Improving plant nutrient management is becoming a more significant part of every farming operation. Today soil sensors do more than measure the water content in the soil. Soil sensors are used more and more by growers for nutrient management help. In the early days of working with soil moisture sensors, there was an understanding of where the irrigation water goes, the nutrients will follow.
Plant Nutrient Management
Over the last few years, the use of sensors that measure EC (Electrical Conductivity) became more popular. Using a sensor that can separate salinity from soil moisture now allows a grower to understand better how fertilizer applications respond in different soil moisture conditions. Measuring soil conductivity can be used to infer salinity or the concentration of many fertilizers. To illustrate this, I pulled data from a site that had very different soil moisture conditions in the soil profile before the fertigation event (Figure 1).
1) Soil Moisture and Salinity
This site illustrates the impact soil moisture conditions have on plant nutrient management through the soil profile. In the example, the grower set a management zone for sensors between the 4″ – 12″ sensor levels. The management zone is based on field visits and what the grower believes is the point they have reached field capacity and the level they have dried to the point that they want to start their next irrigation. You can see this in the first level of the readings chart with an upper blue boundary for wet and a lower red boundary for dry. Their goal was to manage irrigations within this zone.
Before their first series of fertigation events, they brought their soil moisture levels to the range shown in the “High Moisture Content” section of the chart. Reviewing the salinity levels, you can see that the nutrients infiltrated right past the 4″ sensor level and continued to increase to the 16″ sensor level moving the nutrient deeper and deeper with each event. The higher moisture condition in the profile provided a quick path to move the nutrients deep.
Going to the second series of fertigation events the site was allowed to dry down, and the soil moisture levels were within the management zone. The irrigation frequency was stretched out with less water applied. With the dryer soil moisture conditions, the nutrients moved slower through the soil profile with the bulk of the nutrients landing at the 4″ sensor level and slowing by the time it reached the 8″ level. Holding off a bit before applying the next irrigation event provided a longer “opportunity time” for the crop to access the nutrients where irrigation too early may have pushed them deeper into the root zone or even leached the nutrients out of the root zone.
Monitoring salinity can be a great way to improve the use of plant nutrient management and assure what we apply is taken up by the crop and does not leach out of the rooting zone. This helps the plant get the most value out of nutrient applications and allows you to grow more crop per drop.
If you are interested in measuring salinity in your fields there are some options, two popular choices are:
2) SenTek TriScan Profile Probe
The TriSCAN profile probe measures soil moisture, temperature, and salinity. Using a patented measurement technique the TriSCAN sensor can distinguish between soil water content and salt content. This information is then processed using a Sentek derived model to calculate soil volumetric ion content (VIC) separately from the Volumetric Soil Moisture.
The TriSCAN sensor is optimized for one of agriculture’s most common soil textures of sands and sandy loams and is currently not suitable for clays and helps us with plant nutrient management.
3) EnviroPro Profile Probe
The EnviroPro Soil Moisture Probe is suitable for a wide range of perennial and annual crop’s plant nutrient management. The probes provide soil moisture and temperature readings with an option to purchase a key to unlock salinity readings. All probes are fully sealed, mechanically robust, and feature a 5-year manufacturer’s warranty.
Both the SenTek and EnviroPro probes provide measurements at 4″ (10 cm) intervals allowing observation of water infiltration into the soil profile and active uptake during active growth. When used in combination with JAIN Logic, agronomists and growers identify and manage the water delivered to the plant’s primary root zone.
If you have questions or would like to learn if salinity measurements could help in your operation or learn more about plant nutrient management contact us here.