Manuring of Stevia rebaudiana Bertoni M. on andosol

The performance of Stevia rebaudiana Bertoni M. was studied in a 3 NPK factorial field experiment on brown andosol of Pasir Datar estate, Sukabumi, West Java. The experimental site located at about 1000 m above sealevel and an average temperature between 17-27 deg C., had an average annual rainfall of over 4000 mm/year with an average of 10 wet months and one month dry. The experimental plots of 4 x 1,5 m contained cuttings of clone BPP 72 planted at a distance of 25 x 25 cm. The treatment levels were 0 g-0,9 g-1,8 g of urea, 0 g-0,5 g-1,0 g of triple superphosphate and 0 g-0,9 g-1,8 g of muriate of potash. Characteristics of the soil before treatment were the following: a low pH of 4,50, high contents of organic C, N-total, P2O5 and K2O total but low P-Olsen content and a moderate level of available K. Yield response was in accordance with this nutrient status of the soil in the following way. N-fertilizer had no significant effect whereas P and K fertilizers significantly increased biomass production. The response to phosphorus up to the highest level was still linear while that to potassium was quadratic with an optimum dose rate of 1,07 g to 1,08 g of muriate of potash per plant for each application. Fertilization with N, P or K alone exerted an antagonistic effect on the foliar and stem nutrient content of the other elements. However, such effect could be avoided by a complete NPK application. At the end of the experiment some slight changes occurred in the nutrient content of the soil i.e. a small decrease in total N and a small increase of P-Olsen content, furthermore a relatively greater decrease in available K and Mg content. Extrapolated from the results of this field experiment and a previous pot experiment with a different soil an N-fertilizer amount of 0,80 - 0,92 g or approximately 1,0 g of urea could be suggested for a general nitrogen rate. Together with the P and K rate assessed in this experiment a general recommendation for Stevia on andosol of 1,0 g of urea + 1,0 g of triple superphosphate + 1,0 g of muriate of potash per plant for each application during the first year of harvest might be suggested.