Abstract

Few studies have attempted to investigate the combined effects of soil matric potential (Ψ_m) and osmotic potential (Ψ_s) on plant production and water use efficiency (WUE). The purpose of this study is to evaluate the synergistic and antagonistic effects of Ψ_m and Ψ_s associated with nitrogen (N) fertilization on spinach (Spinacia oleracea L.) growth traits and WUE. Five levels of salinity (1, 4, 7, 9, 11 dS m⁻¹), three levels of water use amounts including deficit-irrigation (W–), full-irrigation (W0) and over-irrigation (W+), and four levels of N application rates (0, 50, 75, and 100% of N requirement) were applied. A new parameter namely "WUE_θ" is suggested based on soil water content (θ). Results showed that water deficit combined with high saline irrigation water caused the most reduction in the plant biomass, leaf area index (LAI) and evapotranspiration (ET). The acquired plant yield coefficient (K_y) of 1.003 indicates that the spinach is a moderately salt-sensitive vegetable. The highest WUE was observed under deficit-irrigation and intermediate salinity conditions, which was attributed to an adaptation mechanism in the plant. However, WUE_θ (R² > 0.98) was a better predictor of the plant yield than WUE (R² > 0.48). Nitrogen use efficiency (NUE) decreased with increasing salinity and water deficiency. Also, Ψ_m and Ψ_s had a synergistic interaction on yield and ET, while their effect on WUE and WUE_θ was antagonistic. Salinity greater than drought reduced yield, while both had equal reducing effects on ET. Furthermore, WUE and WUE_θ were more influenced by Ψ_m than Ψ_s.

• Research Highlights

• The new parameter WUE_θ is a better predictor of the spinach plant yield than WUE.

• WUE and WUE_θ are more influenced by water potential (Ψ_m) than osmotic potential (Ψ_s).

• Synergistic interaction of Ψ_m and Ψ_s on yield and ET, but antagonistic effect on WUE and WUE_θ.

• Salinity greater than drought reduces yield, while both have equal reducing effects on ET.

• Ψ_m shows negative effects on yield and ET, but positive effects on WUE and WUE_θ.

摘要

很少有研究试图调查土壤基质势 (Ψ _m ) 和渗透势 (Ψ _s ) 对植物产量和水分利用效率 (WUE) 的综合影响。本研究的目的是评估与氮 (N) 施肥相关的 Ψ _m和 Ψ _s对菠菜 ( Spinacia oleracea L.) 生长性状和 WUE的协同和拮抗作用。五个盐度水平 (1, 4, 7, 9, 11 dS m ^-1 )，三个用水量水平，包括亏缺灌溉 (W–)、充分灌溉 (W0) 和过度灌溉 (W+)，以及应用了四个水平的氮施用率（氮需求的 0、50、75 和 100%）。一个新参数即“WUE _θ" 建议基于土壤含水量 (θ)。结果表明，水分亏缺结合高盐灌溉水导致植物生物量、叶面积指数 (LAI) 和蒸散量 (ET) 的最大减少。获得的植物产量系数 ( K _y ) 为 1.003 表明菠菜是一种中等盐敏感性蔬菜。在亏缺灌溉和中等盐度条件下观察到最高的 WUE，这归因于植物的适应机制。然而，WUE _θ (R ² > 0.98) 是比 WUE (R ² > 0.48)更好的植物产量预测因子。氮利用效率 (NUE) 随着盐度和缺水量的增加而降低。此外，Ψ _m和 Ψ _s对产量和 ET 具有协同相互作用，而它们对 WUE 和 WUE _{θ 的影响呈}拮抗作用。盐度大于干旱会降低产量，而两者对 ET 的降低效果相同。此外，WUE 和WUE _θ受Ψ _{m 的}影响比受Ψ _{s 的}影响更大。

• 研究亮点

• 新参数 WUE _θ比 WUE 更能预测菠菜植物产量。

• WUE 和 WUE _θ受水势 (Ψ _m ) 的影响比渗透势 (Ψ _s ) 的影响更大。

• Ψ _m和 Ψ _s对产量和 ET 的协同相互作用，但对 WUE 和 WUE _{θ 有}拮抗作用。

• 盐度大于干旱会降低产量，而两者对 ET 的降低作用相同。

• Ψ _m对产量和 ET 有负面影响，但对 WUE 和 WUE _{θ 有}积极影响。