Water-soluble organic matter and biological activity of a degraded soil amended with pig slurry.

The effects of pig slurry (PS) addition at rates of 30, 90 and 150 m(3) ha(-1) per year for five consecutive years on total organic C (TOC), water-soluble organic C (WSOC), soil microbial biomass C (MBC), basal respiration (BR) and dehydrogenase (DEH) and beta-glucosidase (GLU) activities of soil were investigated in a field experiment conducted under barley cultivation and semiarid conditions. Cumulative PS addition at 90 and 150 m(3) ha(-1) rates had a significant stimulating effect on MBC content and DEH and GLU activities. In contrast, no significant effect of PS amendment on TOC, WSOC and BR was detected. These results suggest that PS addition revitalizes soil microbial metabolism in transitory form because of the low stability of the added organic matter.