Biochar and nitrogen effects on nitrate leaching, physiological performance, and rhizome quality of turmeric (Curcuma longa L.) in sandy soil

A greenhouse pot experiment found that adding coffee husk biochar was associated with lower nitrate leaching across four nitrogen fertilizer rates in sandy soil, while the combination of 150 kg N ha⁻¹ and 15 t ha⁻¹ of biochar produced the highest measurements for several physiological and rhizome-quality traits in turmeric (Curcuma longa L.).

The factorial experiment, summarized in the study abstract, tested nitrogen rates of 0, 70, 150 and 250 kg N ha⁻¹ with biochar rates of 0 and 15 t ha⁻¹. Researchers measured nitrate leaching and assessed chlorophyll, relative water content and stomatal characteristics. Rhizome analyses covered phenolics, flavonoids, curcuminoids, oleoresin and antioxidant activity. Nitrogen rate, biochar rate and their interaction significantly influenced physiological traits and nitrate leaching, with the reported analysis giving p < 0.001.

Without biochar, measured nitrate loss rose from 360 mg N pot⁻¹ at the zero-nitrogen treatment to 2,906.67 mg N pot⁻¹ at 250 kg N ha⁻¹. With biochar, nitrate loss was 180–280 mg N pot⁻¹ across the tested nitrogen levels. The N150B15 treatment, combining 150 kg N ha⁻¹ with 15 t ha⁻¹ of biochar, recorded the highest chlorophyll content at 41.99 SPAD and relative water content at 92.61%. It also had the highest measured concentrations of phenolics at 39.65 mg gallic acid equivalents g⁻¹, flavonoids at 16.22 mg catechin equivalents g⁻¹ and curcuminoids at 61.67 mg curcuminoid equivalents g⁻¹. Oleoresin reached 61.89% in that treatment.

Antioxidant measurements were also highest under N150B15: 75.03% 2,2-diphenyl-1-picrylhydrazyl activity and 45.56 mg ascorbic acid equivalents g⁻¹ of ferric reducing antioxidant power. The abstract therefore reports improved measured physiology and rhizome phytochemical quality, together with reduced nitrate leaching, for moderate nitrogen combined with biochar in the tested sandy soil. These results are limited to a greenhouse pot experiment using one type and application rate of coffee husk biochar, one soil context and four nitrogen rates. The authors state that field-scale validation using diverse biochar types and rates is required before broader recommendations can be made; the supplied evidence does not establish field performance or wider applicability.

Subject of Research: Effects of coffee husk biochar and nitrogen rates on nitrate leaching and turmeric physiology and rhizome quality in a sandy-soil pot experiment

Article Title: Biochar and nitrogen effects on nitrate leaching, physiological performance, and rhizome quality of turmeric (Curcuma longa L.) in sandy soil

Article References: Eshetu, T., Dessalegn, E., Belew, D., Gobena, A., & Nigusie, A. (2026). Biochar and nitrogen effects on nitrate leaching, physiological performance, and rhizome quality of turmeric (Curcuma longa L.) in sandy soil. BMC Plant Biology. https://doi.org/10.1186/s12870-026-09940-6

Image Credits: AI Generated

DOI: 10.1186/s12870-026-09940-6

Keywords: turmeric, Curcuma longa, biochar, nitrogen fertilization, nitrate leaching, greenhouse pot experiment, sandy soil, rhizome quality, curcuminoids, chlorophyll, nitrogen, effects