An Empirical Model to Predict the Rice Crop Response to the Total Soil Water Potential and Soil Compaction under Irrigation with Alternate Wetting and Drying Technology

Alternate wetting and drying (AWD) is a water-saving technology that flooded rice fields can apply to
reduce water use in irrigated fields. This study aims to predict rice production by the function of total soil water
potentials, and to examine the relationship between the total soil water potential (TSWP, Ψt) and soil compaction.
A field experiment was carried out during the summer season of 2022, the treatments were either maintained
flooded, equilibrated to −10 kPa (A0), or dried to −20 kPa (A1), or dried to −30 kPa (A2) and then re-flooded at the
water potential of −10 kPa (A0 - control). The previous treatments were along with two nitrogen levels (N1 = 124,
and N2 = 165 kg N ha−1) that represents 75 and 100% of the recommended dose with three replications. The AWD
increased the pores percentage slightly, but it has a clear trend in increasing the soil mechanical resistance and
macro-porosity. Also, the TSWP function could be used to predict the rice yield in early time. The AWD technique
(at matric potential of −20 kPa) could save water to about 25% with a relative yield (Yr) of 70% (at 75% N level).
This investigation showed the possibility of using simple empirical tool to describe the rice crop response to the Ψt
changes and soil compaction using a low number of inputs with an accurate and rapid determination. These results
have shown a high agreement between the predicted values and the experimental (R2) at a range of (0.91–0.97).