Modified Biochar effects on phosphorus availability in agricultural soils

What is it about?

Phosphorus (P) limitation is a key challenge for crop productivity in major parts of the world, as P is least mobile and highly fixated in soil. To circumvent phosphorus deficiency, chemical fertilizers are used; however, these are rapidly absorbed in the soil and not accessible for crops creating a need for more P fertilizer. Moreover, substantial amount of P is lost through runoffs and contributes to eutrophication in water bodies. Improving P efficiency to reduce P fertilizer inputs without compromising yield and quality is required for sustainable P use in agriculture. Biochar is carbon-rich material produced by the thermal carbonization of organic waste under total or limited oxygen conditions and has gained considerable interest of the plant scientists in the past 20 years. Enhancing agricultural and environmental benefits of biochar through physical, chemical, or thermal modifications is frequently employed, but information on the concentration, transformation rate and half-life of available phosphorus in chemically modified-biochar amended P-fertilized calcareous soils is yet lacking. For this reason, we investigated here the effect of citric acid-modified biochar derived from low-ash agricultural wastes (wheat straw) on P transformation and changes in its plant availability indices in calcareous sandy soil.

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Photo by Zoe Schaeffer on Unsplash

Photo by Zoe Schaeffer on Unsplash

Why is it important?

The sustainable use of P requires a holistic approach, integrating production with recycling, to minimize existing losses, mitigate environmental effects, preserve scarce resources and ensure P availability for all farmers worldwide. The application of citric acid-modified biochar led to higher concentration of plant available P in soil and improved its half-life in the calcareous sandy soil. These effects were explained by the lower rate of P diffusion to sorption sites in citric acid-modified biochar-amended soil. The results showed that this amendment could initially act as a slow-release source of P, thereby reducing the rate of application of P fertilizers, and then could behave as an adsorbent for the excess of nutrients added at the later stages of plant growth.

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