بررسي اثرات باقيمانده سولفات روي بر رشد، عملكرد و جذب روي توسط سويا

Residual Effects of Zinc Sulfate on Growth and Zinc Uptake of Soybean Plants

A significant portion of zinc( Zn) chemical fertilizers applied to calcareous soils is not absorbed by the first crop and may, therefore , affect the growth and chemical composition of the subsequent crops. This is called the residual effect of Zn. Soil tests may be used to predict such effects. The present experiment was conducted to study the residual effects of zinc sulfate on the subsequent crop of soybean (Glycine max L.). Twenty soils of nourthern Iran (5-39% calcium carbonate equivalent), previously treated with two levels of Zn (0 and 20 mg Zn kg"1 as ZnSO4) and under one crop of soybean, was used in greenhouse to grow a subsequent crop of soybean without addittional Zn fertilizer but with uniform application of nitrogen, phosphorous and potassium. Soils were sampled before the subsequent crop and extracted with Zn extractant DTPA. Dry weight of plant tops and Zn concentration and uptake after eight weeks under the greenhouse conditons were used as the plant responses to residual Zn in soil. Statistical analyses showed that zinc sulphate application significantly increased the dry matter from 16.56 to 20.17 g/pot. Zinc application also increased leaves Zn content and Zn uptake from 53.5 to 90.9 mg/kg and from 0.863 to 1.884 mg/ pot., respectively. The overall effect of previosly- applied Zn on dry matter were nonsignificant, but seed yield, Zn concentration and uptake were significantly increased. In all soil, grain yield increased 10.8% in comparison with the control. The residual effect of Zn on dry matter and seed yield of the third crop in soils were nonsignificant, but Zn concentration increased 21.7% in comparison with the control.. In the fourth crop, residual effect of Zn increased dry matter yield and Zn concentration 3% and 40.2% in comparison with the control, respectively. It was concluded that with attention to similar research results , application of ZnSC>4 can obtain plant need for 4 years in soybean farms. In this context, farther research conduction is suggested.