Maize (Zea mays L.) Grain Protein Composition and Oil Content As Affected By Zinc Sulfate Following Systematic Application of Mineral Fertlizers to Carbonate Chernozem.

A field experiment* was conducted in Moldova to evaluate the maize grain protein content and composition as affected by zinc sulfate following systematic application of mineral fertilizers (Control-no fertilizers, P60, P60Zn10, N60K60, N60P60K60, N60P60K60Zn5, N90P60K60, N90P90K60Zn5, N60P90K60 and N60P90K60Zn10) to carbonate chernozem. The soil at the experiment site was a chernozem, containing: humus 4.3%, total nitrogen 0.29%, CaCO3 1.7%, plant-available phosphorus and potassium averaging 0.88 and 34.5 mg/100 g respectively, extractable cations Ca2+ and Mg2+ 31 and 2.9 meq/100 g respectively, with pHH2O value of 7.9 at the 0-20 cm soil depth. Long term phosphorus application induced zinc deficiency in maize. The results revealed that the greater grain protein content (11.52-12.13%) was achieved when the plants were fertilized with zinc sulfate, nitrogen, phosphorus and potassium compared to without zinc application (9.23-10.54%). The ranges of albumin and globulin value were 1.63-2.42%, zein 3.1-4.17%, glutelin 3.08-4.42%, and were affected by combined applications of micro and macroelements, whereas residue proteins contents were at level 1.15-1.29% and not affected by those fertilizers. The zein and glutelin were the dominant protein fractions, and their ranges were 33.63-35.44% and 32.91-36.43% respectively of the total protein content. The albumin and globulin content was lower (17.61-20.98%), and the residue proteins was the lowest fractions (10.05-12.45%) of the total protein content. Corn oil concentration range was 5.07-5.47%, and its concentration was not affected by micro and macroelements. Hence, the use of zinc sulfate following systematic application of mineral fertilizers to carbonate chernozem is essential to improving maize grain protein composition. *The results were obtained in Moldavian Scientific-Research Institute of Soil Science and Agricultural Chemistry, Chisinau, Moldova.