The current study investigates the phytochemical composition of coffee plant organs and their corresponding antioxidant capacities compared to green and roasted coffee beans. HPLC analysis indicated that the investigated compounds were present in all organs except mangiferin, which was absent in roots, stems and seeds, and caffeine, which was absent in stems and roots. Total phytochemicals were highest in the green beans (GB) at 9.70 mg g⁻¹ dry weight (DW), while roasting caused a 66% decline in the roasted beans (RB). This decline resulted more from 5–CQA and sucrose decomposition by 68% and 97%, respectively, while caffeine and trigonelline were not significantly thermally affected. Roasting increased the total phenolic content (TPC) by 20.8% which was associated with an increase of 68.8%, 47.5% and 13.4% in the antioxidant capacity (TEAC) determined by 2,2–diphenyl–1–picryl hydrazyl radical (DPPH), 2,2–azino bis (3–ethyl benzothiazoline–6–sulphonic acid) radical (ABTS) and Ferric ion reducing antioxidant power (FRAP) assays, respectively. Amongst the leaves, the youngest (L1) contained the highest content at 8.23 mg g⁻¹ DW, which gradually reduced with leaf age to 5.57 mg g⁻¹ DW in the oldest (L6). Leaves also contained the highest TPC (over 60 mg g⁻¹ GAE) and exhibited high TEAC, the latter being highest in L1 at 328.0, 345.7 and 1097.4, and least in L6 at 304.6, 294.5 and 755.1 µmol Trolox g⁻¹ sample for the respective assays. Phytochemical accumulation, TPC and TEAC were least in woody stem (WS) at 1.42 mg g⁻¹ DW; 8.7 mg g⁻¹ GAE; 21.9, 24.9 and 110.0 µmol Trolox g⁻¹ sample; while herbaceous stem (HS) contained up to 4.37 mg g⁻¹ DW; 27.8 mg g⁻¹ GAE; 110.9, 124.8 and 469.7 µmol Trolox g⁻¹ sample, respectively. Roots contained up to 1.85 mg g⁻¹ DW, 15.8 mg⁻¹ GAE and TEAC of 36.8, 41.5 and 156.7 µmol Trolox g⁻¹ sample. Amongst the organs, therefore, coffee leaves possessed higher values than roasted beans on the basis of phytochemicals, TPC and TEAC. Leaves also contain carotenoids and chlorophylls pigments with potent health benefits. With appropriate processing methods, a beverage prepared from leaves (coffee leaf tea) could be a rich source of phytochemicals and antioxidants with therapeutic and pharmacological values for human health.

Coffee plants are seasonally exposed to low chilling temperatures in many coffee-producing regions. In this study, we investigated the ameliorative effects of kinetin—a cytokinin elicitor compound on the nonenzymatic antioxidants and the photosynthetic physiology of young coffee plants subjected to cold stress conditions. Although net CO₂ assimilation rates were not significantly affected amongst the treatments, the subjection of coffee plants to cold stress conditions caused low gas exchanges and photosynthetic efficiency, which was accompanied by membrane disintegration and the breakdown of chlorophyll pigments. Kinetin treatment, on the other hand, maintained a higher intercellular-to-ambient CO₂ concentration ratio with concomitant improvement in stomatal conductance and mesophyll efficiency. Moreover, the leaves of kinetin-treated plants maintained slightly higher photochemical quenching (qP) and open photosystem II centers (qL), which was accompanied by higher electron transfer rates (ETRs) compared to their non-treated counterparts under cold stress conditions. The exogenous foliar application of kinetin also stimulated the metabolism of caffeine, trigonelline, 5-caffeoylquinic acid, mangiferin, anthocyanins and total phenolic content. The contents of these nonenzymatic antioxidants were highest under cold stress conditions in kinetin-treated plants than during optimal conditions. Our results further indicated that the exogenous application of kinetin increased the total radical scavenging capacity of coffee plants. Therefore, the exogenous application of kinetin has the potential to reinforce antioxidant capacity, as well as modulate the decline in photosynthetic productivity resulting in improved tolerance under cold stress conditions.

Sesame is an important oilseed crop cultivated worldwide. However, research has focused on biochar effects on grain crops and vegetable and there is still a scarcity of information of biochar addition on sesame. This study was to assess the effect of biochar addition on sesame performance, with a specific emphasis on growth, yield, leaf nutrient concentration, seed mineral nutrients, and soil physicochemical properties. A field experiment was conducted on an upland field converted from paddy at Tottori Prefecture, Japan. Rice husk biochar was added to sesame cropping at rates of 0 (F), 20 (F+20B), 50 (F+50B) and 100 (F+100B) t ha⁻¹ and combined with NPK fertilization in a first cropping and a second cropping field in 2017. Biochar addition increased plant height, yield and the total number of seeds per plant more in the first cropping than in the second cropping. The F+50B significantly increased seed yield by 35.0% in the first cropping whereas the F+20B non-significantly increased seed yield by 25.1% in the second cropping. At increasing biochar rates, plant K significantly increased while decreasing Mg whereas N and crude protein, P and Ca were non-significantly higher compared to the control. Soil porosity and bulk density improved with biochar addition while pH, exchangeable K, total N, C/N ratio and CEC significantly increased with biochar, but the effect faded in the second cropping. Conversely exchangeable Mg and its plant tissue concentration decreased due to competitive ion effect of high K from the biochar. Biochar addition is effective for increasing nutrient availability especially K for sesame while improving soil physicochemical properties to increase seed yield, growth and seed mineral quality.

