Regional Farmland Soil Moisture Monitoring and Precision Irrigation Technology

As China's water-saving irrigation planning tasks continue to deepen, considering the sustainable development of the national economy, the current planning task for water-saving irrigation is to study various engineering measures, control approaches and methods that are technologically advanced and economically rational, and reduce irrigation. The unprofitable loss of water; the rational allocation of water resources in time and space, and the implementation of scientific irrigation decision-making and precision irrigation control methods in the field, in order to achieve rational use of water resources and promote the sustainable development of agricultural efficient water-saving technologies.

As a new agricultural water-saving technology field, the monitoring of farmland moisture during the crop growing period (farm soil moisture can use soil moisture and drought monitoring or wireless moisture and drought management systems, both of which can measure soil moisture content, of course If necessary, parameters such as soil temperature, water potential and conductivity can also be measured.) More and more attention has been paid to it. It integrates expert knowledge and experience and solves problems through computers. The GSM (Global System for Mobile Communications) wireless transmitter and transmitter of the farmland soil moisture information acquisition system and the GSM wireless center receiving and transmitting device are combined with the system's irrigation decision support software to complete the monitoring of farmland soil and the decision of precision irrigation so that the farmland irrigation can be achieved. There is a reasonable scientific basis for efficient water use. It fully embodies the innovative advantages of GSM network monitoring technology for agricultural soil moisture in the area of ​​water-saving agriculture, especially in areas such as precision irrigation control technology for regional environmental farmland, making full use of computer automatic control technology to deepen the research in various fields of water-saving agriculture, making relevant The interpenetration of disciplines promotes each other to become more obvious.

The Water Saving Agricultural Irrigation Environmental Control System Project is a systematic technological achievement with many technical and complementary forms. Compared with advanced developed countries at home and abroad, there are certain gaps and deficiencies in China's integrated technical systems, which should be based on different regions in China. Ecological climate conditions and economic development level, according to local conditions, formulate and develop China's water-saving agricultural planning and corresponding technologies. Its technical route, system software, application software and hardware devices are as high as possible compatible with high versatility and compatibility to suit different types of water-saving agricultural cultivation environment control systems.

1 Regional Farmland Public Health Surveillance Significance

The spatial and temporal distribution of water resources in China is seriously unbalanced. 81% of the water resources are concentrated in the Yangtze River basin and the area south of the Yangtze River. The population and arable land in the area north of the Yangtze River account for 45. 3% and 64.1% of China respectively, while the water resources are only It accounts for 19% of the country, with a per capita occupancy of 517 m3, which is equivalent to 1/5 of the national per capita and 1/20 of the world's per capita. The degree of incompatibility between water resources and production development is outstanding, and the desertification trend is becoming increasingly serious. Especially in the northwestern arid areas of Xinjiang, Qinghai, and other areas of the Gobi Desert, there is no agriculture because there is no irrigation. Precipitation is unevenly distributed during the year, with less rain in winter and spring, and more rain in summer and autumn. Rainfall in the flood season is too concentrated, often in the form of heavy rain, which is difficult to use and lacks in the non-flood season. The interannual variation of precipitation is large, and the difference between the year of flood and the year of dry water is very different, so that floods and droughts occur frequently. Even the same areas sometimes come into contact with floods and floods and alternately fall into disasters.

From the perspective of the total demand for water resources in the country, in the case of moderate drought, the total water demand in the country is about 550 billion m3, and the water shortage is about 25 billion m3. If we consider the unreasonable water supply factors such as groundwater over-draft in the water supply and over-standard sewage irrigation, the actual water shortage in the country will be 300 to 40 billion m3. Agriculture is a large water user in China, accounting for about 73% of the country's total water use. However, its effectiveness is poor. Water resources are very wasteful. The effective utilization rate of water in the canal irrigation area is 40%, and 60% in the well irrigation area, producing food for every 1 m3 of water. Less than 1 kg. The effective utilization rate of water in some developed countries can reach more than 80%, and the production of grain per 1 m3 of water can reach more than 2 kg, of which Israel reaches 2.32 kg. This shows that the comprehensive application of various water-saving agricultural technologies in China is low, and there is still a big gap compared with developed countries. At the same time, it also saw the great potential and broad prospects for the development of water-saving agriculture in China.

With the rapid development of soil moisture sensor technology, GSM communication technology, and GIS (Geograp hic information system) technologies and the increasing demand for monitoring regional environmental factors, people are increasingly demanding the monitoring of mobile targets. Not only do they need to know the location of moving targets. It is also necessary to monitor and process data such as feedback parameters, alarm information, and operating status of the moving target in real time. Sensors were used to collect environmental factors including soil moisture and moderate air temperature, and the collected information was transmitted to the control center through a local wireless network as a basis for the central control system to implement automatic irrigation of field crops. The above-mentioned regional environmental monitoring network technology has an extremely important role in its automatic irrigation control system. After the technology and products developed in the demonstration area are applied in the demonstration area, under the premise of maintaining the output unchanged or increasing, the irrigation quota within the crop growth period is reduced by 20% compared with the conventional irrigation condition, and the water use efficiency is increased by 25% to 30%.

