The Dynamic Yield Response Factor of Alfalfa Improves the Accuracy of Dual Crop Coefficient Approach under Water and Salt Stress

Abstract

The accurate quantification of crop water use or evapotranspiration (ET) under water and salt stress is needed for efficient water management and precision irrigation in water scarce regions. However, few studies were examined on alfalfa water use and its components under water and salt stress. We carried out two field experiments to quantify alfalfa water use through setting up different water and salt gradients, including two irrigation levels (full and deficit irrigation) and four soil salinity levels (0, 2‰, 4‰ and 6‰ salt of mass ratio) in an arid region of Northwest China. Electrical conductivity of soil saturation extract (ECe), soil water content (SWC), leaf area index (LAI) and soil evaporation (E) were measured. The SIMDualKc model, which uses the FAO56 dual Kc approach, was calibrated and validated using measured SWC and E. Model results show a good agreement between observed and simulated SWC and E without stress. The depletion fraction for no stress (p) and the percent yield reduction per unit increase in soil salinity (b) were 0.50 and 6.0%/(dS m−1), respectively, slightly lower than those of FAO-56 (0.55 and 7.3%/(dS m−1)). The difference indicates that alfalfa has a lower capacity of water use but a greater tolerance to salt stress after soil salinity reached its sensitivity threshold in the arid region. The model performed a reduced accuracy under water and salt stress and the differences tended to increase as stress increased, which was partly attributed to constant yield response factor (Ky) under different soil water and salt stress. The key parameter Ky dynamically increased with the increased degree of stress. Compared to constant Ky, the simulations of SWC and E showed improved accuracy with dynamic Ky. These results suggested that the response and acclimation of alfalfa to stress might be incorporated into the dual Kc model through the diversity of Ky.

Effect of precipitation change on the photosynthetic performance of Phragmites australis under elevated temperature conditions

“…The high limitation on the plant carbon assimilation capacity under soil water deficient conditions has been a major reason for plant growth and crop productivity reduction ( Hussain et al, 2021 ; Nolf et al, 2015 ). It is widely accepted that there are two ways in which water stress affects the photosynthesis of plants: one is the stomatal limitations, such as closing the stoma and lowering the stomatal conductance ( Daryanto, Wang & Jacinthe, 2017 ; Talbi et al, 2020 ); the other is non-stomatal limitations, such as photosynthetic phosphorylation ( Du et al, 2021 ), regeneration of ribulose-1,5-bisphosphate (RuBP) ( Song et al, 2016a ), activation of Rubisco and the synthesis of ATP ( Ashraf & Harris, 2013 ; Hu et al, 2020 ). The stomatal limitation is generally considered as the main factor responsible for the reduction of photosynthesis under drought stress environment ( Liu et al, 2005 ; Song et al, 2020 ).…”

“…The photosynthesis of plants is regarded as the most sensitive process to high temperature stress ( Xalxo et al, 2020 ). High temperature lasting for only a few minutes to several hours will drastically damage the structure and function of photosynthetic apparatus such as thylakoid lamella and stroma, decrease the production of ATP, inhibiting a series of enzyme activities, affect the transport of photosynthetic electrons and reduce the photosynthetic rate finally ( Hu et al, 2020 ). Heat stress can also cause photosynthesis decline through enhancing the generation of reactive oxygen species (ROS) ( Hao et al, 2019 ), destroying the function of PSII ( Jahan et al, 2021 ; Janka et al, 2015 ) suppressing the synthesis of chloroplast ( Song, Wang & Lv, 2016 ), and inhibiting the activity of ribulose1,5-bisphosphate carboxylase/oxygenase (Rubisco) ( Perdomo et al, 2017 ).…”

Dynamics of Spring Regrowth and Comparative Production Performance of 50 Autumn-Sown Alfalfa Cultivars in the Coastal Saline Soil of North China

“…However, high salt concentrations, a shallow saline groundwater table, freshwater shortages, and high evaporation are the major limitations for normal and optimum crop production in these coastal regions [7,9,10]. An early spring with poor rainfall would not leach salts out of the root zone, which can severely restrict crop productivity [4,11]. Therefore, cultivation of salt-and drought-tolerant forage plants is particularly important in this region in order to better utilise these land resources to meet the demands of the livestock population.…”

“…Alfalfa planting and cultivar selection should be primarily recommended, keeping in view the edaphic and environmental conditions of a certain region [11,21], with soil, rainfall, and air temperature as the most important contributors [21]. Salinization is a frequent productivity-limiting factor due to the water deficit.…”

Water Requirements of Crops under Various Kc Coefficient Approaches by Using Water Evaluation and Planning (WEAP)

“…The dual-Kc approach is more accurate to calculate (ETc), where depends on the soil texture, climate conditions and characteristics of crops with requires good knowledge of crop science [7,8]. The simple approach (Single-Kc) mixed coefficient of evaporation from soil (Ke) with the transpiration coefficient (Kcb) in one coefficient (Kc) [9]. But in complex approach (Dual-Kc), it separates two coefficient of soil and of transpiration (Kcb and Ke).…”