苗木从土壤中吸收的水分主要来源于雨水、地下水及灌溉水。在北方干旱地区主要依靠灌水补充土壤中的水分。但如果雨水过多或排水不畅，也会影响苗木的呼吸，严重的会导致烂根甚至死亡。
The water absorbed by seedlings from soil mainly comes from rainwater, groundwater and irrigation water. In the arid areas of northern China, water is mainly added to the soil to supplement the water. But if too much rain or poor drainage, will also affect seedling respiration, serious cause rot and death.
灌溉量和灌溉次数
Irrigation amount and irrigation frequency
不同栽培方式的灌溉
Irrigation with different cultivation methods
播种苗：播种苗播种后要尽量避免表土干燥，特别是在北方地区，一些小粒种子播种后覆土较浅，易受春旱的危害。通过合理灌溉使床面保持湿润，防止小苗失水，还可调节地表温度，防止日灼。一般要求灌水次数多，每次灌水量要少。
Seedlings: Seedling after sowing to avoid dry soil, especially in the northern region, some of the small seed after sowing covering soil is shallow, are vulnerable to drought. Through the reasonable irrigation to maintain moist bed, prevent seedling dehydration, can also adjust the surface temperature to prevent sunburn. Generally require more irrigation, each irrigation amount is less.
扦插、压条、埋条苗：扦插、压条、埋条苗这些苗的生根、发芽都需要较大水量，特别是在刚开始展叶而尚未完全生根（即假活期）阶段，叶面蒸腾量较大，土壤水分供应量较少，一旦断水就将造成植株死亡，及时灌水是关键。在北方，气候干燥季节更应注意。灌水量可适当大些，但水流要细、缓，以免水流冲力移动苗木（特别是扦插苗）。
Cuttage, layering, burying seedling: cutting, layering, rooting, seedling buried these seedlings germination requires a large amount, especially at the beginning of leaf and root (i.e. not completely false current) stage, the leaf transpiration rate is larger, less soil water supply, once the water will cause plant death, in a timely manner irrigation is the key. In the north, the climate is dry and the season should pay more attention. The amount of irrigation can be more appropriate, but the flow should be fine, slow, so as not to flow momentum, moving seedlings (especially cutting seedlings).
分株苗、移植苗：分株苗、移植苗这些苗由于在栽植时根系受伤，苗木内部的水分供应出现不平衡，必须加强供水。在分株和移植后应连续灌水三四次，灌水量要大些，间隔时间也不能太长。
Ramets and transplant seedlings: Seedlings of ramets and transplant seedlings, because the roots were injured when they were planted, the water supply in the seedlings was unbalanced and water supply must be strengthened. After ramets and transplanting, three or four times of continuous irrigation should be adopted, the irrigation amount should be larger, and the interval time should not be too long.
嫁接苗：嫁接苗对水分的需求不是太大，只要能保证砧木的正常生命活动即可。水不能太多，尤其是接口部位不能积水，否则会使伤口腐烂。干旱天气必须灌水时也要注意。
Grafted seedlings: the demand for water in grafted seedlings is not too large, so long as the normal life activities of Rootstocks can be guaranteed. The water can not be too much, especially the interface parts can not be stagnant water, otherwise it will cause the wound to rot. Dry weather must be paid attention to when irrigating.
大苗：大苗除非在干旱季节才需灌水。如果水分过多，还会使苗木抗性降低，影响生长发育。
Seedlings: Seedlings in the dry season to irrigation unless. If the moisture is too much, it will also reduce the resistance of seedlings, affecting growth and development.
不同气候条件下的灌溉
Irrigation under different climatic conditions
灌溉必须根据气候条件的变化灵活掌握。一般来说，春季到初夏，苗木处于旺盛生长期，南方雨水多，只要灌溉三四次即可。北方是干旱期，要灌七八次。播种苗、扦插苗则需要灌溉次数更多。
Irrigation must be flexible according to changes in climatic conditions. Generally speaking, the spring to early summer, the seedlings are in vigorous growth period, the southern rainfall, as long as three or four times irrigation can be. The north is dry and needs to be irrigated seven or eight times. Seedlings and cuttings need more irrigation times.
初夏：南方是阴雨季节，要注意排水。
Early summer: the south is rainy season, we should pay attention to drainage.
