At present, most environmental parameters in smart agriculture such as temperature, humidity, CO2 concentration, soil temperature, foliar humidity and light level in greenhouses are collected in real time by physical sensors, among which temperature and humidity sensors are the most widely used type of sensors in smart agriculture, which are widely used for temperature and humidity monitoring in greenhouses, soil, open-air environment, plant foliage, food and vegetable and fruit storage, etc.

The air temperature and humidity sensors are used to detect the temperature and humidity of the air in the agricultural environment and are usually installed in the shade of the air circulation in the greenhouse or livestock barn. Soil temperature and humidity sensors are installed in the soil at the root of crops, and the depth of the sensors is determined according to the different root depths of crops. Soil temperature and moisture provide a vital role in the growth of plants.

Soil temperature has a great influence on crop fertility and microbial activities in the soil as well as the transformation of various nutrients, soil water evaporation and movement.

General soil microbial life, soil temperature 25℃ ~ 37 ℃is appropriate, the lowest is 5℃, the highest does not exceed 45℃6~ 50℃. In a certain temperature range, the higher the soil temperature, the faster the growth and development of crops; soil temperature is too low, microbial activity is weakened, organic matter is difficult to decompose, the crop's root respiration is reduced, resulting in crop nutrient deficiencies and slow growth.

Soil moisture is the condition of the water content of the soil. Soil moisture directly affects the quality and speed of crop growth. In farming, crops cannot directly obtain inorganic elements in the soil through themselves, and water in the soil acts as a solvent to dissolve these inorganic elements, and crops absorb soil water through their roots to obtain nutrients for growth, so precipitation or irrigation has to be converted into soil water to be absorbed by plants.

Therefore, it is necessary to provide a suitable temperature and humidity environment for plants. Therefore it is crucial to select soil moisture sensors to detect soil moisture.