Subsurface organic amendment of a saline soil increases ecosystem multifunctionality and sunflower yield

Area of Science:

• Agricultural Science
• Soil Science
• Environmental Science

Background:

• Salt stress critically limits crop productivity in arid regions.
• Organic amendments are vital for improving soil fertility and crop yields.
• The impact of organic amendment depth on soil health and ecosystem multifunctionality (EMF) remains understudied.

Purpose of the Study:

• To investigate the effects of surface versus subsurface organic amendment depth on soil quality index (SQI), enzyme activities, EMF, and crop yield in saline soils.
• To compare the efficacy of humic acid and manure applied at different depths.
• To elucidate the relationship between soil properties, EMF, and crop yield under varying amendment strategies.

Main Methods:

• A three-year field experiment was conducted on saline soils.
• Humic acid and manure were applied to the surface (0-15 cm) and subsurface (15-30 cm).
• Soil samples were analyzed for SQI, enzyme activities, microbial diversity, and nutrient content. Crop yield (sunflower) was measured.

Main Results:

• Subsurface organic amendment significantly improved SQI (20-47%) across deeper soil layers (0-45 cm) compared to surface application (15-51% at 0-30 cm).
• Subsurface amendment led to higher soil organic carbon and available nutrients, with lower electrical conductivity.
• EMF increased substantially under subsurface amendment (122-214% at 0-30 cm) compared to surface application (178% at 0-15 cm).
• Sunflower yield increased by 16% with subsurface amendment compared to inorganic fertilizer alone and 8% compared to surface amendment.

Conclusions:

• Subsurface organic amendment is a superior strategy for enhancing soil quality, EMF, and crop yield in saline environments.
• Deep organic matter incorporation effectively mitigates salt stress impacts by improving soil physical and chemical properties.
• Optimizing amendment depth is crucial for maximizing the benefits of organic amendments in agroecosystems facing salinity challenges.