2 Precision Irrigation System Technology

The use of GSM network carriers to collect soil moisture information in the field is an important means of field collection. The information transceiver sends the collected soil water dynamic parameters to the GSM network carrier according to the internal set time rule. The upper patrol radio transceiver (which can be multiple) processes the received soil water dynamic parameters through the GSM network carrier and passes it to the central computer. The computer processes the collected information into computer software monitoring and decision-making systems. The system calculates the state of soil moisture and the amount of irrigation water in each irrigation area according to the physical characteristics of soil characteristics and relative crops. According to the irrigated area and the amount of pumped water, the predicted irrigation time and irrigation water volume time cycle were calculated. At the same time, the system simultaneously monitors the interaction status of field soil moisture information collection and transmission devices and the upper patrol radio transceiver device in each irrigation area. If there is a problem, the computer control center system will promptly perform on-site water potential sensor transmitters, microprocessors of wireless transceivers, and upper patrol radios and transceivers to make time and system corrections to form a stable soil moisture monitoring telemetry system. Farmland public opinion GSM network monitoring and precision irrigation control technology software system can realize wireless two-way data communication, irrigation decision-making and control of large-area multi-channel irrigation program, improve uniformity, and achieve quantitative control of production process.

3 system software

In the whole farmland public opinion GSM monitoring system, the software system can not only provide regional irrigation decision data and corresponding precision automatic control modes, but also preset common control modes. In some applications where the control reliability of the irrigation environment is very demanding, a software module hot backup is also included. Some key modules have one or more backups in the design. When a software or hardware system has a problem, it can pass a special software module. Automatically switch to backup, thus ensuring the continuous operation of the system. The system includes seven parts: platform operation module; GSM two-way communication module; information acquisition module; data analysis module; control decision module; data processing module; interface driver module (Figure 1).

4 system hardware

In the development of control hardware for precision irrigation systems, the controllable range of the system is large, and the versatility, standardization, and extensibility of the hardware are the key. The research and development of advanced wireless communication transceivers provide the hardware basis for large-scale regional irrigation group control. Due to the vast area of ​​irrigation, there is a wireless patrol center communication transceiver device in the central control room to complete the spatial transmission of many dynamic data collected on the site. The entire hardware system not only achieves information processing and processing and security information management under the wireless network carrier, but also controls the system independently. The control parameters are modified for wireless and on-line portability. There are not many lines to be laid and maintained. The system has a certain degree of fault-tolerant performance. Local damage will not affect the entire system.

4.1 One of the important components of the system hardware (embedded soil moisture information acquisition GSM wireless transceiver transmission device)

The upper computer is connected to the wireless patrol center receiving and transmitting device through the serial port, and the wireless communication control mode based on the GSM network as the carrier completes the design of the regional farmland public opinion monitoring network environment monitoring in the form of bidirectional transmission and multi-branch structure. The field soil moisture collection sensor completes the water monitoring and wireless communication control of the underlying area irrigation through the microprocessor. The system not only achieves information processing and processing, security information management, security code detection and modulation, sensor detection, power supply monitoring and lightning strike protection under the GSM network carrier, but also the control of each part of the system is relatively independent.

The moisture collection module is mainly composed of DPA conversion, battery management, and operational amplifiers. The main device for communication control is the SIM card. The E5111 chip integrates the TCPPIP protocol and is connected to the microprocessor through a dedicated interface. Each GSM transceiver for soil moisture collection is powered by a separate battery and has a normal operating time of more than 3 years.

The microprocessor adopts A TMEGA128 device of A TMEL Company of USA. The standby IPO is mainly used for keyboards and display interfaces and can be used for simple human-computer communication. The display driver circuit is mainly used to display the internal state of the system. Embedded soil moisture information collection GSM wireless transceiver consists of the following components, the sensor acquisition part: power supply (high stability voltage), constant flow control, physical sensors, mainly to convert the soil moisture content to the corresponding power; Analog to digital conversion Part: mainly composed of low-pass filter, 10-digit conversion and reference power supply; central control part: microprocessor for data processing and control to send and receive data (including emission unit internal information: battery power, correction time); memory part : Mainly used for microprocessor data buffering and storage; Power supply parts: Mainly high-performance capacity battery, charge and discharge control circuit and battery detection; Communication module part: GSM signal modulation, antenna; Communication expansion and serial port part: mainly provide IPO Expansion and connection with the serial port of the upper computer 485; Lightning protection part: mainly composed of dedicated fast absorption devices; Shell: The main role is to send the sensor signal (Figure 2).

4.2 The second part of the system hardware

The following analysis data was obtained from the adaptability analysis of the soil moisture sensors conducted at the Luancheng test station in Shandong and the Fengqiu test station in Henan: It is assumed that the range of the sensor's measurement frequency is 0-50 kHz. Within this range, according to the calibration curve of the soil moisture sensor, the water potential 2 frequency curve of each sensor is plotted, and the water potential calculated according to the rate determination formula increases with increasing frequency (Figure 3).

