Effects of a new compost-chemical fertilizer mixture on CO2 and N2O production and plant growth in a Chernozem and an Andosol

Composts are an attractive organic-farming alternative to chemical fertilizers and are used for carbon sequestration to increase soil carbon storage. In Japan, a new type of mixed compost fertilizer called compost-compound fertilizer mixture (CCFM) has been registered. It exhibits several merits for organic farming; that is, it is odorless, easy to handle, and has a controllable nutrient content. CCFM consists of compost mixed with chemical fertilizer, such that nutrient content can be effectively adjusted. Although it has been pointed out that pellet composts generate more greenhouse gas emissions (GHGEs), such as carbon dioxide (CO2) and nitrous oxide (N2O), the mechanism involved is not clearly understood. To investigate the effect of CCFM on GHGEs, soil microbial properties and plant growth, incubation and pot experiments were conducted in a Hungarian Chernozem and a Japanese Andosol. Both soils were incubated with 1) CCFM prepared using pig manure mixed with chemical fertilizer, 2) chemical fertilizer only, or 3) no fertilizer. A pot experiment was conducted using Komatsuna (Brassica rapa). In the Chernozem, the maximum N2O production rate was observed after chemical fertilizer treatment. The emission factors of chemical fertilizer and CCFM were 0.25% and 0.19%, respectively. In contrast, N2O production was not detected in the Andosol. Meanwhile, CO2 production was higher (P < 0.05) in the Chernozem than in the Andosol; furthermore, it was higher under CCFM than under chemical fertilizer treatment, with 7.5% of amended carbon changing to CO2, thus suggesting that dominant carbon remained in the soil. Microbial biomass increased faster in the Andosol than in the Chernozem and the change was faster under the CCFM than under the chemical fertilizer or control treatments. In the pot experiment, CCFM tended to enhance plant growth in both soils. These experiments showed that CCFM has a soil-carbon storage effect with less resultant GHGEs, especially in Andosols, thereby leading to a more sustainable agriculture. Nonetheless, further studies are required for long-term experiments with other crops.

Automated summary

CCFM is a mixed compost fertilizer registered in Japan, which combines compost with chemical fertilizer. It is odorless, easy to handle, and has controllable nutrient content, making it beneficial for organic farming. In experiments conducted using CCFM, it was found to enhance soil-carbon storage with lower greenhouse gas emissions and promote plant growth, especially in Andosol soils. Further studies are needed for long-term experiments with different crops to confirm its sustainability.