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3.推广喷灌、滴灌先进方法,提高灌溉质量美国大多数商品性生产的苹果园都进行灌溉,特别是西部干旱区。灌溉是提高产量的很重要的因素。一般地表灌溉每年灌水量相当于3000毫米的年降雨量,这样,空气湿度低而土壤经常保持湿润,最有利于苹果的生长发育。有些苹果园土壤肥沃,田间持水力强,进行大量的地面覆盖和其它保水措施也能渡过干旱时期。但是一旦新梢年生长量低于20.3～25.4厘米时,果变小,品质差,仍要考虑灌溉。一般是根据美国气象局的降雨量记载,掌握本地区干旱出现的次数,如果干旱威胁着苹果的生长发育,就必须设置灌溉设施。美国广泛地应用土壤水分测定仪器,经常测定土壤水分状况,作为灌溉依据。当土壤含水量低于土壤最大田间持水量的60～80％时,就需要灌溉。
3. Promote sprinkler irrigation, drip irrigation advanced methods to improve irrigation quality Most commercial production of apple orchards in the United States are irrigated, especially in the western arid zone. Irrigation is a very important factor in increasing production. General surface irrigation annual irrigation equivalent to 3000 mm of annual rainfall, so that the air humidity is low and the soil is often kept moist, the most conducive to the growth and development of apples. Some apple orchards have fertile soils, strong field capacity for water holding, extensive surface coverage and other water conservation measures to survive the drought. However, once the annual shoot growth of less than 20.3 ~ 25.4 cm, the fruit becomes smaller, poor quality, still have to consider irrigation. It is generally based on rainfall recorded by the United States Bureau of Meteorology to know the number of occurrences of drought in the area. If the drought threatens the growth and development of apples, irrigation facilities must be set up. The United States widely uses soil moisture measurement equipment, often determine the status of soil moisture, as an irrigation basis. Irrigation is required when soil moisture is less than 60-80% of the maximum field capacity of the soil.