Abstract:
Deficiencies in soil zinc (Zn) may limit yield of rice and wheat in rice tract of the Punjab (Gujranwala and Lahore Divisions). The build-up of phosphorus (P) due to its continuous application could also reduce the plant Zn concentration. Therefore, this three seasons study in randomized complete block (Factorial) design investigates the effects of P and Zn fertilizer on yield of wheat and rice (in rotation) and their concentration in plant tissue to predict the specific P and Zn need of the crops. There were two levels of P (100 and 200 kg
P2OS ha1) and three levels of Zn i. e. 0, 3.5, and 7 for wheat and 0, 5, and 10 kg ha'for rice. Wheat yield data revealed that Zn addition at the rate of 3.5 kg ha'improved the grain yield significantly while there was no difference in the yield in treatments receiving 100 and 200 kg PiOsha1 . A reverse situation was attained in rice where high P (200 kg PiOf ha') did increase the paddy yield significantly while Zn at the rate of 5 - 10 kg ha'1 was not successful to enhance the yield. The reason was satisfactory levels of soil Zn built-up to 1.6 - 2.8 mg kg ' 'soil due to residual effect of Zn applied to previous crop i.e. wheat. Yield, tissue concentrations, utrients (P & Zn) uptake and soil test levels did not show P induced Zn limitation on this alkaline soil. Higher soil test P and Zn values at the harvest of last wheat season were found in the treatment of 7 kg Zn ha'when applied in combination with 200 kg P2O3 ha 'compared to other treatments.
