Investigations on soil nitrogen. I.—The influence of nitrogen fertilizers and rainfall on soil nitrate concentrations

Abstract Changes in the concentration of nitrate in soils taken during field experiments on cereals were followed for two months in Spring, 1955. At centres where nitrogen fertilizer increased yields of wheat and barley, soil nitrate at planting did not exceed 7 p.p.m. of N; in two experiments where the crops did not respond to fertilizer nitrogen there were 10 p.p.m. or more of nitrate present. Soil nitrate levels were markedly increased by additions of calcium nitrate and to a lesser extent by ammonium sulphate. Light rainfall which did not percolate deeply into the soil did not reduce nitrate concentrations seriously in the surface layers, but nitrate was reduced to very low levels at all centres by rain which percolated through 20 in. of soil.