— 42 IREC Farmers' Newsletter No. 200 — Spring 2018 Simple sensor installation The installation of MCPs in rice fields is similar to that used in non-ponded crops. However, rather than install the probe to full depth, half of the probe is installed in the soil and the other half of the probe above soil level. This allows a single probe to measure both the soil moisture and root zone temperatures as well as measure ponded water depth and crop temperatures, all at 10 cm intervals. Common probe lengths are 80 cm, 100 cm, 120 cm, so that at least 40 cm is available for soil measurement and 40 cm for water and ambient measurement. Data at your finger tips The MCP sensors can be linked to WiFi data loggers developed by Deakin University and sold through Goanna Telemetry, called WiFields. This approach provides up-to-the-hour data on websites that can be viewed from computers or mobile phones. One advantage of using MCPs in this application is the range of useful data available. As well as water depth, soil moisture and temperature readings at fine intervals (10 cm) can be obtained. The soil moisture data is shown in the lower graph of Figure 1. Early in the season before permanent ponded water is applied, the soil at 50 mm and 150 mm starts to dry out considerably during the delayed permeant water phase and the sensors can be used to trigger irrigation events to ensure the rice root system is not stressed. Figure 1 shows that it starts to dry again after the ponded water is drained in early-April. Using the soil moisture information is particularly important in these early and late parts of the rice growing season to ensure the soil does not reach moisture stress levels, which would be detrimental to yield. Figure 1 also shows associated crop temperature data over the growing season. It can be seen that there are periods when the crop temperature is falling below the critical 15 °C level which is likely to have impacts on crop yield. The MCPs can be used to see the impacts of ponded water depth and its effect on temperature buffering the crop from cold weather events and can be used modify water depth management. Figure 1. MCP sensor data for a comparison of DPW and conventional rice growing systems. Water depth, minimum and maximum daily temperatures at 15 cm above the soil and total relative soil moisture are shown. The multi-level capacitance probe (MCP) sensor just prior to rice harvest. — 42 IREC Farmers' Newsletter No. 200 — Spring 2018 In-field water sensing