Field Evaluations of Zinc Sources Band Applied in Ammonium Polyphosphate Suspension
1984
Hergert, G. W. | Rehm, G. W. | Wiese, R. A.
Although the importance of the addition of Zn to a fertilizer program for corn (Zea mays L.) production has been recognized for some time, the question of effectiveness of source and rate has not been completely resolved. This is especially true for situations where Zn is applied in fluid fertilizers. The objective of this study was to evaluate the effect of five Zn sources [ZnEDTA, Zn-NH₃ complex, ZnO, ZnSO₄, and Zn(NO)₃)₂] applied at five rates (0, 0.11, 0.33, 1.12, and 3.36 kg Zn ha⁻¹) on the growth and yield of irrigated corn on sandy soils. The experiments were conducted at four locations during a 2-yr period. All Zn sources were suspended in ammonium polyphosphate and applied to the side of and below the seed at planting. Whole corn plants were collected at two growth stages and analyzed for Zn. Significant differences among Zn sources for Zn uptake were shown. ZnEDTA performed poorly at two sites due to early season leaching; however, it was the superior source at a calcareous site. The Zn-NH₃ complex was the superior source at one of the sites. The 0.1M HCl and DTPA soil tests correlated well with early Zn uptake for the noncalcareous sites. The critical DTPA soil test level for grain response at these locations was near 0.4 mg kg⁻¹. Grain yields were increased by Zn fertilization at only two locations and there were no differences among Zn sources or significant Zn rate by source interactions. Regression equations for the responsive sites showed that between 1 and 2 kg Zn ha⁻¹ was required to attain maximum yield. Although Zn uptake indicated differences in performance of Zn sources, the differences were not reflected in grain yield.
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