Phytomanagement: Biowastes to biofortify food and fodder plants with zinc

Some 40% of agricultural soils are deficient in zinc (Zn), an essential micronutrient for plants, animals and humans. Zinc deficiency reduces agricultural productivity and detrimentally affects the health of one-fifth of humanity. Biowaste application can alleviate Zn deficiency and improve soil fertility. In poor countries,  applying correctly treated human waste to land has the double benefit of correcting Zn deficiencies and protecting vulnerable waterways.

Biofortification has several advantages over simply adding essential trace elements to the final product, e.g. flour, or taking dietary supplements. Physiologically accumulated trace elements in plants provide a constant source of the trace element with less risk of toxicity due to an overdose, or deficiency caused by gaps in supply of the trace element-spiked product. Physiologically accumulated trace elements in plant parts are also more bioavailable to humans. If the biofortification arises from genetic modification of the crop, via either traditional breeding or in vitro gene manipulation, then recurrent costs are low, and the germplasm could be shared internationally, reaching people with limited access to commercially fortified food or supplements.

Biofortification is not restricted to humans. Livestock commonly suffer from trace element deficiencies where the trace elements occur at low concentrations in the soil. Pasture species tend to take up low concentrations of trace elements from soil compared to trees and shrubs. Poplars and willows accumulate high concentrations of Zn and Co relative to pasture species and this may be linked to observed health benefits in sheep and cattle when the trees are used as stock fodder. A potential problem of using poplars and willows as stock fodder is their high accumulation of Cd; although varieties exist that accumulate high Zn and Co, but low Cd.

On contaminated sites where the contaminant is also an essential nutrient, food or fodder crops can be produced that contain high concentrations of an essential nutrient. Broccoli and Brassica juncea (L.) could supplement Se to animal diets, when these plants are grown on contaminated soil.