Effects of zinc fertilization on grain yield and shoot concentrations of zinc, boron, and phosphorus of 25 wheat cultivars grown on a zinc-deficient and boron-toxic soil

Field experiments were carried out to study the grain yield, shoot concentr ations of zinc (Zn), boron (B) and phosphorus (P), and tolerance to Zn defi ciency of 21 bread wheat (Triticum aestivum) and four durum wheat (Triticum durum) cultivars grown in a B-toxic and Zn-deficient calcareous soil in Ce ntral Anatolia with (+Zn = 23 kg Zn ha(-1)) and without Zn fertilization in 1993-1994 and 1994-1995 cropping seasons. Tolerance to Zn deficiency (Zn e fficiency ratio) was measured by considering the ratio of grain yield under Zn deficiency to that with Zn fertilization. Zinc fertilization significan tly increased grain yield of all cultivars in both years. On average, incre ases in grain yield of 25 wheat cultivars by Zn fertilization were 37% in t he first and 40% in the second year. When results of the 2 cropping seasons were averaged, Zn efficiency ratios or the cultivars ranged from 40% to 84 %, with an average of 62%. Despite large genotypic variation in Zn efficien cy, shoot Zn concentrations under Zn-deficient conditions did not differ am ong Zn-efficient and Zn-inefficient cultivars. There were large differences in B concentration in shoots of cultivars under both Zn deficiency and Zn fertilization. However, on average for 25 wheat cultivars, Zn fertilization did not influence B concentration. In contrast to B, Zn fertilization cons istently decreased shoot concentration of P in all cultivars. The results p resented show that wheat cultivars growing in Zn-deficient and B-toxic soil conditions vary considerably in their grain yield, and these differences w ere not related to the shoot concentrations of Zn and B. Nevertheless, For many cultivars there was a close relationship between tolerance to Zn defic iency and tolerance to B toxicity. This relationship was discussed in terms of high Zn efficiency-enhanced tissue tolerance to B toxicity.