Quantifying water stress of safflower (Carthamus tinctorius L.) cultivars by crop water stress index under different irrigation regimes

Ehsan Bijanzadeh,Seyed Mojtaba Moosavi,Fatemeh Bahadori

doi:10.1016/j.heliyon.2022.e09010

Abstract

Infrared thermometry allows evaluating water status of the crop by measuring crop water stress index (CWSI), without the need of physical contact to leaves. In order to quantify water stress by CWSI and finding the best irrigation regime a two-year field experiment was conducted in safflower during 2017 and 2018 growing seasons at Darab, Fars province, Iran. Two safflower cultivars (Goldasht and Local Isfahan) and four irrigation regimes consisted of well-watered [Irrigation based on 100% field capacity (FC)], mild (75% FC), severe (50% FC), and most severe (25% FC) water stress were arranged as split plot according to randomized completely block design with four replicates. The relationship between vapor pressure deficit (VPD) and canopy-air temperature differences (Tc-Ta) was plotted under upper (fully stressed) and lower baselines (non-stressed) equations. In two cultivars, by VPD increment, the distance between upper and lower base lines increased. In Goldasht, the upper baseline (Tc-Ta)ul, was 7.8 °C in 2017 and 8.9 °C in 2018. From April to July when air warmed, Tc-Ta differential was increased up to July and the highest seasonal CWSI (0.72–0.77) were obtained in Local Isfahan under most severe water stress. In 2017, under water stress, the highest relative water content (RWC; 55%), color quality (6–7) and water use efficiency (WUE; 2.69 g m−2 mm−1) was observed in Goldasht under mild water stress which was more than 2018 and Local Isfahan. It might be attributed the more tolerance of Goldasht to water stress and lower air temperature and evaporation in the first year. CWSI with total water consumed (R2 = 0.88∗∗), RWC (R2 = 0.87∗∗), color quality (R2 = 0.75∗) and seed yield (R2 = 0.83∗∗) related, negatively. Overall, a mild water stress (75% FC) with 0.28–0.33 seasonal CWSI had higher RWC, color quality, WUE, with an acceptable yield, which could be the best irrigation regime under water deficit conditions for safflower.

Highlights

Safflower (Carthamus tinctorius L.) is a main crop in arid and semiarid fields of the world because of water stress limitations and cultured in marginal lands which are dry, periodically (McPherson et al, 2004)
Results showed that mean seasonal crop water stress index (CWSI) amounts in second year was more than the first year due to higher mean temperature and evaporation from April to July of the 2018 growing season (Table 2), and in Local Isfahan was higher than Goldasht which demonstrated the susceptibility of Local Isfahan to water stress
Our results showed that in all water stress levels, seed yield in Goldasht was more than Local Isfahan and in might be related to better adaptation of this cultivar to water stress conditions from flowering to seed maturity stages compared to Local Isfahan

Summary

Introduction

Safflower (Carthamus tinctorius L.) is a main crop in arid and semiarid fields of the world because of water stress limitations and cultured in marginal lands which are dry, periodically (McPherson et al, 2004). Vegetative and reproductive stages of safflower are sensitive to water stress (Koutroubas et al, 2009; Bijanzadeh et al, 2013). These main developmental stages are affected by some physiological reactions, which may decrease crop growth and seed yield. The onset of dry and hot conditions during the seed filling phase affected the photosynthesis rate, dry matter remobilization, and the sink size of safflower seeds The abiotic stresses such as water stress decline photosynthesis and crop nutrient uptake which caused decreasing of safflower seed yield (Koutroubas and Papakosta, 2010). Water stress in the soil during the flowering to seed filling of safflower, declined yield components and yield, negatively (Movahhedy Dehnavy et al, 2009; Koutroubas et al, 2009; Tabib Loghmani et al, 2019)

Methods

Results

Conclusion