MATURITY ASSESSMENT OF WHEAT-STRAW COMPOSTS BY THERMOGRAVIMETRIC ANALYSIS

Thermogravimetric analysis in oxidizing atmosphere has been used to characterize composts prepared from wheat straw with different organic and mineral additives. After a wide range of classical parameters were determined for the chemical maturity of composts, plant yield improvement was studied in a greenhouse experiment. It was found that most chemical and agrobiological maturity indices paralleled peak area values in the differential thermogravimetric curves. In particular, the weight loss corresponding to compost material destroyed between 360 and 540 degrees C showed a very significant correlation with the germination index and the plant yield of the soils amended with compost. As expected, the extent of such thermal effects reflected also the H/C, O/C, and C/N ratios and the lignin content of the composts. Experiments during the methodological optimization of thermogravimetric analyses have shown the importance of removing the compost water-soluble fraction to prevent spurious results, probably due to the effect of salts on thermal decomposition in the lignocellulosic substrate.