Potassium accumulation in ‘Huangguan’ pear fruits and leaves and their response to different potassium application

Objectives The aim was to study responses of pear trees to different K₂O application rates during the growth periods and accumulation characteristics of K in fruits and leaves in two different output orchards.

Methods A field experiment was carried out in two 14 year old ‘Huangguan’ pear orchards in same area. One is high-yield orchard (60–70 t/hm²) and the other is a medium-yield orchard (30–40 t/hm²). Four rates of K₂O (0, 150, 300 and 450 kg/hm²) were applied in each orchard. Leaves and fruits were sampled at five periods including the young-fruit stage, expanding Ⅰ stage, expanding Ⅱ stage, mature period and a month later after maturation. Effects of increasing K on outputs, fruit quality, K contents and accumulation in fruits and leaves and K use efficiency were explored.

Results The yields were significantly increased in the high-yield orchard with the increasing of K₂O application, and the yield under K450 was increased by 16.9 % compared to the control. However, in the medium-yield orchard, the K300 treatment led to the maximum output, and the yield was 27.2 % higher compared to the control. The fruit soluble sugar contents and sugar-acid ratios were enhanced by the increasing of K₂O application, while the titrable acid contents were declined. The K contents in fruits and leaves were decreased gradually from the young fruit period to maturation. Anyway, the K contents were increased at different degrees by increasing fertilization rates. The leaf K accumulation amount reached the maximum during the expendingⅠstage, and then decreased slowly. The fruits accumulated the most amount of K during the expanding stage, which accounted for 60%–79% of the K that accumulated in the whole growth period. The fruit K accumulation rate was found to be increased after the expanding period in the high-yield orchard, while it slowed down in the medium-yield orchard. Leaf K was withdrew back to the tree body before leaf senescence, and the reflux degree in the high-yield orchard was higher than that in the medium-yield orchard. The removal of K by fruit harvest and fallen leaves in the high-yield orchard was 258–314 g/plant and was 166–192 g/plant in the medium-yield orchard. The K physiology efficiencies(KPE) were 414.0 kg/kg and 405.2 kg/kg under K450 in the high-yield orchard and K300 in the medium-yield orchard respectively.

Conclusions The K application resulted in an increase in K absorption of pear trees, fruit output and quality. The fruit expanding stage was the maximum efficiency period of K absorption and utilization and topdressing. K fertilizer before this period was a practical fertilization way. Taking account of the yield, K physiological efficiency and fruit quality index, we recommended the K₂O application rate of 450 kg/hm² in the high-yield orchard and 300 kg/hm² in the medium-yield orchard.