Intensive vegetable farming can produce large harvests, but it often comes with heavy fertilizer use and low nitrogen use efficiency. A new field study in Southern China suggests that adding the right amount of biochar could help farmers grow more vegetables while making better use of nitrogen fertilizer and improving soil quality.
Researchers found that applying 20 metric tons of rice-straw biochar per hectare produced the strongest overall benefits. Over the two-year experiment, this treatment increased vegetable yields by 10% to 29%, nitrogen use efficiency by 18% to 160%, and plant nitrogen uptake by 14% to 33% compared with plots receiving no biochar.
"Our results show that more biochar is not necessarily better," said Bo Li, corresponding author of the study from South China Agricultural University. "A moderate application rate provided the best balance between improving soil conditions, supporting soil microorganisms, and helping vegetable crops use nitrogen more efficiently."
The findings were published in Nitrogen Cycling in the study, "Biochar enhanced the vegetable production and nitrogen use efficiency by improving soil quality in intensive vegetable fields in Southern China."
The researchers conducted a two-year field experiment in Guangdong Province, China, using intensive vegetable fields planted with lettuce varieties. Five biochar application rates, ranging from zero to 40 t ha⁻¹, were compared under conventional nitrogen fertilization. The biochar was produced from rice straw by pyrolysis at 500 °C.
The benefits extended well below the vegetables themselves. Biochar improved the physical structure of the soil, including the formation and stability of water-resistant soil aggregates. It also increased microbial biomass and altered nutrient availability. At the optimal 20 t ha⁻¹ rate, the soil quality index was 39.7% higher in the first year and 50.6% higher in the second year than in the control treatment.
Statistical modeling provided further clues about how these improvements translated into better crop performance. The researchers found that biochar influenced vegetable production and nitrogen utilization largely by changing soil nutrient availability, microbial communities, and soil structure. Higher soil quality was positively associated with vegetable yield, nitrogen uptake, and nitrogen use efficiency.
Importantly, the response was not linear. Vegetable yield and nitrogen-related indicators generally increased as biochar application rose to around 20 t ha⁻¹, then declined at higher rates. Applying 30 or 40 t ha⁻¹ did not produce additional yield benefits and could disturb nutrient balance or microbial conditions.
This finding could have practical implications because biochar can be costly. The researchers calculated that, under the conditions of the experiment, 20 t ha⁻¹ offered the most favorable amendment rate when both crop benefits and biochar costs were considered.
The authors caution that the study covered only two years. Longer-term experiments will be needed to determine how long the benefits persist and whether repeated moderate applications are needed in warm, high-rainfall regions.
Together, the findings suggest that carefully optimized biochar application could provide a practical route toward more productive and nitrogen-efficient intensive vegetable farming while improving degraded soils.
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Journal Reference: Chen Z, Liu Y, Hu J, Lu Y, Elsgaard L, et al. 2026. Biochar enhanced the vegetable production and nitrogen use efficiency by improving soil quality in intensive vegetable fields in Southern China. Nitrogen Cycling 2: e026 doi: 10.48130/nc-0026-0013
https://www.maxapress.com/article/doi/10.48130/nc-0026-0013
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Nitrogen Cycling (e-ISSN 3069-8111) is a multidisciplinary platform for communicating advances in fundamental and applied research on the nitrogen cycle. It is dedicated to serving as an innovative, efficient, and professional platform for researchers in the field of nitrogen cycling worldwide to deliver findings from this rapidly expanding field of science.
