Objectives Reasonable fertilization and effective mulching of soil have been the key measurement for high and stable agriculture production in the dry land of north Shaanxi Province. An optimized practice was proposed and its effectiveness in improving apple yield and quality was studied in the base of the farmer’s mode and the currently recommended measurement.

Methods Field experiments were conducted in consecutive two years in three orchards each year. In farmers’mode, no organic fertilizer was used and the soil around the apple trees was cleared. The basal amount of N, P₂O₅, K₂O was 300, 160, 120 kg/hm², and the top dressing amount was 150, 80, 60 kg/hm² at germinating stage (March 20); The currently recommended management includes mulching the tree base soil with black film but cleared the soils between the tree rows, applying manure 22.5 t/hm², the basal amount of N, P₂O₅, K₂O was 200, 120, 180 kg/hm², top dressing amount was 100, 60, 90 kg/hm² at fruit enlarging stage (August 10); the optimized measurement was: mulching tree base with black film and growing small rape in between the tree rows, organic manure amount was increased to 45 t/hm², both the basal and top dressing amount of N, P₂O₅, K₂O were 150, 90, 135 kg/hm², but the dressing time was brought advanced at early stage of fruiting enlarging (July 10). The nutrient uptake in different growth periods of apple trees and the yield and quality of fruits were investigated, and the yield and quality of fruit were investigated.

Results Compared with the extension pattern, the NPK contents of leaves in optimized model were averagely increased by 1.4%, 8.4% and 5.9% in young fruit period; by 5.6%, 15.5% and 8.1% in fruit enlargement period, and by 6.9%, 5.9% and 11.6% in ripening period. The fruit nutrient uptake was in order of optimized model > extension model > farmer model, and the difference between the optimized model and the farmer model was significant ( P < 0.05). Compared with farmer model, the NPK uptake in fruits under optimized model was increased by 77.9%, 62.9% and 41.4%, and the vitamin C, soluble solid, hardness, soluble sugar, and sugar-acid ratio were all increased significantly and the contents of titratable acidity decreased. The highest percentage of apple sizes with diameters>80 mm was in optimized model, and the excellent fruit rate was averagely 22.2% and 17.4% higher than in extension and farmer models.

Conclusions The organic manure input, the ratio and time of N, P₂O₅, K₂O fertilizer in the currently recommended mode should be modified in the experimental area. For the more effective mode, organic manure should be increased to 45 t/hm², the amount of basal and topdressing of N, P₂O₅, K₂O should be adjusted to 150, 90, 135 kg/hm², and the topdressing date should be brought advanced to early fruit enlarging stage at July 10. Double mulching with black film around tree truck and covering the soil in between the tree rows is also suggested in the apple orchards in Weibei dry land area, Shaanxi Province.