Having surface and/or subsurface water does not necessarily mean you must install an expensive drainage system. Make sure that you get it right the first time around – if drainage is confused with infiltration, permeability, water-logging and similar problems, it can become outrageously expensive and detrimental to soils, which is never cheap nor easy to reverse.
Soil profile morphologies similar to these provide a priceless tool to assess soil drainage in the field. Even so, the drainage cannot be based exclusively on profile morphology, because it is governed by numerous internal and external soil factors that my act separately or together.
Very poorly drained soils. Excess water is removed from the soil so slowly that the water table remains near or at the ground’s surface during much of the growing season. All horizons may remain wet to saturated more or less all year round. The internal free water is very shallow and persistent or stagnant and strong gleying and accumulation of surface organic matter are usually features of these soils. Soils may range widely in texture and depth, often occur in depressions, and are frequently ponded. Unless the soil is artificially drained, most plants that don’t like wet feet cannot be grown (i.e. Mesophytes). Drainage time: Unspecified.
Poorly drained soils. Excess water is removed very slowly in relation to supply so that the soil is wet at shallow depths periodically during the growing season or remains wet for long periods. Internal free water at shallow depth is persistent, and is commonly near the surface long enough during the growing season so that most mesophytic plants cannot be grown. This temporary water table is commonly the result of low permeability, lack of gradient, nearly continuous rainfall, seepage from higher ground, or some combination of these. Some horizons may remain wet for periods of several months, however, the soil is not continuously wet directly below cultivation depth. Some accumulation of surface organic matter is usually a feature of these soils. Soils range widely in texture and depth, and usually have horizons that are gleyed, mottled, or possess orange or rusty linings of root channels. Drainage time: Months.
Imperfectly drained soils. Excess water is removed slowly in relation to supply so that the soil is wet at a shallow depth for significant periods during growing season. The occurrence of internal free water commonly is shallow to moderately deep and transitory to permanent. Some horizons are mottled and/or have orange or rusty lining of root channels, and are wet for periods of several weeks after addition of water. Wetness markedly restricts the growth of mesophytic plants for a significant period in most growing seasons, unless profile alteration and/or artificial drainage are provided. Soils range widely in texture, depth, structure and position in landscape but they have one or more of the following common characteristics: the layer of low permeability at shallow to moderate depth, additional water from seepage and/or nearly continuous rainfall. Drainage time: Several Weeks to <1 Month.
Moderately drained soils Excess water is removed somewhat slowly in relation to supply, due to reduced permeability within the upper 1 metre, periodically received high rainfall, or both. Some horizons may remain wet for more than one week after addition of water. The soils are wet for only a short time within the rooting depth during the growing season, but long enough that most mesophytic plants are affected. Soils are usually lacking a gradient, are loamy or clayey in texture, and have a weak to poor structure, or combination of these. Internal free water occurrence is moderately deep and transitory to permanent. Drainage time: >1 Week.
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