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High rainfall areas are best avoided. However, the season in which the precipitation occurs is important. Heavy spring rains can delay spring operations such as adding soil amend-ments, starting a cover or green manure crop, or sowing tree seed. Summer rains tend to be a problem only when they occur as cloudbursts and result in flooding, erosion, or seed-ling wash-out. Frequent summer rains may be detrimental, however, because rains may disrupt stock hardening processes already induced by withholding irrigation. Areas with heavy winter rains should be avoided; heavy rain saturates nursery soil to the point of hindering lifting, damaging soil structure, and causing flooding and erosion.Wind.—Areas with frequent, long-lasting, high-velocity winds-particularly where humidity is low and winds are drying and from the east—should be avoided. Winds will affect irriga-tion application and uniformity and may result in soil movement. High winds can desiccate seedlings, and soil carried by winds can blast stems and foliage. Wind can restrict spraying of pesticides, cause tree-seed cover to be blown away, and dis-place or scatter seedbed mulches.2.2.2.2 SoilPerhaps the most important factor in establishing a nursery is the correct choice of soil (see chapter 6, this volume). Other site features, including fertility, moisture, and microclimate, can be manipulated by the nursery manager [2], but moving or significantly modifying large masses of soil is, at the very least, impractical and costly. An intensive soil survey, coupled with representative soil sampling, will help the selection team choose the site with the most suitable soil.Texture.—Sandyloams or loamy sands with good drain-age are excellent for nurseries. Light soils can be worked in weather conditions too wet for heavier soils—an important consideration in the Northwest. The content of clay and silt (particles < 0.05 mm in diameter) in the soil should be within 15 to 25%.Depth.—The top 4 feet of soil should be free of claypan, hardpan, shale, iron concretions, calcareous substrata, or mot-tled gley layers [9]. Without artificial drainage, this depth seems a reasonable minimum; where artificial drainage has been in-stalled, however, a minimum clear soil depth of 2 feet is probably acceptable [8]. The top 18 inches of soil should be free of stones, which are expensive to remove, make the soil difficult to work, and interfere with nursery cultural practices
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