Root and Shoot Dry Matter Yield of Soybean Plants Subjected to Nickel Rates and Two Soil Base-Cation Saturation Ratios.

Nickel (Ni) was established as a micronutrient for higher plants for over thirty years.  The existence of Ni deficiency is becoming increasingly apparent in crops, especially for those ureide-transporting Fabaceae species, like soybean. Notwithstand, it is not included in programs of fertilization for Brazilian crops.  The aim of this study was to evaluate the effect of Ni rates to soybean plants subjected by two soil base-cation saturation ratios in order to evaluate the root and shoot dry matter yield. The experiment was carried out in greenhouse conditions. was used two soil base-cation saturation ratios (50 to 70%) with five Ni rates (0, 0.1, 0.5, 1.0 and 10 mg dm^-³) applied to Hapludox soil. Soybean plants was grown until the early grain filling stage (R5), when it was harvested and fractionated, on shoot  and root (without nodules). The base-cation saturation ratios did not influence the roots development. Applying regression analysis to Ni rates as function to soil base-cation saturation ratios was not observed difference at saturation of 50% while at saturation of 70% the highest dry matter yield was observed. Besides, Ni rate as related to highest dry matter increase was of 5.46 mg dm^-³ Ni. The highest dry matter shoot accumulation was reached by the base-cation saturation ratio of 50%. The regressions for Ni rates as regarding to that base-cation saturation ratio showed a negative linear response from the lower to higher Ni rate to shoot dry matter production.  Ni interferes negatively on shoot dry matter yield of soybeans while its effects to soil are depending of base-cation saturation ratio.