How Biochar Affects Crop Yields in Field Studies

Can adding biochar to soil help farmers grow more food? Researchers have studied this question across many crops, soils, and growing regions. The results show that biochar can improve crop yields, especially when it is used alongside fertilizer.

A 2019 study led by Jie Ye brought together results from many field studies to look for larger patterns. Instead of focusing on one crop or one farm, the researchers compared results from different soils, climates, crops, and types of biochar. This type of study is called a meta-analysis.

What the Researchers Studied

The researchers reviewed short-term field studies involving different crops, soils, climates, and biochars. For their main analysis, they focused on studies using no more than 20 metric tons of biochar per hectare. They also separated studies using inorganic fertilizer from those using organic materials.

One part of the study was especially useful. The researchers compared biochar plus fertilizer with fertilizer alone. This helped them see how much benefit came from adding biochar rather than simply measuring the effect of fertilizer.

What the Study Found

The researchers found clear differences in average crop yield. Compared with crops receiving no fertilizer, inorganic fertilizer increased yield by 26%. When biochar and inorganic fertilizer were used together, yield increased by 48% compared with the unfertilized crops.

The direct comparison showed biochar’s added effect more clearly. Crops receiving both biochar and inorganic fertilizer produced an average of 15% more yield than crops receiving the same type of fertilizer without biochar.

These results support an important idea about how biochar fits into agriculture. Biochar does not need to replace fertilizer to provide value. Instead, it can work with a fertility program by improving the soil where plants get their water and nutrients.

Biochar’s Benefits Can Build Over Time

Biochar is different from many farm inputs because it can remain in soil for a long time. Its porous structure can help soil hold water and nutrients, provide space for beneficial microbes, and improve other soil conditions that support plant growth.

The meta-analysis found signs that crop benefits can continue over time. Studies that followed a single biochar application for three years or longer reported an average 31% increase in crop yield. There were fewer long-term studies available, so more research is needed to understand how these effects develop over many growing seasons.

Why Results Differ From Farm to Farm

Not every field responds to biochar in the same way. The research found that benefits often depended on the condition of the soil before biochar was added. Acidic and lower-fertility soils often showed stronger responses, while already productive soils sometimes showed smaller changes.

The biochar itself also matters. Different feedstocks and production methods create biochars with different pH, nutrient levels, pore structures, and other properties. This helps explain why choosing a biochar suited to the soil and crop is important. These differences do not take away from the overall findings. Instead, they help explain why researchers see strong results in some fields and smaller changes in others.

What We Can Take From the Research

The 2019 meta-analysis provides strong evidence that biochar can support crop productivity. Across the studies reviewed, adding biochar to inorganic fertilizer increased yields by an average of 15% compared with fertilizer alone. The research also shows that biochar works best as part of a larger soil and nutrient program. Its value comes from improving the growing environment and helping soil make better use of water and nutrients, rather than simply replacing fertilizer.

For farmers, the larger lesson is straightforward: biochar can be a useful tool for building healthier soils and supporting crop production, and its benefits can continue beyond a single growing season.