Effects of soil drying and rate of re-wetting on concentrations and forms of phosphorus in leachate |
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Authors: | M S A Blackwell P C Brookes N de la Fuente-Martinez P J Murray K E Snars J K Williams P M Haygarth |
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Institution: | (1) North Wyke Research, Okehampton, Devon, EX20 2SB, UK;(2) Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK;(3) Centre for Sustainable Water Management, Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK |
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Abstract: | The drying and re-wetting of soils can result in the modification of the amounts and forms of nutrients which can transfer,
via leachate, from the soil to surface waters. We tested, under laboratory conditions, the hypothesis that the rate of re-wetting
of a dried soil affects the solubilisation and concentrations of different forms of phosphorus (P) in leachate. A portion
of grassland pelostagnogley soil (sieved moist <2 mm) was dried at 35°C and another portion maintained at approximately 40%
water-holding capacity. Water (25 ml) was added at ten regularly spaced time intervals in 2.5-ml aliquots to the surfaces
of both soils over periods of 0, 2, 4, 24 and 48 h, resulting in different rates of application. The leachate was collected
and analysed for dissolved (<0.45 μm) and particulate total P and molybdate reactive and unreactive P. The rate of re-wetting
significantly changed the concentrations of P, especially dissolved forms, in the leachate. Dissolved P concentrations were
highest in leachate from the 2-h treatment, while particulate P concentrations were highest in the 0-h treatment leachate.
In all cases, most P was unreactive and, therefore, likely to be in an organic form. Soil drying decreased microbial biomass,
but this could not be directly linked to an increase of P in leachate. These results suggest that changes in patterns of rainfall
frequency and intensity predicted by climate change scenarios could significantly affect the quantities of P leached from
soils. |
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Keywords: | Drying– re-wetting Phosphorus Leachate Soil microbial biomass |
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