Application of Zinc Modified Biochars to Enhance Zinc Availability, Speciation and Pearl Millet Growth in Zn-Deficient Soil

Abstract

Zinc deficiency poses a serious threat to numerous crops and global human population. Recently, soil biochar
amendment has been promoted as a sustainable farming method. However, its consequence on the bioavailability of Zn
in cereal crop has not been fully addressed. In the present study, 0.01% Zn-SO4 (w/w) was loaded in fruit waste, farmyard
manure and coconut shell pyrolysis at 400℃, for 2 h to make fruit waste Zn-modified biochar (FWZn-MBC), farmyard
manure Zn-modified biochar (FYZn-MBC) and coconut shell Zn-modified biochar (CSZn-MBC). Except control
treatment, all the modified biochars were applied at 1, 2 and 4% doses on zinc availability, speciation, pearl millet growth
and chemical properties in Zn-deficient soil. The obtained results show that Zn mobility in soil was 70.04% with
application of FYZn-MBC 4% as compared to other treatments. The maximum uptake of Zn in shoot and root by pearl
millet plant was observed by 74.02 and 53% with addition of FYZn-MBC 4% as compared to control soil, due to increase
of soil organic matter. The chlorophyll SPAD values in the pearl millet aerial surface increased from 30.23 to 39.24%
with application of FYZn-MBC 4% than control soil. The exchangeable fraction of Zn increased from 7.34 to 14.71%
with application of FYZn-MBC 4%. The correlation matrix results indicated that CaCO3 positively correlated with soil
pH, and soil organic matter had strong correlation with chlorophyll. Overall, future studies must be carried out to examine
the long-term impact of FYZn-MBC 4% on Zn phyto-availability in Zn-deficient soil.