In order to achieve a high yield and quality of apple fruit, more effective ways of fertilization are required in the modern, high density apple orchards. The objective of this research was to determine the efficiency (partial nutrient balance, PNB) of different methods (foliar and fertrigation) and forms (chelates and salts) of microelements application in relation to the levels of N fertilization in apple orchard cultivar (‘Golden Delicious’). The combined effects of these fertilizers on the number of apple fruits per tree and on the yield per tree were also studied. Foliar application of Mn, Zn and Fe had significantly higher partial nutrient balance values compared to the soil application in both years of the experiment. However, most of the PNB values were below 10% indicating relatively low efficiency of the applied fertilizers with microelements.

Biofortification of forage crops has an important role in improving the quality of plants used for animal nutrition. The field experiments were conducted in three consecutive years in Subotica, Serbia, in order to investigate the effect of Se, Zn, and Cu foliar fertilization on the yield, Se and Zn contents and nutrient efficiency, as well as on other mineral compositions of alfalfa hay. The treatments were as follows: i) control without fertilization, ii) 5 g Se ha-1 , iii) 10 g Se ha-1 , iv) 0.5 kg Zn ha-1 , v) 1 kg Zn ha-1 , vi) the combination of these two elements (0.5 kg Zn ha-1 and Se 10 g ha-1) and vii) 2% Cu solution. The application of Se, Zn, and Cu had no effect on dry yield or on crude protein, P, K, Ca, Mg, Fe, Mn, Mo, and Co contents in alfalfa hay. However, Se, Zn, and Cu fertilization significantly increased the contents of Se, Zn, and Cu in alfalfa hay. The results showed that Se and Zn contents in plant biomass were significantly correlated with the applied doses of Se (r=0.99) and Zn (r=0.99). The production years of alfalfa and the weather conditions proved to be significant factors in fertilization efficiency.

Context Biofortification of forage crops has become even more important, due to the improvement in livestock nutrition, but it has also had an indirect positive impact on the human diet. Aim This study investigated the effect of nitrogen and microelement (Zn and Se) fertilisation on yield and on the microelement composition of maize (Zea mays L.) silage. Methods Two field experiments were conducted using a two-factorial split-plot design with nitrogen fertilisation in three doses: 0, 120, 180 and 240 kg N/ha. The first experiment included foliar Zn fertilisation as the second factor (0, 1.5 kg Zn/ha and 1.5 kg Zn/ha + urea solution). The second experiment studied the effect of Se (10 g Se/ha). Key results Nitrogen fertilisation increased biomass yield, Cu and Mn concentration in silage maize. Application of Se and Zn did not affect the biomass yield, but it had a positive effect on Se and Zn concentration in plants. Zn and urea application in combination proved to be more efficient in increasing Zn concentration in plants when compared to Zn applied alone. Conclusions Nitrogen and fertilisation with Zn and Se can be a good tool in fodder plant biofortification because their application led to a yield increase (Zn), but at the same time to an improvement in the mineral composition of maize biomass, with essential elements (Zn and Se). Implications Although biofortification with 1.5 kg Zn/ha has achieved the concentration in maize biomass that can meet the nutritional needs of dairy cows, further research is needed to examine the adjuvant doses and forms of Zn to obtain high yields and Zn concentration in forage crops.

Recycling organic waste is most important for preserving natural resources. The research objective was to quantify the effect of the application of vermicompost and vermicompost leachate on the yield and quality of strawberries and compare it with a standard fertilization program with mineral fertilizers during a 3-year production cycle. Five fertilization treatments were studied: control—without fertilizer (Ø); vermicompost (V); vermicompost + foliar application of vermicompost leachate (VL); vermicompost leachate through fertigation and foliar application (L); and mineral NPK fertilizers (NPK). The application of V positively affected strawberry yield only in the first year. In all three years of fruiting, the highest yield was measured for NPK treatment. In the first year, fertilization had no effect on fruit quality, while in the second and third years, the application of leachate led to a significantly higher concentration of total soluble solids, total anthocyanins, antioxidant activity of the fruit, and a lower concentration of total acid. Strawberries are grown for a two- or three-year production cycle, so the application of V and VL cannot maintain the yield level as was with the application of mineral NPK fertilizers. The quality of strawberry fruit, however, can be improved significantly.

Digestate is a residue of the anaerobic decomposition of organic waste for biogas extraction, but it can be reused as a source of nutrients. To examine the effect of digestate in kohlrabi production, field experiments were conducted during three seasons in two calendar years. The fertilization treatments included the application of solid digestate (two rates—DS1 and DS2), liquid digestate (two rates—DL1 and DL2), solid manure (two rates—MS1 and MS2), and mineral fertilizer (NPK) and were compared with a plot without fertilization (Ø). The results showed a significant increase in the yield with the use of solid and liquid digestate, as well as with NPK, in all growing seasons, while the microelement contents (Zn, Mn, and Cu) in the leaves were at optimum level. The applied treatments did not increase the plant-available nutrients (AL-P2O5, AL-K2O, Fe, Cu, and Zn) in the soil (except Mn). The application of DL2, MS1, and MS2 led to a higher Pb content in kohlrabi stems compared to the control, but the Pb content remained below the maximum permitted limit. Our research showed that digestate can be used as a valuable source of nutrients for kohlrabi production, with a low risk of soil and plant contamination by heavy metals. However, the control of soil, digestates, and manure quality is recommended.