The Brigalow Catchment Study: V*. Clearing and burning brigalow (Acacia harpophylla) in Queensland, Australia, temporarily increases surface soil fertility prior to nutrient decline under cropping or grazing

In the Brigalow Belt bioregion of Australia, clearing brigalow (Acacia harpophylla) scrub vegetation for agriculture has altered nutrient cycling over millions hectares. order to quantify effect this and land use change on soil fertility, Catchment Study commenced in 1965. Initial burning resulted a temporary increase mineral nitrogen, total available phosphorus, exchangeable potassium sulfur surface (0–0.1 m) as result heating ash bed effect. Soil pH also increased, but did not peak immediately after burning. fertility declined significantly subsequent 32 years. Under cropping, organic carbon by 46%, nitrogen 55%, phosphorus 29%, bicarbonate-extractable 54%, acid-extractable 59%, 49%, 9% 63% from post-burn, pre-cropping concentrations. Fertility under grazing different pattern that observed cropping. Organic showed clear fluctuation it was until natural variation time separated anthropogenic effects significant decline observed. Total 22%. 14%, equating only half Bicarbonate-extractable 64% 66%; both greater than 23%; less A similar uses, with 10% grazing. Exchangeable 59%. The primary mechanism loss depended specific question.