Influence of foliar application of iron on the mineral composition of 'Joly' strawberry fruit

Tijekom 2021. godine provedeno je istraživanje kvalitete plodova jagode sorte 'Joly' uzgajane hidroponski u Petrovini Turopoljskoj gdje je na početku cvatnje obavljena folijarna prihrana jagoda sa željezom kod tretmana B i C te potom samo tretman C u punoj cvatnji i to s Fe - Fe-EDDHA 6% (Poly-Feed™). Tijekom dozrijevanja ubrani su plodovi za istraživanje fizikalnog, kemijskog i mineralnog sastava jagoda. Istraživana fizikalno-kemijska svojstva bila su masa (g), tvrdoća (kg/cm2), topljiva suha tvar (°Brix), ukupne kiseline (% kao limunska kiselina), omjer topljive suhe tvari i ukupnih kiselina te pH. Analiza mineralnog sastava provedena je adekvatnim metodama i to modificiranom Kjeldahlovom metodom, spektofotometrom, plamenim fotometrom i atomskim adsorpcijskim spektrometrom. Istraživani parametri mineralnog sastava bili su podijeljeni na markoelemente (N, P, K, Ca, Mg) te mikroelemente (Fe. Zn, Mn, Cu). Utvrđene su značajne razlike u dobivenim vrijednostima pojedinih mjerenih svojstava kvalitete ploda pod utjecajem dodatne primjene željeza. Dodatno tretiranje folijarnim Fe znatno je smanjilo ukupne kiseline čime se povećao odnos topljive suhe tvari i ukupnih kiselina te je sam okus plodova bio bolji. Jedno folijarno tretiranje početkom cvatnje dovelo je do povećanja sadržaja K u plodu u odnosu na kontrolu. Tretiranje s dodatnim Fe dovelo je do signifikantnog smanjenja nekih istraživanih mikroelemenata kao što su Zn, Mn i Cu.During 2021, a research was done on the quality of strawberry fruits of the cultivar 'Joly' grown hydroponically in Petrovina Turopoljska. At the beginning of flowering foliar fertilization of strawberries with iron was performed in treatments B and C and then only in treatment C during the full bloom with Fe - Fe- EDDHA 6% (Poly-Feed ™). During ripening, the fruits were harvested to study the physical, chemical and mineral composition of the strawberries. The physicochemical properties tested were mass (g), hardness (kg /cm2), soluble solids (° Brix), total acidity (% as citric acid), ratio of soluble solids to total acidity and pH. The analysis of mineral composition was carried out using appropriatemethods, namely the modified Kjeldahl method, spectrophotometer, flame photometer and atomic adsorption spectrometer. The studied mineral composition parameters were divided into marcoelements (N, P, K, Ca, Mg) and microelements (Fe. Zn, Mn, Cu). On the basis of the obtained results, significant differences were found in the obtained values of individual measured fruit quality properties under the influence of additional iron application. The additional treatment with foliar iron resulted in a significant reduction of total acids, increasing the ratio of soluble solids to total acids, and the taste of the fruit itself was better. Foliar treatment at the beginning of flowering resulted in an increase in the K content in the fruit compared to the control. Treatment with additional Fe led to a significant decrease in some of the trace elements studied, such as Zn, Mn and Cu