Seed treatment with magnesium nanoparticles alters phenology and increases grain yield and mineral content in maize

Magnesium is an essential macronutrient for maize crop and its efficiency of absorption and utilization by plants can be improved when used in the form of nanoparticles. The objective of this work was to evaluate the efficiency of different sources of magnesium oxide via seed treatment in the agronomic performance of maize. The experiments were carried out under field conditions in three locations in the state of Santa Catarina, Brazil. In all experiments, the P4285HYR-hybrid maize seeds were used, with three sources of magnesium: MgO-NPs, MgO@C-NPs and Mg(NO3)2; and six concentrations: 0 (control); 37.5, 75, 150, 300 and 600 mg L-1. The following variables were analyzed: SPAD reading, NDVI, plant height, ear insertion height, number of grains per ear, grain moisture, thousand grain weight, yield and quantification of Mg, Ca, P and K in the grains. The results showed that the seed treatment with magnesium oxide alters the V4 and V5 phenological stages (fourth and fifth developed leaves), shortening the plant life cycle by four to five days (P<0.05). All applied concentrations increased maize grain yield, with greater improvement in the order of 38% with 150 mg L-1 of MgO-NPs and 57% with 300 of MgO@C-NPs in comparison to control, respectively. The use of 75 and 150 mg L-1 of magnesium nitrate increased grain yield by only 2.3% and 6.6%, respectively, when compared to the control. The P>K>Mg>Ca levels in the harvested grains were increased by seeds treated with Mg. The results were significantly influenced by the nanoparticles, when comparing with conventional Mg nitrate or with the control. Therefore, it was concluded that the use of magnesium nanoparticles via seed treatment is a viable strategy to increase maize grain yield.