Mole drainage

Mole drainage is a cheap method which can be used in some fields. Although mole drains are sometimes used on peat soils, the system is normally applied to fields which have ... 

Fig. 8.8 Layout of mole drainage (with field main) in a 4-ha area.

The above textural groups are used in advisoiy work for making recommendations on dose rates for soil-acting hetbicides and for assessing available-water capacity, suitability for mole drainage, woikability and stabiUty of soils. 

The phosphate concentrations of waters draining from soils usually are about 10-7 M. Worldwide, this amounts to a phosphate loss of 17 x 1010 moles yr-1 (10 mol ha-1 yr-1 or 1 kg ha-1 yr-1). Phosphate in eroded soil particles reaching the sea is estimated to be an additional 13 x 1010 mol yr-1. Fertilization affects the phosphate content of sediments eroded from surface soils, and increases the phosphate concentrations of drainage waters and groundwaters. Preventing erosion has the added benefit of reducing phosphate inputs to streams and lakes. 

The net result of these reactions is that 4 moles of pyrite are oxidized to produce 4 moles of Fe(OH)3 sj, which causes the yellow-brown discoloration of the water 12 moles of H+ (strong acid) are produced which then react with calcareous minerals in the soil to give rise to waters that have a high hardness and high total dissolved solids content. Another reaction of importance in acid mine drainage is the oxidation of FeS2(s) ferric iron (Fe ). Stoichiometrically, this reaction is... 

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