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.

The objective of this study was to determine the effects of potassium fertilization (applied to soil at 150, 250, and 350 kg K₂O ha⁻¹) and irrigation on the yield (fresh matter yield and dry matter yield of above-ground biomass and tubers) and the health status of tubers and leaves of three Jerusalem artichoke—JA (Helianthus tuberosus L.) cultivars (Topstar, Violette de Rennes, Waldspindel). The Topstar cultivar was characterized by the highest total tuber yield (60.53 Mg FM ha⁻¹) and the highest above-ground biomass yield (65.74 Mg FM ha⁻¹). An increase in the rate of potassium fertilizer to 350 kg K₂O ha⁻¹ did not affect total tuber yields. The greatest increase in above-ground biomass yields was observed in response to the potassium fertilizer rate of 150 kg K₂O ha ⁻¹ (64.40 Mg FM ha⁻¹). Irrigation increased tuber yields by 59% and above-ground biomass yields by 42% on average. Phytopathological analyses revealed that JA leaves were most frequently colonized by fungi of the genera Alternaria, Fusarium, and Epicoccum. Alternaria and Fusarium fungi were more prevalent in non-irrigated than in irrigated plots. A higher number of fungal pathogens was isolated from the leaves of cv. Violette de Rennes grown in a non-irrigated plot fertilized with 250 kg K₂O ha⁻¹. Tubers were most heavily colonized by fungi of the genera Penicillium, Fusarium, Alternaria, Botrytis, and Rhizopus. Fungal species of the genus Fusarium were isolated from tubers in all irrigated treatments, and they were less frequently identified in non-irrigated plots. Only the tubers of cv. Topstar grown in non-irrigated plots and supplied with 150 kg K₂O ha⁻¹ were free of Fusarium fungi. The number of cultures of pathogenic species isolated from Jerusalem artichoke tubers had a minor negative impact on fresh and dry matter yield.

The aim of this study was to determine the effects of soil potassium fertilization (150, 250 and 350 kg K₂O ha⁻¹) and irrigation on the tuber quality (content of ά-tocopherol, β-carotene, essential and endogenous amino acids) of three Jerusalem artichoke (Helianthus tuberosus L.) cultivars (Topstar, Violette de Rennes, Waldspindel). Jerusalem artichokes were grown during a field experiment in the Agricultural Experiment Station in Tomaszkowo (53°42′ N, 20°26′ E, north-eastern Poland). The content of ά-tocopherol and β-carotene was determined at 1.60–2.65 and 0.75–1.00 mg kg⁻¹ DM, respectively, in all Jerusalem artichoke cultivars produced in north-eastern Poland. High rates of potassium fertilizer (250 and 350 kg K ha⁻¹) increased the content of ά-tocopherol in tubers by 47% and 66% on average, respectively. The stimulatory effects of high potassium rates on the content of ά-tocopherol (2.5-fold increase) were observed only in response to irrigation. High rates of potassium fertilizer induced a particularly high increase (3.2-fold) in ά-tocopherol concentrations in Jerusalem artichokes cv. Waldspindel. Irrigation increased ά-tocopherol levels (by 40%) and decreased the concentrations of β-carotene (by 25%) and most essential and endogenous amino acids (isoleucine, leucine, lysine, phenylalanine, valine, alanine, glycine, histidine, serine, threonine). The Topstar cultivar accumulated the highest quantities of essential and endogenous amino acids. Leucine, methionine + cysteine were the limiting amino acids in Jerusalem artichoke tubers. The analyzed tubers were characterized by very high nutritional quality of dietary protein (Essential Amino-Acid Index, 66–78).

The purpose of this study was to determine optimum rates of soil dressing with nitrogen (N) and potassium (K) fertilization in the cultivation of potato with purple–blue peel and flesh, affecting the qualitative composition of tubers of a less known potato cultivar called Blue Congo. The experimental results proved that the optimum rates of fertilizers applied to soil for the cultivar Blue Congo are 80 kg N ha⁻¹ and 150 kg K ha⁻¹. Application of 120 kg N ha⁻¹ caused a decrease in the content of all macro- and micro-nutrients. In contrast, the content of all macronutrients was observed to increase up to the rate of 150 kg K ha⁻¹. Micronutrients responded to the increase in the K rate in different ways. No effect of the differentiated rates of K was noted in the case of iron. Vitamin C responded by its lower content to the increased rates of both N and K. It was determined that isoleucine was the limiting amino acid for the cv. Blue Congo potato. The highest level of isoleucine was found at the N rate of 80 kg ha⁻¹.

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.