Interactive effects of drought, organic fertilizer, and zinc oxide nanoscale and bulk particles on wheat performance and grain nutrient accumulation.

Drought (40% field moisture capacity), organic fertilizer (O-F; 10%), and nano vs. bulk-ZnO particles (1.7 vs. 3.5 mg Zn/kg) were assessed in soil to determine their interactive effects on wheat performance and nutrient acquisition. Drought significantly reduced (6%) chlorophyll levels, whereas nano and bulk-ZnO alleviated some stress, thereby increasing (14-16%) chlorophyll levels, compared to the control. O-F increased (29%) chlorophyll levels and counteracted Zn's effect. Drought delayed (3-days) panicle emergence; O-F, nano and bulk-ZnO each accelerated (5-days) panicle emergence under drought, relative to the control and absence of O-F. Drought reduced (51%) grain yield, while O-F increased (130%) yield under drought. Grain yield was unaffected by Zn treatment under drought but increased (88%) under non-drought condition with bulk-ZnO, relative to the control. Drought lowered (43%) shoot Zn uptake. Compared to the control, nano and bulk-ZnO increased (39 and 23%, respectively) shoot Zn in the absence of O-F, whereas O-F amendment enhanced (94%) shoot Zn. Drought increased (48%) grain Zn concentration; nano and bulk-ZnO increased (29 and 18%, respectively) grain Zn, relative to the control, and O-F increased (85%) grain Zn. Zn recovery efficiency was in the order O-F > nano-ZnO > bulk-ZnO, regardless of the water status. Grain Fe concentration was unaffected by drought, under which O-F significantly reduced grain Fe, and nano-ZnO significantly reduced grain Fe, in the absence of O-F. Nano and bulk-ZnO also significantly reduced grain Fe, with O-F amendment under drought. Drought can have dire consequences for food and nutrition security, with implications for human health. This study demonstrated that drought-induced effects in food crops can be partially or wholly alleviated by ZnO particles and Zn-rich O-F. Understanding the interactions of drought and potential mitigation strategies such as fertilization with Zn-rich organic manure and ZnO can increase options for sustaining food production and quality under adverse conditions.