Manures prove their worth in a fertiliser program

Author: Sarah Jeffrey | Date: 17 Jul 2014

Key Points

  • Manures can be a cost effective means of supplementing traditional in-organic fertilisers to help replace nutrients such asnitrogen (N) and phosphorus (P) which are extracted from the soil during a crop’s growth cycle and removed from the paddock in grain.
  • Before applying manure, it is vital growers undertake initial soil testing to establish the baseline level of macronutrients (N, P, K and S) and micronutrients such as zinc and copper present in the soil.
  • On-going soil testing is necessary to monitor and manage the potential build-up of nutrients and other chemicals in the soil over time.
  • On current prices, the combined value of N and P in feedlot manure is nearly $60/tonne and close to $100/t in poultry manure from egg layers.

With fertiliser inputs remaining a serious financial investment, growers are seeking cost-effective alternatives to provide crops with essential nutrients.


Caption: Dr Peter Wylie, Principal
Consultant, Agripath, Dalby.

Manures from beef cattle feedlots and poultry farms are increasingly being used to supplement traditional in-organic fertilisers in helping replace nutrients such as nitrogen (N) and phosphorus (P) which are extracted from the soil during a crop’s growth cycle and removed from the paddock in grain. 

However the use of manures requires careful and on-going management according to Department of Agriculture, Fisheries and Forestry (DAFF) senior research scientist, crop nutrition, David Lester.

He said it was vital that growers considering using manures undertake initial soil testing to establish the baseline level of macronutrients (N, P, K and S) and micronutrients such as zinc and copper present in the soil.

“From there on-going soil tests are necessary to monitor and manage the potential build-up of nutrients and other chemicals in the soil over time.” he said.

“Growers also need to consider what they hope to gain from using manures as the outcomes and benefits will depend on inherent soil fertility, the crop to be grown and the target yield.

“Nutrients should be applied at rates equal to or greater than the nutrients removed by the crop over time so that soil fertility can be maintained and that will vary between individual farms, paddocks and crops.”

The economics of manure use have been documented by principal consultant at Agripath, Dalby, Dr Peter Wylie who believes that the use of manure in a farming system can reduce fertiliser costs by up to 50 percent.

“The use of manure can help growers to replace nutrients removed from cropping land and keep farm costs down,” Dr Wylie said.

He said on recent pricing trends for urea and MAP, the combined value of N and P in feedlot manure comprising approximately 7kg P/t and 16kg N/t, was nearly $60/tonne.

In poultry manure (layers) comprising approximately 13kg P and 20kg N/t, the figure was closer to $100/t. Additional value is derived from the potassium (K), sulfur (S), zinc and organic carbon (C) present in manure compounds.

He said while poultry manure from egg layers has more N and P than feedlot manure, it contains less organic matter and K.

The cost of manure spread on to farms, incorporating $12 freight and $5/t spreading costs, is close to $27/t for aged beef manure and $32/t for poultry manure.

Caption: Dr Mike Bell, QAAFI.

“When the additional value of potassium is considered, the value of the manure as compared to commercial fertilisers is $92/t for aged beef manure and $118/t for poultry manure,” Dr Wylie said.

“Sulfur and zinc can add at least an extra $1.50/t in nutrient value in instances where these nutrients are of value. 

 “Taking all these nutrients into account, manure can replace nutrients in the soil for around half the cost of inorganic fertilisers, such as urea, MAP and muriate of potash which means the use of manure is particularly valuable in situations where K is needed.”

Replacement strategies are particularly appropriate for very high nutrient removal land uses such as silage or hay production where the majority of above ground plant material is extracted.

Growers are increasingly considering soil K and sulfur levels and the potential impact of any deficiencies on crop performance given the aging and soil nutrient rundown of Australian cropping land.

This is particularly evident in the cotton growing regions as cotton removes K from the soil at three times the rate of cereal grain – approximately 60kg/hectare removed in a 10 bale/ha crop.

“Until recently K hasn’t been an issue. It is a nutrient required by plants in similar quantities to nitrogen however most of this remains in the leaf and straw and only three to four kilograms of potassium is removed per tonne of grain,” Dr Wylie said.

“This adds up though with more than 200 tonnes of grain being harvested from soils on the Darling Downs that have been cultivated for 50 to 70 years. This means a removal of 600 to 800kg of K without any replacement.”

Dr Mike Bell from the University of Queensland’s Alliance for Agriculture and Food Innovation (QAAFI) agrees that manure can be an extremely valuable component of an on-going soil amendment/soil conditioning program but stressed that it is not a balanced fertiliser.

“It is very difficult to guarantee what percentage of the nutrients in the manure will become available to plants and when,” Dr Bell said.

“There has been trial work conducted using manure for P and this demonstrated that it was a valuable resource but incorporation was necessary.”

The Grains Research and Development Corporation (GRDC) advises growers to assess the chemical make-up of recycled organics to determine the potential nutrients available, correctly calculate application rates and identify any potential benefits and risks.

A copy of the GRDC’s Recycled Organic Fertiliser Factsheet can be found at http://www.grdc.com.au/uploads/documents/GRDC_FS_RecycledOrganics.pdf

Value of nutrients at fertiliser prices – Peter Wylie, Agripath

Aged Manure

Poultry Manure

Water content

33%

33%

Nitrogen (kg/t)

16

20

Phosphorus (P) (kg/t)

7

13

Potassium (K) (kg/t)

20

11

Value of N and P*

$59

$97

Value of N, P & K*

$92

$115

Cost at source: ($/t)

$10

$18

Cost with Freight $12, and spread $5

$27

$35

Extra value compared to bag fertiliser ($/t)

$32

$62

(NB: Freight costs will vary depending on location and spreading costs may be as high as $7/t.)

ENDS

Contact Details 

For Interviews

Dr Mike Bell, QAAFI, UQ
07 4160 0730
m.bell4@uq.edu.au

Dr Peter Wylie, Principal Consultant, Agripath, Dalby
0429 361 301
peterwylie@agripath.com.au

Contact

Sarah Jeffrey, Senior Consultant Cox Inall Communications
0418 152 859
sarahj@coxinall.com.au

GRDC Project Code APT00001; More Profit From Crop Nutrition 11 - UQ00063 & UQ00066

Region North