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Soil Nutrient Management with Sensor

Food is very important for the growth, development and well-being of a human being, and just like all living organisms, plants also require nutrients to grow well which are provided by water, air , sunlight and soil. And when these essential nutrients are not available in sufficient quantities, there occurs nutrient deficiency and this hinders the growth of the plant.

Read more: Top Cash Crop Farming In India.

Healthy soils have a functioning biogeochemical cycle which supplies nutrients in the required amount for the growth of a crop. Overcoming the Nutrient limitations is one of the main obstacles in producing quality crops and increasing yields worldwide.

The farmers need accurate information about the nutrient of soils if they are to apply the correct amount of fertilizer, so it is very important to monitor the soil so as to maximize the yield and reduce diseases and optimise their resources.

There are different techniques for monitoring the soil like IoT sensors using Arduino and ESP32.

This article focuses on ‘Soil Nutrient management using Sensors’. 

Nutrients in Plants

Plants require some nutrients in large quantities which are called Macronutrients while some in smaller quantities known as Micronutrients and there are about 18 essential nutrients that are very important for the growth and development of plants of which 14 comes from soil.

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Macronutrients including Nitrogen, Potassium, Phosphorus, Calcium, Magnesium and Sulphur are required for photosynthesis, production of plant cellular structures and functioning of plant enzymes and biochemical processes, where as Micronutrients including Molybdenum, Iron, Copper, Boron, Manganese, Chlorine, Nickel and Zinc are used in smaller quantities but their absence can become a limiting factor.

The deficiency of these nutrients can inhibit the growth of plants, affecting their life cycle, processes and also decrease the immunity against diseases. These nutrients can be added in the form of manure and fertilizers and it can increase the fertility of soil as well.

The nutrients requirement varies by crop type and the growing stage of the plant. The effective soil nutrient management strategies are concerned with the amount, source, placement, form and timing of the plant nutrients application and soil amendments.

Some of the nutrient sources like Phosphorus and Nitrogen are already present in the soil. Also, the Organic Nutrient sources include the soil organic matter and decomposing plant residues, while Inorganic Nutrient sources include primary minerals which lie under the soil as well as some added mineral fertilizers.

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These nutrients can be affected by the abIoTic soil parameters such as CEC and pH but they also depend upon the activity of the soil microbial community. The soil microbes decompose these organic nutrient sources that the plants may not be able to take up and turn them into bio available forms.

Some of the Traditional agriculture practices focus on adding inorganic nutrient sources such as the traditional NPK fertilizer. Also, the research has shown that Integrated Nutrient Management plan is found to be effective and sustainable in preventing more macro and micro nutrient deficiencies where both organic and inorganic nutrient resources are used.

Diagnosis of Nutrients

The deficiency of nutrients can be diagnosed through visual observations, soil testing and plant testing of which soil and plant testing are the most effective diagnoses which allows for early detection and treatment of nutrient limitations. The soil should be tested after every 1 to 3 years based on the type of soil and state requirements or recommendations. They usually report pH, Phosphorus, Potassium, Calcium, Magnesium, Sulphur and micronutrients.

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From the soil analysis report, the nutrient recommendations can be offered based on the local field trials and experience of the land Grant University and this information helps the farmer know how much lime and fertilizer is required for a particular crop on a particular soil.

The sampling depends on the type of Crop and suspected limiting nutrient, but the youngest mature leaf collected from multiple plants can be one of the most common sampling methods. Visual observation is one of the common diagnosis methods.

The difficulty of diagnosing nutrient deficiency visually can be understood by the fact that plants may experience multiple nutrient deficiencies at the same time and the symptoms for these nutrient deficiencies can also be similar.

Some of the visual symptoms includes:

• discoloration (yellow and purplish-red colour are most common)
• retarded development of leaves, roots and shoots
• tissue death

Nutrient Management

Nutrient management refers to the efficient use of nutrients to improve productivity of the crops as it is very necessary to balance the nutrient input with the requirement of a crop. If the nutrients are applied at the right time and in adequate quantities, optimum crop yield can be obtained.

