Stimulation and suppression of mineralisation and nitrification in incubated soil

Abstract

Priming, induced through the addition of oxidisable organic matter, releases or immobilises nitrogen and other nutrients in the soil. Moisture plays a very important role in priming as it stimulates microbial activity after a dry soil is wetted, especially with the addition of organic material and reduced mineral nitrogen fertilisers. This phenomenon was observed in the incubation experiments with different organic material and mineral fertiliser additions. The resulting graphs could be divided into three phases: Phase 1—nitrogen flush; Phase 2—growth; and Phase 3—depletion and expiration. Ammonium-nitrogen can be available for plant uptake two days after fertiliser application if a dry soil is wetted. When organic matter is added to soil, microbial activity is stimulated and immobilisation of ammonium can take place. The ammonium can be released later in the season for plant uptake, thus regulating its availability.