Potassium Management in Apple Production in North China

A 3-year experimental study on the effect of source, rate and time of K application on apple fruit yield and quality in Shaanxi indicated that application of KCl at 0.15 to 0.60 kg K₂O/tree produced 15 to 32% more fruit and US$7,070 to 14,470/ha more return over the control without K fertilization. Application of 0.30 to 0.45 kg K₂O/tree resulted in higher fruit yield, more economic benefit, and better fruit quality such as higher soluble solid, more sugar/acid ratio and vitamin C content than other K rates. Potassium fertilization increased the N, P and K concentration, but decreased the Ca and Mg concentration in the leaves of new shoots and apple fruits, resulting in lower fruit firmness.

The effect of K source on apple yield and quality varied between experimental years, but the average of 3-year results indicated no significant difference between KCl and K₂SO₄ on fruit yield, fruit weight and firmness, while KCl resulted in higher contents of soluble solid, sugar and sugar/acid ratio.

Experiments on the time of K fertilization indicated that application of 50% K at flowering plus 50% K at fruit expansion increased fruit yield by an average of 32% compared with K omission plots, higher than other application times. There was no significant difference between the time of K fertilization on fruit quality.