Fly ash and zeolite decrease metal uptake but do not improve rice growth in paddy soils contaminated with Cu and Zn.

Area of Science:

• Environmental Science
• Soil Science
• Agronomy

Background:

• Fly ash (FA) and zeolite (Z) are used to immobilize metals like copper (Cu) and zinc (Zn) in contaminated soils.
• However, these amendments can reduce the availability of essential nutrients such as nitrogen (N) and phosphorus (P).

Purpose of the Study:

• To evaluate the effects of FA and Z application on nutrient and metal availability in metal-contaminated paddy rice soils.
• To assess the impact of these amendments on rice growth and biomass accumulation.

Main Methods:

• Field study involving paddy rice (Oryza sativa L.) cultivation.
• Application of fly ash and zeolite at rates of 0%, 5%, and 10% to metal-contaminated soils.
• Analysis of soil nutrient (N, P) and metal (Cu, Zn) availability, metal uptake by rice, and rice growth parameters (tillering, biomass).

Main Results:

• Both FA and Z significantly reduced Cu and Zn uptake by rice and increased metal retention in soil.
• Despite reduced metal uptake, rice growth was inhibited, particularly at the 10% amendment rate.
• This growth inhibition was linked to decreased nutrient (N and P) availability, affecting tillering and overall biomass.

Conclusions:

• FA and Z effectively reduce metal bioavailability in contaminated soils but can concurrently decrease nitrogen and phosphorus availability.
• The immobilization of nutrients by FA and Z can negatively impact rice growth, outweighing the benefits of metal reduction.
• Careful consideration of both metal and nutrient immobilization is crucial when using FA and Z as amendments in metal-contaminated rice paddies.