Potassium Management in Apple Production in North China

Investigations and field trials were conducted in apple orchards at selected sites in Shaanxi, Shandong, and Liaoning provinces to (1) demonstrate the current status of apple production and fertilizer use and (2) study the effects of source, rate, and time of potash application on fruit yield and quality. The K balance in apple orchards was also estimated.

Results showed that average N-P₂O₅-K₂O applied in apple orchards in Shaanxi, Shandong and Liaoning through fertilizers and manures were 734-465-325, 1,550-502-1,028, and 491-371-330 kg/ha, respectively. The average apple fruit yields obtained were 32, 49, and 15 to 21 t/ha. Nutrients (N, P and K) from manure accounted for 24, 23 and 36% of total respective nutrient application in Shaanxi, 5.2, 6.9 and 2.5% in Shandong, and 61, 55 and 49% in Liaoning. Application of 0.15 to 0.3 kg K₂O/tree through KCl or K₂SO₄ could meet the K needs of apple trees in the three provinces.

Application of K improved fruit quality (increased Vitamin C content and fruit hardness and reduced total acid). No significant differences existed between the effects of KCl and K₂SO₄ on fruit yield/quality at the same application rate of K₂O. Application of 50% of the recommended K fertilizer in later plant growth stages (such as after flowering and fruit expending) could be beneficial for fruit yield and quality. Application of fertilizer K increased farmer incomes compared to the control (no K) treatment. The income generated from K application was highest in Shaanxi (5,538 to US$22,152), followed by that in Liaoning (1,031 to $9,976), while the least increase in farmer incomes with K application was observed in Shandong province (431 to $1,215). NWCE Apple K