Influence of Nitrogen and Potassium Fertilization on Yield and Quality of Rosemary in Relation to Harvest Number

Rosemary is an important aromatic and spice plant. Its cultivation for production of its essential oil has gained importance in recent years. An experiment was conducted in a red sandy loam (Kandiustalf) soil to study the impact of cultivation of this multiharvest crop at different nitrogen (N) and potassium (K) application regimes on soil fertility and crop yield at the farm of the Central Institute of Medicinal and Aromatic Plants, Resource Center, Bangalore, during 2003-2005. The treatments consisted of all combinations of N levels (0, 150, and 300kg per hectare per year) and K levels (0, 50, and 100kg per hectare per year). Five harvests were taken at about 5-month intervals. The results showed that initially the soil alone was able to meet the crop requirements for K, but with the progress of time, addition of K to the soil in the form of fertilizer became necessary for obtaining optimum yields. At the end of five harvests, exchangeable K in soil was significantly lower as application of K decreased from 100 to 50 and 0kg per hectare per year. Soil fertility could be maintained and oil yields of rosemary from four harvests could be increased from 146.6L to 344.7L per hectare by application of 150kg N and 100kg K.