# Phosphorus Distribution in Soils from Australian Dairy and Beef Rearing Pastoral Systems
## 2 Materials and Methods  
### Sampling Site Descriptions  
Soil samples were collected from selected agricultural sites situated in two areas in the Gippsland region of south-east Victoria, near Mafra and Warragul (Figure 1). These areas were selected as geographically close agricultural areas (approximately 120 km range) with varying agricultural management practices, particularly irrigation application. The average annual rainfall for the two areas is 582 mm for Maffra and 1021 mm for Warragul. Average ambient air temperatures range from 8.4 \({}^{\circ}\)C (min) to 19.2 \({}^{\circ}\)C (max) for Warragul and 8.1 \({}^{\circ}\)C (min) to 20.0 \({}^{\circ}\)C (max) for Maffra. Rainfall and temperature may be variable between individual locations within each of these areas.  
All sites of the Maffra area receive irrigation as part of the Macalister Irrigation District (MID). On the other hand, the Warragul area is predominantly a rain-fed system, and none of the soils from the Warragul area were irrigated. The number of irrigations applied to sampling sites of the Maffra area varied. Based on available information, irrigations for the Macalister Research Farm (38\({}^{\circ}\)00\({}^{\prime}\) S 146\({}^{\circ}\)54\({}^{\prime}\) E), a dairy farm situated in the MID, typically vary between 10 and 16 per annum. Stocking rates varied between agricultural areas, ranging between 1.8 to 2.8 cattle ha\({}^{-1}\) for the Warragul area (Laidlaw, personal communication, 2009) and between 3.0 to 4.3 cattle ha\({}^{-1}\) (Tyndal, personal communication, 2009) for the Maffra area. The higher stocking rates in the Maffra area can be attributed to availability of irrigation water during the dryer periods of the year.  
Dairy production pastures were mainly grazed with Friesian cattle, however milking herds often contained some Jersey cattle. Beef production cattle herds were predominantly of Angus or Hereford cattle. Selected sites were not grazed for at least one week prior to sampling. As the sites were grazed, nutrients were returned to soil unhindered through faeces and urine. Urine of ruminants generally only has trace amounts of P, however this does increase as P intake increases [30; 31]. Livestock faeces have been shown to have an increased inorganic and organic P content compared to the ingested pasture [32]. Hence, cattle dung contributes to localised, high intensity inputs of nutrients including P [33; 34]. The overall P contribution and speciation from cattle faeces varies depending on a number of factors including water regime [35] and weather/seasonal conditions [36]. To minimise possible effects on the results obtained in this study, areas with excreted wastes were carefully avoided during soil sampling, and large number of soil cores (200+) were bulked to minimise contribution from animal excretions.  
Figure 1: Selected sampling areas within the Gippsland region of south-eastern Victoria. Adapted from Nash [37].  
The locations sampled carried permanent pastures which were predominantly perennial ryegrass (_Lolium perenne_), white clover (_Trifolium repens_) and contained assorted invasive species, particularly dock (_Rumex_ spp.), cape weed (_Arctotheca calendula_), marshallow weed (_Malva parviflora_) and disticulum (_Paspalum paspaloides_). Pastures were maintained with the addition of varying rates of inorganic fertiliser blends which included P. Available information indicated that the sampled sites received no cultivation and/or cropping for at least 10 years prior to sampling. The exception was site M6, which was laser graded six years prior to sampling. Laser-grading involved cultivation using a disk plough followed by minor cutting and filling as the bay had previously been formed (>20 years prior) [38].