Impact of Nitrogen Level and Form On Growth of Vetiver Grass

Vetiver grass (Chrysopogon zizanioides L. Roberty) is a warm season perennial grown for essential oil production, erosion control, and as a phytoremediation plant.  It has also recently been proposed as a feedstock for biofuel production.  Previous studies have focused on applications in treating various environmental problems; however, limited information exists on Vetiver fertility management practices in cropping systems. This study was undertaken to better understand the effects of nitrogen (N)-level and N-form on Vetiver growth and development.  Plant slips of C. zizanioides ‘Sunshine’ (Florida Vetiver Systems, Maitland, Fla.) with 2-3 tillers were greenhouse-grown in Normal, Ill. (lat. 40°30’N) using nutrient solution culture in a randomized complete block design with four replications.  In the first experiment, N-level treatments were 26.3, 52.5, 105, 210 and 410 mg N/L with a ratio of 3:1 nitrate-N:ammonium-N.  In a second experiment, the ratio of nitrate-N: ammonium-N was varied from 0:100, 25:75, 50:50, 75:25, and 100:0 while keeping a total N level of 210 mg/L.  Weekly observations on plant height and tiller number were taken for both studies.  After 12 weeks of solution culture, accumulated shoot, root and total fresh weights, total leaf number, and chlorophyll content were assessed.  Plant height increased, then decreased quadratically (P=0.03) in response to increasing N levels up to 10 weeks after transplanting (WAT) with maximum plant height at the 210 mg N/L treatment. However, at 12 WAT, there were no statistical differences among the N levels (P=0.67).  In the second experiment, the greatest plant height was observed at 50:50 nitrate-N:ammonium-N (P=0.01) at 12 WAT.  Vetiver accumulated the highest shoot fresh weight at 105 mg N/L and at 75:25 nitrate-N:ammonium-N.  The greatest tiller number was observed at 26.3 mg N/L treatment (P=0.10) and at 0:100 nitrate-N:ammonium-N (P=0.08).  Leaf number decreased linearly (P=0.10) and chlorophyll content increased, then decreased quadratically (P=0.10) as N level increased.  Leaf number increased linearly (P=0.01) as the ratio of nitrate-N:ammonium-N changed from 100:0 to 0:100.  Results demonstrate Vetiver has a tolerance to ammonium-N and may successfully be cultured under lower N fertility in cropping systems.