Comparative Effects of Superhydrophobic Sand and Plastic Mulches on Growth and Yield of Sweet Pepper (Capsicum annum L.) under Arid Environments

Superhydrophobic sand (SHS) is a plastic-free mulching technology that reduces surface evaporation of water from irrigated soils. Here, we present the results of two experimental field trials conducted in the 2019-20 and 2021-22 cropping seasons, comparing the efficacy of SHS with those of traditional plastic mulches on the growth and yield performance of sweet pepper (Capsicum annum L.) plants. The experiments were conducted at the King Abdulaziz University (KAU) agriculture research station at Hada Al-Sham (21 & ring;48'3''N, 39 & ring;43'25''E), Al-Jamoom, Saudi Arabia. The effects of bare soil (i.e., control treatment), 5 mm SHS thickness, and 10 mm SHS thickness, along with white and black plastic mulches (120-lm-thick polyethylene) were recorded on the plants via a randomized complete block design with three replicate plots. We found significant benefits of all of the mulches during the 2021-22 season, as evidenced by 51% (P < 0.001), 31% (P = 0.0102), and 32% (P = 0.0048) more fruits for the 10-mm SHS, white plastic, and black plastic mulches, respectively, compared with the unmulched controls. Consequently, the total fruit yield per plant increased by 112% (P = 0.000), 71% (P < 0.001), and 83% (P < 0.001), under 10 mm SHS, white plastic, and black plastic mulches, respectively. Curiously, the field trial conducted in 2019 in an adjacent field did not reveal significant benefits of SHS, which we attribute partially to erratic rain showers and field heterogeneity. Taken together, this study and our previous work show that 10-mm-thick SHS mulch is optimal for boosting irrigation efficiency in regions where water is a limiting factor. Unlike plastic mulches, SHS biodegrades in < 1 year and becomes a part of the sandy soil matrix, thereby obviating landfilling. Thus, the benefits of SHS exceed those of plastic mulches in terms of closing the yield gap and carbon footprint. These findings underscore the potential of SHS as a sustainable solution for growing plants in hot and dry arid regions in Saudi Arabia and globally.