The present work had the objective of evaluating the liberation of the nitrogen associated to the labile carbon oxidized with KMnO4 (333 mmol L-1) and to verify the supply capacity of nitrogen by its correlation with the nitrogen absorbed by the plants. The soil used belongs to a Cambic Yellow Red Podzol, cultivated with corn since 1984, and its productivity is being evaluated as a function of the doses of 0 and 40 m³ ha-1 year-1 of organic compost (beans and soybean straw with manure), combined with 0, 250 and 500 kg ha-1 year-1 of the formula 4-14-8 applied at planting and 0, 100 and 200 kg ha-1 year-1 of ammonium sulphate as top dressing. The results showed that the use of the organic material contributed to a higher amount of nitrogen soluble in KMnO4 (333 mmol L-1). The content of soluble nitrogen in KMnO4 (333 mmol L-1) was found to be superior than that obtained by the anaerobic method and correlated significantly with the total carbon, labile carbon, total nitrogen, ammonium and nitrate content and with the nitrogen bioavailability.
organic carbon; oxidation of the carbon; long-term experiment; continuous fertilization
