IMPORTANCE OF SEED ZN CONTENT FOR WHEAT GROWTH ON ZN-DEFICIENT SOIL .1.. VEGETATIVE GROWTH

Seed nutrient reserves may be important for an early Seed nutrient reserves may be important for an early establishment of crops on low-fertility soils. This glasshouse of Excalibur (Zn efficient) and Gatcher (Zn inefficient) wheats were sown in a Zn-deficient siliceous sand fertilised with 0, 0.05, 0.2, 0.8 or 3.2 mg Zn kg(-1) soil. After 3 weeks, plants derived from the high-Zn seed had better root and shoot growth; the cv. Excalibur accumulated more shoot dry matter than the cv. Gatcher. After 6 weeks, greater root and shoot growth of plants grown from the high-Zn seed compared to those from the low-Zn seed was obvious only at nil Zn fertilisation. A fertilisation rate of 0.2 mg Zn kg(-1) soil was required for achieving 90% of the maximum yield for plants grown from the high-Zn seed compared to 0.8 mg Zn kg(-1) soil for plants derived from the low-Zn seed. The critical Zn level in youngest expanded leaves for 90% maximum yield was 16 mg Zn kg(-1) dry matter for both genotypes. Zn-efficient Excalibur had greater net Zn uptake rates compared to Zn-inefficient Gatcher after 3 weeks but they were not different at the 6-week harvest. Zinc-deficient plants had greater net uptake rates of Cu, Mn, B, P, and K but a reduced uptake rate of Fe. It is concluded that higher seed Zn content acted similar to a starter-fertiliser effect by improving vegetative growth and dissipating differences in Zn efficiency of wheat genotypes.