SA01SEQ-01: Site Selection Layout and Drainage


Research Site / Demonstration Number: SA01SEQ-01
Grower Collaborator: Pinata Farms – Wamuran
Location 1: Pates Road, Wamuran
Initiation Date: February 2019


OUTLINE

To evaluate the benefits of farm planning using in-field surveying to reduce/mitigate surface and subsurface off-farm deposition, on low to moderate slopes.


OBJECTIVES

  1. To improve the methodologies of implementing better surface and sub-surface erosion management practices.
  2. To reduce soil erosion over light to moderate soil types.
  3. To evaluate the benefits of improved drainage on yield.
  4. To undertake a cost analysis of implementing soil erosion practices.

METHODOLOGY

The trial site followed a previous crop of 73-50 hybrid, which was only taken to plant crop due to poor health. The previous crop harvested below industry standards in spring 2018, with major issues of Phytophthora root rot, nematode, black beetle/white grub and natural flowering.

The soil was prepared to standard industry conditions with good soil tilth, no crop residue and good soil moisture with a soil pH of 4.3.  The average slope of the block is 2-3% with each contour drain surveyed and established at 1–2%.

Trial site prior to contour draining (left). Soil opened up with plough to assist with drying out (right).


Trial site showing contour drains marked in yellow


DEMONSTRATION PRACTICE


ASSESSMENT / EVALUATION METHOD AND DELIVERY SCHEDULE


PROGRESS REPORT

February 2019
Grower identified
Site selected
Trial planned

March 2019
Block was land prepped
Pre-plant pesticide and nutrition applied

April 2019
Bed-formed
Treatments been applied.
Site planted

October 2019
Initial rainfall event
First assessment

March 2020
Assessment after wet season

ISSUES ENCOUNTERED
Constant rainfall disrupting land preparation during establishment of block. The site has been relatively dry since planting for most of the initial trial period.


RESULTS

The initial results have indicated contour drains are highly successful in mitigating soil erosion and off-farm deposition.  After the first rainfall event of 20mm, the contour drains/banks and silt traps reduced soil movement and erosion in comparison to the control treatment.

The initial 20mm rainfall, the site has had another 785mm of rainfall over the last 6 months.  The highest recorded daily rainfall event was 86mm over a 24 hour period.

Images taken in March 2020 after wet season:

Over the last six months, the treatments with contour drains have had significantly less erosion than standard practices. This can be seen in the amount of soil erosion captured in the contour drains and silt traps (refer to table of results). The soil captured in the contour drains can be easily cleaned out using a grader at any point in the growing cycle of the crop.  The width of the contour drains is wide enough to be accessed by a grader. The soil in the contour drain can be shifted onto the contour bank. The great advantage of the contour drains has been to maintain the majority of the soil within the confines of the block.

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