Wirkung hoher Phosphatdüngung auf die Wachstumsrate, den Zinkgehalt und das P/Zn‐Verhältnis in Weinreben (Vitis vinifera)

Abstract

Effect of high phosphate fertilization on growth rate, zinc content and P/Zn ratio in grapevines (Vitis vinifera)In a 2 years' pot experiment with a soil low in available Zn, high doses of phosphate fertilizer induced Zn deficiency in grapevines (var. „Riesling”︁ on 5 C root stock). This negative effect of phosphate fertilization could almost be prevented by simultaneous application of Zn to the soil.The negative effect of high phosphate fertilization on the Zn status of the soil was well reflected in both the content of available Zn as well as in the diffusion rate of Zn (65Zn) in the soil.In young leaves of grapevines, Zn deficiency can be expected at Zn contents lower than 20 μg/g DM and P/Zn ratios larger than 170. These values, however, cannot be generalized as external factors modify them considerably. This latter holds true for the P/Zn ratio in particular.The most obvious Zn deficiency symptom was restricted elongation of the shoot due to shorter internodes. Typical for severe Zn deficiency were smaller leaves with intervenal chlorosis or even necrosis and the disappearance of the normally deeply lobed shape of the leaf blade. As a result of the growth inhibition of the shoot apex, growth of axillary buds had been enhanced and this led to a bushy shape of the Zn‐deficient plants.