Gippsland - How Now Gippy Cow
October 2010 Edition
Soil fertility levels on Australian dairy farms
There is a substantial opportunity for Australian dairy farmers to reduce fertiliser inputs without a loss of production.
Australian farmers have traditionally relied on recycling nutrients to drive productivity. However, modern agriculture increasingly relies on bringing in nutrients in the form of fertilisers and feed. This is particularly the case in intensive animal production systems, such as dairy production. There is both an increasing environmental and economic imperative to increase the efficiency of nutrient use while driving improvements in productivity.
The Victorian Department of Primary Industries, in partnership with the dairy and fertiliser industry and other state agencies, has recently completed a four-year project ‘Accounting for Nutrients’ which has monitored nutrient imports, exports and within-farm nutrient flows on 44 dairy farms across Australia. The project was led by Dr Cameron Gourley.
“These farms represent a broad range of herd and farm sizes, geographic locations, milk productivity, and soil types, and are applicable to the Australian dairy industry as a whole,” Dr Gourley said.
“One of the key messages from the study was the large amount of nutrients imported and cycling around dairy farms and the accumulation of these nutrients,” said Cameron. “The net surplus of these nutrients is reflected in the soil test results.”
More than 80 per cent of the 2000 paddocks sampled were found to have soil nutrients levels above agronomic requirements (Olsen-P 20mg/kg, Colwell-K 200mg/kg, KCl-S 10mg/kg). This suggests that there was unlikely to be additional pasture response from fertiliser inputs that increase soil nutrients levels above these requirements.
Key indicators of elevated soil fertility were overall milk production and stocking rate. These indicators reflected the overall intensity of the dairy operation and the likely higher amounts of nutrients imported in feed and fertiliser.
Higher soil nutrient levels of phosphorus, potassium and sulphur were driven by paddock stocking density, proximity to the dairy, frequency of effluent applications and feeding strategies.
Nutrient loadings from the deposition of animal excreta were clearly a key driver of elevated soil nutrient levels. Paddocks with high densities of animals per hectare had very high nutrient accumulation, while those infrequently visited and with low stocking densities generally had lower soil nutrient levels.
High nutrient areas on the farm might also have degraded soil structure and low plant cover, increasing the risk of nutrient losses. An additional negative consequence from high potassium loads from manure, effluent applications and fertiliser were high plant potassium uptake and potential metabolic disorders in livestock.
There are substantial opportunities on dairy farms to reduce fertiliser inputs. In many cases, high levels of soil test phosphorus, potassium and sulphur might supply necessary plant nutrients for a number of years before maintenance nutrient applications might be required.
Where fertiliser applications are warranted for increasing pasture and crop productivity, a more strategic approach should be undertaken. This will include mapping soil nutrient levels and providing a map to the fertiliser contractor so they can strategically spread the fertiliser.
Table 1: Mean soil pH, available P, K and S and PBI levels of different land uses from 40 conventional and four organic dairy farms.
| Management/Use | Distance to dairy (m) |
pH (CaC12) |
Olsen P (mg/kg) |
Colwell P (mg/kg) |
Collwell K (mg/kg) |
KC140 S (mg/kg) |
PBI (mg/kg) |
|---|---|---|---|---|---|---|---|
| Organic Pasture n = 141 * |
625.5 | 5.4 (0.6) ^ | 16.7 (13.8) | 65 (62) | 271 (199) | 18.4 (20) | 302 (166) |
| Conventional Pasture n = 1773 |
881.4 | 5.3 (0.7) | 35.6 (20) | 127 (76) | 296 (224) | 23.4 (33) | 263 (230) |
| Bull paddock n = 6 | 444.0 | 5.3 (0.9) | 48.8 (26) | 169 (82) | 703 (602) | 45.3 (29) | 262 (24) |
| Feeding areas n = 12 | 53.1 | 6.8 (1.2) | 319.9 (285) | 1151 (1286) | 4471 (3945) | 263.5 (263) | 321 (277) |
| Holding area n = 13 | 400.4 | 5.8 (0.9) | 143.5 (171) | 510 (685) | 1515(1271) | 73.8 (71) | 251 (252) |
| Sick paddock n = 16 | 46.9 | 5.6 (0.9) | 71.4 (61) | 280 (282) | 771 (711) | 27.5 (19) | 178 (180) |
| Other animal n = 104 | na | 5.1 (0.6) | 27.4 (15) | 100 (58) | 269 (180) | 14.6 (12) | 301 (281) |
* n = number of areas sampled ^ Standard deviation in parenthesis
For further information please:
Email Jessie.Horton@dpi.vic.gov.au or Cameron.Gourley@dpi.vic.gov.au
or visit the website http://www.accounting4nutrients.com.au/
