Early growth and development of maize on sandy soils fertilised with zinc sources at different application rates

The grain yield and quality of maize is often negatively influenced by zinc (Zn) deficiencies during early growth and development. Application of Zn to soil is therefore a necessity, especially when it is sandy. Glasshouse experiments were carried out to test the effects of Zn sources and application rates on plant-available Zn and on early growth and development of maize grown in a sandy soil. Soil Zn concentration was increased most by ZnSO4 and least by ZnO. The Na2EDTA method was superior to four other methods in extracting soil Zn. For most plant parameters that were measured (leaf number, stem thickness, plant height, photosynthesis rate, leaf area, dry mass, root length and root mass) ZnEDTA was the most effective chelated source, followed by ZnHEDTA, ZnDTPA or ZnEDDHA. Regarding inorganic sources ZnSO4 was superior, followed by ZnCO3, ZnCl2 and ZnO. As a group the inorganic sources performed more poorly than the chelated sources. These rankings differed in terms of Zn concentration and uptake by the plants. The results must be verified in field trials that last for several years accommodating a wider range of climate and soil conditions to develop reliable Zn fertilisation guidelines for maize cultivated on sandy soils.