夏季：北方常逢雨季，可不灌水。南方则不同，如果高温又干旱，必须增加灌水次数。
Summer: the north often rainy season, but not irrigation. The south is different. If the temperature is high and dry, the irrigation rate must be increased.
秋季：虽然南北方雨量不同，但为了让苗木组织充实和木质化，准备越冬，一般不灌水。
Autumn: Although the rainfall in the South and the north is different, in order to allow the seedlings to be enriched and lignification, they are ready to pass the winter without irrigation.
冬季：南方不灌水，北方则要在土地冰冻前灌一次冻水，以利于苗木越冬。
Winter: no irrigation in the south, the north will be frozen in the land before the freezing of water, in order to help the seedlings survive.
不同土壤条件的灌溉
Irrigation under different soil conditions
黏重土壤保水力强，灌水量应适当减少；砂壤保水力差，灌水量应适当增加。
The viscosity soil is strong in water conservation, the amount of irrigation should be reduced appropriately, the water holding capacity of sand soil is poor, and the amount of irrigation should be increased appropriately.
不同树种的灌溉
Irrigation of different tree species
不同树种对水的要求各不相同，幼苗期差别并不太大，一般都需要有足够的水分。随着苗龄的增长，差别越来越明显。
The water requirement of different tree species is different, and the difference of seedling stage is not too big. Generally, they need plenty of moisture. With the seedling growth, the difference is more and more obvious.
耐旱树种：如臭椿、刺槐、丁香等更应注意，水多时要立即排水。
Drought resistant species: Ailanthus altissima, Robinia pseudoacacia, clove should be paid more attention to, much water to drain immediately.
一般树种：则要经常保持湿润状态，结合地下水位和降雨情况，确定适宜的灌水量。
General tree species: often keep moist state, combined with the water level and rainfall conditions, determine the appropriate amount of irrigation.
灌溉方法
Irrigation method
地面灌溉
Surface irrigation
高床和垄式作业区：可由灌溉渠把水引入步道或垄沟里，水从侧面渗入床内或垄中。其优点是灌溉后土壤仍具有良好的通气性，可以减少松土的次数，也比较省工，但耗水量太大，苗床宽的会产生灌水不均的现象。
High bed and ridge type operation area: the irrigation canal brought water into trails or furrows, water from the side into the bed or ridge in. The utility model has the advantages that the soil still has good aeration after the irrigation, and the number of soil loosing can be reduced, and the labor saving is also saved, but the water consumption is too large, and the width of the seedbed can cause uneven irrigation.
低床或大田式育苗区：可由灌溉渠把水直接引入低床或畦面，水布满床面或畦面而逐渐深入土壤之中，这是漫灌。此法灌水时比较方便，但应注意水流速度要慢，以免冲倒或淹没苗木。灌溉后土壤易板结，通气不良，要增加松土次数?比较费工。
Low bed or field seedling area: by irrigation canal water directly into the lower bed or ridge surface covered with water, bed surface or surface gradually into the soil, it is flooding. This method is convenient for irrigation, but attention should be paid to the water flow rate to slow down, so as not to flush or drown seedlings. After irrigation, soil harden, poor ventilation, to increase the number of soil work?.
喷灌和滴灌
Sprinkler irrigation and drip irrigation
喷灌一般适用于大苗灌溉，滴灌适用于苗床灌溉，都是比较先进的灌溉方式。
Sprinkler is generally applicable to seedling irrigation, drip irrigation for bed irrigation, are relatively advanced irrigation methods.
排水
drainage
降雨或大量灌溉后应及时排除地面积水，苗圃地不应有积水，否则会降低土壤有机质的分解速度，破坏苗木根系的正常呼吸，常引起根系腐烂甚至死亡。
A lot of rainfall or irrigation should be promptly remove ground water, nursery water should not be, otherwise it will reduce the decomposition rate of soil organic matter, normal respiratory failure of seedlings, often causing root rot and even death.
要做好排水工作，首先应平整圃地，其次，建立完善的排水系统，做到外水不浸、内水能排。
To do drainage work, first of all, we should smooth the fields, and secondly, establish a perfect drainage system, so that the water can not be soaked outside and the water can be discharged.