Yield, quality, and nutrient uptake of stevia under continental Mediterranean climate

Stevia (Stevia rebaudiana Bertoni) is gaining attention due to its sweetening power. The stevia crop is still relatively unknown in Europe, and very little is known about its nutrient requirements. Therefore, agronomic studies are needed.  Field trials were carried out in inland Spain in 2014 and 2015, in order to evaluate the yield, quality, and nutrient requirements of stevia according to planting density and harvest regime, under a continental Mediterranean climate. In 2014, the dynamics of growth, quality and accumulation of nutrients were studied during the vegetative period according to three planting densities (5.0, 7.5, and 10.0 plants m-2). No significant influence was found. The steviol glycosides concentration decreased sharply at flowering, while the leaf and steviol glycosides yields continued to increase for another 30 days or more. Yield, quality and nutrient uptake were studied during 2015 according to the three same planting densities, and three harvest regimes (one, two, and three cuts per year; all before flowering). Both factors had significant influence on most of the studied parameters. The best quality and the highest yield were not obtained under the same crop management. The highest yield was achieved with 10 plants m-2 and with 2 cuts per year, achieving around 6000 kg ha-1 of dry leaf and 650 kg ha-1 of steviol glycosides. The best quality was achieved with one cut just before flowering (12.2 % of steviol glycosides, 0.35 of Reb A to Stev ratio). The average uptakes of N, P, K, Ca, Mg and S were 35.6, 4.8, 59.9, 14.2, 5.2, and 1.6 kg t-1 of leaf.