Zinc-coated urea and zinc-solubilizing microbes: synergistic strategies for improving zinc bioavailability in dry region soils

Abstract

Zinc (Zn) is the most limiting micronutrient responsible for malnutrition. World Health Organization (WHO) reported deficiency of Zn is the 5^th most significant cause of death and disease in underdeveloped world. However, 70% Pakistani soils are Zn deficient and responsible for Zn deficiency in crops. The present study aimed to mitigate Zn deficiency and improve them a nd Zn use efficiencies through synergizing dry region Zn solubilizing plant growth promoting rhizobacteria (PGPR) by coating on Zn coated urea. Pre-isolated dry region Zn solubilizing isolates were evaluated for zinc solubilization, urease activity, siderophores production, organic acid production and ACC-deaminase activity. Four effective strains Bacillus amyloliquefaciens (IUB-34), Klebsiella variicola (IUB-96), Klebsiella variicola (IUB-80) and Klebsiella pneumoniae subsp. pneumoniae (IUB-93) and their consortium coated on Zn coated urea. This improved product was tested for N and Zn release pattern, growth promotion and Zn biofortification in pot trial on wheat. Results showed that SPAD chlorophyll value, root, shoot length and their dry weight was significantly improved (p≤ 0.05) by 19.4, 20.3, 45.9, 27.3 and 39.5%, respectively, over control. Similarly, N, P, K, Zn, Fe in grains and 100-grain weight was significantly increased (p≤ 0.05) by 97.5, 23.5, 61.1, 63, 32 and 50.5%, respectively, over control. The results confirmed that dry region Zn solubilizing bacterial consortium coated on Zn coated urea is an efficient method for the biofortification of Zn in wheat grains and can effectively overcome Zn deficiency in humans.