaporation in Corn Fields during Corn Growth

Corn germinates on May 27, and on June 25, 50% of the plant’s first root is 2 cm above the ground. Nitrogen fertilizer is applied to the fields where corn grows fastest on July 6. Stem nodes increase during this period, which promotes the enlargement of the upper lobe and acetylation photosynthesis. At the same time, the increase of precipitation has an impact on corn growth, soil evaporation, model modification, and simulation.The precipitation during the grouting period was 68.8 mm, which was less than the extraction period and higher than that of the seedling period. During dry periods, Daqing’s weather is warmer in summer, but the average daily evaporation during that period is lower than in the following period. Corn leaves get bigger and wider, blocking sunlight from the surface of the soil. At the same time, precipitation has become frequent. In this case, the evaporation becomes weak. The field during the distribution test of calculated corn evaporation and experimental evaporation.The precipitation during the grouting period is 38.8 mm, which is lower than the grouting, extraction, and seeding periods. During this period, the soil was full of water. Higher temperatures ofα are the first three periods. The roots of the corn are yellowed, the leaves at the bottom begin to wither, and the flowers become thinner.In the mature period, it is in early autumn, so the temperature, sunshine conditions, and other conditions are worse than the festival period, pulping period, and filling period. The fruit of corn has matured. Leaves, stems, and roots wither yellow. The daily evaporation decreases gradually, as does the soil moisture content and precipitation.The calculated distribution of corn growth evaporation and experimental evaporation is shown in Figure12.Figure 12
Distribution of the calculated evaporation and the tested evaporation in maize growth period.As can be seen from Figure12, the calculated evaporation of corn fields is basically the same as the experimental evaporation of seedlings, and in most cases, the calculated value is higher than the measured value. At the beginning of the experiment, the surface of the test site can be regarded as a bare soil site, and the measured data evaporation law is the same as the evaporation law of bare soil. The calculated evaporation of the extraction period is slightly less than the test value of the extraction period. It can be seen that the matching degree of the curve is better than that of the seedling period and the extraction period. It can be seen that the calculated evaporation is slightly larger than the effective value tested. Grout from August 1 to September 4, with large temperature changes in the morning and night, and the calculated evaporation is much greater than the test value. The fitted curve is the same as the engagement curve, which is worse than the pumping period curve. During the maturity period, it can be seen that the calculated evaporation is slightly lower than the test value in early September and slightly higher than the test value in mid-September.The evaporation calculation and evaporation test values for each of the corns mentioned above are linearly fitted, as shown in Figure13.Figure 13
Curve fitting of the calculated evaporation and the tested evaporation during maize growth period whenα value was modified.As can be seen from Figure13, the relationship between calculated evaporation and experimental evaporation is linear:
(8)y=0.7758x+0.5057,R2=0.91seedling,y=0.893x+0.2121,R2=0.93jointing,y=1.0549x−0.0051,R2=0.94tasseling,y=0.983x−0.2492,R2=0.93filling,y=1.0142x−0.0168,R2=0.96mature.TheP<0.01can be calculated from the variance analysis, indicating a significant difference in variance. Compared with other corn growths, the ripening curve matches best.The soil moisture content, soil precipitation, and evaporation of the whole corn in Daqing saline soil test area were observed. The relationship between corn precipitation and soil evaporation is established, and the relationship between soil moisture content and corn soil evaporation is established. Suitable parameter values: the seeding period of the Ritchie model of saline soilα is 3.72 mm·d-0.5, the extraction period is 4.55 mm·d-0.5, and the extraction period is 2.68 mm·d-0.5. The grouting period is 1.50 mm·d-0.5. Maturity is 0.60 mm·d-0.5.


## 5.3.3. A Comparative Analysis before and after Model Correction

As can be seen from Table7, the degree of fit between the evaporation calculated by the modified Ritchie model and the evaporation of corn is 0.91-0.96, and the model error is significantly reduced, indicating that the modified Ritchie model can accurately simulate the evaporation of saline soil.Table 7
Contrast before and after correction of Ritchie model.
Nameα value/(mm·d-0.5)U valueModel error rate/(%)Regression coefficient/R2Seedling stage3.7283.920.91Shooting period4.554.000.93Tasseling stage2.680.600.94Postulation period1.500.600.93Maturation period0.600.690.96


## 6. Conclusions and Discussions

Thanks are due to the Heilongjiang Natural Science Foundation (LH2019E072) for their help in this study; through the study, water content, rainfall, and evaporation between trees were observed in the test area of Daqing salt-alkali land. This paper analyzes the distribution law between the monthly average rainfall and the monthly average of evaporation between corn trees, obtains the relationship curve between soil moisture content and the evaporation between corn trees, and revises theα parameters of the Ritchie model for the appropriate value of each fertility period of corn, respectively, the seedling period 3.72 mm·d-0.5, the extraction period 4.55 mm·d-0.5 and 2.68 mm d-0.5, grout 1.50 mm·d-0.5, and maturity 0.60 mm·d-0.5.The linear fit between the evaporation measured values of the modified Ritchie model and the evaporation measurement between the corn trees was between 0.91 and 0.96, which shows that the modified Ritchie model simulates the evaporation between saline soil trees with good accuracy.



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*Source: 2558267-2022-04-22.xml*