Could regulated and sustained deficit irrigation be applied in temperate climates? A case study of soybean production under field conditions

A field experiment was conducted to study the effects of full (F), regulated (RDI), and sustained deficit irrigation (SDI) on yield (Y), evapotranspiration (ET), and water use efficiency (WUE) of drip irrigated soybean. The yield response factor (Ky) was calculated to express the effect of water stress on soybean yield. The water balancing approach was used to schedule irrigation. Daily water used for plants' evapotranspiration was calculated by multiplying reference evapotranspiration with crop coefficients. Irrigation started when readily available water in the soil layer of 0.4 m was completely depleted by plants. There were statistical differences in yield between F (4.60 t ha−1) and SDI (3.71 t ha−1) treatments, but not between F and RDI (4.44 t ha−1). The evapotranspiration rate varied between 439 and 535 mm under irrigation and between 193 and 306 mm under rainfed conditions. The WUE values were consistent with the yield of the treatments. The statistical difference in soybean yield between F and SDI strategies suggests that the SDI cannot be used in the region's soybean farming. As no water savings were recorded for the same level of soybean yield between F and RDI, it indicates that RDI is not beneficial under the temperate climate of the Vojvodina region. The yield response factors of 0.69 and 0.71 in 2022 and 2023, respectively, show that soybean is tolerant to water stress and could be grown in rainfed conditions in Vojvodina's temperate climate. However, to achieve high and consistent yields, irrigation is advised. •Regulated deficit irrigation did not contribute to water savings.•Sustained deficit irrigation is not suitable for soybean production in regions with temperate climates.•The yield response factors of 0.69 and 0.71 in 2022 and 2023, respectively, show that soybean is tolerant to water stress.•The rate of soybean evapotranspiration varied between 439-535 mm under irrigation and 193-306 mm under rainfed conditions.