What is an NPK value? Why is it important to monitor and maintain plants?

The NPK value of a soil indicates how much nitrogen, phosphorus, and potassium are present in the soil or substrate. All plants need these three essential macronutrients. Knowing the NPK value of your soil or substrate is important because you can provide your plants with the right amount of external NPK fertilizer based on their needs. Soil NPK sensors are very important and can help you better understand the growth of plants.

Let’s break down how these 3 macronutrients can help your plants.

N stands for nitrogen. Nitrogen is necessary for the growth of plants with good leaf growth and color.
P stands for phosphorus. Phosphorus promotes root formation and flower and fruit development.
K stands for potassium. Potassium aids in the transfer of water and nutrients in plants and aids in photosynthesis, it also increases disease resistance and supports healthy root systems.

Providing excess NPK can result in:

Nitrogen: Overgrowth reduces fruiting and flowering ability, attracts insects and reduces stem strength.
Phosphorus: Reduces the ability to absorb zinc and iron and small amounts of micronutrients, even if they are present in the soil.
Potassium: Causes inability to absorb key nutrients like nitrogen, magnesium, and calcium, causing them to be deficient.
Therefore, it is important to monitor these values and provide the amount of NPK required for healthy plant growth. So with that in mind, let’s build a soil NPK monitoring device with sensors and Arduino.

JXCT soil sensor is more convenient

Previously testing soil for NPK could only be done by collecting samples and bringing them to a laboratory where researchers tested soil, which was time-consuming, labor-intensive, costly, and even impossible to detect soil NPK status in the field. Later optical NPK sensors using spectrometers kicked into action and couldn’t even give accurate results by stopping at 60-70% accuracy. Therefore, to overcome this, a few technology manufacturers such as JXCT have developed a sensor that can detect the NPK value of soil in situ with almost acceptable accuracy. Before we start, let’s have a look at sensors and their working specifications.

Soil NPK Sensor (JXBS-3001 Soil NPK Sensor)

The JXBS-3001 soil NPK sensor is manufactured by JXCTIOT in Weihai, China. Low cost, fast response, high accuracy and portable NPK sensor consists of 3 probes made of austenitic 316 steel for long term operation and is not corroded by rust, salinity and electrolytic action. The protective shell is filled with high-quality epoxy resin, which prevents moisture from entering the sensor body and ensures long-term healthy operation of the sensor.

The chipset used inside the sensor creates highly sensitive measurements with stable signals at low power consumption. The sensor is rated IP68 for water and dust resistance.

Technical features

This sensor does not require any chemical components, this sensor has a Modbus communication port, we cannot interface it directly with a microcontroller, but use an intermediate Modbus module. We can connect it to most microcontrollers like Arduino, ESP32 and measure the value of Nitrogen, Phosphorus and Potassium in real time just by inserting the probe into the soil. The sensor also detects soil types like acidic soil, alkaline soil. You need an external Modbus module such as RS485/MAX485 to interface the sensor and microcontroller.

The sensor has an operating voltage range of 9v-24V and a maximum power consumption of less than 0.15 watts. Operates in a temperature range of 41-113°F (5-45°C). Many microcontrollers such as Arduino, PIC microcontrollers, 8051 microcontroller family, ESP etc. support this soil NPK sensor as they have baud rates of 2400, 4800 and 9600. This soil NPK sensor is said to have high-precision measurement with an accuracy of ± 2%, a measurement resolution of 1mg/Kg (mg/liter), and can measure nitrogen, phosphorus, and potassium in the range of 0-1999mg/kg (mg/liter) .

Voltage: 9-24 Volts
Power Consumption: <0.15W
Working temperature: 5-45 degrees Celsius (41-113 degrees Fahrenheit)
Baud rates: 2400, 4800 and 9600.
Measurement resolution: 1mg/kg (kg/l)
Measuring range: 0-1999mg/kg
Accuracy: ±2%
Communication method: Modbus RS485
Protection class: IP68