Three cultivars of Jerusalem artichoke Albik, Rubik and Gute Gelbe were grown under different nitrogen fertilization regimens: 0, 80 and 120 kg N·ha⁻¹. Phenolic compounds were extracted from tubers using 80% (v/v) methanol. The total phenolics were determined with the Folin–Ciocâlteu reagent and antioxidant activity was assessed using the ABTS (2,2’-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)), FRAP (ferric-reducing antioxidant power), and DPPH (2,2-diphenyl-1-picrylhydrazyl) assays. The content of individual phenolic compounds was determined by HPLC. The effect of nitrogen fertilization on the total phenolics content was observed for the Albik cultivar. In the Rubik variety the lowest content was recorded at fertilization zero, and in the Gute Gelbe variety at this fertilization level the content of phenols was the highest. At fertilization 120 kg N·ha⁻¹, the highest ABTS test results were noted for all cultivars. For the Albik variety no effect of fertilization on the FRAP test results was noted; for the Rubik variety at zero nitrogen fertilization, the value for FRAP was the lowest, and it was the highest Gute Gelbe. The results of the DPPH test in the Gute Gelbe variety did not depend on the fertilization used. In the other two varieties, the lowest DPPH results were obtained at zero nitrogen regimen. Three main phenolic compounds were determined using HPLC. One of them was chlorogenic acid and the other two were derivatives of caffeic acid. The content of chlorogenic acid in tubers of the Gute Gelbe variety depended on nitrogen fertilization; the highest content of this compound was found in the case of fertilization zero. Statistical analysis showed a correlation between the content of phenolic compounds in tubers and their antioxidant potential. The results of this study suggest great potential for using Jerusalem artichoke tubers as a rich source of phenolic compounds with high antioxidant capacity.

In this study, the influence of potato cultivars Irga, Satina, Valfi, Blaue St. Galler and Highland Burgundy Red (HB Red), growth regulators: Bio-Algeen S‑90, Kelpak SL and Trifender WP, and the biostimulator Asahi SL on the health status of potato plants and tuber yield was investigated. The severity of late blight and early blight was estimated during the growing season. After harvest, potato tuber yield was determined according to size fractions. The applied treatments significantly reduced the severity of late blight in cv. Irga (Kelpak SL), Valfi (Bio-Algeen S-90, Kelpak SL, Trifender WP) and Blaue St. Galler (Trifender WP) in 2013. In 2015, the symptoms of early blight were significantly reduced in cv. Irga after the application of all tested bioregulators. HB Red was characterized by the best health status among the evaluated cultivars. Kelpak SL and Bio-Algeen S-90 increased the tuber yield of cvs. Irga and HB Red, respectively, in 2013, and Trifender WP increased the tuber yield of cv. Satina in 2014. In the first year of the study, the applied growth regulators and biostimulator significantly increased the percentage of medium-sized tubers of cv. Blaue St. Galler, and Bio-Algeen S-90 increased the percentage of medium-sized tubers of cv. HB Red. In den Untersuchungen wurde die Wirkung der Kartoffelsorten: Irga, Satina, Valfi, Blaue St. Galler, Highland Burgundy Red (HB-Red) und der Anwendung von Wachstumsregulatoren: Bio-Algeen S-90, Kelpak SL, Trifender WP und des Biostimulators Asahi SL auf die Gesundheit der Pflanzen und den Ertrag der Kartoffelknollen untersucht. Während der Vegetation wurde der Intensitätsgrad der Kartoffelfäule und der Dürrfleckenkrankheit eingeschätzt und nach der Ernte wurde der Knollenertrag mit Berücksichtigung der Unterteilung in Fraktionen berechnet. Angewandte Wachstumsregulatoren haben im Jahr 2013 die Intensität der Kartoffelfäule an der Kartoffelsorte Irga (Kelpak SL), Valfi (Bio-Algeen S-90, Kelpak SL, Trifender WP) und Blaue St. Galler (Trifender WP) deutlich reduziert. Im Jahre 2015 waren die Anzeichen von Dürrfleckenkrankheit an der Kartoffelsorte Irga nach Anwendung aller angewandten Wachstumsregulatoren deutlich eingeschränkt. Die Kartoffelsorte HB Red erwies sich als die gesündeste der getesteten Sorten. Kelpak SL und Bio-Algeen S-90 führten im Jahr 2013 zu einer Erhöhung des Knollenertrags entsprechend der Sorte Irga und HB Red, und Trifender WP verursachte im Jahr 2014 das Wachstum des Knollenertrags der Sorte Satina. Im ersten Untersuchungsjahr haben angewandte Wachstumsregulatoren und der Biostimulator den prozentuellen Anteil an mittelgroßen Knollen der Sorte Blaue St. Galler wesentlich gesteigert, und Bio-Algeen S-90 verursachte eine Erhöhung des prozentuellen Anteils der mittelgroßen Knollen der Sorte HB Red.

