The effect of nitrogen fertilization and foliar nutrition on yield, nut quality and kernel phenolic content of the walnut cultivar \u27Elit\u27 (Juglans regia L.)

Ustrezna založenost s hranili ima pomemben vpliv na rast in razvoj sadnega drevja. Pomanjkanja in presežki makro- in mikroelementov so še posebej opazni v intenzivni pridelavi, kjer lahko mineralna prehrana odločilno vpliva na količino in kakovost pridelka. S poskusom, ki je vključeval talno gnojenje z dušičnima gnojiloma KAN in apneni dušik (AD) ter škropljenje s foliarnimi gnojili in biostimulatorji (FP) smo preverili povezavo med mineralno prehrano nasada ter rodnostjo, pomološkimi lastnostmi plodov in vsebnostjo fenolov v jedrcih oreha sorte \u27Elit\u27. Učinke gnojenja smo ugotavljali s pomočjo tehtanja skupnega pridelka, pomoloških analiz plodov ter analize topnih in vezanih fenolov v jedrcih pri obravnavanjih KAN, AD, KAN + FP, AD + FP in kontrola (negnojeno). Zaradi neugodnih vremenskih razmer v spomladanskih mesecih so bili pridelki majhni. Največ (5,1 kg/drevo) so rodila drevesa iz obravnavanja KAN + FP, za tretjino več od kontrolnih dreves. Pri kombinaciji AD + FP smo zabeležili težje plodove in jedrca ter večjo širino plodov. Trikratno talno gnojenje z gnojilom KAN je vplivalo na največji izplen jedrc, pri obravnavanju AD + FP pa je bil izplen jedrc najmanjši. Programi prehrane niso vplivali na obliko plodov, debelino in gladkost ter spojenost luščine, ločljivost in barvo jedrc. Jedrca so vsebovala 3,5 do 4,4 krat več vezanih fenolov v primerjavi s topnimi. V jedrcih kontrolnih dreves je bilo najmanj vezanih, za zdravje zelo koristnih fenolov. Glede na izjemne vremenske razmere v rastni dobi 2018 je potrebno poskus ponoviti še v nekaj letih in vključiti tudi druge zanimive sorte, da bi dobili bolj zanesljive rezultate o vplivu talne in listne mineralne prehrane na količino in kakovost pridelka pri orehu.Optimal nutrient intake has an important effect on the growth and developement of fruit trees. Deficiency and toxicitiy of macro- and micronutrients is especially noticeable in intensive farming, where mineral nutrition can be a decisive factor contributing to yield size and fruit quality. With an experiment, which included fertilization with two nitrogen fertilizers KAN and calcium cyanamide (AD), as well as aplication of foliar fertilizers and biostimulators (FP), we studied the correlation between the mineral nutrition and yield, pomological value of nuts and kernel phenolics content of the walnut cultivar \u27Elit\u27. We analysed the effects of fertilization by collective yield weighing, pomological analysis of the fruit and laboratory extraction of soluble and insoluble phenolic compounds in the kernels of each of the treatements KAN, AD, KAN + FP, AD + FP and the control (unfertilized). Due to adverse weather conditions in spring, the yields were low. The trees in the KAN + FP treatement gave the highest yield (5.1 kg/tree), a third more than the control. With the AD + FP combination, we got heavier nuts and kernels, as well as a greater width of the nuts. A three-time KAN fertilization gave the highest kernel ratio, while the AD + FP treatement had the lowest kernel ratio. The different nutrition treatements did not affect the nut shape, thickness and smoothness of the shell, seam closeness, ease of removal form shell or kernel color. The kernels contained 3.5 to 4.4 times more insoluble phenolics compared to the soluble fraction. The kernels in the control had the lowest insoluble phenolics content, which is very beneficial to our health. Considering the exceptional climatic conditions in 2018, further research is needed, as well as an inclusion of other cultivars, to provide a more reliable research outcome and confirm the effect of mineral nutrition on yield and nut quality in common walnut