Maize is stressed by salt rather than water under drip irrigation with soil matric potential higher than −50 kPa in an arid saline area

Water scarcity and soil salinization are the top abiotic stresses impeding agricultural production in arid and semi‐arid regions. To evaluate maize growth is depressed by water stress or salt stress independently as well as in combination under drip irrigation, a 3‐year field experiment was conducted in the Hetao Irrigation District, north‐west China. The soil was moderately saline with ECe (electrical conductivity of saturated extract) of 7.1 dS/m. Five threshold values of soil matric potential (SMP): −10 kPa (S1), −20 kPa (S2), −30 kPa (S3), −40 kPa (S4), and −50 kPa (S5), were used to trigger a 10‐mm drip irrigation. With triplicate for each treatment, 15 plots were arranged in a randomized block design permanently during the experimental period. Results showed that the higher SMP facilitated the formation of low‐salinity zone. The water holding depths in root zone were generally above the refill point (threshold of readily available water, 0.23 cm3/cm3 for maize) during the growing seasons for all treatments, indicating maize could extract water easily from soil. Controlling SMP > −30 kPa (S1, S2, S3) produced the higher leaf area index, specific leaf area, biomass and grain yield significantly than S4 and S5; however, no significant difference in relative chlorophyll contents was detected among treatments. Grain yield was reduced by 6.8% per dS/m increase in soil ECe beyond salt tolerance of maize. Based on the soil readily available water for maize growth, crop's responses and data analysis, it could be concluded that salt stress, rather than water stress, was the key factor causing the reduced grain yield in this study. Taking into account the grain yield and water‐use efficiency, SMP threshold of −30 kPa was recommended for drip irrigation maize in this saline soil. These findings are conducive to the extension of drip irrigation, and increasing the resilience of crop production under the arid saline condition.