Influences of phosphorus fertilization on zinc status in maize

The field experiment was conducted on calcaric soil of Knespolje area (Republic of Srpska, Bosnia and Herzegovina). By preliminary soil test (autumn 2003) were found values as follows: pH in KCl = 6.84 ; humus = 4.24 % ; NH4-Acetate + EDTA (pH 4.65) extractable P and Ca = 10 and 22559 mg kg-1. Four rates of P fertilization were applied (May 7, 2004) as follows: a) ordinary fertilization (kg ha-1: 200 N + 80 P2O5 + 120 K2O) ; b) a + 500 kg P2O5 ; c) a + 1000 kg P2O5 ; and d) a + 1500 kg P2O5. The triplephoshate enriched with sulphur and zinc (45% P2O5 + 1, 2% S + 0, 06% Zn) was used for increased P fertilization. Maize hybrids Bc5984 and OsSK494 (2004 and 2005, respectively) were grown on the experimental plot. In the next year, residual effects of P fertilization were tested and the experiment fertilized uniformly (kg ha-1: 200 N + 80 P2O5 + 120 K2O). The ear-leaf of maize was taken at beginning of silking (25 leaves in the mean sample: total 16 samples). The total amount of the elements in the leaf samples was measured by the ICP-AES technique after their microwave digestion using concentrated HNO3+H2O2. Applied fertilization resulted by increases of grain yield up to up to 32% and 17% compared to the control, for 2004 and 2005, respectively. In our study, P fertilization significantly influenced on decreases of the leaf, Zn by 48% (45.2 and 23.7 Zn mg/kg, respectively), but only in the first year of testing. In the next year, residual influences of ameliorative P fertilization on Zn status in corn leaves were not found. However, Zn status in corn grain were independent on P fertilization for 2004, but in the next year Zn contents for ameliorative P treatments were reduced for near 40% (31.3 and 17.4 Zn mg/kg). compared to the control.