Effect of nitrogen fertilisation on nitrous oxide emission and the abundance of microbial nitrifiers and denitrifiers in the bulk and rhizosphere soil of Solanum lycopersicum and Phaseolus vulgaris

Abstract

Aims: To determine the effect of three N-fertilisers on NO emission and abundance of nitrification and denitrification genes in bulk and rhizosphere soil of tomato and common bean, two vegetable crops representative of main horticultural crops in South Spain. Methods: Four consecutive harvests of tomato and common bean fertilised with urea, ammonium or nitrate were carried out. The total abundance of bacteria, archaea, nitrifiers and denitrifiers was estimated by quantitative PCR. Soil physicochemical properties and NO emission were also determined. Results: Regardless of the plant species, the highest NO emission was produced by the soil treated with urea, followed by ammonium and nitrate. Bacteria were more abundant than archaea in the bulk and rhizosphere soil. The abundance of the ammonia-oxidising archaea was greater than the ammonia-oxidising bacteria in the rhizosphere, but lower in the bulk soil. N-fertilisation increased the gene copy number of denitrifiers, which were more abundant in the bulk soil. Conclusions: N-fertilisation decreases NO production due to increased abundance of the nosZ gene. The abundance of nitrification and denitrification genes in bulk and rhizosphere soils is dependent on the type of fertiliser. For both plant species, the ratio of the genes involved in production and reduction of NO by bulk and rhizosphere was similar.