Zinc Uptake from Soils

Abstract

Characterizing zinc availability by soil testing provides important information on the pool size of zinc potentially available for uptake. Concentrations of zinc in soil solution, particularly at high soil pH, however, are very low and mobility and transport to the root surface are usually rate limiting factors of soil supply. Utilization of potentially available zinc is thus mainly or exclusively confined to rhizosphere soil. Root-induced changes in the rhizosphere are of particular imporatance for zinc uptake from soils. In soils of high pH, rhizosphere acidification by supply of ammonium nitrogen, or for legumes by N2 fixation, are effective mechanisms in enhancing zinc mobilization. The same holds true for rhizosphere acidification or enhanced excretion of organic acids and chelators as root responses to deficiency of phosphorus or iron. Root colonization by V A mycorrhizae increases spatial availability of zinc similarly to that of phosphorus. Mycorrhizal plants usually have higher zinc contents in the shoot dry matter and are less sensitive to zinc deficiency than non-mycorrhizal plants. As a rule, all factors which impair root colonization by V A mycorrhizae, including high levels of soil or fertilizer phosphorus, tend to decrease zinc contents in plants and increase the risk of zinc deficiency in plants grown on soils low in extractable zinc. Marked genotypical differences in zinc efficiency are usually caused by differences in zinc acquisition from soils. In lowland rice zinc deficiency is widespread in neutral and alkaline soils. Elevated bicarbonate concentrations are the major factor responsible for low zinc contents in rice plants grown on high pH soils, high in organic matter. In such soils the high bicarbonate concentrations impair zinc uptake by direct inhibition of root growth and activtiy.

Long-term effect of high phosphorus doses on zinc status of maize on a non-calcareous loamy soil

“…As it was observed before, the extractable Zn in soils had not decreased at all, or only slightly at high P supply (Warnock 1970, Marschner 1993). In our former greenhouse experiment (Kremper and Seres 2010) we also observed that Zn deficiency occurred even at high extracted Zn content when The effect of treatments on the yield elements of maize.…”

Variable Responses of Lowland Tropical Forest Nutrient Status to Fertilization and Litter Manipulation

“…In the plots with added N, we can attribute the greater availability of Zn to the decrease in soil pH as a consequence of N-fertilization. The concentrations of Zn in solution are inversely related to soil pH (Marschner 1993) and the sorption of Zn in clay soils increases rapidly above a pH of 5 (Cavallaro and McBride 1984). The decrease in soil pH of half a unit in the plots with added N (from 5.4 to 4.9) appears to have been sufficient to mobilize extra Zn.…”

Hydrolysed wool: a novel soil amendment for zinc and iron biofortification of wheat

“…Zinc fertilization, e.g. applied as zinc sulphate (ZnSO 4 ), is an effective method to increase Zn plant uptake, but its effect is often of short duration, especially on calcareous soils (Marschner 1993). Similarly, decreasing pH, e.g.…”