Read more: Aquaponic Farming Complete Information Guide.

If the nutrients are applied in huge amounts, it can harm the crop and if applied in small quantities, it can limit the yield and the nutrients which are not utilized by the crops can leach into groundwater or nearby surface water.

Nutrient management is a process of managing the amount, source, timing and method of nutrient application while minimising the loss of nutrients which could create environmental problems and it has a primary goal of optimising the productivity of a Farm.

It includes developing nutrient budgets that consists of knowing the amount of nutrients that is already present in the soil and determining the amount of nutrients which is needed by the crop accounting for all the potential sources of the nutrients and then applying manures, compost, irrigation water or inorganic fertilizers for meeting the nutrient need of the crop.

The management practices also use site management practices for increasing and maintaining the soil quality for reducing the potential for erosion and nutrient transportation into surface water or leaching into groundwater. The quality of soil is a very important component of nutrient management as it affects the nutrient retention and water movement through the soil.

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The Nutrient management plans focuses on these 4 R’s:

1. Right amount – Proper rate of application
2. Right source – Proper type of application
3. Right placement – Using the appropriate method of application
4. Right timing – Proper time of application

Integrated Nutrient Management

Integrated nutrient management is the combined application of chemical fertilizers and organic manures for the crop production with the main aim of maintaining the soil fertility and supplying the plant nutrients in adequate amounts. It is ecologically, socially and economically viable.

Importance of Nutrient Management

Nutrient Management is important for the following reasons:

• It helps in reducing contamination to waterways by plant nutrient
• It improves the fertility of soil.
• It enhances the productivity of a plant.
• It reduces the cost of chemical fertilizers.
• It provides balanced nutrition to crops.
• It promotes carbon sequestration and prevents the deterioration of soil, water, ecology and it also prevents the leaching of nutrients from the soil.

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Soil Nutrient Monitoring using IoT

Soil is the base of agriculture and it provides nutrients for the growth of a crop. Some of the chemical and physical properties of soil such as moisture, temperature and soil‘s NPK content can heavily affect the yield of a crop and these properties can be sensed by the open-source hardware which can be used in the field.

The soil monitoring with IoT uses technology which empowers the farmers and growers to maximize their yield, reduce disease and optimise resources. They can measure soil temperature, NPK, volumetric water content, photosynthetic radiation, soil water potential and soil oxygen levels. These parameters can be monitored wirelessly on a mobile phone or a PC system.

The data from these are transmitted back to a central point (or cloud) for analysis, visualisation and trend analysis. The resultant data is then used for optimising the farming operations, identifying the trends and making subtle adjustments to maximize the yield of Crop and its quality. The use of IoT in agriculture is known as Smart Agriculture/Farming and IoT is also a Central component of Precision farming.

All the sensors can be easily interfaced with Arduino.

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The most common IoT sensors are:

• Soil Temperature Sensors

The temperature of soil is a very essential factor in the below ground plant activity which influences root growth, respiration, decomposition and mineralisation of Nitrogen. IoT sensors can estimate the temperature of soil by measuring the air temperature and other factors and give accurate measurements using a probe buried in the soil.

Depending on the structure of the root of the plant, multiple crops can be installed at different depths. The temperature of Surface soil can be monitored using a different type of IoT sensor that uses IR Technology.

The temperature of the soil is measured using the DS18B20 Waterproof Temperature sensor which is a pre wired and waterproof version of the DS18B20 sensor which is used for measuring something far away or in wet conditions. This sensor can measure the temperature between -55 to 125 degree Celsius.

• Soil Moisture Sensors

Soil moisture content is very essential because the water is a critical nutrient for all the crops and plants and it helps in regulating soil temperature and it is an important carrier of soluble food nutrients for plant growth. It also serves some important role in the process of photosynthesis and the crop yield is also heavily influenced by the availability of water in the soil.

