EFFECTS OF ZINC FERTILIZATION AND IRRIGATION ON GRAIN-YIELD AND ZINC CONCENTRATION OF VARIOUS CEREALS GROWN IN ZINC-DEFICIENT CALCAREOUS SOILS

Effects of varied irrigation and zinc (Zn) fertilization (0, 7, 14, 21 kg Zn ha(-1) as ZnSO(4)7 . H2O) on grain yield and concentration and content of Zn were studied in two bread wheat (Triticum aestivum), two durum wheat (Triticum durum), two barley (Hordeum vulgare), two triti cale (xTriticosecale Wittmark), one rye (Secale cereale), and one oat (Avena sativa) cultivars grown in a Zn-deficient soil (DTPA-extractabl e Zn: 0.09 mg kg(-1)) under rainfed and irrigated field conditions. On ly minor or no yield reduction occurred in rye as a result of Zn defic iency. The highest reduction in plant growth and grain yield due to Zn deficiency was observed in durum wheats, followed by oat, barley, bre ad wheat and triticale. These decreases in yield due to Zn deficiency became more pronounced under rainfed conditions. Although highly signi ficant differences in grain yield were found between treatments with a nd without Zn, no significant difference was obtained between the Zn d oses applied (7-21 kg ha(-1)), indicating that 7 kg Zn ha(-1) would be sufficient to overcome Zn deficiency. Increasing doses of Zn applicat ion resulted in significant increases in concentration and content of Zn in shoot and grain. The sensitivity of various cereals to Zn defici ency was different and closely related to Zn content in the shoot but not to Zn amount per unit dry weight. Irrigation was effective in incr easing both shoot Zn content and Zn efficiency of cultivars. The resul ts demonstrate the existence of a large genotypic variation in Zn effi ciency among and within cereals and suggest that plants become more se nsitive to Zn deficiency under rainfed than irrigated conditions.