Influence of copper mine tailings on the soil fertility status and growth of rice in Luzon, Philippines

Abstract

The lack of local empirical data to answer questions on the effects of possible depositions of copper mine tailings on the production of some agricultural alluvial floodplains along the Boac River in Marinduque, Philippines, led to the conduct of this research with the following objective: to determine the influence of copper mine tailings and fertilization on soil chemical properties, grain yield, nutritional status and nutrient uptake, including some heavy metals, of lowland rice. For the characterization of mine tailings and soil profiles, bulk samples were collected in Hinapulan, Bamban and Daypay, Marinduque. Two field experiments were conducted for three seasons on a Maranlig clay in San Antonio. The addition of 5-20 cm tailings resulted in lower organic matter, lower cation exchange capacity (CEC), increase in pH up to 4.26 which was still extremely acidic, high exchangeable Cu which was within the phytotoxic range in soils, higher available P, critical K level and slight increase in Cd and Zn but which were below the critical phytotoxic level. The low grain yields in the soils with 5-cm and 20-cm thick mine tailings were corrected with 130-240-180 kg N-P2O5-K2O per hectare. At this fertilization rate, grain yields were significantly higher and were not adversely affected by the thickness of the mine tailings. The average nutrient requirement for plants producing 5 tons grain per hectare was 127-78-121 kg N-P2O5-K2O per hectare. With the use of fertilizer, the concentrations of N, P and K in the grain and straw were not significantly affected by thickness of the mine tailings. The nutrient concentrations were significantly lower when fertilizer was not used and only the N concentration was significantly lowered by the 5- to 20-cm mine tailings. Copper in the grain was slightly higher with the 20 cm tailings added. Zinc concentration was also higher in the 20 cm tailings added but these were within the allowable range in cereal foodstuff. The cadmium concentration ranging from 0.5 to 1.0 mg kg-1 reached the allowable limit of 1 mg kg -1 for unpolished rice but it was below the 2 mg kg-1 concentration in the diet that is considered toxic to man. The concentrations of Cu, Zn and Fe in the straw increased with thickness of the mine tailings but these were below their respective critical phytotoxic level. The mine tailings had no significant effect on the cadmium in the straw. Manganese concentration in the straw increased with thickness of mine tailings, exceeding the lower limit of the phytotoxic level in rice. On a Maranlig clay treated with 20-cm tailings, fertilization with 130 (CAF)-240-0 or 130-240-180 increased the yield significantly compared to the unfertilized rice. The yield increments were comparable with that of the fertilized soil alone.

Source or Periodical Title

Philippine Agricultural Scientist

ISSN

317454

Page

396-407

Document Type

Article

Subject

Copper, Heavy metals, Lowland rice, Mine tailings, Soil fertility

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