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  • organic phosphorus  (2)
  • centrifugation  (1)
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  • 1
    ISSN: 1573-5036
    Keywords: Cambisol ; defoliation ; fertilizer ; grass/clover sward ; organic phosphorus ; phosphate ; soil solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of defoliation and NPK fertilizer addition on the amounts of inorganic orthophosphate (Pi), organically combined phosphorus (Po), total phosphorus (Pt) and the residual fraction Pr=Pt−(Po+ Pi) in soil solution from three P-deficient Cambisols with grass/clover swards were determined. The defoliation treatments, carried out in the first year, were regular cutting every 2–4 weeks to 2 cm, and cutting at the end of the growing season. The fertilizer treatments, applied in the second year, were 25 g m-2 of 25:5:5 and 20:10:10 NPK fertilizer. In both years, soil solution was also taken from bare soil plots. Defoliation influenced the concentration of Pi, Po, Pr and Pt in soil solutions, which mostly increased in the order no cut〉cut 2 cm〉bare soil treatment. Fertilizer additions increased dry matter production, and the amount of P in the crop, but had relatively little influence on soil solution concentrations of Pi, Po, Pr and Pt compared with the previous year. There were no significant differences in either dry matter production, P uptake or the Pi, Po, Pr and Pt concentrations of soil solution between the plots receiving 25:5:5 or 20:10:10 fertilizer treatments. Phosphorus in soil solutions from the most acid of the three cropped soils was significantly correlated with Fe during August and October. The linear correlation coefficients (r) between Fe and Pi, Po or Pt were between 0.73 and 0.94.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5036
    Keywords: cambisol ; centrifugation ; organic phosphorus ; phosphate ; season ; soil solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil solutions from three P-deficient Cambisols were analyzed for inorganic orthophosphate (Pi), organically combined phosphorus (Po), total phosphorus (Pt) and residual phosphorus (Pr=Pt−(Po+Pi)). The solutions were obtained by centrifugation of soil samples wetted-up to 90% field capacity. Increasing the centrifugal force from 750 to 1400×g (for 60 minutes) increased the volume of soil solution obtained by 17–35%. Increasing the centrifugation period from 30 to 90 minutes (at 1000×g) increased the volume by 2–12%. The effect of the different centrifugation conditions on the P composition of soil solutions were not critical and had little effect on either Pt concentration or on the distribution of P between Pi, Po and Pr fractions. Soil solutions were also obtained on a seasonal basis over a 2-year period. The soils, fresh from the field, were wetted-up to 90% field capacity and centrifuged at 1000×g for 60 minutes to isolate the soil solution. Although the soils were derived from contrasting parent rock, and had different Fe and Al sesquioxide contents, the Pt concentrations of the soil solutions and the distribution between the fractions were similar. Annual average Pt concentrations for the 3 soils ranged from 93 to 114 and 63 to 89 μg dm-3 during the first and second year, respectively. Seasonal changes were of a similar order as those resulting from differences in soil type. During May, June, August and October soil solutions had average Pt concentrations ranging from 82 to 111 and 51 to 119 μg P dm-3 in 1989 and 1990, respectively. Po was a major P component in soil solution and exceeded the amount of Pi by about 5–20 times.
    Type of Medium: Electronic Resource
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