Effects of superhydrophobic sand mulching on evapotranspiration and phenotypic responses in tomato (Solanum lycopersicum) plants under normal and reduced irrigation

Abstract

Irrigated agriculture in arid and semi-arid regions is a vital contributor to the global food supply. However, these regions endure massive evaporative losses that are compensated by exploiting limited freshwater resources. To increase water-use efficiency in these giga-scale operations, plastic mulches are utilized; however, their non-biodegradability and eventual land-filling renders them unsustainable. In response, we have developed superhydrophobic sand (SHS) mulching technology that is comprised of sand grains or sandy soils with a nanoscale coating of paraffin wax.Here, we investigate the effects of 1 cm-thick SHS mulching on the evapotranspiration and phenotypic responses of tomato (Solanum lycopersicum) plants as a model system under normal and reduced irrigation inside controlled growth chambers.Experimental results reveal that under either irrigation scenario, SHS mulching suppresses evaporation and enhances transpiration by 78% and 17%, respectively relative to the unmulched soil. Comprehensive phenotyping revealed that SHS mulching enhanced root xylem vessel diameter, stomatal aperture, stomatal conductance, and chlorophyll content index by 21%, 25%, 28%, and 23%, respectively, in comparison with the unmulched soil. Consequently, total fruit yields, total dry mass, and harvest index increased in SHS-mulched plants by 33%, 20%, and 16%, respectively compared with the unmulched soil. We also provide mechanistic insights into the effects of SHS mulching on plant physiological processes. These results underscore the potential of SHS for realizing food-water security and greening initiatives in arid regions.

Superhydrophobic Sand Mulch and Date Palm Biochar Dramatically Boost Growth ofMoringa oleiferain Sandy Soil: Insights into Evapotranspiration Budgeting and Metabolomic Profiling

“…In related studies, plastic mulching significantly improved flowering and panicle number in M. oleifera plants 34 ; while Gliricidia biochar also showed significant positive effects on the growth of Moringa in terms of plant height, stem diameter, dry matter yield and root: shoot ratio 35 . Consistent with our findings under SHS mulching, soil water availability positively correlates with leaf area, stomatal conductance, transpiration, and biomass 24, 36 .…”

“…On account of its extreme water repellency 23, 25 , our SHS significantly reduced evaporation of water from the soil and substantially contributed to enhanced soil water retention. The water retained in the soil due to the suppressed evaporation gets channeled towards transpiration by the plant’s vascular systems 24, 26 , as was demonstrated by the significant increases in transpiration due to the SHS and SHS+biochar treatments under N or R irrigation ( Fig. 1-2 ).…”

“…The SHS used was produced using our lab-scale batch reactor by direct melting of paraffin wax via a heating process, which obviated the use of organic solvent as reported in our previous protocol [23][24][25] . A known mass of paraffin wax mixed with a known mass of sand (1:600 ratio) was heated in a rotating cement mixer for about 30 minutes until the surface of the sand particles was coated with a thin layer of the wax, i.e.…”

“…SHS is a water-repellent material comprising of sand grains coated with thin layer of paraffin wax. Applying a 0.5–1 cm-thick SandX layer as a mulch can reduce evaporative water loss from the soil by 50-80%; plants transpire more and withstand the water/heat stress, and grow better in arid environments 23, 24 . The biochar used is a nutrient-enriched biochar derived from the pyrolysis of date palm biomass as feedstock.…”

Adopting the circular model: opportunities and challenges of transforming wastewater treatment plants into resource recovery factories in Saudi Arabia

“…When applied as a 5-10 mm layer on the topsoil, SHS acts as a dry diffusive barrier and dramatically curtails evaporative water loss (Figure 4). As a result, the moisture content is significantly higher in the mulched soil that plants utilize for transpiration, nutrients uptake, and so on; consequently, plant health and yield are significantly higher as evidenced from multiyear field trials (Gallo et al 2022) and controlled environment studies on a variety of crops (Odokonyero et al 2022). Ongoing experiments in this translational research programme include quantifying the effects of SHS mulching when irrigation is facilitated via treated wastewater effluent from an anaerobic process; time-dependent loss of SHS wax layer and water repellence due to microbial activity in the soil; and scaling up SHS manufacturing.…”