Biofortification of Silage Maize with Zinc, Iron and Selenium as Affected by Nitrogen Fertilization.

Agronomic biofortification is one of the main strategies for alleviation of micronutrient deficiencies in human populations and promoting sustainable production of food and feed. The aim of this study was to investigate the effect of nitrogen (N)fertilization on biofortification of maize crop (Zea mays L.) with zinc (Zn), iron (Fe) and selenium (Se) grown on a micronutrient deficient soil under greenhouse conditions. Factorial design experiment was set under greenhouse conditions. The experiment consisted of two levels of each N, Zn, Fe and Se. The levels for N were 125 and 250 mg N kg-1 soil; Zn were 1 and 5 mg Zn kg-1 soil; levels of Fe were 0 and 10 mg Fe kg-1 soil; levels of Se were 0 and 0.02 mg Se kg-1 soil. An additional experiment was also conducted to study the effect of the Zn form applied as a ZnO or ZnSO4 on shoot growth, shoot Zn concentration and total shoot Zn uptake per plant. Shoot Zn concentrations increased by increasing soil Zn application both with ZnSO4 and ZnO treatments, but the shoot Zn concentration and total Zn uptake were much greater with ZnSO4 than the ZnO application. Under given experimental conditions, increasing soil N supply improved shoot N concentration; but had little effect on shoot dry matter production. The concentrations of Zn and Fe in shoots were significantly increased by increasing N application. In case of total uptake of Zn and Fe, the positive effect of N nutrition was more pronounced. Although Se soil treatment had significant effect, N application showed no effect on Se concentration and accumulation in maize shoots. The obtained results show that N fertilization is an effective tool in improving the Zn and Fe status of silage maize and contribute to the better-quality feed.

Effect of nitrogen and zinc fertilization on zinc and iron bioavailability and chemical speciation in maize silage.

Agronomic biofortification is one of the main strategies for alleviation of micronutrient deficiencies in food and feed. The objective of this study was to investigate the effect of N supply on total concentration of Zn and Fe and their chemical species in the soluble extracts of maize silage grown under field conditions. Total concentrations of Zn, Fe, Cu, Mn, S and P were measured by flow-injection inductive coupled plasma (ICP) - mass spectrometer (MS). Soluble Fe and Zn were extracted and analyzed by size exclusion-inductively coupled plasma mass spectrometry. Using the same set-up for total elemental and speciation analysis enabled direct quantitative comparison of the detected speciated molecules with the total element sample content. N or Zn treatment, except in control plots, did not significantly affect concentrations of Zn and Fe in the maize silage and grain samples. Significant positive correlation was observed between Zn and Fe maize silage (r = 0.64, p < 0.01) and maize grain (r = 0.85, p < 0.01) concentrations. N and Zn treatment did not affect solubility of Zn and Fe, while available Zn and Fe were affected by increase in Zn soil treatment. Soluble Zn was speciated in LMW complexes, while soluble Fe was speciated in MMW and LMW complexes.