Moisture of the soil can be monitored using buried probes with electrodes. Soil science and Agricultural moisture content plays a vital role in soil chemistry, plant growth and ground water recharge.

Read more: Use of Chemical Fertilizers & Its Impact on Agriculture.

IoT and Smart Agriculture Technology from Libelium can measure these properties in the soil:

1. Soil moisture (up to three times depth)
2. Conductivity
3. Volumetric water content
4. Soil water potential

For measuring soil moisture level, we need soil moisture sensors and generally, Capacitive types of soil moisture sensors are preferred because they have the advantage that they are made of a corrosion resistant material which provides long service life. This type of sensor operates between 3.3 volt to 5.5 volt DC voltage and the output is in the form of Analog up to 3 volt maximum.

• NPK Soil Sensors

The soil NPK sensor is suitable for detecting the content of Nitrogen, Phosphorus and Potassium in the soils and it also helps in determining the fertility of the soil. These sensors can be buried in the soil for a long period of time. NPK IoT sensors use various technologies but the most common method used by the sensors is TDR.

This sensor supports RS485 to be integrated into IoT solutions including LoRaWAN and data loggers. These sensors don’t require any chemical reaction and have a high measurement accuracy, fast responding speed and good interchangeability and it can also be used with any type of microcontroller. The sensor operates on 9 to 24 volts with an accuracy up to within 2%.

Read more: Importance of Potash for Crop Production.

The combined NPK sensors can measure:

1. Nitrogen
2. Phosphorus
3. Potassium
4. pH
5. EC
6. Temperature
7. Moisture

• Solar Radiation Sensors

Solar radiations have a real impact on the growth of plants and therefore IoT monitors the Solar levels to understand correlations and trends. IoT sensors can measure different types of solar radiations that plays a vital role in Photosynthesis and beyond light levels of Lux, it can also measure:

1. Solar – Photosynthetically active radiation
2. Solar – UV
3. Solar – Shortwave

• Weather Sensors

Rainfall/Precipitation, Wind, Humidity and Atmospheric pressure all play an essential role in the growth of plants and the Smart Agriculture system supports several advanced weather stations which along with the Soil Sensors gives a 360° view of your farming operations.

Read more: How Artificial Intelligence (AI) can help the farmers?

IoT weather stations measures the following:

1. Precipitation
2. Temperature
3. Humidity
4. Air pressure
5. Wind speed
6. Wind direction

• Other Sensors

There are many other IoT sensors for agriculture which are very important and these sensors monitor the soil as well as enhance the IoT deployment.

These sensors measures:

1. Vapour pressure
2. Soil oxygen levels
3. Leaf wetness
4. Trunk, Stem and Fruit diameter

Wireless Communications for IoT & Smart Agriculture

IoT solutions provide a wide range of wireless communication options as it is not just limited to urban areas with extensive mobile coverage but it also supports for LoRaWAN, 4G, Zigbee, Sig Fox, Wi-Fi and Satellite which means Smart farming solutions work can be found in both urban, rural and very remote environments.

Read more: Natural Farming vs Factory Farming.

IoT systems’ low power nature means nodes and sensors can also be powered by batteries, solar or any type of other Renewable Sources.

Many types of crops or farming businesses can be optimised using IoT. Some of them are:

• Cannabis and Hemp
• Soybeans
• Potato
• Almonds
• Cherries, Apples

NRF24L01 Wireless Transceiver Module is a wireless transceiver module and each module can both send and receive data. It works within the frequency of 2.4 Ghz which can be operated efficiently and can cover a distance of 100 metres. The module operates at 3.3 volt but its SPI pins are only 5 volt tolerable and the module works with the help of SPI communications and therefore you can use the module with any type of microcontroller with SPI pins like ESP32 Wi-Fi module for Arduino boards.