ABSTRACT
The vast cultivation of lemongrass (Cymbopogon flexuosus) as an essential oil-bearing plant worldwide relies heavily on its compound citral that holds immense industrial potential. Soil fertility practices greatly affect the growth and quality of these plants, with a majority of the agricultural land globally grappling with water scarcity. In this respect, field experiments were conducted at the University of Embu research farm during the November 2021-September 2022 growing period and aimed to investigate the influence of two different factors, namely; (i) two watering regimes (rainfed and irrigated) and (ii) four soil conditioner levels (control (T1), cow manure (T2), cow manure plus NPK fertilizer (T3), and NPK fertilizer alone (T4)) on the growth and essential oil parameters of C. flexuosus. The field trials were arranged in a split-plot design with three replicates for each treatment. The essential oil from C. flexuosus was obtained using steam distillation method and analyzed for quality using gas chromatography with mass spectrometry (GC-MS) technique. Results revealed that treatments T4 and T3 improved the growth of C. flexuosus under rain-fed conditions, implying the plant's sensitivity to soil fertility practices and watering regimes. Herbage from rain-fed plants harvested after 120 days had high oil content, ranging from 0.17 to 0.23 %, while herbage from irrigated plants harvested after 180 days had the lowest oil content, ranging from 0.11 to 0.17 %. Using GC-MS, the main components of C. flexuosus oil were citral (75.97-87.70 %), geranyl acetate (0.80-4.91 %), geraniol (0.80-4.26 %), isogeranial (1.83-3.45 %), and isoneral (1.29-2.78 %). Notably, citral, a racemic mixture of geranial and neral, was found in a high concentration (87.70 %), meeting the acceptable international market standards for its use. Altogether, the major oil compounds, oil yield and growth properties of C. flexuosus in this experiment differed as a function of different soil conditioners under the two watering regimes, and so with the time scale. The outcomes of this research highlight implications for enhancing and bolstering the production of high-value lemongrass oil in Kenya, where it holds potential significance as a vital economic and export-oriented crop.
ABSTRACT
Sorghum is an important food crop in the world that exhibits a predominant role in fulfilling the nutritional requirements, particularly in low-income group populations of marginal areas in Kenya. It is a principal source of proteins, carbohydrates, fats, and crude fibers (CFs), which are important nutrients necessary for human development and health. Reduced tannin in sorghum grains is desirable since it affects the availability of nutrients. This study aimed at assessing the nutrient content in filial generation one (F1) developed between Gadam (sorghum), which is low in tannin and hard coat tannin (sorghum) cultivars. The nutrient content analyses were carried out from samples collected in a completely randomized design experiment. Crude protein (CP) and tannin content were analyzed using the modified Kjeldahl method and vanillin-HCl methanol method, respectively, whereas moisture, fat, CF, ash, and carbohydrate contents were determined using Association of Official Analytical Chemists methods. Data collected were subjected to analysis of variance using R statistical software. Among the F1s, Kari/Mtama-1 x Gadam recorded the highest CP value of 10.390%. This differed significantly from Gadam x Kari/Mtama-1 which recorded CP content of 9.770%. Kari/Mtama-1 x Gadam recorded the highest fat and moisture contents of 2.299% and 8.600%, respectively. The highest CF content of 3.433% was recorded in Gadam x Serena. Gadam x Kari/Mtama-1 recorded the highest ash content of 1.619%, whereas the highest carbohydrate (84.503%) and tannin content (0.771 mg/g) means were recorded in Seredo x Gadam. Results demonstrated that the choice of maternal and paternal parent influence CP, CF, and carbohydrate contents. Among the F1s, tannin content ranged from 0.106 to 0.771 mg/g compared to 0.953 to 1.763 mg/g recorded in Serena and Seredo (hard coat seeded cultivars). This is an indication that tannin can be downregulated through hybridization.
ABSTRACT
In this work, we examined the influence of different soil amendments namely cow manure alone (Cm), cow manure plus fertilizer (Cm + F), fertilizer alone (F) and unamended check, control on rosemary growth rate, fat content, oil yield and oil quality. Plant height (PLH), number of primary branches per plant (NOPB) and survival rate were assessed at 0, 90, 180, 270 and 360 days after planting during the 2020-2021 growing season. Rosemary plant essential oil and fat content were extracted using steam distillation and Soxhlet methods, respectively, and determined for quality using the gas chromatography with mass spectrometry (GC-MS) method. Plants grown under Cm had a higher PLH and NOPB, whereas the F treatment largely affected the survival rate of rosemary plants than the control. A total of 26 constituents were identified from the obtained rosemary oil grown under different treatments by use of GC-MS analysis with Cm treatment containing the highest number of oil compounds. The main rosemary oil compounds in the present work were alpha-pinene (29.80%-34.34%), eucalyptol (27.15%-30.26%), verbenone (7.63%-8.14%) and geraniol (4.47%-5.22%). The oil yield from the steam distillation method ranged from 0.45% (v/w) to 0.59% (v/w) while the fat content as measured using the Soxhlet method ranged between 11.22% and 13.36% across various treatments. The essential oil yield and fat content from rosemary grown under Cm, Cm + F, or F conditions were not significantly different. This study shows that Cm markedly influenced rosemary oil quality when compared to other soil amendments.
