Critical limits and zinc requirement for maize (Zea mays L.) production in acid soils of south-eastern Nigeria
Abstract
The study was conducted to determine available Zn in the soils, evaluate the critical limits of Zn for maize and then establish optimum rate of Zn fertilizer required to achieve maximum Zn uptake and grain yield in maize producing area of southeastern Nigeria. Results of the 20 surface (0-20 cm) soil samples analyzed were sandy loam (SL), very strongly acidic (4.62) in reaction, low in organic carbon (0.98 gkg-1) and in ECEC (8.15 cmol kg-1). The status of available Zn in the soils by different extractants were found to be very low and ranged from 0.38 mgkg-1 to 2.24 mgkg-1 extracted by NH4OAc, and Coca-Cola methods, respectively. The critical limits of Zn in the soils and maize plant, below which high response of applied ZnSO4 to maize could be expected were determined by Cate-Nelson according to the extraction methods as: 0.90-1.52, 1.10-1.65, and 0.70- 1.13, 2.40-3.92 and 2.50-4.24 mgkg-1 for Coca-Cola, EDTA, HCl, NH4OAc + EDTA and NH4OAc, respectively. The results of the pot and field experiments shows that levels of Zn significantly (P<0.05) increased both DMY and grain yields. Approximately 11 kg Zn ha-1 was estimated to be the optimum level of ZnSO4 required for Zn uptake in maize producing for soils of southeastern Nigeria. Similarly, in the field experiment, Zn fertilizers significantly improved grain yields. The application of ZnSO4 fertilizer yielded maximum grain yield of 7.9 and 5.1 tha-1 at the optimum rates of 9.0 and 9.6 kg ha-1 in the 2009 and 2010 plantings.
Keywords: Acid sand, critical limit, extractable Zn, maize grain, optimum yield and ZnSO4 fertilizer
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