Studies on mineralization of nitrogen and sulphur in a climo-sequence of soils in Central Otago : A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Agricultural Science in the University of Canterbury

Abstract

The aims of the present investigation were as follows: 1. To examine relationships between various properties of each soil in the sequence, such as pH , total N, NH⁺ ⁴-N,NH⁻ ³-N, total S, SO₄⁻₋s, total C, water holding capacity and the C:N, C:S, N:S and C:N:S ratios. 2. To study the rates of mineralization of nitrogen and sulphur upon incubation of the soils. The amounts of NH⁺ ⁴-N,NO⁻ ³-N, SO₄⁻₋s in each soil were measured at intervals during incubation. 3. To assess the most probable number of the nitrifying bacteria in each soil in order to assist evaluation of its nitrifying power . 4. To investigate the effect of air drying on the mineral - N and sulphate contents of unincubated soils and on the mineralizable nitrogen and sulphur values upon incubation. 5. To investigate the effect of lime on nitrogen and sulphur mineralization in all soils.