Studying the impact of residual soil nanomaterials is a promising challenge for sustainable agricultural development to improve soil health and crop productivity. The objective of this study is to assess the long-term impacts of 50, 100, and 250 mg kg⁻¹ soil of nanobiochar (nB) and nano-water treatment residues (nWTR) on the fertility, biological activity, and yield of maize (Zea mays L.) growing in heavy metal-contaminated soils. The results showed that when nB and nWTR were added in larger quantities, the concentrations of lead (Pb), nickel (Ni), cadmium (Cd), and cobalt (Co) extracted with DTPA decreased. With the addition of nB or nWTR, it also showed a significant increase in exchangeable cations, cation exchange capacity (CEC), soil fertility, soil organic matter (OM), microbial biomass carbon (MBC), and a decrease in soil salinity and sodicity. Catalase and dehydrogenase activities rose as nB addition increased, while they decreased when nWTR addition increased. In comparison to the control, the addition of nB and nWTR greatly boosted maize yield by 54.5–61.4% and 61.9–71.4%, respectively. These findings suggest that the researched nanomaterials’ residual effect provides an eco-friendly farming method to enhance the qualities of damaged soils and boost maize production. Our research suggested that adding recycling waste in the form of nanoparticles could immobilize heavy metals, improve soil characteristics, and increase the soil’s capacity for productivity.

The variety of navel orange known as “Cara Cara” trees are greatly affected by soil salinity, which adversely influences yield and quality. Therefore, adopting the use of safe and inexpensive materials is crucial in this case. Herein, bio-stimulants (whey protein hydrolysates, and humic acid), and ascorbic acid could be utilized to promote plant growth in both normal and salt-stress environments. Two field trials were implemented to investigate the response of navel orange trees to whey proteins hydrolyzed (WPH) with pepsin (PEH at a concentration of 1000 mg L ⁻¹ ) and papain (PAH at a concentration of 1000 mg L ⁻¹ ), or ascorbic acid (ASA) at a concentration of 1000 mg L ⁻¹ , and/or humic acid (HA) (applied to the soil at a concentration of 1000 mg L ⁻¹ ). The changes in fruit yield, fruit quality, physio-biochemical attributes, and antioxidant defense systems under salinity stress (with an electrical conductivity of 5.14 dS m ⁻¹ ) were estimated. All treatments involving HA with WPH or ASA significantly improved various fruit yield and quality traits, physiological and photosynthetic performance attributes as well as enzymatic and non-enzymatic antioxidants, comparing to the check treatment in both seasons. In this context, PEH + HA treatment was the efficient practice for increasing fruit yield per tree by 80.3 and 82.7%, total acidity by 162.3 and 250.0%, vitamin C by 10.7 and 13.6%, total soluble solids by 12.5 and 8.3%, net photosynthetic rate by 82.3 and 80.9%, relative water content by 27.9 and 28.0%, and membrane stability index by 44.2 and 43.0%, while decreasing electrolyte leakage by 56.0 and 57.0%, and malondialdehyde by 57.8 and 58.3% during two seasons, respectively, as compared to check treatment. Also, PEH + HA treatment showed the highest potentiality for ameliorating the defensive mechanism indices elevating catalase by 17.3 and 17.2%, super oxide dismutase by 122.2 and 122.1%, and glutathione by 97.9 and 99.0%, while suppressing hydrogen peroxide by 45.7 and 45.6% and superoxide radical by 47.9 and 49.3%, during the two seasons, respectively, as compared to the check treatment. Furthermore, it should be mentioned that the values of most fruit yield and quality traits, photosynthetic efficiency, physiological performance and ant-oxidative indices obtained with application of PAH + HA and ASA + HA treatments were as similar as those of gained by PEH + HA. Therefore, the outcomes of the current study indicated that using integrated PEH + HA, PAH + HA and ASA + HA treatments are considered helpful practices for growing citrus plants and maintaining yield and quality in saline soil circumstances.

Recycling plant residues for use as mulch avoids negative environmental impacts and promotes sustainable agriculture by providing a safe and low-cost substrate. Toward this goal, a field experiment was conducted over two successive seasons (2023 and 2024), on 13-year-old ‘Le-Conte’ pear trees to investigate the effects of different organic mulch materials applied at two coverage areas (1 and 2 m ² ) on soil properties, vegetative growth, productivity, fruit quality, and weed growth. The results demonstrated an overall positive effect of mulching on evaluated parameters in general. Mulching with sugarcane stalks at 2 m ² showed the highest values of soil nutrients, i.e., P (0.006% and 0.0037%) and K (0.017% and 0.009%) in the first and second seasons, respectively. On the other hand, mulching with rice straw at a 2-m ² coverage area showed the greatest reduction in soil temperature, approximately 3.25°C in the first season and 3.42°C in the second season, while increasing soil moisture content by approximately 3.49% and 5% in both seasons, respectively. In addition, it increased leaf relative water content (RWC) by approximately 42.8% and 22.5% in the first and second seasons, respectively. Moreover, mulching with rice straw at a 2-m ² coverage showed improvements in vegetative growth and also increased tree yield by 60.27% and 43.18% in the first and second seasons, respectively. In addition, it improved fruit quality, including firmness, vitamin C content, and soluble solids content (SSC) in both seasons. The study confirms that recycling agricultural residues into mulch supports key SDGs, including zero hunger (SDG 2) through increased yield and climate action (SDG 13) through improved soil health. Adopting this practice is a significant step toward sustainable food systems.