Abstract
Bio-activated organic fertilizers (BOZ) were produced by enriching the zinc oxide (ZnO)-orange peel waste composite with Zn solubilizing bacteria (ZSB: Bacillus sp. AZ6) in various formulations (BOZ1 (9:1), BOZ2 (8:2), BOZ3 (7:3) and BOZ4 (6:4)). The produced BOZs, along with ZnO, ZnSO4, ZSB were applied to maize crop (Zea mays L.) under field conditions in two different cropping season and the growth, yield, physiology, plant Zn contents and quality of maize were investigated. Results revealed significant variation in the aforementioned parameters with the applied amendments. The BOZ4 performed outclass by exhibiting the highest plant growth, yield, physiology, Zn contents, and quality. On average, an increase of 53%, 49%, 19%, 22%, 10%, 4%, and 30% in plant height was noticed with BOZ4 application over control, ZnO, ZnSO4, BOZ1, BOZ2, BOZ3, and ZSB, respectively. BOZ4 enhanced the dry shoot-biomass 46% than control. Likewise, the photosynthetic rate, transpiration rate, stomatal conductance, chlorophyll contents, carotenoids, and carbonic anhydrase activity were increased by 47%, 42%, 45%, 57%, 17%, and 44%, respectively, under BOZ4 over control in both cropping seasons. However, BOZ4 reduced the electrolyte leakage by 38% as compared to control in both cropping seasons. BOZ4 increased the Zn contents of grain and shoot by 46% and 52%, respectively, while reduced the phytate contents by 73% as compared to control. Application of BOZ4 revealed highest average fat (4.79%), crude protein (12.86%), dry matter (92.03%), fiber (2.87%), gluten (11.925%) and mineral (1.53%) contents, as compared to control. In general, the impact of cropping seasons on maize growth, yield, physiology, Zn contents, and quality were non-significant (with few exceptions). Thus, bio-activation of ZnO with ZSB could serve as an efficient and economical strategy for boosting up the growth, yield, physiological, and quality parameters of maize under field conditions.
Highlights
Zinc (Zn) is a necessary plant micronutrient owing to its substantial role in catalyzing several metabolic reactions in plants
Crude protein, fiber, gluten, and mineral contents were increased by 34%, 59%, 37%, and 32%, respectively with BOZ4, control, and 25%, 46%, 21%, and 14%, respectively, Zn solubilizing bacteria (ZSB) application
AZ6 was used as an inoculant for the production of bio-activated organic fertilizers (BOZ) with various formulations (BOZ1 (9:1), BOZ2 (8:2), BOZ3 (7:3) and BOZ4 (6:4))
Summary
Zinc (Zn) is a necessary plant micronutrient owing to its substantial role in catalyzing several metabolic reactions in plants. It is an indispensable cofactor in thousands of proteins in a biological system and involved in triggering of >300 enzymes [1]. It is needed to accomplish various essential processes in plants including resistance against environmental stresses, photosynthesis, metabolism of nitrogen and carbohydrates, cell membrane integrity, synthesis and formation of proteins and pollen, regulation of auxin, and production of antioxidant enzymes [2,3,4,5]. Despite the essential role in many plant processes, Zn deficiency in soil is posing a severe risk for sustainable agriculture worldwide. Its deficiency ranked fifth in causing disorder and death in humans in developing countries [11]
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