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This article in SSSAJ

  1. Vol. 68 No. 5, p. 1635-1644
     
    Received: Aug 11, 2003
    Published: Sept, 2004


    * Corresponding author(s): c.meisner@cgiar.org
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doi:10.2136/sssaj2004.1635

Inorganic and Organic Phosphorus Fertilizer Effects on the Phosphorus Fractionation in Wetland Rice Soils

  1. M. A. Salequea,
  2. U. A. Nahera,
  3. A. Islama,
  4. A. B. M. B. U. Pathana,
  5. A. T. M. S. Hossaina and
  6. C. A. Meisner *b
  1. a Soil Science Division, Bangladesh Rice Research Institute, Gazipur 1701
    b Natural Resource Group, CIMMYT, Bangladesh

Abstract

Long-term effects of rice (Oryza sativa L.) cultivation with varying nutrient management on soil P fraction are important to understand from soil nutritional and environmental point of view. Soil P fractionation gives an idea about the soil P supplying capacity to plants. The present experiment was conducted to evaluate the effect of different nutrient management in wetland rice on the changes of soil P fraction at different depths. Soil samples from five depths (0–5, 5–10, 10–15, 15–30, and 30–50 cm) were collected from a long-term experimental field classified as a Chhiata clay loam, hyperthermic Vertic Endoaquept. The field received six treatments for 10 yr: absolute control with no fertilizer applied (T1), one-third of recommended fertilizer doses (T2), two-thirds of recommended fertilizer doses (T3), full doses of recommended fertilizers (T4), T2 + 5 Mg cow dung (CD) and 2.5 Mg ash ha−1 (T5), and T3 + 5 Mg CD and 2.5 Mg ash ha−1 (T6). The apparent balance of P compared with the initial P status after 10 yr varied from −115 kg ha−1 under T1 to 348 kg ha−1 under T6 The P fractionation study was conducted over the treatments and soil depth. Treatment and depth had no significant effect on solution P. Larger concentrations of NaHCO3 soluble P, NaOH extracted inorganic P (Pi), and acid P were observed under treatments with organic fertilizers (T5 and T6) than with other treatments at 0- to 5-, 5- to 10-, and 10- to 15-cm depths. The concentrations of NaHCO3–P, NaOH-Pi and acid P fractions were lowest under T1 and T2 treatments. At 15 to 30 cm or lower soil depths, none of the P fractions were affected by treatments. The change in NaOH organic P (Po) and residual P (extracted with HNO3 + HClO4) with soil depth was not significant, and the differences in these P fractions under the tested P treatments were not large. The depletion of NaHCO3–P and NaOH-Pi at the 0- to 15-cm depth under control and T2 suggests that the rice plant depends upon these fractions of P. The P depletion profile in wetland rice appears to be confined within the first 15-cm depth. The mean P uptake by rice showed a polynomial relationship with NaHCO3–P and NaOH-Pi (average of 0–15 cm) and it was linearly correlated with acid P (0–15 cm).

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