Year of study:
1998-99
Lead organisation & collaborators (if any):
Department of Natural Resources and Environment
Department of Agricultural Sciences, LaTrobe University
Contact:
Cameron Gourley
E: cameron.gourley@dpi.gov.au
Best available science assessment:
Overall Score: 32
Overall rating: Very high
|
Objectives |
Conceptual model |
Study design |
Soil analysis |
Production & financial |
Method reporting |
Data analysis |
Results reporting |
Publication |
|
3 |
4 |
4 |
4 |
1 |
4 |
4 |
4 |
4 |
Project details
Objectives:
Research was conducted on nine sites with different soil types and phosphorus buffering capacities to assess how the effectiveness of P fertiliser application (expressed as the change in extractable phosphorus per unit of P applied) varied.
Hypotheses:
Phosphorus is a limiting nutrient for production, but the use of P fertiliser and how it reacts with soil and consequential impacts on plant uptake of N is an important process. Previous trials have considered the impact on P fertiliser effectiveness over time across various fertilisers, but this trial considers the impact of P fertiliser effectiveness across different soil types.
Basis of trial:
The effectiveness of P Fertiliser over different soil types is not well established and is considered in this trial.
Location details
Trial Site Details:
Dry Conditions during trial.
Mean rainfall >800mm/a
| Soil Type | 1 Outtrim | 2 Athlone | 3 Yarragon | 4 Ellinbank | 5 Strzelecki | 6 Tynong | 7 Caurdievale | 8 Glenormiston | 9 Terang | ||||||||
| Coarse sand (%) | 17.8 | 6.8 | 4.3 | 3.1 | 2.5 | 12.8 | 22 | 10.3 | 3.7 | ||||||||
| Fine sand (%) | 40.8 | 37.4 | 30.2 | 20.2 | 18.4 | 15.3 | 53.6 | 15.8 | 50.2 | ||||||||
| Silt (%) | 18.3 | 31.3 | 37.8 | 27 | 32.5 | 17 | 11.3 | 22.8 | 20.8 | ||||||||
| Clay (%) | 5.3 | 12.3 | 17.5 | 35.8 | 30.8 | 31 | 6 | 32.3 | 15.3 | ||||||||
Pre-trial management:
Sites 2,3,6 and 7 were rotationally grazed (dairy)
Sites 1,4,5,8 and 9 were set-stocked or rotationally grazed (beef).
Various stocking rates
Permanent pasture (perennial ryegrass and white clover)
Methods and Measures
Management practices tested:
P Fertiliser and lime application
Soil sampling method:
Soil from each site was sampled immediately prior to treatment.
Tested every 6 months. Tested for:
- pH(CaCl2)
- Olsen P
- Colwell P
- Organic C (Walkley Black)
- Exch H
- Exch Al
- ECEC
- Oxalate-extr Fe
- Oxalate-extr Al
- PBC (P sorption curve)
- PBI
Summary of key findings of trial:
The application of P fertiliser to low P buffered soils was generally more efficient in the short-medium term (6-30 months) (due to greater extractable P/kg of P fertiliser applied). Application of smaller rates of P fertiliser resulted in significantly higher DEP compared to singular applications (smaller applications had stronger results).
The application of SSP, TSP and TSP with lime had little impact on DEP values 18-30 months after treatments were applied (pH changes cannot be attributed to differences in DEP in this trialTable of results
Variations in soil pH with time and management influence:
The application of lime had no consistent effect on DEP values (change in extractable P per unit of P applied).
Other soil treatments:
The application of P fertiliser to low P buffered soils was generally more efficient in the short-medium term (6-30 months) (due to greater extractable P/kg of P fertiliser applied).
Experimental design
Treatments
The following treatments were applied to each site:
| Treatment no. | Treatment | Treatment no. | Treatment | |||
| 1 | Control | 10 | SSP 35 | |||
| 2 | TSP 17.5 | 11 | SSP 70 | |||
| 3 | TSP 35 | 12 | SSP140 | |||
| 4 | TSP 52.5 | 13 | Control with lime | |||
| 5 | TSP 70 | 14 | TSP 35 with lime | |||
| 6 | TSP 105 | 15 | TSP 70 with lime | |||
| 7 | TSP 140 | 16 | TSP 140 with lime | |||
| 8 | TSP 210 | 17 | TSP 35 (applied every 6 months) | |||
| 9 | TSP 280 | 18 | TSP 70 (applied every 6 months) | |||
Where TSP (triple superphosphate) and SSP (single superphosphate) are provided in kg P/ha, and lime is a 5t/ha treatment.
The treatments were applied in a single application in 1998. Treatment 17 and 18 was reapplied every 6 months.
Trial design/Layout
At each site, 18 treatments were applied. The layout included 3 replicates to 2 x 10m plots (randomised resolvable incomplete block design- each of the treatments were split in 3 blocks with 6 treatments/block)
Reporting
How results have been reported:
Journal article
Burkitt L, Gourley C., Sale P. (2002): Changes in bicarbonate-extractable phosphorus over time when P fertiliser was withheld or reapplied to pasture soils, Australian Journal of Soil Research, CSIRO, 40, 1213-1229
How can a copy of any relevant reports be obtained:
Online journal article
http://www.publish.csiro.au/paper/SR02012.htm
or
cameron.gourley@dpi.gov.au
Level of review of results:
External peer review
Next steps
P fertiliser application at 35 or 70kg P/ha were greater than the soil maintenance requirements of the soils tested in this trial.
Further research is required to determine maintenance P fertiliser requirements.