APSRU PROJECT SUMMARY

PROJECT NO.

237

Project Title

Managing the fallow period for optimum water use and nitrogen availability

Project Leader

Kirsten Verburg

Organisation

CSIRO Land and Water

APSRU Representative

Kirsten Verburg

Funding Body

GRDC, CSIRO Land and Water, CSIRO Sustainable Ecosystems, Charles Sturt University

Administration Contact

Lesley Geldenhuys

CSIRO Land and Water

Private Bag #2, PO

Glen Osmond, SA 5064 Ph: 08 8303 8508 Fax: 08 8303 8555

Commencement Date

1/7/2003

Completion Date

30/6/2006

Research Proposal Summary

Successful control of deep drainage by agricultural systems requires careful management of all factors affecting the water balance of crops. Research on farms in the vicinity of Wagga Wagga (GRDC project CSO197; LWA project CDS20) has shown that the soil surface condition of the paddock during the summer fallow period can have a large effect on the amount of water that is left behind in the profile. The way the stubble and weeds are managed affects the water balance, the rate of stubble breakdown, and the release or immobilisation of nitrogen. This is not a new result, but it has previously been studied from the perspective of maximising water storage for use for the subsequent crop rather than for control of deep drainage.

Currently there is a lack of critical data for evaluating the benefits and risks of different fallow management practices that may be introduced to control deep drainage. This project, therefore, aims to (1) evaluate the effect of fallow management on soil water storage and evapotranspiration during the non-growing season following crops grown as part of the cereal rotation in southern Australia, (2) determine the effect of management on the rate of stubble decomposition and nutrient release, and (3) develop fallow management strategies that minimise deep drainage without detrimentally affecting the subsequent crop by limiting water and nitrogen availability.

As it is not possible to quantify the long-term effects of any management option on deep drainage by field studies alone, simulation modelling will be used as an adjunct to field measurements to provide extrapolation to a wider range of weather sequences. The data will therefore also be used to test the APSIM model to ensure that it predicts the key processes occurring during the fallow accurately.

Aims

(1) evaluate the effect of fallow management on soil water storage and evapotranspiration during the non-growing season following crops grown as part of the cereal rotation in southern Australia,

(2) determine the effect of management on the rate of stubble decomposition and nutrient release, and

(3) develop fallow management strategies that minimise deep drainage without detrimentally affecting the subsequent crop by limiting water and nitrogen availability

Potential Outcomes

Increased farmer awareness of the consequences of alternative managements of summer fallows in terms of the risk of deep drainage and effects on productivity of following crops.

Milestones

1. Selection of paddock and treatments for summer fallow management and agreement reached with GRDC on treatments to be applied.

a. 31/10/2003 (repeated 2004)

2. Progress Report to GRDC

a. 31/3/2004 (repeated 2004, 2005)

3. Completion of summer fallow experimentation

a. 30/9/2004 (repeated 2005)

4. Completion of growing season drainage monitoring and crop performance assessment. Fallow management principles discussed with growers.

a. 31/3/2005 (repeated 2006)

5. Completion of evaluation of modelling capability

a. 31/1/2006

6. Completion of modelling scenarios evaluating optimum fallow management strategies

a. 30/4/2006

7. Promotion of project findings

a. 30/6/2006

8. Submission of Final Report to GRDC

a. 30/9/2006

Budget

2003-04 2004-05 2005-06 Total

$191,325 $223,344 $199,638 $596,495

Staff	% / year
K Verburg	25% / 3 years
WJ Bond	10% / 3 years
Merv Probert	2% / 3 years
Neil Huth	2% / 3 years
Don Gaydon	10% / 2 years

And other non-APSRU staff

Resource Requirements

& Contributions

Prior Provision of IP &

Rights of Ownership

APSIM - APSRU, SWIM - CLW

Ownership, equity in and use of IP to be developed

This project will lead to improvements in the RESIDUE and SOILN modules of APSIM. These attribution of ownership of these improvements will be dictated by the annual IP equity calculation for APSRU core partners

Rights of Publication

Joint publications intended

Strategic Plan Goal No.

KRA 4 (Program VII) and KRA1 (Program I)

Relevance to Strategic Plan

Project addresses the following specific strategies from APSRU’s Strategic Plan:

KRA4 (Program VII): Maintain and build APSIM to meet a growing range of applications

KRA1 (Program I): Develop and deliver tools that allow assessment and management of production, [economic,] and environmental risk at a paddock level.