MINERALIZATION OF CARBON AND NITROGEN FROM FRESH AND ANAEROBICALLY STORED SHEEP MANURE IN SOILS OF DIFFERENT TEXTURE

A sandy loam soil was mixed with three different amounts of quartz san d and incubated with ((NH4)-N-15)(2)SO4 (60 mu g N g(-1) soil) and fre sh or anaerobically stored sheep manure (60 mu g g(-1) soil). The mine ralization-immobilization of N and the mineralization of C were studie d during 84 days of incubation at 20 degrees C. After 7 days, the amou nt of unlabelled inorganic N in the manure-treated soils was 6-10 mu g N g(-1) soil higher than in soils amended with only ((NH4)-N-15)(2)SO 4. However, due to immobilization of labelled inorganic N, the resulti ng net mineralization of N from manure was insignificant or slightly n egative in the three soil-sand mixtures (100% soil+0% quartz sand; 50% soil+50% quartz sand; 25% soil+75% quartz sand). After 84 days, the c umulative CO2 evolution and the net mineralization of N from the fresh manure were highest in the soil-sand mixutre with the lowest clay con tent (4% clay); 28% fo the manure C and 18% of the manure N were net m ineralized. There was no significant difference between the soil-sand mixtures containing 8% and 16% clay, in which 24% of the manure C and -1% to 4% of the manure N were net mineralized. The higher net mineral ization of N in the soil-sand mixture with the lowest clay content was probably caused by a higher remineralization of immobilized N in this soil-sand mixture. Anaerobic storage of the manure reduced the CO2 ev olution rates from the manure C in the three soil-sand mixtures during the initial weeks of decomposition. However, there was no effect of s torage on net mineralization of N at the end of the incubation period. Hence, there was no apparent relationship between net mineralization of manure N and C.