Lemongrass (Cymbopogon flexuosus) agronomic traits, oil yield and oil quality under different agro-ecological zones

This paper investigated the influence of three agroecological zones (AEZs) in Kenya, namely upper, middle and lower zones on Cymbopogon flexuosus agronomic traits, oil yield and oil quality. Plant height (PHT), number of leaves per clump (NoLC), number of tillers per clump (NoTC), survival rate, herbage yield and oil yield were evaluated at the harvesting time (90 and 150 days after planting) during February and April 2022. The C. flexuosus oil was recovered by steam distillation technique and subsequently assessed for quality using gas chromatography with mass spectrometry (GC-MS) analysis. Results showed that C. flexuosus grown in lower and middle zones had higher PHT, NoLC and NoTC compared to those grown in the upper zone. Plant survival ranged from 73.75 to 90.50%, herbage yield ranged between 10,200 and 13,027 kg/ha and oil yield ranged from 25.34 to 31.74 l/ha across the zones. In total, 49 compounds were identified from the extracted C. flexuosus oil cultivated under the three AEZs using the GC-MS method, with the middle zone characterized by the greatest number of constituents, out of which, 11 oil compounds differed significantly among the three AEZs. The oil yield of C. flexuosus on a fresh weight basis across the three zones ranged from 0.17 to 0.24%, and the main constituents in the essential oil were citral (54.80-71.45%), geranyl acetate (3.73-7.96%), geraniol (3.04-7.02%) and isogeranial (2.29-2.71%). Further, citral, a racemic compound of two isomers neral and geranial, was 69.92 and 71.45% in the oil in upper and lower zones, respectively, indicating that the oil from the two zones attained acceptable quality for its applications. The citral content was lower in the middle ecological zone (54.80%) as compared to the other two zones. The present work reflects that AEZs in Kenya affected the C. flexuosus oil yield, oil quality and various agronomic traits.