Quantitative evaluation of the grain zinc in cereal crops caused by phosphorus fertilization. A meta-analysis

Zinc (Zn) deficiency is a well-documented worldwide problem for crops and humans. Although phosphorus (P) fertilizer application achieves high grain yield in intensive agricultural systems, it can reduce Zn availability in cereal grains. Therefore, a quantitative evaluation of the P–Zn antagonism is needed. A global meta-analysis of 51 publications with wheat, maize, and rice was performed to quantitatively analyze the effect of P application on grain Zn concentration. Phosphorus application reduced grain Zn concentration by 16.6% for wheat, 20.2% for maize, and 0% for rice. Phosphorus application did not affect soil available Zn concentration but, averaged across the three crops, significantly decreased root Zn concentration by 9.94%; the reduction was associated with a reduction in colonization of roots by arbuscular mycorrhizal fungi. Phosphorus application did not affect shoot-to-root or grain-to-straw ratios of Zn concentration, indicating that Zn translocation and remobilization within the plant were not reduced by P application. Especially for wheat and maize, the P–Zn antagonism was explained by a “dilution effect” and the suppression of Zn uptake efficiency by roots rather than by a suppression of translocation and remobilization. In addition to partially explaining the cause of the P–Zn antagonism, this is the first study using meta-analysis method to quantitatively demonstrate a P–Zn antagonism for Zn concentration in wheat and maize. Biofortification for increasing the grain Zn concentration may benefit from an increased understanding of how P application affects rhizosphere and root processes.