Abstract
•Boron nanoparticles (BNs) improved pomegranate trees productivity.•Macronutrients rich-biochar (MNB) reduced Na+ uptake.•BNs were more effective in increasing the fruit quality in the presence of MNB.•MNB reduced reactive oxygen species and controlled oxidative stress.•The results could be helpful for saline irrigated soil management.
Boron nanoparticles (BNs) have been used to enhance the quality of pomegranate fruits, but high sodium (Na+) concentrations in the plant tissues cause oxidative stress and lessen the impact of BNs. The current study aims to study the mechanism of reducing Na+ uptake by pomegranate trees through adding biochar rich in macronutrients (MNB) such as potassium (K) and calcium (Ca), which makes BNs spraying more effective in improving the fruit quality. Pomegranate trees planted in a sandy soil and irrigated with saline water (6.18 dS m−1) were sprayed with BNs (0, 25, 50, 100 mg L−1). MNB was added to the soil at the doses of 0 or 5 kg tree−1. A two-season field experiment was conducted in a randomized complete block design with five replications. In comparison to the control, MNB resulted in a 14 and 17% increase in soil organic carbon and CEC, respectively. MNB increased the soil's available N, P, Ca, and K by 25, 23, 20, and 20%, and increased the uptake of these nutrients by 20, 40, 11, and 19% as compared with the control treatment. MNB and BNs significantly increased the fruit yield and quality compared to the control. MNB significantly increased the K+/Na+ and Ca++/Na+ ratios by 69 and 59%, respectively, while significantly reducing the leaf-Na+ by 30%. Reactive oxygen species (ROS) were mitigated by MNB, which also strengthened antioxidant defences and increased the plant's ability to produce chlorophyll. The foliar spray of BNs significantly increased the leaf-chlorophyll, soluble carbohydrates, relative water content, and proline in pomegranate plants. BNs and MNB significantly reduced the fruit cracking, and improved the quality characteristics, i.e., vitamin C, anthocyanin, and total sugar. The efficiency of BNs in decreasing the negative effects of salt stress on pomegranate productivity was improved by the soil application of MNB. The use of foliar spraying with BNs alone is not advised; instead, an integrated parenteral management strategy that relies on the addition of organic amendments, such as macronutrient-rich biochar, to the arid degraded soils, is required, especially under saline conditions.
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