Effects of irrigation and fertilization on soil microbial biomass and functional diversity.

摘要

Optimal water and nutrient treatment effects on soil microbial characteristics, including microbial functional diversity and microbial biomass carbon (C) and nitrogen (N) were assessed at a loblolly pine (Pinus taeda) plantation on a Sandhills site (Scotland County, North Carolina, USA) after 6 years of continuous fertilizer application and irrigation. The soil is of the Wakulla series (excessively drained, sandy, siliceous, thermic Psammentic Hapludult). Nutrient additions were initiated in March 1992 to maintain optimum nutrition. Irrigation was initiated in April 1993 to supplement the rainfall to maintain at least 40% of available soil moisture in the surface 50 cm of soil. Application of fertilizers significantly increased soil C and N and microbial C and N. Irrigation significantly increased soil C and N, and microbial C. Fertilizer application, irrigation, and their interaction changed soil microbial selection of carbon compounds, but did not influence the numbers of carbon compounds utilized by soil microbes, as measured by the BIOLOG method suggesting that soil microbial species may have changed. The increases in soil microbial biomass and soil C and N indicate that the fertilizer application and irrigation treatments have had a positive effect on soil productivity on this very sandy site..