Phosphorus Fertility Assessment of Intensively Farmed Areas of Catchments Draining to the Great Barrier Reef World Heritage Area; 1: Soil Phosphorus Status

Abstract

Australia's reef water quality protection plan has a key objective: “reduce the load of pollutants from diffuse sources in the water entering the Reef.” This article reports on a survey to assess the contemporary phosphorus (P) status of fertilized cropping soils across 21 catchments in coastal Queensland, Australia. The survey focused on surface soils from cane farms, vegetable and subtropical/tropical fruit tree sites. There were sampling depth effects on P levels in sugar and fruit tree sites (lower with depth). Importantly, 84% of 105 sugarcane sites were excessively fertile and only 3% rated low (P deficient). Some 75% of 16 vegetable sites and 38% of 8 fruit tree sites had excess ratings for extractable soil P fertility. Highest total P levels (0–10 cm) occurred in fruit tree sites, followed by vegetable and sugarcane soils. There are regional differences in P soil fertility, and the recycling of mill by‐products needs attention. Part 2 (Bloesch and Rayment 2006) examines the potential of these soils to release soluble P in a nutrient‐sensitive area.

Keywords:

• By‐products
• fruit trees
• phosphorus
• reef
• soil tests
• sugarcane
• vegetables

Acknowledgments

Funding from the Queensland Department of Natural Resources (NRMW), Indooroopilly, and the former CRC Sugar is acknowledged. We also acknowledge the help received in soil sampling. Colleagues Dave Lyons and Phil Moody of NRMW were also involved in the wider study, particularly Dave Lyons in helping with the laboratory assessment of universal extractants.