We evaluated the fatty acid compositions in relation to yield and soil nutrients from four fields A, B, C, and D with continuous monocropping histories of 0–3 years, respectively, in Japan from 2015 to 2016. Results showed that, in both evaluation years, seed yield did not significantly differ among the fields although field A produced the highest mean seed yield and 1000-seed weight. Between fields A and C, 1000-seed weight showed significant differences. The contents of seed-saturated fatty acids lauric and myristic decreased in only fields C and D whereas oleic, linoleic, and linolenic acids increased in field D. Only field A produced the highest contents of lauric and myristic acids whereas field D produced the highest contents of linoleic and linolenic acids. The soil total N and exchangeable K contents tended to decrease as exchangeable Mg content significantly increased on the fields with long duration of cropping, fields C and D. Principal component analysis revealed significant positive correlations between soil exchangeable K, and total N contents with 1000-seed weight and lauric acid, as exchangeable Mg content was related with oleic, linoleic, and linolenic acids. Therefore, the high oleic, linoleic, and linolenic acids from field D were mainly attributed to high soil exchangeable Mg content, whereas the high 1000-seed weight, lauric acid and myristic acid were due to the high soil exchangeable K content in field A. Overall, the fatty acid composition quality on the long-duration continuously monocropped fields could show high economic value at the expense of yield under this management practice in continuous monocropping.

Sesame (Sesamum indicum L.) is an important oilseed crop, but is negatively affected by continuous cropping. There is still a lack of information on the effect of continuous cropping on soil chemical properties and mineral nutrition related to sesame growth and yield decline. Therefore, we investigated sesame growth and yield, nutrient concentration and soil chemical properties on five fields with continuous cropping history: non-continuous cropping (Year 0) and durations of two, four, five and six years on an upland field converted paddy in Tottori, Japan. Results show that plant height significantly decreased by 18.76%, 15.22%, and 13.64% in the Year 4, Year 5 and Year 6 fields, respectively, compared to Year 0. The effect of continuous cropping was more pronounced on the 1000-seed weight decline than seed yield. Compared to Year 0, seed yield decreased by 52.86% in Year 2 with no significant differences among the Year 2, Year 4, Year 5 and Year 6 fields, whereas the 1000-seed weight decreased by 6.68% and 12.20% in the Year 2 and Year 5 fields, respectively, compared to Year 0. Plant leaf tissue N concentration significantly decreased in the Year 2, Year 4 and Year 6 fields compared to Year 0, whereas leaf tissue K concentration decreased in the Year 6 field. The increase in duration of continuous cropping years gradually altered soil chemical properties. Soil pH, exchangeable Ca and Mg and cation exchange capacity (CEC) gradually increased in the long duration of continuous cropping, whereas total N and C, exchangeable NH₄⁺-N, urease, dehydrogenase and catalase activities decreased. Our study suggested that the decrease in soil available N and enzyme activities, and decrease in K nutrition due to competitive ion effect as a result of increase in soil Ca and Mg could possibly contribute to the growth and yield decline of continuous sesame on upland field converted paddy.

Biochar can reduce N₂O emissions and it can be added to the soil once, whereas fertilizers are often applied every cultivation season. The aging of biochar in soil affects its functioning but it is unclear whether palm shell biochar (PSB) could still mitigate N₂O emissions even when additional basal N fertilizers are applied 1 year after the initial biochar application. We studied the impact of fresh and aged PSB (0%, 6%, 12%, and 18% w/w of dry soil) on N₂O emissions, soil properties, nutrient content and yield of Komatsuna (Brassica rapa var. perviridis) under sandy soil conditions. The aged PSB non-significantly reduced N₂O emissions but significantly offset soil acidification, and maintained a high soil nutrient status. Biochar application with fertilizer significantly increased plant tissue K and Ca content but decreased N, P and Mg content compared to the treatments without biochar. At higher application rates, biochar had negative effects on crop yield but as it aged, the negative effects were offset as a result of the similar variation in plant N uptake. Since seasonal N fertilizer application seems to be inevitable in Komatsuna cultivation, addition of biochar could be a possible way of counteracting the effects of excessive fertilizer use. Further research is needed to assess the feasible biochar application rates for Komatsuna fields in various soil types under field conditions.