Effect of potassium fertiliser., soil magnesium status, and soil type on uptake of magnesium by pasture plants from magnesium fertilisers

Abstract

Abstract Comparisons were made between low rates of dolomite (D) and superphosphate (SP) applied separately or in a dry mixture (SP + D), dolomite- “reverted” superphosphate (DSP), serpentine-reverted superphosphate (SSP), superphosphate plus ground serpentine rock (SR), and superphosphate plus calcined magnesite (MgO), supplying 27.5 to 55kg total Mg/ha, in the presence and absence of K fertiliser, as sources of Mg for uptake by pasture plants in 23 experiments on a range of soil types (pH 5.2 to 6.6) of variable Mg status (0.28 to 4.17 me. exchangeable Mg per 100g soil). Dolomite and ground limestone (L) at 2510 kg/ha were included in 13 experiments. No consistent yield responses were obtained from any of the Mg treatments or L. but some significant K responses were found. Mg concentrations in herbage from control (no Mg) treatments ranged from 0.16 to 0.26% in spring and from 0.23 to 0.35% in autumn. At the low rates used, mean absolute increases in herbage Mg concentrations were very small, ranging fr...