Preliminary Design for Establishing Compost Maturity by Using the Spectral Characteristics of Five Organic Fertilizers

The maturity of compost is involved in the availability of nutrients to crops and improvement of soil properties after fertilization. The determination of composts maturity mostly required analyses in the laboratory previously and it must consume a lot of time and cost. This studies were conducted to use Fourier Transform Infrared (FTIR) spectroscopy and solid 13 C Nuclear Magnetic Resonance ( 13 C NMR) spectroscopy to understand the mature characteristics of five type of common composts. The FTIR analysis showed that all composts contained aromatic groups. In addition, the surface of composts were enriched with the functional groups including hydroxyl group, carboxyl group, amino group etc. However, these functional groups changed along with maturity degree. It is preliminarily recognized that the aliphatic group located at 2,930 cm -1 and 2,850 cm -1 showed a decreasing peak, and amino acid at 1,385 cm -1 was disappearing gradually due to the decomposition by bacteria. There may be used to identify the maturity degree of composts. Productions of aromatic group at 1,650 cm -1 , carboxy (-COOH) and phenolic OH groups at 1,385 cm -1 may prove the full maturity of composts. 13 C NMR analysis showed that five type of matured composts are mainly consisted with aliphatic groups and aromatic groups. The surfaces of the composts contained C-O bounds (CO carbons-alcohols, ester, ethers, carbohydrates and other functional groups), COO - (carboxyl and ester carbons) and C = O bond (aldehydes and ketones). The strength of different absorptive characteristics of FTIR and 13 C NMR may be a clue of the maturity of composts for future designing reference of detective instruments.