西北黄土高原是我国苹果优势产业带,该地区苹果园土层深厚、土质疏松;土壤有机质含量较低,多在1%左右;土壤pH值在7.2～8.5之间,呈中性至弱碱性;光照足、气温高、蒸发量大,降雨量少而分布不匀。80%以上的果园为完全雨养果园或者保障率极低的人工灌水果园,普遍水分供应不足。春末 The Northwest Loess Plateau is an apple belt in China. The apple orchard in this area is rich in soil with loose soil. The content of soil organic matter is relatively low, mostly about 1%. The pH value of soil is between 7.2 and 8.5, ; Sufficient light, high temperature, evaporation, rainfall and uneven distribution. More than 80% of the orchards are fully irrigated orchards or artificial irrigated orchards with very low guaranteed rates. Generally, the water supply is inadequate. Spring late