Influence of plant growth on denitrification in relation to soil moisture and potassium nutrition

Abstract

Abstract The effect of soil moisture content and K nutrition on denitrification measured by the acetylene inhibition method in short‐term assays was studied in pot experiments with wheat on a low‐nutrient sandy soil. Increasing the soil moisture from 60 to 80 or 100% water holding capacity (whc) increased denitrification which was further increased when the soil moisture was raised to 100% whc 24 h before the assay. This effect was not observed with unplanted pots. Denitrification increased with progressing plant age, provided sufficient nitrate was present. N 2 O production was particularly high after removal of the shoots as decaying root matter improved conditions for denitrification. Optimal plant growth reduced denitrification through more rapid nitrate uptake and lower soil moisture, whereas poor plant growth, induced by K deficiency, restricted NO 3 uptake and sustained high soil moisture causing higher N 2 O production. In a separate experiment it was demonstrated that denitrification occurs mainly in the immediate vicinity of the roots.