Responses of four soybean varieties to foliar zinc fertilizer

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Abstract
The soybean varieties Lee, Forrest, Bragg and Dodds were studied in zinc fertilization experiments at three sites in central and north-west New South Wales. At each site foliar sprays of ZnSO47H2O were applied before flowering. At Narrabri one spray of 4 kg ha-1 gave a yield increase of 13%. At Trangie and Breeza, two sprays each of 4 kg ha-1 increased yield by 57% and 208%, respectively. Lee was the least responsive variety at each site and Dodds or Forrest the most responsive to applied zinc. Zinc fertilizer increased plant height, foliar zinc concentration, oil content (at two sites) but decreased leaf phosphorus content. Leaf concentrations of phosphorus in untreated plots were indicative of varietal sensitivity to zinc deficiency both within and between sites. The yield increases at Narrabri were obtained even though no visual symptoms were observed. Improvement of soybean yields with zinc fertilizer in seemingly healthy crops is worthy of further investigation.