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In many countries, Jerusalem artichoke (JA) is a source of biomass for renewable energy production and alternative biofuel feedstock, and it is used for feed and food production. The species also has medicinal properties, and it is used in soil reclamation. The aim of this study was to evaluate the effect of N fertilization on the yield and macronutrient concentrations in JA tubers. The effect of N fertilization (control plot, unfertilized, 80 and 120 kg ha⁻¹) on aerial biomass yield, tuber yield, and the mineral composition of tubers in three JA cultivars (“cv.”) (Rubik, Albik, and Gute Gelbe) was investigated in a field experiment. Tuber yield (40.99 Mg ha⁻¹) and aerial biomass yield (62.76 Mg ha⁻¹) were highest in cv. Gute Gelbe fertilized with 120 kg N ha⁻¹ in the warm and moderately wet growing season of 2018. Agronomic N-use efficiency (AE) was highest in cv. Gute Gelbe. In the treatment supplied with 80 kg N ha⁻¹, the fresh matter yield (FMY) of tubers was determined at 66.4 kg kg⁻¹ N, whereas in the treatment fertilized with 120 kg N ha⁻¹, the FMY of tubers reached 101.8 kg kg⁻¹ N. The evaluated JA cultivars differed in their responses to an increase in the N fertilizer (marginal efficiency—ME) rate from 80 to 120 kg ha⁻¹. The strongest response was observed in cv. Gute Gelbe, where the tuber yield increased by 172.6 kg kg⁻¹ N. The tubers of cv. Gute Gelbe were characterized by significantly higher concentrations of N, K, Mg, and S compared with the other cultivars. The concentrations of macronutrients in the tubers (without Mg) were higher in spring. Nitrogen fertilization did not cause differences in the concentrations of P, K, Ca, Mg, and S, but it increased the N concentration in tubers.

Three varieties of rapeseed (Castilla, California, and Nelson F1) were cultivated using medium–intensive (control), intensive, and economical (spare) technologies with different nitrogen and sulfur fertilization techniques. The antioxidant potential of rapeseeds was investigated using ABTS, FRAP, and DPPH assays. The content of total phenolic compounds was determined using the Folin–Ciocalteu phenol reagent. The profile of phenolic compounds was determined using high-performance liquid chromatography (HPLC). Diversifying fertilization in various ways influenced the content of phenolic compounds in extracts of rapeseed. In extracts from the Nelson F1 rapeseeds, intensive cultivation resulted in a lower content of phenolic compounds compared to the control group. Economic fertilization reduced the content of phenolic compounds in seeds from the California variety. HPLC chromatograms of the extracts were characterized by the presence of five (California and Castilla) and six (Nelson F1) main phenolic compounds. Two compounds were identified as sinapine and sinapic acid; others were classified as derivatives of sinapic acid. The effect of fertilization on the antioxidant activity of the seeds and their extracts varied depending on the plant variety and antioxidant assay. For the Castilla and California varieties, no differences were found in the results of the ABTS assay. The antiradical activity against ABTS^•+ of extracts from the Nelson F1 intensive and spare cultivated seeds was higher than that of extracts from control seeds. The FRAP values of extracts/seeds from the Castilla variety cultivated using different methods did not differ significantly. The results of the DPPH assay were not affected by fertilization in the case of extracts from the California and Castilla varieties. However, the extracts from spare cultivated seeds of Nelson F1 exhibited stronger antiradical activity against DPPH^•. These findings highlight the complex relationship between fertilization practices, phenolic compound accumulation, and antioxidant activity in rapeseed. Integrating varietal traits and cultivation practices is crucial for optimizing the nutritional benefits of rapeseed.