Effects of N and K on growth, herbage, oil yield and nutrient uptake patterns in rosemary (Rosmarinus officinalis L.) under semi-arid tropical conditions

Essential oil of rosemary (Rosmarinus officinalis L.) possesses good olfactory properties and is suitable for use in perfumes, soaps and fragrances. Field experiments were conducted over 2 years (2003-2005) in an area experiencing a semi-arid tropical climate, to study the influence of two N levels (150 or 300 kg N ha(-1) year(-1)) and three K levels (41.5, 83.0 or 124.5 kg K ha(-1) year(-1)), or no fertiliser, on the growth, herbage and oil yields and nutrient uptake patterns of rosemary. The results showed that application of 300 kg N ha(-1) year(-1) produced higher herbage and oil yields in rosemary, compared with 150 or 0 kg N ha(-1) year(-1). The application of 83.0 kg K ha(-1) year(-1) produced maximum herbage and oil yields, compared with 0 or 41.5 kg K ha(-1) year(-1). Total N and K uptake levels were increased significantly by the application of N and K. Nitrogen uptake increased by 85.2% and 137.7%, and K by 80.9% and 123.9%, respectively, with the application of 150 or 300 kg N ha-1 compared to controls (no N). Similarly, N uptake increased by 96.1%, 130.2% and 113.6%, and K by 79%, 124.3% and 110.4%, respectively, with the application of 41.5, 83.0, or 124.5 kg K ha(-1) compared to controls (no K). Oil content and oil composition were not influenced by nitrogen or potassium levels.