Biochar as a soil amendment in agriculture

Improving yields and water retention

Biochar has some valuable characteristics for use in agriculture. Although it is not a fertilizer in the sense that the nutrient input is relatively low, it has a high value as a soil amendment. 

The following mechanisms contribute to its positive impact on agriculture:

  • High porosity, and therefore biochar has a high water retention capacity. This is very beneficial for improving the efficiency of water use by crops
  • High catalytic capacity for reactions in the soil that facilitates the availability and absorption of nutrients by plants
  • It promotes microbiological activity in the soil, accelerating the degradation of organic matter and increasing the availability of nutrients for crops.

Significant increases in yield are possible when the application of biochar resolves specific soil constraints in terms of nutrient and/or water availability. Scientific studies show average increases in agricultural yield of 10% to 42%, with the best results in acidic and sandy soils and when biochar has been applied in combination with organic and/or mineral fertilizers.

Image 1: Summary of the impact of biochar on agricultural yields of some crops.

The concept of biochar is rooted in an ancient Amazonian practice

The practice of adding charred biomass to improve soil quality is not new. The process is modeled after a 2,000-year-old practice in the Amazonian basin, where indigenous people created areas of rich, fertile soils called terra preta (meaning “dark earth”).

Whether these soils were intentionally made or are simply a by-product of farming and/or cooking practices is still unclear. But one thing’s for sure: The fertility of terra preta is significantly higher than the otherwise famously infertile soils of the Amazon. This explains why plants grown in terra preta soil grow faster, and are more nutrient-dense, than plants grown in neighboring soils. In fact, terra preta soils continue to hold carbon still today.

Affinity with organic and regenerative agriculture

Organic and regenerative agriculture is characterized by a focus on natural biological processes to optimize agricultural yields, and by rejecting the use of chemicals for pest control and to improve soil fertility. Soil health is a fundamental pillar for an agricultural production system that is resilient to pests and diseases and has high agricultural yields.

Biochar is a chemical-free soil amendment. Considering the limited package of tools and inputs to improve soil fertilization in organic and regenerative agriculture, biochar represents an especially valuable opportunity for:

  • Increase the amount of organic carbon in the soil.
  • Encouraging microbial life in the soil, taking advantage of the contributions of beneficial fungi and bacteria for nutrient absorption.
  • Maximizing agricultural yields without using synthetic fertilizers.


It is worth mentioning that – depending on the production process and the raw material used – biochar may have contaminants that make it unsuitable for organic farming. However, with good quality control and third-party certification, biochar can perfectly meet the demands of certified organic farming.

Mitigating heavy metal contamination

Contamination of agricultural soils with heavy metals is a serious problem for farmers and consumers in Peru. According to a recent study, cadmium contamination has been identified in cocoa beans from farmers in northern Peru. According to the study, the Piura region was particularly affected, as 89% of the samples analyzed had a cadmium concentration higher than 0.8 mg/kg.

Peru is the world’s 8th largest producer of cocoa. The high levels of cadmium found in agricultural soils and cocoa bean samples endanger this important sector and export market for Peruvian farmers. In addition, at the national level the contamination of crops with heavy metals represents a risk to the health of consumers.

 A 2001 study summarizes the levels of heavy metal contamination in fruits and vegetables in Peru and concludes that the abundance of chemical contaminants in agricultural products indicates a significant food safety problem, which increases the risks of chronic human diseases, such as cancer, one of the leading causes of death in Peru.

(2) Image: Map of the presence of cadmium in soils in Peru. A focus of high soil contamination in the northern regions of Peru is clearly shown.

Many scientific papers have concluded that biochar is effective in reducing the uptake of heavy metals by plants. By adsorbing heavy metal ions and increasing the pH in soils (leading to lower solubility of metal ions), metals become immobilized and are no longer a danger to agriculture. By applying biochar designed for maximum metal adsorption, combined with other good agricultural practices to minimize the impact of heavy metal uptake by plants, the risk of contaminated soils for agriculture can be minimized.

(3) Image: Summary of the impact of biochar to reduce the absorption of heavy metals in plants.

Improving yields in saline soils

Salinization is a process of soil degradation that has been worsening and expanding along the coast of Peru. This process of degradation is negative for the inhabitants of the affected districts, as it prevents them from carrying out traditional agriculture throughout the year.

The use of biochar is a recognized practice to mitigate the effects of salinity stress on plants. Applying biochar to saline soils improves growth and yield by improving the uptake of essential nutrients (Ca, Mg, Fe, Zn, Mn, and K), soil porosity, aggregate stability, organic matter, and decreasing the concentration of toxic ions.

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(1)Image: Summary of the impact of biochar on agricultural yields of some crops.

(2) Image: Map of the presence of cadmium in soils in Peru. A focus of high soil contamination in the northern regions of Peru is clearly shown.

(3) Image: Summary of the impact of biochar to reduce the absorption of heavy metals in plants.

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