Effect of iron fertilization on nut traits and nutrient composition of 'Tombul' hazelnut (Corylus avellana L.) and its potential value for human nutrition

Abstract

Iron (Fe) is an essential element for plants and its deficiency is a well-documented problem, causing decreased yields and nutritional quality. An orchard experiment was carried out to investigate the effect of iron fertilization on some nut traits and mineral compositions of 'Tombul' hazelnut (Corylus avellana L.) variety cultivated in the Black Sea Region of Turkey. In addition, the contributions of these nuts on human nutrition were determined. Hazelnuts were fertilized with 0, 4, 8, 12, and 16 kg ha(-1) iron in each year during three consecutive years. Iron fertilization significantly affected nut traits and mineral compositions of the nuts. The amounts of total oil, kernel percentage, and kernel weight increased and the amounts of empty and wrinkle nuts decreased with 12 kg ha(-1) Fe fertilization. Different iron doses caused slightly different protein content and kernel shape in the kernels. The phosphorus, iron, and boron contents of nut increased significantly with 8 kg ha(-1) Fe fertilization. In order to improve some nut traits and mineral compositions of hazelnut, 8 kg ha(-1) and 12 kg ha(-1) Fe fertilizations could be recommended for practice. According to daily nutrition element requirements, the quantity of 100 g hazelnut provided about 43.12% for P, 12.93% for K, 19.09% for Ca, 36.97% for Mg, 0.18% for Na, 50.88% for Fe, 25.00% for Zn, 14.15% for B, and 77.33% for Mo of the recommended dietary allowances. Cu and Mn contents of 100 g hazelnut were higher than the respective daily requirements. This research indicated that hazelnut is a rich source of mineral elements, and 'Tombul' hazelnut can be an important source of mineral elements for human nutrition with health beneficial impact.