Effect of Polyhalite on Tea Productivity and Quality on Basaltic Soil in Lam Dong, Vietnam

Tea plants have high demand of potassium (K), calcium (Ca), magnesium (Mg) and sulphur (S), but in Lam Dong tea mainly grown on basaltic soil (rhodic ferrasols) which poor in these elements. Polyhalite is introduced as the new 4-in-1 fertilizer, which contain 48 % SO3, 14 % K2O, 6 % MgO and 17 % CaO. This is research on effect of polyhalite to tea productivity and quality in Lam Dong province, Vietnam. An experiment with 5 treatments of 0, 200, 400, 600 and 800 kg polyhalite ha-1 with background of 750N in urea, 250 P2O5 in fused magnesium phosphate and 240 K2O in KCl or polyhalite was conducted on basaltic soil in Lam Dong province of Vietnam during 2015-2016. The trials were designed to Randomized Complete Bock (RCB) with 4 replications and plot area of 180 m2. The results showed that polyhalite demonstrated the ability to supply plant K, Ca, Mg and S requirements, enhanced the density, weight and size of tea buds, thus increasing tea productivity by 3.3-6.0 t ha-1, corresponding 11.6-19.8 % in comparison with control. Also, polyhalite slightly improved tea quality parameters such as dry matter content and the concentrations of soluble substances, tannins and caffeine. Polyhalite dose gave highest tea yield was 600 kg ha-1, with tea productivity of 3.95 t ha-1.