Thirty-seven years of soil nitrogen and phosphorus fertility management shapes the structure and function of the soil microbial community in a Brown Chernozem

Andre Freire Cruz¹, Chantal Hamel², Keith Hanson², Fernando Selles³ and Robert P. Zentner²

Abstract
We tested whether levels of soil available nitrogen (N) and phosphorus (P) control the composition and function of the soil microbial community in a Brown Chernozemic soil on the Canadian Prairie.

Soil dissolved organic carbon, N and P, and microbial communities structure (phospholipid fatty acid profile) and function (enzyme activity) were evaluated in the fallow and first wheat (Triticum aestivum L. cv. AC Eatonia) phases of fallow-wheat-wheat rotations where the wheat received soil test recommended rates of mineral N and P fertilizers (+N+P), or where N (-N+P) or P (+N-P) fertilizer use was withheld for 37 years.

Differential fertilization modified soil N and P availability, and microbial community structure. Low N level was a major constraint when a rapidly growing wheat crop (heading stage) was drawing on the resource, reducing both plant N uptake and soil microbial biomass-C in -N+P soils. Available P level in +N-P soils was about half that measured in P-fertilized soils, but P did not limit plant productivity or microbial development at that time.

Changes in the microbial community structure seemingly buffered the impact of lower P availability in +N-P soils. Phosphatase activity was not involved, but increased abundance of arbuscular mycorrhizal fungi might be associated with this effect. Low soil N availability explained lower specific denitrification and higher specific nitrogenase activities in -N+P soil growing wheat. Higher denitrification activity in +N+P soil could be attributed to higher soil C level and fertilization-induced shifts observed in the structure of the soil microbial community.

Irrespective of the fertility level of the soil, all microbial communities grew at the relative growth rate of 17% day-1 in a nutrient limitation assay that revealed no C, N or P limitation in these communities. We conclude that mineral fertilization, which modifies soil available N and P fertility, can be a selective force causing structural and functional shifts in the soil microbial community with a resulting impact on soil quality and nutrient fluxes.


Source
Plant and Soil (2009) 315: 173-184

Author Locations & Affiliations
(1) Graduate School of Agriculture, Kyoto Prefectural University, 1-5 Shimogamohangi-cho, Sakyo-ku, Kyoto 606-8522, Japan
(2) Semiarid Prairie Agricultural Research Centre AAFC, P.O. Box 1030, 1 Airport Rd, Swift Current, Saskatchewan, S9H 3X2, Canada
(3) Brandon Research Centre AAFC, 18th Street North and Grand Valley Road, P.O. Box 1000A, R.R. #3, Brandon, Manitoba, R7A 5Y3, Canada


Posted March 2010