Decision Support Tool to Predict Panicle Initiation in Aerobic Rice

Aerobic rice cultivation offers the potential to reduce irrigated water use. A multitude of challenges, such as cold sterility, drought stress, and labor shortages, limit its adoption in temperate rice-growing regions. Increasing the duration and extent of soil moisture tension between irrigation events has been demonstrated to slow crop development. Delaying panicle initiation (PI) beyond the optimal window can expose rice to cold nighttime temperatures during the cold sensitive early pollen microspore, severely reducing yield. Tools to assist Australian temperate farmers and researchers in the irrigation management of aerobic rice to ensure PI occurs during the optimal window do not yet exist. Using data collected from an aerobic rice experiment conducted in temperate Australia in 2020-2021 and 2021-2022, a predictive model was built to assist in forecasting PI based on the timing of irrigation. Estimation of the area on an hourly basis of the cumulative evapotranspiration with rainfall subtracted from pre-emergent irrigation to PI, defined as the irrigation deficit integral, was used to account for the frequency, duration, and extent of soil moisture deficit between irrigation events. The relationship between the irrigation deficit integral and the number of days from pre-emergent irrigation to PI (R-2 = 0.91) was used to build a model to predict PI with a root mean square error of 1.8 days for the validating data set. Furthermore, an example is provided of how the model can be used as a decision support tool to assist researchers and growers to schedule irrigation of aerobic rice to ensure PI occurs in a timely manner. This will increase the likelihood of high-yielding aerobic rice and may enhance the adoption of water-saving rice cultivation.