ABSTRACT
Microbial nutrient limitation was investigated in a 53-year-old field experiment in the Central-West of Burkina Faso under sorghum-cowpea rotation, comparing three fertilization practices: mineral fertilizer (MIN), mineral fertilizer and farmyard manure (MINFYM), and a non-fertilized control (CON). We assessed microbial N and P limitation after removal of C limitation by (i) determining microbial N and P, (ii) assessing respiration kinetics in incubated soil samples amended with easily available C (glucose) alone or in combination with N and/or P, or not amended, and (iii) evaluating changes in microbial biomass and community composition at the peak of microbial respiration by microbial P and phospholipid fatty acid (PLFA) analyses. Microbial N and P were very low in all fertilization practices, but greater in MINFYM than in CON. Easily available C was the first factor limiting microorganisms in all fertilization practices. After removal of C limitation, most indicators suggested N and P co-limitation in CON. In contrast, respiration kinetics in MINFYM and MIN were only N-limited, while biomass formation in MINFYM was also P-limited. PLFA analyses indicated preferential fungal growth on the added C, and P limitation of changes in microbial community composition in MIN. Long-term application of fertilizers mostly alleviated secondary microbial nutrient limitation by P but not by N, and C always remained the primary limiting factor for microbial growth.
Reference:
Traoré, O., Kiba, D., Arnold, M., Fliessbach, A., Oberholzer, H., Nacro, H., Lompo, F., Oberson, A., Frossard, E., Bünemann, E., Fertilization practices alter microbial nutrient limitations after alleviation of carbon limitation in a Ferric Acrisol, Biology & Fertility of Soils, Volume: 52 Issue: 2 Pages: 177-189 Published: FEB 2016.