Responses of two genotypes of Lupinus albus L. to zinc application on an alkaline soil

Abstract

Lupinus albus L. grown on alkaline soils shows symptoms resembling zinc (Zn) deficiency. This study tested whether Zn deficiency is an important cause of poor growth of this species on alkaline soils. We examined the responses of two L. albus genotypes (75B09–02 and Kiev Mutant) to application of zinc sulfate (ZnSO₄) (0–200 mg Zn per 3 kg soil) on an alkaline soil (pH 7.7), and compared plant growth on the alkaline soil with the growth on an acid loam (pH 4.8) and an acid sand (pH 5.1). The possible effects of iron (Fe) chlorosis and impaired nitrogen (N₂) fixation on the growth were minimized by foliar spray of ferrous sulfate (FeSO₄) and urea, respectively. The results showed that plants on the alkaline soil with low Zn supply showed Zn‐deficiency symptoms, and 75B09–02 was less sensitive to the deficiency than cv. Kiev Mutant. Increasing Zn application greatly increased Zn concentration in plant and reduced the deficiency symptoms, but only slightly improved plant growth. Zinc concentrations in the youngest fully expanded leaflets of Kiev Mutant were generally higher than those of 75B09–02 at given Zn levels. At the treatment of 10 mg Zn per 3 kg soil, shoot growth decreased by 22–41 % for 75B09–02 and by 31–44% for Kiev Mutant grown on the alkaline soil compared to that on the acid soils. In conclusion, 75B09–02 appeared to be more tolerant to Zn deficiency and be better adapted to the alkaline soil than Kiev Mutant. However irrespective of genotypes, plant growth was more responsive to soil alkalinity (high pH associated factors) than to Zn deficiency on the alkaline soil.