Effect of nickel on yielding and mineral composition of the selected vegetables

Over the three-year pot experiment the investigations were made on nickel influence on yielding and mineral composition (K, Ca, Mg, P, Fe and Ni content) of lettuce and spinach leaves as well as zucchini and bean fruits. The experiment was differentiated regarding nickel content (NiSO4 ·7H2O) introducing: 0 (control); 10; 40 and 60 mg Ni·kg -1 sand, at the same time considering various nutritive requirements of the plant species studied. The obtained results indicate that even the lowest nickel dose applied (10 mg Ni·kg-1 substrate) has caused a significant decrease of yield of the usable parts of lettuce, spinach, zucchini and bean. Further increase of nickel content in the substrate (40–60 mg Ni·kg-1) resulted in more intensive yield drop of lettuce and spinach leaves. Under such conditions due to improper generative development, no generative yield of zucchini and bean was obtained. Nickel at amount 10 mg Ni·kg-1 substrate affected the significant growth of potassium concentration in the leaves of lettuce, phosphorus in spinach leaves, while it decreased phosphorus and potassium concentration in the zucchini and bean fruits causing at the same time significant fall in magnesium content in zucchini fruits and increase in Mg concentration in bean pods. Nickel dose growth in the substrate has differentiated changes in the plant mineral composition to a greater extent. Nickel at amount 10 mg Ni·kg-1 substrate influenced a significant iron growth in spinach leaves, zucchini fruits and bean pods, whereas it decreased Fe content in lettuce biomass. Increased nickel doses have reduced Fe concentration significantly in the usable organs of the vegetable species examined. Generally the growing nickel quantity in substrate affected the successive increase of this metal content in the usable organs of the vegetable species investigated.