Compost with biochar and DCD cuts ammonia losses while sustaining yields

Adding biochar and dicyandiamide (DCD) to compost can cut ammonia losses from nitrogen fertilizer without sacrificing yields, according to a study from the Jiangsu Academy of Agricultural Sciences published in Agricultural Ecology and Environment on June 22, 2026 (DOI 10.48130/aee-0026-0016).

Organic fertilizers are often paired with mineral nitrogen to recycle farm residues and build soil fertility. Conventional compost does not consistently reduce nitrogen losses, and it can increase ammonia emissions by speeding urea breakdown. Biochar, a porous material made by heating biomass with little oxygen, can promote ammonia release under some conditions. DCD, an inhibitor of microbial nitrogen conversion, works differently depending on soil properties. Most earlier studies applied these additives directly to soil, which leaves open how adding them during composting affects crops and emissions.

How the experiment was run

The team ran a soil-column experiment from 2022 to 2024 through two complete rotations, rice and then wheat. Four treatments, each replicated three times, compared conventional urea with three organic options supplied alongside 70% of the conventional mineral nitrogen rate: unmodified compost, compost with 15% biochar, and compost with 15% biochar plus 0.5% DCD.

Researchers measured ammonia with gas-flow enclosures and nitrous oxide with static chambers and gas chromatography. They also tracked ammonium, nitrate, pH, urease activity and microbial communities. To model economics, they ran 10,000 Monte Carlo simulations using production costs, fertilizer savings, environmental and health costs, and assumed crop price premiums.

Ammonia losses fell while rice yields held

The combined additive gave the most persistent ammonia reduction, cutting cumulative losses by 27.1% relative to urea alone across the two rotations. Compost alone and biochar-only compost increased overall ammonia emissions relative to urea and reduced rice yields by about 19.5% to 19.6%. The combined treatment kept rice yields comparable to the urea control.

Nitrous oxide emissions stayed low, with no significant differences among treatments. Chemical analysis linked ammonia losses to ammonium availability and pH, particularly in floodwater above rice soils.

Results varied by crop and season

The benefits were more consistent in rice than in wheat, and responses varied between crops and seasons. Sequencing showed shifts in microbial composition, including reduced representation of Nitrospirota, a group involved in nitrogen conversion. The researchers said these shifts suggest possible functional changes but did not directly establish a microbial mechanism.

Economic estimates are illustrative

The simulations estimated potential benefits of about CNY 36,600 per hectare a year for the combined treatment (USD equivalent not verified). The estimates include assumed price premiums and modeled environmental benefits, so the authors present them as scenarios rather than demonstrated farm income.

What the study does not yet show

The work was done in soil columns, not open fields, so it does not show field-scale performance. The authors call for larger field trials across different soils, climates and management practices before practical performance and economic viability can be established. Their broader conclusion is that fertilizer formulation matters when recycled organic material replaces part of the mineral nitrogen supply.