Grain & Graze 3 - The impact of livestock on paddock health

2015

Research organisatons
Funding source

Trial details

Aims

The majority of farms in low rainfall areas use sheep to provide enterprise diversity, however grazing also offers a range of other system benefits that are generally not accounted for in mixed farming enterprises. Studies have shown that grazing offers a useful tool for managing weeds and pests, improving crop nutrition and yields and providing an option to mitigate risk in pasture crop rotations. In these systems there is a perception of declining performance of the pasture ley, as a result of increasing cropping intensity. As a result, there has been work to show the benefits of increasing crop and pasture inputs, as opposed to district practice crop seeding and fertiliser rates and pasture regeneration from residual seed banks.

A long-term study was established at the Minnipa Agricultural Centre from 2008 to 2015 (EPFS Summaries 2008 to 2014) to assess the impact of grazing on crop and pasture production and soil health and also to evaluate this from a systems perspective.

The eight year demonstration with a wheat, wheat, pasture (volunteer and sown annual medic), wheat, pasture (self-regenerating annual medic), wheat and wheat rotation was also established to determine whether productivity could be improved under a higher input system compared to a lower input and more traditional system and what affect this had on soil fertility.

Medics are a common and attractive break ‘crop’ option in low rainfall mixed farming systems due to their natural regeneration, good quality feed value, low cost maintenance and valuable nitrogen (N) fixation qualities. To capture these advantages, medic pastures need to be kept in a productive state to ensure that the seed bank is adequate and that the plant is fixing the N that is needed for the following crop.

 

In recent years, some medic pastures have been of poor quality due to a range of factors including chemical usage, incorrect grazing methods, mechanical damage and other modern farming practices, resulting in reduced production and subsequent N2-fixation. Best practice medic production guidelines have already been established, however some of these techniques are not adopted due to the time and expense involved. For these reasons, many farmers are looking for simple practices to establish medic pastures and boost their production using cost and time efficient methods.

 

The aim of this trial was to look at current techniques used by farmers, or recommended by consultants, to improve medic pastures and determine the most effective method to optimise N2-fixation. Biomass, nodulation and N2-fixation differences between management practices, including inoculation treatments on both sown and regenerating medic stands were measured. The trial also investigated if grazing medic pastures in the break phase of the rotation benefits or impedes nodulation and subsequent N2-fixation.

Key messages
  • Grazing sheep have not damaged soil health over eight years of several crop/pasture rotations.
  • In 2015 total annual biomass was greater in higher input and grazed rotations. High input grazed systems carried twice the stocking rate of a low input system.
  • The paddock utilised for the trial had a significant number of effective naturalised medic rhizobia. There was no rhizobial inoculation response.
  • Total annual biomass was higher in the regenerating medic plots versus sown treatments due to earlier germination and growth of naturalised medic.
  • Grazing increased overall medic production.
Lead research organisation Southern Farming Systems
Host research organisation SARDI Minnipa Agricultural Centre
Trial funding source GRDC SFS00028,SFS00028
Related program Grain & Graze 3
Acknowledgments

I gratefully acknowledge the help of Mark Klante and Brett McEvoy for site management and John Kelsh for data collection. The Eyre Peninsula Grain and Graze 3 project is funded by GRDC (SFS00028).


I gratefully acknowledge Jake Howie and Ross Ballard for their guidance throughout the trial and Leigh Davis, Brenton Spriggs, Brett McEvoy and John Kelsh for site establishment and management. The Eyre Peninsula Grain and Graze 3 project is funded by GRDC (SFS00028).


Other trial partners EP, BCG, MSF, Ag Excellence Alliance
Download the trial report to view additional trial information

Method

Crop type Forage: Medic
Treatment type(s)
  • Fertiliser: Rate
  • Grazing: Regime
  • Sowing: Rate
Trial type Demonstration
Trial design Unknown
Sow rate or Target density Not specified
Sowing machinery Not specified
Plot size 350m x 100m
Plot replication 1
Plot blocking Not specified
Plot randomisation Not specified
Paddock history 2014: Wheat 2013: Wheat 2012: Medic pasture
Fertiliser

In 2015 the trial was retained as a self-regenerating annual medic, with a fertiliser treatment of 18:20:00 DAP broadcast @ 100 kg/ha to the high input areas on 23 April.

Herbicide

Grass weeds were sprayed-out of the ungrazed sections on 7 October. No spraying was required on grazed treatments.

Insecticide Not specified
Fungicide Not specified
Pesticide Not specified
Soil amelioration Not specified
Seed treatment Not specified
Inoculant Not specified
Tillage Not specified
Other trial notes Not specified
Download the trial report to view additional method/treatment information
Observed trial site soil information
Trial site soil testing
Not specified
Soil conditions
Trial site Soil texture
Site 17, Minnipa Agricultural Centre, SA Red sandy loam
Derived trial site soil information
Australian Soil Classification Source
Trial site Soil order
Site 17, Minnipa Agricultural Centre, SA Calcarosol
National soil grid Source
NOTE: National Soil Grid data is aggregated information for background information on the wider area
Actual soil values can vary significantly in a small area and the trial soil tests are the most relevant data where available

Soil properties

Loading

Climate

Site 17, Minnipa Agricultural Centre SA 2015


Observed climate information
Rainfall avg ann (mm) 325mm
Rainfall avg gsr (mm) 241mm
Rainfall trial total (mm) 333mm
Rainfall trial gsr (mm) 258mm
Derived climate information
Loading
Loading
BOM Data source MINNIPA PIRSA [4269] 0km proximity to trial site location


Loading

Site 17, Minnipa Agricultural Centre SA 2015


Observed climate information
Rainfall avg ann (mm) 325mm
Rainfall avg gsr (mm) 241mm
Rainfall trial total (mm) 333mm
Rainfall trial gsr (mm) 258mm
Derived climate information
Loading
Loading
BOM Data source MINNIPA PIRSA [4269] 0km proximity to trial site location


Loading

Some data on this site is sourced from the Bureau of Meteorology

SILO weather estimates sourced from https://www.longpaddock.qld.gov.au/silo/
Jeffrey, S.J., Carter, J.O., Moodie, K.B. and Beswick, A.R. (2001). Using spatial interpolation to construct a comprehensive archive of Australian climate data , Environmental Modelling and Software, Vol 16/4, pp 309-330. DOI: 10.1016/S1364-8152(01)00008-1.

Trial report and links

2015 trial report

2015 trial report