Untilled dairy pasture has the potential to release more phosphorus to the environment than a regularly ploughed pasture. In this paper we report the initial results of a study comparing the effects of cultivation, phosphorus (P) fertiliser (10, 35, and 100？kg？P/ha), and two types of vegetation (ryegrass (Lolium perenne) or ryegrass mixed with clover (Trifolium repens)) in a randomised complete block design. Phosphorus was measured in soil samples taken from depths of 0–20？mm and 0–100？mm. Waters extracted from the 0–20？mm samples were also analysed. In all cases, the P concentrations (Olsen P, Colwell P, Total P, CaCl2 extractable P, Dissolved Reactive P, and Total Dissolved P) in the top 20？mm declined with ploughing. Dissolved Reactive P measured in the soil water was 70% less overall in the ploughed plots compared with the unploughed plots, and by 35 weeks after P treatments the decrease in Dissolved Reactive P was 66%. The effects of the fertiliser and pasture treatments were inconclusive. The data suggest that ploughing can lower the risk of P exports from intensive dairy farms in the trial area. 1. Introduction Excessive phosphorus (P) in surface waters is a major environmental issue in Australia [1]. In many freshwater ecosystems, P limits primary production and excessive P inputs contribute to eutrophication and the development of cyanobacterial blooms [2] which can be hazardous to human health [3–5]. This is especially true in the Gippsland Region of south-eastern Australia which contains the Tambo, Mitchell, Thomson, and Latrobe rivers and an estuarine lakes system of international significance, the Gippsland Lakes [6]. Agricultural enterprises, particularly dairy farms [7–9], contribute to excessive P concentrations and the associated increasing prevalence of algal blooms in the Gippsland Lakes [10, 11]. For the Victorian coastal plains (Gippsland through to Melbourne at less than 200？m elevation), annual 75th percentile targets for total P (TP) and total nitrogen (TN) have been established for nutrients in rivers and streams; these targets are 0.045？mg/L and 0.6？mg/L, respectively [12]. A broad range of strategies have been instigated to lessen P inflows to the Gippsland Lakes [13, 14]. These strategies include on-farm measures such as minimising water lost to drains, construction of reuse ponds, stock exclusion from waterways, control of soil erosion, and management of fertiliser application and timing, as well as various off-farm measures to reuse irrigation drain water and minimise inputs from stream erosion, forestry activities, and
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