<div>Currently, the cultivation of citronella grass (Cymbopogon nardus L.) is widely developed in highland areas dominated by Andosol soil. Andosol possesses low phosphorous availability, strongly bound to Al and Fe. This research was aimed to examine the effect of P fertilizer on C. nardus L. at Andosol. The research was conducted from June 2014 to August 2015. Phosphate fertilization stimulated plant growth, yield and oil quality of citronella grass on Andosol. The most suitable Phosphorus dosage at 1.08 g plant-1 (10.8 kg ha-1) produced high total fresh herb yield and oil quality of citronella grass. Total fresh herb yield increased 21.2% (3.4 kg plant-1 year-1) compared to control. Whereas citronella content, oil content and oil yield were 35.2%, 1.64% and 1.27 % respectively. The phosphate residue in Andosol can be potentially utilized for the next planting season.&nbsp;</div>

<div>Response of Citronella Grass on Several Phosphate Levels Application at Andosol</div>

Background: Citronella oil from Cymbopogon nardus L. is used in various fields, including health, industry and pharmaceuticals. Efforts to increase the content and quality of essential oils in this research were made with the application of magnesium sulfate. Rhizosphere microorganisms, which act as biological fertilizers, are applied to assist in the absorption of nutrients. This research aims to determine the interaction between the type of rhizosphere microorganisms and the dose of MgSO4&nbsp;on growth, essential oil yield and essential oil content in C. nardus. 
 
Methods: The research was carried out from February to August 2023. The research used a randomized block design arranged factorially with three replications. The first factor is the type of rhizosphere microorganisms (without RM, PGPR and AMF) and the second factor is the MgSO4&nbsp;fertilizer dose (0, 190, 285 and 280 kg ha-1). 
 
Result: Providing MgSO4&nbsp;fertilizer can increase the growth and yield of essential oils of C. nardus. The application of PGPR and AMF can increase efficiency of MgSO4&nbsp;fertilization. Treatment without administering rhizosphere microorganisms required a higher dose of MgSO4&nbsp;compared to PGPR and AMF treatments. To increase growth variables and essential oil quality, treatment without rhizosphere microorganisms requires MgSO4&nbsp;of 380 kg ha-1, while PGPR and AMF only require MgSO4&nbsp;at a dose of 190-285 kg ha-1.

Response of Citronella Grass on Several Phosphate Levels Application at Andosol

Effect of Magnesium Sulfate and Rhizosphere Microorganisms on the Growth and Biosynthesis of Cymbopogon nardus L. Essential Oil