Soybean seed treatment with micro and nanofertilizer based on nickel hydroxide and nickel sulfate: evaluation of the BNF efficiency and plant growth

Abstract

Nickel (Ni) is an essential element for the metabolism of plants, being considered a micronutrient. It is a structural component of urease and hydrogenase, which in turn perform nitrogen (N) metabolism in many legume species. The objective of this work is to evaluate the application of Ni sources in the treatment of seed or leaf (in V4), if there are differences in the agronomic efficiency between the sources: 1) Ni hydroxide - micrometric dimension (5 µm), 2) sulfate of Ni and 3) nanometric (20 nm) Ni hydroxide in soybean plants; and if there is an increase in the efficiency of biological N fixation (BNF), with increase in N content in the grains produce. The accumulation (and concentration) of Ni in the grains will be determined by ICP-OES analysis. The spatial distribution of Ni in seeds treated with the sources will be done by micro-fluorescence mapping of X-ray (¼-XRF). The activities of the enzyme urease, nitrogenase, nitrate reductase, N nodulation, fresh nod mass and N accumulation in leaves and grains in the phenological stages R3.5 or R5 will be quantified as well as the evaluation of the biological nitrogen fixation (BNF), using the isotopic technique of natural abundance of 15N (´15N 0). The dry mass of grains, roots and shoot will be evaluated in R7. The cultivated species will be Glycine max, in a greenhouse, grown in sandy soil with low amount of Ni available, making six treatments, varying the sources of Ni, applied in the treatment of seeds - with Co, Mo and Bradyrhizobium japonicum - and via foliar at the phenological stage V4. The experimental design used will be the complete randomized blocks, with three Ni sources and four replicates. The biological nitrogen fixation will be quantified by determining the ureides content, by the nitrogenase activity and by means of the ´15N 0. At the end of the experiment, the plants will be harvested and separated in stem, leaves (limbus and petiole) and roots, to determine the concentrations of Ni and N. Grains will also be harvested at the end of the experiment to determine the productivity and quantity of 15N translocated to soybean seeds.