Nickel sources affect soil biological properties but do not affect sorghum growth.

Nickel (Ni) is an essential element, but it can be phytotoxic in high concentration, which may be caused by high availability in soil solution. The objective of this study was to evaluate the effect of sources and doses of Ni applied to a dystrophic Red Latosol cultivated with sorghum on i) the availability of the metal in the soil; ii) the impact on biological and biochemical properties of the soil; iii) the absorption and distribution in sorghum plants; and iv) crop productivity. The experiment was carried out within a completely randomized design with two nickel sources [nickel(II) nitrate, Ni(NO) and nickel(III) oxide, NiO], three doses (35, 70, and 140 mg Ni kg soil), plus controls without Ni, with 3 replications.