Effect of Fertilization Systems on Soil Microbial Biomass and Mineral Nitrogen during Canola (Brassica napus L.) Development Stages

Abstract

The dynamics of microbial biomass and mineral nitrogen (N) during two growth stages were compared in soils under different fertilization treatments. At stem elongation, the fertilizer system had more N in the mineral pools, whereas manure and integrated systems had more N in the microbial biomass, indicating shifts in N pools between the two systems. At the flowering stage, integrated (manure + fertilizer) and manure systems had more N in two pools, indicating release of plant-available N from the microbial biomass. The carbon (C) / N ratio of the microbial biomass was significantly greater in manure and integrated treatments than in fertilizer treatments. Soil mineral N was significantly positively correlated with seed yield at the stem elongation stage, whereas it was positively correlated with soil microbial biomass C at the flowering stage. Stepwise regressions revealed that seed yield was significantly associated with mineral N at stem elongation and microbial biomass N at the flowering stage.

Keywords:

• Canola
• fertilization system
• manure
• microbial biomass
• mineral N

Acknowledgment

This study was financed by Shahid Beheshti University, G.C. The authors thank the Soil and Water Research Institute, Soil Microbiology Laboratory, for providing facilities for soil biochemical analyses.