Using the water characteristics curve of the soil at Fengcheng Station and Fengqiu Station, respectively, the water potential was converted into volumetric soil moisture.

Moisture characteristics curve of loess soil at Rucheng Station:

Where θ is the volumetric moisture content (cm3/cm3) and ψ is the water potential (kPa).

Fengqiu station soil moisture characteristics curve:

θ = 0. 45p - 0. 2611

Where θ is the volumetric moisture content (cm3Pcm3) and P is the soil water potential (kPa).

Draw the soil water potential-soil moisture curve at Luancheng Station and Fengqiu Station (Figure 4).

5 System Communication and Precision Irrigation Drive

According to the soil and crops of different farmland soils, a reasonable distribution of buried soils is used to sample the moisture information monitoring points, and a GSM network-based centralized monitoring and irrigation site monitoring system consists of sending and receiving process control stages and central computer-controlled decision stages. Relatively decentralized, flexible configuration, convenient configuration, and highly-reliable practical system with highly concealed field device devices.

SMS (Short Messaging Service) Short message service is a value-added service of the GSM network. It transmits data through a control channel and supports point-to-point message services and message broadcast services. Moisture collection data is sent to the short message service center through the GSM network. The monitoring center obtains data from the short message service center through the DDN (Digital Data Network).

The design method of soil moisture monitoring SMS transmission data using GSM (Fig. 5), the system is set to use the wireless network as the carrier's communication drive control DDC (Digital Data Converter), will be distributed in the irrigation monitoring site of a variety of related hardware device drive control Wireless data is exchanged through the wireless network to implement wireless driving, which fully realizes the wireless operation of two-way information transmission and irrigation drive for regional farmland monitoring.

Communication drive control, which is based on a wireless network, can scan and monitor specified devices and automatically determine the required control functions. According to the programmed application requirements, the operation of each system component is completed independently, and communication and operation are performed with any designated terminal and electric actuator, and data exchange and two-way remote operation are performed. Since the field controller is relatively independent, it is improved. The reliability of the entire control system.

As a DDC universal controller, the field controller performs (DDC) operation instructions to complete the process driving and direct control of the electric actuators throughout the irrigation area, and is responsible for monitoring and adjusting the process parameters of the entire control process, and is suitable for the field and facility cultivation environment. Apply more complex subsystems. Most of the interface design of this system is to meet the compatibility requirements. The analog input (AI) is compatible with the digital input (DI) and can use a variety of expansion boards to meet the needs of field control, with scalability and changeability.

6 user operating system

In the entire farmland and facility soil moisture monitoring system, the system can not only provide regional irrigation decision data and corresponding precision automatic control modes, but also preset common control modes, and the user can conveniently select the desired mode. During the operation process, the user can freely set the control process according to his own needs, and set several irrigation groups to work in one or several groups to achieve arbitrary setting of farmland and facility system irrigation order, and complete the opening of any irrigation group in the region. Or close. Users can automatically complete farmland and facility irrigation according to the set time sequence, and start the preset irrigation work schedule at regular time. After the system completes the irrigation workflow, the user can save the control flow that he has set for reuse, and does not need to be set before each job. Computer system operation platform working status icon and real-time status of irrigation site to achieve tracking and synchronization.

7 Conclusion

Using the research results of regional farmland and facility soil moisture monitoring systems, modern precision irrigation technology and biotechnology are used to comprehensively regulate the necessary conditions for crop growth, provide crops with suitable soil moisture nutrient conditions, make crops with high quality and high yield, and reduce ineffective evaporation. Loss, to achieve the goal of water saving, energy saving and environmental protection in agriculture. Integrate the research results in the field of efficient utilization of agricultural water resources and digital precision operations, and implement regionalized soil moisture monitoring and precision irrigation techniques for medicinal plants, fruit trees, flowers, and Daejeon economic crops that have regional representativeness and are planted. Its water-saving and yield-increasing effects are extremely obvious.

Simultaneously with the monitoring of soil moisture content, combined with the water requirement for planting crops, scientifically determine the irrigation water plan. Irrigation area soil moisture monitoring is used as the main basis for irrigation water management. According to meteorological observation data, soil moisture data, crop growth data, etc., the irrigation water quantity and irrigation time of crops are determined, and water supply information is provided in time, so that agricultural irrigation management is more scientific and accurate.

Because of the different climatic and ecological conditions and the conditions of the irrigated area, the relative water saving strategies should also have their own characteristics. Regional precision irrigation of farmland and facilities has not only achieved large-scale crop planting, high-quality and high-yield production, but also effectively prevented soil salinization and consolidation, and served to protect the ecological environment and drought relief. With the continuous demand for water-saving agricultural technology in water-scarce regions in China, the GMS network monitoring, irrigation decision-making, and precision irrigation control technologies in the regional farmland soils have received increasing attention and will surely replace traditional irrigation control technologies. The more extensive it is, it has important application value and scientific significance, and it also provides technical support for the sustainable development of China's green agriculture.