During the growing season, potatoes are well responsive to irrigation, but their need for moisture during growth and development is not the same. For example, low soil moisture (65 - 70% of the FPV) before germination and during their emergence is needed in order to form a powerful root system that penetrates deep into the soil, which cannot be damaged during inter-row cultivation. Also, good root development makes it possible to better absorb nutrients from the soil.
During irrigation, it is necessary to use weather stations with soil sensors. Soil sensors provide information about what processes are currently taking place in the soil, how moisture is consumed by the root system of the plant and with what intensity.
ET0 station and profile sensor
On June 27, employees of Metos LLC installed a weather station kit to monitor the water balance and available moisture in the soil in the field of AgroAlliance-NN LLC farm for growing potatoes.
The ET0 weather station is equipped with the following set of sensors:
- Logger for data transfer to the cloud platform,
- rain gauge,
- Temperature and humidity sensor,
- Total solar radiation sensor,
- Ultrasonic wind speed and direction anemometer.
In accordance with the FAO recommendations, it is this configuration that allows calculating the reference and actual evapotranspiration (the amount of moisture evaporated from the surface of plant leaves and soil in a given time period).
Also, a profile sensor of the volumetric moisture content in the soil is connected to the station. The advantage of sensors of this type is the ability to actively monitor available soil moisture in increments of 10 cm. In the current case, a monitoring depth of 60 cm is chosen to monitor the active root zone of potatoes during critical phases of vegetation. Volumetric moisture sensors show values in %: where 1% in a particular layer can be reduced to 1 mm in a 10 cm layer. At the same time, our specialists choose an expensive, but high-quality model with a measurement error of less than 1%. This is especially critical when working with light soils, where available moisture can be extremely low (4-7 mm). Under such conditions, sensor errors of 2-3% or more can nullify their value and the significance of such readings. Potato planting was carried out approximately on May 24th. A weather station with a Sentek profile soil sensor was installed in the field on June 27th. During the operation of the weather station and the soil sensor from June 28 to July 12, we can understand how the root system develops and how intensively moisture consumption occurs on different soil horizons.
Schedule 1
On the graph (Graph. 1) we can observe the following dynamics of the available moisture consumption by the plant. The root system of the plant is very well developed, since the consumption of available moisture occurs from a depth of 0 - 50 cm. The active root zone is located at a depth of about 20 - 40 cm.
Active water consumption is due to the fact that in the period from July 3 to July 9 (Figure 2) there was an increase in soil temperature at depths of 0–40 cm, as a result of which the plant began to actively consume available moisture.
Schedule 2
The decrease in the volumetric moisture content in the soil is affected not only by the process of water consumption of the plant, but also by evaporation. Between July 3 and July 9 (Figure 3), about 25 mm of available moisture evaporated from the leaf surface and the soil surface. And therefore, when we plan to carry out the next irrigation, it is necessary to pay attention not only to how much moisture remains in the soil, but also how much moisture evaporates into the atmosphere, so that when choosing the irrigation rate, we compensate for the lost moisture not only due to water consumption, but also also due to evaporation.
Schedule 3
Also, when working with a soil sensor, we have the opportunity to set up “Budget lines”. This function allows you to quickly assess the state of available moisture for the plant and correctly select irrigation rates.
Schedule 4
Paying attention to the graph (Graph. 4), we can say that the plant vegetates in optimal conditions for growth and development (green Zone). As mentioned earlier, from July 3 to 9, there is an active water consumption of the plant, due to the fact that these days there were high indications for air temperature. As a result, there was a high transpiration of moisture into the atmosphere, as well as an increase in soil temperature. Prolonged precipitation, which began on July 9 and lasted until July 12, was recorded by the weather station in the amount of about 94 mm. Due to atmospheric precipitation, the volumetric moisture content in the soil increased so much that it moved into the zone of waterlogged state (blue zone). Due to this, watering is not necessary for the next week.
At different phases of the growing season, the lack and excess of moisture adversely affect the growth and development of the plant.
Thanks to the installed station and the sensor, we have the opportunity to calculate the water balance, as well as the moisture available to the plant. This information, combined with expected weather conditions, growing season, soil texture, and irrigation equipment, allows fine-tuning of irrigation rates.
Tasks of agricultural support and the project
Starting this week, we plan to publish a weekly report as part of agricultural support. By agricultural support, we mean the active interaction of our specialists with responsible employees of the farm, as well as the creation of both an operational and a comprehensive picture of the selected control area. In our case, we are talking about soil moisture monitoring, water balance and irrigation optimization.