Enhancing productivity, quality, and economics of rose scented geranium (Pelargonium graveolens L.) through a novel integrated approach to phosphorus application

Phosphorus limitation is a major factor that adversely affects rose scented geranium (Pelargonium graveolens L.) herbage followed by essential oil yield which is extracted from the green herbage of this high-value aromatic plant. To ensure sustainable yield, the need to improve phosphorus use efficiency in geranium cultivation is inevitable. Current study was undertaken to develop a cost-effective integrated phosphorus management package for the grower’s community to maximize yield, quality, and economics of geranium by combining optimizing phosphorous dose with paddy straw mulch and inoculation with vesicular arbuscular mycorrhiza (VAM). Field experiments were conducted for two consecutive years (2020–21 and 2021–22) at the research farm of CSIR-Central Institute of Medicinal and Aromatic Plants, Lucknow, India. Twelve treatment combinations were executed in a split plot design. Treatment comprised of two levels of paddy straw mulch (7.5 t ha−1 and no mulch), two levels of vesicular-arbuscular mycorrhizae (VAM) inoculation (6.5 kg ha−1and no VAM), and three levels of phosphorous doses (100 kg P2O5 ha−1, 150 P2O5 kg ha−1, and no Phosphorus). Mean data of two years revealed that rose scented geranium is a highly responsive crop towards all the variables applied. Growth parameters, yield attributes, herbage and oil yield, and essential oil quality were significantly improved. Nutrient uptake which is a prime concern of this study was also enhanced due to improvement in soil enzymatic activity, soil microbial biomass carbon, and soil nutrient status due to the combined effect of paddy straw mulching, VAM application, and optimum P doses. Maximum fresh herb yield (657.41 kg ha−1) was recorded in M1V1P1 while the highest volatile oil content, and oil yield (0.131% and 69.11 kg ha−1 respectively) were found in M1V1P2. At both the crop stages, maximum nutrient uptake (N = 1.44% and 1.85%, P = 0.30% and 0.35%, and K= 2.03% and 2.45% respectively) were also recorded with M1V1P2. The same treatment combination (M1V1P2) was recorded with maximum gross return (10403.3 US$ ha−1), total net profit (7795.5 US$ ha−1), and B:C ratio (2.99). Thus, this study recommends that geranium should be grown with appropriate phosphorus dose i.e. 150 kg P2O5 ha−1 along with VAM application (6.5 kg ha−1) and paddy straw mulching @ 7.5 t ha−1 for higher, cost-effective, and better quality oil production.