The Supply Capacity Of Magnesium And The Effect Of The Magnesium Fertilizer In The Soils Of Oolong Tea Plantations

An investigation on magnesium status of Tieguanyin tea leaves and the corresponding surface soils of tea plantations was conducted over Anxi, Hua'an and Yongchun Counties in southern Fu jian. Some field feitilization experiments were carried out to study the effects of different Mg fertilization on the tea yields. The main results were as follows:1.The total Mg contents of the surface soil (0～25cm) was between 0.70 g@@@kg^-1 and 5.39g·kg^-1 with an average of 1.77g·kg^-1. The soils derived from metamorphic rocks contained the highest Mg while those from granites the lowest. The total soil Mg had highly significant correlations with the contents of organic matter, 0.02～0.002mm particles and CEC, indicating that the 0.02～0.002mm particles are the main mineral fraction for storing magnesium.2.The available Mg contents were from 0.19 g.kg^-1 to 53.33 mg.kg^-1 with an average of 9.63mg.kg^-1, much lower than the requirement for tea production. The soils developed from sandstones contained the highest available Mg whereas those derived from metamorphic rocks the lowest. The soil available Mg was highly significantly correlated with pH, the contents of organic matter and 0.02～0.002mm particles. The soil available Mg was significantly correlated with CEC whereas negativly correlated with<0.002mm particles.3.The Mg concentration of the tea leaves was 1.29～2.54 mg.kg^-1 with a mean of 1.78 g.kg^-1, showing highly significan correlation with the soil available Mg. The available Mg of 89.3% of the soils were less than 20 mg.kg^-1 and of 7.9% were between 20 mg.kg^-1 and 40 mg.kg^-1, suggesting that most of the tea plantation soils were extremely poor in Mg.4.Field experiments showed that the application of 22.5 kg.667m^-2 dolomite powder into the soils was the best in improving the agroromonic properties of the leaves of Tieguanyin, Baiyaqilan and Cuiyu among four Mg application levels. The application of dolomite powder increased the thinkness and mummber of tea leaves, the germination density and the weight of tree tops and consequently the tea yields. The spring tea yields of Tieguanyin, Baiyaqilan and Taiwan Cuiyu were increased by 1.9%～24.3%,1.5%～23.5% and 4.3%～43.4%, respectively while the autumn tea yields were increased by 18.3%～56.0%,3.6%～22.9% and 0.8%～19.8%, respectively.5.Field experiments showed that foliar spraying of magnesium sulfate also improved the yields. It was shown that among the different foliar fertilization rates, 300 L of magnesium sulfate (Density 0.5%) was best in improving the agronomic properties of three tea varieties. Compared with the blank treatment, the spring Tea yields were increased by 23.9%～43.9%, and the autumn tea outputs by 24.2%～58.9%.6.According to the field experiment, the best quantity fertilizer were 25.5 kg/667m² of the dolomite powder, and 300 L/667m²(Density 0.5%)Magnesium sulfate , the tea output and quality can achieve good effect.