Status of K availability and efficiency of potash application in tea fields of China

摘要

In order to see the current status of K availability and efficiency of potash application in tea fields of China, a national survey together with field and pot trials was carried out during 1999 to 2002. A total number of 620 soil samples were collected from 13 major tea producing provinces and the exchangeable K content was analyzed. The soils with exchangeable K below 80 mg/kg accounted for 62.0% and 78.9% of the total samples in the surface soil (0-20 cm) and subsoil (20-40cm), respectively, exhibiting a zonal distribution with their values declining gradually from the northern to the southern tea growing provinces. The results of 6 field experiments conducted in main tea producing provinces showed tea yield in 4 trial sites increased significantly by means of 11.6% and 18.5% with K_2O application rate of 187.5 and 375 kg/ha, respectively, the increase rate by SOP (17.5%) was better than by MOP (12.6%). The chemical analysis indicated that K application improved the quality of tea and especially increased amino acids, the most important factor for the quality of green tea. Sensory determination also showed that aroma and taste of green, oolong and black teas were improved by K application. The quality of tea was slightly better in application of SOP than MOP. Pot experiments with SOP application in 3 different soils with exchangeable K from 47-184 mg/kg showed the yield of fresh leaf and biomass were significantly increased by 34.4%-98.7% and 17.5%- 47.9%, respectively. The concentrations of free amino acids, polyphenols and caffeine increased by means of 16.4%, 5.7% and 3.3%, respectively. K application significantly increased the K and P concentrations in tea plant. However, the Mg contents decreased. The chlorophyll content and photosynthesis in mature leaves were also enhanced slightly.