Eco-physiological and growth responses of two halophytes to saline irrigation and soil amendments in arid conditions

In dry-land regions, salinity stress and poor soil structure can cause significant challenges to agricultural productivity, posing a growing threat to global food security. This study explores the performance of two halophytic plant species Sweet Clover (Melilotus officinalis) and Salt-bush (Atriplex canescens) under both fresh water and saline water irrigation, combined with four soil amendment treatments: manure + sandy, compost + sandy, clay + sandy, and sandy soil. Saline irrigation led to a marked decline in key chlorophyll fluorescence parameters, such as chlorophyll content (SPAD), the quantum efficiency of photochemical processes (Φ_PSII), apparent electron transport rate (ETR), and maximal photochemical efficiency (F_V/F_M) in sandy soil. Photosynthetic pigments, including chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids, were similarly reduced by 20 to 35% under saline conditions in sandy soil. However, oxidant and antioxidant enzyme activities, such as hydrogen peroxide (H₂O₂), malondialdehyde (MDA), protein content, and ascorbate peroxidase (APX), increased by 15 to 28%, while catalase (CAT) activity decreased by 17%, under the same conditions. Saline irrigation also altered ion balance, with a rise in chloride levels and in reduced nitrate and ammonium concentrations in sandy soil. Remarkably, growth traits such as plant height, dry weight per plant, and overall yield of both species increased under saline irrigation in sandy soil. Yet, soil amendments, particularly manure + sandy and compost + sandy, alleviated the harmful effects of salinity, reducing the impact on all measured parameters. Under saline irrigation, plant height and yield were notably 20 to 37% higher with these amendments than other treatments. The findings highlight that soil amendments with manure and compost significantly improve plant productivity under saline conditions, offering a sustainable and eco-friendly approach to farming in dry-land regions. This study provides valuable insights into enhancing agricultural production by fostering resilient halophytes in challenging environments.